diff --git a/.codeclimate.yml b/.codeclimate.yml
new file mode 100644
index 0000000..ec80874
--- /dev/null
+++ b/.codeclimate.yml
@@ -0,0 +1,15 @@
+engines:
+  duplication:
+    enabled: true
+    config:
+      languages:
+      - python
+  fixme:
+    enabled: true
+  radon:
+    enabled: true
+ratings:
+  paths:
+  - "**.py"
+exclude_paths:
+- tests/
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..2029c77
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,13 @@
+language: python
+python:
+  - "2.7"
+  - "3.3"
+  - "3.4"
+  - "3.5"
+install:
+  - pip install psutil
+  - pip install netifaces
+script: nosetests -v tests/
+#addons:
+#  code_climate:
+#    repo_token: 40cb00907f7a10e04868e856570bb997ab9c42fd3b63d980f2b2269433195fdf
diff --git a/README.md b/README.md
index d039179..0157695 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,7 @@
 # bumblebee-status
 
+[![Build Status](https://travis-ci.org/tobi-wan-kenobi/bumblebee-status.svg?branch=engine-rework)](https://travis-ci.org/tobi-wan-kenobi/bumblebee-status) [![Code Climate](https://codeclimate.com/github/tobi-wan-kenobi/bumblebee-status/badges/gpa.svg)](https://codeclimate.com/github/tobi-wan-kenobi/bumblebee-status) [![Issue Count](https://codeclimate.com/github/tobi-wan-kenobi/bumblebee-status/badges/issue_count.svg)](https://codeclimate.com/github/tobi-wan-kenobi/bumblebee-status)
+
 bumblebee-status is a modular, theme-able status line generator for the [i3 window manager](https://i3wm.org/).
 
 Focus is on:
diff --git a/bin/customupdates b/bin/pacman-updates
similarity index 99%
rename from bin/customupdates
rename to bin/pacman-updates
index 3176c9d..baf0b93 100755
--- a/bin/customupdates
+++ b/bin/pacman-updates
@@ -1,4 +1,5 @@
 #!/usr/bin/bash
+
 if ! type -P fakeroot >/dev/null; then
 	error 'Cannot find the fakeroot binary.'
 	exit 1
diff --git a/bumblebee-status b/bumblebee-status
index 42258a4..248ff52 100755
--- a/bumblebee-status
+++ b/bumblebee-status
@@ -1,16 +1,36 @@
 #!/usr/bin/env python
 
 import sys
-import bumblebee.config
+import bumblebee.theme
 import bumblebee.engine
+import bumblebee.config
+import bumblebee.output
+import bumblebee.input
 
 def main():
     config = bumblebee.config.Config(sys.argv[1:])
-
-    engine = bumblebee.engine.Engine(config)
-    engine.load_modules()
+    theme = bumblebee.theme.Theme(config.theme())
+    output = bumblebee.output.I3BarOutput(theme=theme)
+    inp = bumblebee.input.I3BarInput()
+    engine = bumblebee.engine.Engine(
+        config=config,
+        output=output,
+        inp=inp,
+    )
 
     engine.run()
+#    try:
+#    except KeyboardInterrupt as error:
+#        inp.stop()
+#        sys.exit(0)
+#    except bumblebee.error.BaseError as error:
+#        inp.stop()
+#        sys.stderr.write("fatal: {}\n".format(error))
+#        sys.exit(1)
+#    except Exception as error:
+#        inp.stop()
+#        sys.stderr.write("fatal: {}\n".format(error))
+#        sys.exit(2)
 
 if __name__ == "__main__":
     main()
diff --git a/bumblebee/config.py b/bumblebee/config.py
index 501393d..2a72599 100644
--- a/bumblebee/config.py
+++ b/bumblebee/config.py
@@ -1,116 +1,50 @@
-import os
+"""Configuration handling
+
+This module provides configuration information (loaded modules,
+module parameters, etc.) to all other components
+"""
+
 import argparse
-import textwrap
+import bumblebee.store
 
-import bumblebee.theme
-import bumblebee.module
+MODULE_HELP = ""
+THEME_HELP = ""
+PARAMETER_HELP = ""
 
-class print_usage(argparse.Action):
-    def __init__(self, option_strings, dest, nargs=None, **kwargs):
-        argparse.Action.__init__(self, option_strings, dest, nargs, **kwargs)
-        self._indent = " "*4
+def create_parser():
+    """Create the argument parser"""
+    parser = argparse.ArgumentParser(description="display system data in the i3bar")
+    parser.add_argument("-m", "--modules", nargs="+", default=[],
+        help=MODULE_HELP)
+    parser.add_argument("-t", "--theme", default="default", help=THEME_HELP)
+    parser.add_argument("-p", "--parameters", nargs="+", default=[],
+        help=PARAMETER_HELP)
+    return parser
 
-    def __call__(self, parser, namespace, value, option_string=None):
-        if value == "modules":
-            self.print_modules()
-        elif value == "themes":
-            self.print_themes()
-        else:
-            parser.print_help()
-        parser.exit()
+class Config(bumblebee.store.Store):
+    """Top-level configuration class
 
-    def print_themes(self):
-        print(textwrap.fill(", ".join(bumblebee.theme.themes()),
-            80, initial_indent = self._indent, subsequent_indent = self._indent
-        ))
+    Parses commandline arguments and provides non-module
+    specific configuration information.
+    """
+    def __init__(self, args=None):
+        super(Config, self).__init__()
+        parser = create_parser()
+        self._args = parser.parse_args(args if args else [])
 
-    def print_modules(self):
-        for m in bumblebee.module.modules():
-            print(textwrap.fill("{}: {}".format(m.name(), m.description()),
-                80, initial_indent=self._indent*2, subsequent_indent=self._indent*3))
-            print("{}Parameters:".format(self._indent*2))
-            for p in m.parameters():
-                print(textwrap.fill("* {}".format(p),
-                    80, initial_indent=self._indent*3, subsequent_indent=self._indent*4))
-            print("")
-
-class ModuleConfig(object):
-    def __init__(self, config, prefix):
-        self._prefix = prefix
-        self._config = config
-
-    def set(self, name, value):
-        name = self._prefix + name
-        return self._config.set(name, value)
-
-    def parameter(self, name, default=None):
-        name = self._prefix + name
-        return self._config.parameter(name, default)
-
-    def increase(self, name, limit, default):
-        name = self._prefix + name
-        return self._config.increase(name, limit, default)
-
-class Config(object):
-    def __init__(self, args):
-        self._parser = self._parser()
-        self._store = {}
-
-        if len(args) == 0:
-            self._parser.print_help()
-            self._parser.exit()
-
-        self._args = self._parser.parse_args(args)
-
-        for p in self._args.parameters:
-            key, value = p.split("=")
-            self.parameter(key, value)
-
-    def set(self, name, value):
-        self._store[name] = value
-
-    def parameter(self, name, default=None):
-        if not name in self._store:
-            self.set(name, default)
-        return self._store.get(name, default)
-
-    def increase(self, name, limit, default):
-        self._store[name] += 1
-        if self._store[name] >= limit:
-            self._store[name] = default
-        return self._store[name]
-
-    def theme(self):
-        return self._args.theme
+        for param in self._args.parameters:
+            key, value = param.split("=")
+            self.set(key, value)
 
     def modules(self):
-        result = []
-        for m in self._args.modules:
-            items = m.split(":")
-            result.append({ "name": items[0], "alias": items[1] if len(items) > 1 else None })
-        return result
+        """Return a list of all activated modules"""
+        return [{
+            "module": x.split(":")[0],
+            "name": x if not ":" in x else x.split(":")[1],
+        } for x in self._args.modules]
 
-    def _parser(self):
-        parser = argparse.ArgumentParser(description="display system data in the i3bar")
-        parser.add_argument("-m", "--modules", nargs="+",
-            help="List of modules to load. The order of the list determines "
-            "their order in the i3bar (from left to right)",
-            default=[],
-        )
-        parser.add_argument("-l", "--list",
-            help="List: 'modules', 'themes' ",
-            choices = [ "modules", "themes" ],
-            action=print_usage,
-        )
-        parser.add_argument("-p", "--parameters", nargs="+",
-            help="Provide configuration parameters to individual modules.",
-            default=[]
-        )
-        parser.add_argument("-t", "--theme", help="Specify which theme to use for "
-            "drawing the modules",
-            default="default",
-        )
-
-        return parser
+    def theme(self):
+        """Return the name of the selected theme"""
+        return self._args.theme
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/engine.py b/bumblebee/engine.py
index 1625ee7..0698171 100644
--- a/bumblebee/engine.py
+++ b/bumblebee/engine.py
@@ -1,34 +1,145 @@
+"""Core application engine"""
+
+import os
+import time
+import pkgutil
 import importlib
-import bumblebee.theme
-import bumblebee.output
+import bumblebee.error
 import bumblebee.modules
 
-class Engine:
-    def __init__(self, config):
-        self._modules = []
+def all_modules():
+    """Return a list of available modules"""
+    result = []
+    path = os.path.dirname(bumblebee.modules.__file__)
+    for mod in [name for _, name, _ in pkgutil.iter_modules([path])]:
+        result.append({
+            "name": mod
+        })
+    return result
+
+class Module(object):
+    """Module instance base class
+
+    Objects of this type represent the modules that
+    the user configures. Concrete module implementations
+    (e.g. CPU utilization, disk usage, etc.) derive from
+    this base class.
+    """
+    def __init__(self, engine, config={}, widgets=[]):
+        self.name = config.get("name", self.__module__.split(".")[-1])
         self._config = config
-        self._theme = bumblebee.theme.Theme(config)
-        self._output = bumblebee.output.output(config)
+        self.id = self.name
+        self._widgets = []
+        if widgets:
+            self._widgets = widgets if isinstance(widgets, list) else [widgets]
 
-    def load_module(self, modulespec):
-        name = modulespec["name"]
-        module = importlib.import_module("bumblebee.modules.{}".format(name))
-        return getattr(module, "Module")(self._output, self._config, modulespec["alias"])
+    def widgets(self):
+        """Return the widgets to draw for this module"""
+        return self._widgets
 
-    def load_modules(self):
-        for m in self._config.modules():
-            self._modules.append(self.load_module(m))
+    def widget(self, name):
+        for widget in self._widgets:
+            if widget.name == name:
+                return widget
+
+    def widget_by_id(self, uid):
+        for widget in self._widgets:
+            if widget.id == uid:
+                return widget
+        return None
+
+    def update(self, widgets):
+        """By default, update() is a NOP"""
+        pass
+
+    def parameter(self, name, default=None):
+        """Return the config parameter 'name' for this module"""
+        name = "{}.{}".format(self.name, name)
+        return self._config["config"].get(name, default)
+
+    def threshold_state(self, value, warn, crit):
+        if value > float(self.parameter("critical", crit)):
+            return "critical"
+        if value > float(self.parameter("warning", warn)):
+            return "warning"
+        return None
+
+class Engine(object):
+    """Engine for driving the application
+
+    This class connects input/output, instantiates all
+    required modules and drives the "event loop"
+    """
+    def __init__(self, config, output=None, inp=None):
+        self._output = output
+        self._config = config
+        self._running = True
+        self._modules = []
+        self.input = inp
+        self._aliases = self._read_aliases()
+        self.load_modules(config.modules())
+
+        self.input.register_callback(None, bumblebee.input.WHEEL_UP,
+            "i3-msg workspace prev_on_output")
+        self.input.register_callback(None, bumblebee.input.WHEEL_DOWN,
+            "i3-msg workspace next_on_output")
+
+        self.input.start()
+
+    def load_modules(self, modules):
+        """Load specified modules and return them as list"""
+        for module in modules:
+            self._modules.append(self._load_module(module["module"], module["name"]))
+        return self._modules
+
+    def _read_aliases(self):
+        result = {}
+        for module in all_modules():
+            mod = importlib.import_module("bumblebee.modules.{}".format(module["name"]))
+            for alias in getattr(mod, "ALIASES", []):
+                result[alias] = module["name"]
+        return result
+
+    def _load_module(self, module_name, config_name=None):
+        """Load specified module and return it as object"""
+        if module_name in self._aliases:
+            config_name is config_name if config_name else module_name
+            module_name = self._aliases[module_name]
+        if config_name is None:
+            config_name = module_name
+        try:
+            module = importlib.import_module("bumblebee.modules.{}".format(module_name))
+        except ImportError as error:
+            raise bumblebee.error.ModuleLoadError(error)
+        return getattr(module, "Module")(self, {
+            "name": config_name,
+            "config": self._config
+        })
+
+    def running(self):
+        """Check whether the event loop is running"""
+        return self._running
+
+    def stop(self):
+        """Stop the event loop"""
+        self._running = False
 
     def run(self):
+        """Start the event loop"""
         self._output.start()
-
-        while True:
-            self._theme.begin()
-            for m in self._modules:
-                self._output.draw(m.widgets(), self._theme)
+        while self.running():
+            self._output.begin()
+            for module in self._modules:
+                module.update(module.widgets())
+                for widget in module.widgets():
+                    widget.link_module(module)
+                    self._output.draw(widget=widget, module=module, engine=self)
             self._output.flush()
-            self._output.wait()
+            self._output.end()
+            if self.running():
+                self.input.wait(self._config.get("interval", 1))
 
         self._output.stop()
+        self.input.stop()
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/error.py b/bumblebee/error.py
new file mode 100644
index 0000000..129f02d
--- /dev/null
+++ b/bumblebee/error.py
@@ -0,0 +1,15 @@
+"""Collection of all exceptions raised by this tool"""
+
+class BaseError(Exception):
+    """Base class for all exceptions generated by this tool"""
+    pass
+
+class ModuleLoadError(BaseError):
+    """Raised whenever loading a module fails"""
+    pass
+
+class ThemeLoadError(BaseError):
+    """Raised whenever loading a theme fails"""
+    pass
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/input.py b/bumblebee/input.py
new file mode 100644
index 0000000..ba41362
--- /dev/null
+++ b/bumblebee/input.py
@@ -0,0 +1,122 @@
+"""Input classes"""
+
+import sys
+import json
+import uuid
+import time
+import select
+import threading
+import bumblebee.util
+
+LEFT_MOUSE = 1
+RIGHT_MOUSE = 3
+WHEEL_UP = 4
+WHEEL_DOWN = 5
+
+def read_input(inp):
+    """Read i3bar input and execute callbacks"""
+    while inp.running:
+        for thread in threading.enumerate():
+            if thread.name == "MainThread" and not thread.is_alive():
+                return
+
+        rlist, _, _ = select.select([sys.stdin], [], [], 1)
+        if not rlist:
+            continue
+        line = sys.stdin.readline().strip(",").strip()
+        inp.has_event = True
+        try:
+            event = json.loads(line)
+            inp.callback(event)
+            inp.redraw()
+        except ValueError:
+            pass
+    inp.has_event = True
+    inp.clean_exit = True
+
+class I3BarInput(object):
+    """Process incoming events from the i3bar"""
+    def __init__(self):
+        self.running = True
+        self._callbacks = {}
+        self.clean_exit = False
+        self.global_id = str(uuid.uuid4())
+        self.need_event = False
+        self.has_event = False
+        self._condition = threading.Condition()
+
+    def start(self):
+        """Start asynchronous input processing"""
+        self.has_event = False
+        self.running = True
+        self._condition.acquire()
+        self._thread = threading.Thread(target=read_input, args=(self,))
+        self._thread.start()
+
+    def redraw(self):
+        self._condition.acquire()
+        self._condition.notify()
+        self._condition.release()
+
+    def alive(self):
+        """Check whether the input processing is still active"""
+        return self._thread.is_alive()
+
+    def wait(self, timeout):
+        self._condition.wait(timeout)
+
+    def _wait(self):
+        while not self.has_event:
+            time.sleep(0.1)
+        self.has_event = False
+
+    def stop(self):
+        """Stop asynchronous input processing"""
+        self._condition.release()
+        if self.need_event:
+            self._wait()
+        self.running = False
+        self._thread.join()
+        return self.clean_exit
+
+    def _uuidstr(self, name, button):
+        return "{}::{}".format(name, button)
+
+    def _uid(self, obj, button):
+        uid = self.global_id
+        if obj:
+            uid = obj.id
+        return self._uuidstr(uid, button)
+
+    def deregister_callbacks(self, obj):
+        to_delete = []
+        uid = obj.id if obj else self.global_id
+        for key in self._callbacks:
+            if uid in key:
+                to_delete.append(key)
+        for key in to_delete:
+            del self._callbacks[key]
+
+    def register_callback(self, obj, button, cmd):
+        """Register a callback function or system call"""
+        uid = self._uid(obj, button)
+        if uid not in self._callbacks:
+            self._callbacks[uid] = {}
+        self._callbacks[uid] = cmd
+
+    def callback(self, event):
+        """Execute callback action for an incoming event"""
+        button = event["button"]
+
+        cmd = self._callbacks.get(self._uuidstr(self.global_id, button), None)
+        cmd = self._callbacks.get(self._uuidstr(event["name"], button), cmd)
+        cmd = self._callbacks.get(self._uuidstr(event["instance"], button), cmd)
+
+        if cmd is None:
+            return
+        if callable(cmd):
+            cmd(event)
+        else:
+            bumblebee.util.execute(cmd, False)
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/module.py b/bumblebee/module.py
deleted file mode 100644
index 6152777..0000000
--- a/bumblebee/module.py
+++ /dev/null
@@ -1,63 +0,0 @@
-import os
-import pkgutil
-import importlib
-
-import bumblebee.config
-import bumblebee.modules
-
-def modules():
-    result = []
-    path = os.path.dirname(bumblebee.modules.__file__)
-    for mod in [ name for _, name, _ in pkgutil.iter_modules([path])]:
-        result.append(ModuleDescription(mod))
-    return result
-
-class ModuleDescription(object):
-    def __init__(self, name):
-        self._name = name
-        self._mod =importlib.import_module("bumblebee.modules.{}".format(name))
-
-    def name(self):
-        return str(self._name)
-
-    def description(self):
-        return getattr(self._mod, "description", lambda: "n/a")()
-
-    def parameters(self):
-        return getattr(self._mod, "parameters", lambda: [ "n/a" ])()
-
-class Module(object):
-    def __init__(self, output, config, alias=None):
-        self._output = output
-        self._alias = alias
-        name = "{}.".format(alias if alias else self.__module__.split(".")[-1])
-        self._config = bumblebee.config.ModuleConfig(config, name)
-
-        buttons = [
-            { "name": "left-click", "id": 1 },
-            { "name": "middle-click", "id": 2 },
-            { "name": "right-click", "id": 3 },
-            { "name": "wheel-up", "id": 4 },
-            { "name": "wheel-down", "id": 5 },
-        ]
-        for button in buttons:
-            if self._config.parameter(button["name"], None):
-                output.add_callback(
-                    module=self.instance(),
-                    button=button["id"],
-                    cmd=self._config.parameter(button["name"])
-                )
-
-    def critical(self, widget):
-        return False
-
-    def warning(self, widget):
-        return False
-
-    def state(self, widget):
-        return "default"
-
-    def instance(self, widget=None):
-        return self._alias if self._alias else self.__module__.split(".")[-1]
-
-# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/battery.py b/bumblebee/modules/battery.py
index 2a570df..90e58f6 100644
--- a/bumblebee/modules/battery.py
+++ b/bumblebee/modules/battery.py
@@ -1,52 +1,76 @@
-import datetime
-import bumblebee.module
-import os.path
+# pylint: disable=C0111,R0903
 
-def description():
-    return "Displays battery status, percentage and whether it's charging or discharging."
+"""Displays battery status, remaining percentage and charging information.
 
-def parameters():
-    return [ "battery.device: The device to read from (defaults to BAT0)" ]
+Parameters:
+    * battery.device  : The device to read information from (defaults to BAT0)
+    * battery.warning : Warning threshold in % of remaining charge (defaults to 20)
+    * battery.critical: Critical threshold in % of remaining charge (defaults to 10)
+"""
 
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-        self._battery = config.parameter("device", "BAT0")
+import os
+
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
+
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.capacity)
+        )
+        battery = self.parameter("device", "BAT0")
+        self._path = "/sys/class/power_supply/{}".format(battery)
         self._capacity = 100
-        self._status = "Unknown"
+        self._ac = False
 
-    def widgets(self):
-        self._AC = False;
-        self._path = "/sys/class/power_supply/{}".format(self._battery)
+    def capacity(self, widget):
+        if self._ac:
+            return "ac"
+        if self._capacity == -1:
+            return "n/a"
+        return "{:03d}%".format(self._capacity)
+
+    def update(self, widgets):
+        widget = widgets[0]
+        self._ac = False
         if not os.path.exists(self._path):
-            self._AC = True;
-            return bumblebee.output.Widget(self,"AC")
+            self._ac = True
+            self._capacity = 100
+            return
 
-        with open(self._path + "/capacity") as f:
-            self._capacity = int(f.read())
+        try:
+            with open(self._path + "/capacity") as f:
+                self._capacity = int(f.read())
+        except IOError:
+            self._capacity = -1
         self._capacity = self._capacity if self._capacity < 100 else 100
 
-        return bumblebee.output.Widget(self,"{:02d}%".format(self._capacity))
-
-    def warning(self, widget):
-        return self._capacity < self._config.parameter("warning", 20)
-
-    def critical(self, widget):
-        return self._capacity < self._config.parameter("critical", 10)
-
     def state(self, widget):
-        if self._AC:
-            return "AC"
+        state = []
 
-        with open(self._path + "/status") as f:
-            self._status = f.read().strip()
+        if self._capacity < 0:
+            return ["critical", "unknown"]
 
-        if self._status == "Discharging":
-            status = "discharging-{}".format(min([ 10, 25, 50, 80, 100] , key=lambda i:abs(i-self._capacity)))
-            return status
+        if self._capacity < int(self.parameter("critical", 10)):
+            state.append("critical")
+        elif self._capacity < int(self.parameter("warning", 20)):
+            state.append("warning")
+
+        if self._ac:
+            state.append("AC")
         else:
-            if self._capacity > 95:
-                return "charged"
-            return "charging"
+            charge = ""
+            with open(self._path + "/status") as f:
+                charge = f.read().strip()
+            if charge == "Discharging":
+                state.append("discharging-{}".format(min([10, 25, 50, 80, 100] , key=lambda i:abs(i-self._capacity))))
+            else:
+                if self._capacity > 95:
+                    state.append("charged")
+                else:
+                    state.append("charging")
+
+        return state
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/brightness.py b/bumblebee/modules/brightness.py
index 114c11e..99712f0 100644
--- a/bumblebee/modules/brightness.py
+++ b/bumblebee/modules/brightness.py
@@ -1,33 +1,33 @@
-import bumblebee.module
+# pylint: disable=C0111,R0903
 
-def description():
-    return "Displays brightness percentage"
+"""Displays the brightness of a display
 
-def parameters():
-    return [
-        "brightness.step: Steps (in percent) to increase/decrease brightness on scroll (defaults to 2)",
-    ]
+Parameters:
+    * brightness.step: The amount of increase/decrease on scroll in % (defaults to 2)
+"""
 
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
+
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.brightness)
+        )
         self._brightness = 0
-        self._max = 0
-        self._percent = 0
 
-        step = self._config.parameter("step", 2)
+        step = self.parameter("step", 2)
 
-        output.add_callback(module=self.instance(), button=4, cmd="xbacklight +{}%".format(step))
-        output.add_callback(module=self.instance(), button=5, cmd="xbacklight -{}%".format(step))
+        engine.input.register_callback(self, button=bumblebee.input.WHEEL_UP,
+            cmd="xbacklight +{}%".format(step))
+        engine.input.register_callback(self, button=bumblebee.input.WHEEL_DOWN,
+            cmd="xbacklight -{}%".format(step))
 
-    def widgets(self):
-        with open("/sys/class/backlight/intel_backlight/brightness") as f:
-            self._brightness = int(f.read())
-        with open("/sys/class/backlight/intel_backlight/max_brightness") as f:
-            self._max = int(f.read())
-        self._brightness = self._brightness if self._brightness < self._max else self._max
-        self._percent = int(round(self._brightness * 100 / self._max))
+    def brightness(self, widget):
+        return "{:03.0f}%".format(self._brightness)
 
-        return bumblebee.output.Widget(self, "{:02d}%".format(self._percent))
+    def update(self, widgets):
+        self._brightness = float(bumblebee.util.execute("xbacklight -get"))
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/caffeine.py b/bumblebee/modules/caffeine.py
index 39f20d5..bf57be6 100644
--- a/bumblebee/modules/caffeine.py
+++ b/bumblebee/modules/caffeine.py
@@ -1,38 +1,44 @@
-import subprocess
-import shlex
+# pylint: disable=C0111,R0903
 
-import bumblebee.module
+"""Enable/disable automatic screen locking.
+"""
 
-def description():
-    return "Enable/disable auto screen lock."
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-        self._activated = 0
-        output.add_callback(module="caffeine.activate", button=1, cmd=[ 'notify-send "Consuming caffeine"', 'xset s off' ])
-        output.add_callback(module="caffeine.deactivate", button=1, cmd=[ 'notify-send "Out of coffee"', 'xset s default' ])
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.caffeine)
+        )
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE,
+            cmd=self._toggle
+        )
 
-    def widgets(self):
-        output = subprocess.check_output(shlex.split("xset q"))
-        xset_out = output.decode().split("\n")
-        for line in xset_out:
-            if line.startswith("  timeout"):
-                timeout = int(line.split(" ")[4])
-                if timeout == 0:
-                    self._activated = 1;
-                else:
-                    self._activated = 0;
-                break
-
-        if self._activated == 0:
-            return bumblebee.output.Widget(self, "", instance="caffeine.activate")
-        elif self._activated == 1:
-            return bumblebee.output.Widget(self, "", instance="caffeine.deactivate")
+    def caffeine(self, widget):
+        return ""
 
     def state(self, widget):
-        if self._activated == 1:
+        if self._active():
             return "activated"
-        else:
-            return "deactivated"
+        return "deactivated"
 
+    def _active(self):
+        for line in bumblebee.util.execute("xset q").split("\n"):
+            if "timeout" in line:
+                timeout = int(line.split(" ")[4])
+                if timeout == 0:
+                    return True
+                return False
+        return False
+
+    def _toggle(self, widget):
+        if self._active():
+            bumblebee.util.execute("xset s default")
+            bumblebee.util.execute("notify-send \"Out of coffee\"")
+        else:
+            bumblebee.util.execute("xset s off")
+            bumblebee.util.execute("notify-send \"Consuming caffeine\"")
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/cmus.py b/bumblebee/modules/cmus.py
index b847ad2..991a1a1 100644
--- a/bumblebee/modules/cmus.py
+++ b/bumblebee/modules/cmus.py
@@ -1,78 +1,85 @@
-import string
-import datetime
-import subprocess
+# pylint: disable=C0111,R0903
+
+"""Displays information about the current song in cmus.
+
+Parameters:
+    * cmus.format: Format string for the song information. Tag values can be put in curly brackets (i.e. {artist})
+"""
+
 from collections import defaultdict
 
+import string
+
 import bumblebee.util
-import bumblebee.module
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def description():
-    return "Displays the current song and artist playing in cmus"
-
-def parameters():
-    return [
-        "cmus.format: Format of the displayed song information, arbitrary tags (as available from cmus-remote -Q) can be used (defaults to {artist} - {title} {position}/{duration})"
-    ]
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-        self._status = "default"
-        self._fmt = self._config.parameter("format", "{artist} - {title} {position}/{duration}")
-
-        output.add_callback(module="cmus.prev", button=1, cmd="cmus-remote -r")
-        output.add_callback(module="cmus.next", button=1, cmd="cmus-remote -n")
-        output.add_callback(module="cmus.shuffle", button=1, cmd="cmus-remote -S")
-        output.add_callback(module="cmus.repeat", button=1, cmd="cmus-remote -R")
-        output.add_callback(module=self.instance(), button=1, cmd="cmus-remote -u")
-
-    def _loadsong(self):
-        process = subprocess.Popen(["cmus-remote", "-Q"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-        self._query, self._error = process.communicate()
-        self._query = self._query.decode("utf-8").split("\n")
-        self._status = "default"
-
-    def _tags(self):
-        tags = defaultdict(lambda: '')
-        self._repeat = False
-        self._shuffle = False
-        for line in self._query:
-            if line.startswith("status"):
-                status = line.split(" ", 2)[1]
-                self._status = status
-            if line.startswith("tag"):
-                key, value = line.split(" ", 2)[1:]
-                tags.update({ key: value })
-            if line.startswith("duration"):
-                sec = line.split(" ")[1]
-                tags.update({ "duration": bumblebee.util.durationfmt(int(sec)) })
-            if line.startswith("position"):
-                sec = line.split(" ")[1]
-                tags.update({ "position": bumblebee.util.durationfmt(int(sec)) })
-            if line.startswith("set repeat "):
-                self._repeat = False if line.split(" ")[2] == "false" else True
-            if line.startswith("set shuffle "):
-                self._shuffle = False if line.split(" ")[2] == "false" else True
-
-        return tags
-
-    def widgets(self):
-        self._loadsong()
-        tags = self._tags()
-
-        return [
-            bumblebee.output.Widget(self, "", instance="cmus.prev"),
-            bumblebee.output.Widget(self, string.Formatter().vformat(self._fmt, (), tags)),
-            bumblebee.output.Widget(self, "", instance="cmus.next"),
-            bumblebee.output.Widget(self, "", instance="cmus.shuffle"),
-            bumblebee.output.Widget(self, "", instance="cmus.repeat"),
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        widgets = [
+            bumblebee.output.Widget(name="cmus.prev"),
+            bumblebee.output.Widget(name="cmus.main", full_text=self.description),
+            bumblebee.output.Widget(name="cmus.next"),
+            bumblebee.output.Widget(name="cmus.shuffle"),
+            bumblebee.output.Widget(name="cmus.repeat"),
         ]
+        super(Module, self).__init__(engine, config, widgets)
+
+        engine.input.register_callback(widgets[0], button=bumblebee.input.LEFT_MOUSE,
+            cmd="cmus-remote -r")
+        engine.input.register_callback(widgets[1], button=bumblebee.input.LEFT_MOUSE,
+            cmd="cmus-remote -u")
+        engine.input.register_callback(widgets[2], button=bumblebee.input.LEFT_MOUSE,
+            cmd="cmus-remote -n")
+        engine.input.register_callback(widgets[3], button=bumblebee.input.LEFT_MOUSE,
+            cmd="cmus-remote -S")
+        engine.input.register_callback(widgets[4], button=bumblebee.input.LEFT_MOUSE,
+            cmd="cmus-remote -R")
+
+        self._fmt = self.parameter("format", "{artist} - {title} {position}/{duration}")
+        self._status = None
+        self._shuffle = False
+        self._repeat = False
+        self._tags = defaultdict(lambda: '')
+
+    def description(self, widget):
+        return string.Formatter().vformat(self._fmt, (), self._tags)
+
+    def update(self, widgets):
+        self._load_song()
 
     def state(self, widget):
-        if widget.instance() == "cmus.shuffle":
-            return "on" if self._shuffle else "off"
-        if widget.instance() == "cmus.repeat":
-            return "on" if self._repeat else "off"
+        if widget.name == "cmus.shuffle":
+            return "shuffle-on" if self._shuffle else "shuffle-off"
+        if widget.name == "cmus.repeat":
+            return "repeat-on" if self._repeat else "repeat-off"
+        if widget.name == "cmus.prev":
+            return "prev"
+        if widget.name == "cmus.next":
+            return "next"
         return self._status
 
+    def _load_song(self):
+        info = ""
+        try:
+            info = bumblebee.util.execute("cmus-remote -Q")
+        except RuntimeError:
+            pass
+        self._tags = defaultdict(lambda: '')
+        for line in info.split("\n"):
+            if line.startswith("status"):
+                self._status = line.split(" ", 2)[1]
+            if line.startswith("tag"):
+                key, value = line.split(" ", 2)[1:]
+                self._tags.update({ key: value })
+            for key in  ["duration", "position"]:
+                if line.startswith(key):
+                    dur = int(line.split(" ")[1])
+                    self._tags.update({key:bumblebee.util.durationfmt(dur)})
+            if line.startswith("set repeat "):
+                self._repeat = False if "false" in line else True
+            if line.startswith("set shuffle "):
+                self._shuffle = False if "false" in line else True
+
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/cpu.py b/bumblebee/modules/cpu.py
index b156b37..79e9229 100644
--- a/bumblebee/modules/cpu.py
+++ b/bumblebee/modules/cpu.py
@@ -1,30 +1,33 @@
-import bumblebee.module
+# pylint: disable=C0111,R0903
+
+"""Displays CPU utilization across all CPUs.
+
+Parameters:
+    * cpu.warning : Warning threshold in % of CPU usage (defaults to 70%)
+    * cpu.critical: Critical threshold in % of CPU usage (defaults to 80%)
+"""
+
 import psutil
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def description():
-    return "Displays CPU utilization across all CPUs."
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.utilization)
+        )
+        self._utilization = psutil.cpu_percent(percpu=False)
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE,
+            cmd="gnome-system-monitor")
 
-def parameters():
-    return [
-        "cpu.warning: Warning threshold in % of disk usage (defaults to 70%)",
-        "cpu.critical: Critical threshold in % of disk usage (defaults to 80%)",
-    ]
+    def utilization(self, widget):
+        return "{:06.02f}%".format(self._utilization)
 
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-        self._perc = psutil.cpu_percent(percpu=False)
+    def update(self, widgets):
+        self._utilization = psutil.cpu_percent(percpu=False)
 
-        output.add_callback(module=self.instance(), button=1, cmd="gnome-system-monitor")
-
-    def widgets(self):
-        self._perc = psutil.cpu_percent(percpu=False)
-        return bumblebee.output.Widget(self, "{:05.02f}%".format(self._perc))
-
-    def warning(self, widget):
-        return self._perc > self._config.parameter("warning", 70)
-
-    def critical(self, widget):
-        return self._perc > self._config.parameter("critical", 80)
+    def state(self, widget):
+        return self.threshold_state(self._utilization, 70, 80)
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/date.py b/bumblebee/modules/date.py
deleted file mode 120000
index bde6404..0000000
--- a/bumblebee/modules/date.py
+++ /dev/null
@@ -1 +0,0 @@
-datetime.py
\ No newline at end of file
diff --git a/bumblebee/modules/datetime.py b/bumblebee/modules/datetime.py
deleted file mode 120000
index 5a370f9..0000000
--- a/bumblebee/modules/datetime.py
+++ /dev/null
@@ -1 +0,0 @@
-time.py
\ No newline at end of file
diff --git a/bumblebee/modules/datetime.py b/bumblebee/modules/datetime.py
new file mode 100644
index 0000000..4141a53
--- /dev/null
+++ b/bumblebee/modules/datetime.py
@@ -0,0 +1,35 @@
+# pylint: disable=C0111,R0903
+
+"""Displays the current date and time.
+
+Parameters:
+    * datetime.format: strftime()-compatible formatting string
+    * date.format    : alias for datetime.format
+    * time.format    : alias for datetime.format
+"""
+
+from __future__ import absolute_import
+import datetime
+import bumblebee.engine
+
+ALIASES = [ "date", "time" ]
+
+def default_format(module):
+    default = "%x %X"
+    if module == "date":
+        default = "%x"
+    if module == "time":
+        default = "%X"
+    return default
+
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.get_time)
+        )
+        self._fmt = self.parameter("format", default_format(self.name))
+
+    def get_time(self, widget):
+        return datetime.datetime.now().strftime(self._fmt)
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/disk.py b/bumblebee/modules/disk.py
index 679e271..e052b88 100644
--- a/bumblebee/modules/disk.py
+++ b/bumblebee/modules/disk.py
@@ -1,40 +1,45 @@
+# pylint: disable=C0111,R0903
+
+"""Shows free diskspace, total diskspace and the percentage of free disk space.
+
+Parameters:
+    * disk.warning: Warning threshold in % of disk space (defaults to 80%)
+    * disk.critical: Critical threshold in % of disk space (defaults ot 90%)
+    * disk.path: Path to calculate disk usage from (defaults to /)
+"""
+
 import os
-import bumblebee.util
-import bumblebee.module
 
-def description():
-    return "Shows free diskspace, total diskspace and the percentage of free disk space."
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def parameters():
-    return [
-        "disk.warning: Warning threshold in % (defaults to 80%)",
-        "disk.critical: Critical threshold in % (defaults to 90%)"
-    ]
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.diskspace)
+        )
+        self._path = self.parameter("path", "/")
+        self._perc = 0
+        self._used = 0
+        self._size = 0
 
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-        self._path = self._config.parameter("path", "/")
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE,
+            cmd="nautilus {}".format(self._path))
 
-        output.add_callback(module=self.instance(), button=1, cmd="nautilus {}".format(self._path))
+    def diskspace(self, widget):
+        return "{} {}/{} ({:05.02f}%)".format(self._path,
+            bumblebee.util.bytefmt(self._used),
+            bumblebee.util.bytefmt(self._size), self._perc
+        )
 
-    def widgets(self):
+    def update(self, widgets):
         st = os.statvfs(self._path)
-
         self._size = st.f_frsize*st.f_blocks
         self._used = self._size - st.f_frsize*st.f_bavail
         self._perc = 100.0*self._used/self._size
 
-        return bumblebee.output.Widget(self,
-            "{} {}/{} ({:05.02f}%)".format(self._path,
-            bumblebee.util.bytefmt(self._used),
-            bumblebee.util.bytefmt(self._size), self._perc)
-        )
-
-    def warning(self, widget):
-        return self._perc > self._config.parameter("warning", 80)
-
-    def critical(self, widget):
-        return self._perc > self._config.parameter("critical", 90)
+    def state(self, widget):
+        return self.threshold_state(self._perc, 80, 90)
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/dnf.py b/bumblebee/modules/dnf.py
index ead5065..f6acf2a 100644
--- a/bumblebee/modules/dnf.py
+++ b/bumblebee/modules/dnf.py
@@ -1,98 +1,79 @@
-from __future__ import absolute_import
+# pylint: disable=C0111,R0903
+
+"""Displays DNF package update information (<security>/<bugfixes>/<enhancements>/<other>)
+
+Parameters:
+    * dnf.interval: Time in seconds between two consecutive update checks (defaulst to 1800)
+
+"""
 
 import time
-import shlex
 import threading
-import subprocess
 
-import bumblebee.module
 import bumblebee.util
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def description():
-    return "Checks DNF for updated packages and displays the number of <security>/<bugfixes>/<enhancements>/<other> pending updates."
+def get_dnf_info(widget):
+    try:
+        res = bumblebee.util.execute("dnf updateinfo")
+    except RuntimeError:
+        pass
 
-def parameters():
-    return [ "dnf.interval: Time in seconds between two checks for updates (defaults to 1800)" ]
+    security = 0
+    bugfixes = 0
+    enhancements = 0
+    other = 0
+    for line in res.decode().split("\n"):
 
-def get_dnf_info(obj):
-    loops = obj.interval()
+        if not line.startswith(" "): continue
+        elif "ecurity" in line:
+            for s in line.split():
+                if s.isdigit(): security += int(s)
+        elif "ugfix" in line:
+            for s in line.split():
+                if s.isdigit(): bugfixes += int(s)
+        elif "hancement" in line:
+            for s in line.split():
+                if s.isdigit(): enhancements += int(s)
+        else:
+            for s in line.split():
+                if s.isdigit(): other += int(s)
 
-    for thread in threading.enumerate():
-        if thread.name == "MainThread":
-            main = thread
+    widget.set("security", security)
+    widget.set("bugfixes", bugfixes)
+    widget.set("enhancements", enhancements)
+    widget.set("other", other)
 
-    while main.is_alive():
-        loops += 1
-        if loops < obj.interval():
-            time.sleep(1)
-            continue
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        widget = bumblebee.output.Widget(full_text=self.updates)
+        super(Module, self).__init__(engine, config, widget)
 
-        loops = 0
-        try:
-            res = subprocess.check_output(shlex.split("dnf updateinfo"))
-        except Exception as e:
-            break
+        self._next_check = 0
+        widget
 
-        security = 0
-        bugfixes = 0
-        enhancements = 0
-        other = 0
-        for line in res.decode().split("\n"):
-
-            if not line.startswith(" "): continue
-            elif "ecurity" in line:
-                for s in line.split():
-                    if s.isdigit(): security += int(s)
-            elif "ugfix" in line:
-                for s in line.split():
-                    if s.isdigit(): bugfixes += int(s)
-            elif "hancement" in line:
-                for s in line.split():
-                    if s.isdigit(): enhancements += int(s)
-            else:
-                for s in line.split():
-                    if s.isdigit(): other += int(s)
-
-        obj.set("security", security)
-        obj.set("bugfixes", bugfixes)
-        obj.set("enhancements", enhancements)
-        obj.set("other", other)
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-
-        self._counter = {}
-        self._thread = threading.Thread(target=get_dnf_info, args=(self,))
-        self._thread.start()
-
-    def interval(self):
-        return self._config.parameter("interval", 30*60)
-
-    def set(self, what, value):
-        self._counter[what] = value
-
-    def get(self, what):
-        return self._counter.get(what, 0)
-
-    def widgets(self):
+    def updates(self, widget):
         result = []
-        for t in [ "security", "bugfixes", "enhancements", "other" ]:
-            result.append(str(self.get(t)))
+        for t in ["security", "bugfixes", "enhancements", "other"]:
+            result.append(str(widget.get(t, 0)))
+        return "/".join(result)
 
-        return bumblebee.output.Widget(self, "/".join(result))
+    def update(self, widgets):
+        if int(time.time()) < self._next_check:
+            return
+        thread = threading.Thread(target=get_dnf_info, args=(widgets[0],))
+        thread.start()
+        self._next_check = int(time.time()) + self.parameter("interval", 30*60)
 
     def state(self, widget):
-        total = sum(self._counter.values())
-        if total == 0: return "good"
-        return "default"
-
-    def warning(self, widget):
-        total = sum(self._counter.values())
-        return total > 0
-
-    def critical(self, widget):
-        total = sum(self._counter.values())
-        return total > 50 or self._counter.get("security", 0) > 0
+        cnt = 0
+        for t in ["security", "bugfixes", "enhancements", "other"]:
+            cnt += widget.get(t, 0)
+        if cnt == 0:
+            return "good"
+        if cnt > 50 or widget.get("security", 0) > 0:
+            return "critical"
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/layout.py b/bumblebee/modules/layout.py
deleted file mode 100644
index 084d27d..0000000
--- a/bumblebee/modules/layout.py
+++ /dev/null
@@ -1,67 +0,0 @@
-import subprocess
-import shlex
-import bumblebee.module
-import bumblebee.util
-
-def description():
-    return "Showws current keyboard layout and change it on click."
-
-def parameters():
-    return  [
-        "layout.lang: pipe-separated list of languages to cycle through (e.g. us|rs|de). Default: en"
-    ]
-
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-
-        self._languages = self._config.parameter("lang", "en").split("|")
-        self._idx = 0
-
-        output.add_callback(module=self.instance(), button=1, cmd=self.next_keymap)
-        output.add_callback(module=self.instance(), button=3, cmd=self.prev_keymap)
-
-    def next_keymap(self, event, widget):
-        self._idx = self._idx + 1 if self._idx < len(self._languages) - 1 else 0
-        self.set_keymap()
-
-    def prev_keymap(self, event, widget):
-        self._idx = self._idx - 1 if self._idx > 0 else len(self._languages) - 1
-        self.set_keymap()
-
-    def set_keymap(self):
-        tmp = self._languages[self._idx].split(":")
-        layout = tmp[0]
-        variant = ""
-        if len(tmp) > 1:
-            variant = "-variant {}".format(tmp[1])
-        bumblebee.util.execute("setxkbmap -layout {} {}".format(layout, variant))
-
-    def widgets(self):
-        res = bumblebee.util.execute("setxkbmap -query")
-        layout = None
-        variant = None
-        for line in res.split("\n"):
-            if not line:
-                continue
-            if "layout" in line:
-                layout = line.split(":")[1].strip()
-            if "variant" in line:
-                variant = line.split(":")[1].strip()
-        if variant:
-            layout += ":" + variant
-
-        lang = self._languages[self._idx]
-
-        if lang != layout:
-            if layout in self._languages:
-                self._idx = self._languages.index(layout)
-            else:
-                self._languages.append(layout)
-                self._idx = len(self._languages) - 1
-        lang = layout
-
-        return bumblebee.output.Widget(self, lang)
-
-# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/load.py b/bumblebee/modules/load.py
index fba5dbd..c44ae5a 100644
--- a/bumblebee/modules/load.py
+++ b/bumblebee/modules/load.py
@@ -1,37 +1,41 @@
-import bumblebee.module
-import multiprocessing
+# pylint: disable=C0111,R0903
+
+"""Displays system load.
+
+Parameters:
+    * load.warning : Warning threshold for the one-minute load average (defaults to 70% of the number of CPUs)
+    * load.critical: Critical threshold for the one-minute load average (defaults to 80% of the number of CPUs)
+"""
+
 import os
+import multiprocessing
 
-def description():
-    return "Displays system load."
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def parameters():
-    return [
-        "load.warning: Warning threshold for the one-minute load average (defaults to 70% of the number of CPUs)",
-        "load.critical: Critical threshold for the one-minute load average (defaults 80% of the number of CPUs)"
-    ]
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-        self._cpus = 1
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.load)
+        )
+        self._load = [0, 0, 0]
         try:
             self._cpus = multiprocessing.cpu_count()
         except multiprocessing.NotImplementedError as e:
-            pass
+            self._cpus = 1
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE,
+            cmd="gnome-system-monitor")
 
-        output.add_callback(module=self.instance(), button=1, cmd="gnome-system-monitor")
+    def load(self, widget):
+        return "{:.02f}/{:.02f}/{:.02f}".format(
+            self._load[0], self._load[1], self._load[2]
+        )
 
-    def widgets(self):
+    def update(self, widgets):
         self._load = os.getloadavg()
 
-        return bumblebee.output.Widget(self, "{:.02f}/{:.02f}/{:.02f}".format(
-            self._load[0], self._load[1], self._load[2]))
-
-    def warning(self, widget):
-        return self._load[0] > self._config.parameter("warning", self._cpus*0.7)
-
-    def critical(self, widget):
-        return self._load[0] > self._config.parameter("critical", self._cpus*0.8)
+    def state(self, widget):
+        return self.threshold_state(self._load[0], self._cpus*0.7, self._cpus*0.8)
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/memory.py b/bumblebee/modules/memory.py
index 70b10b2..0ab1176 100644
--- a/bumblebee/modules/memory.py
+++ b/bumblebee/modules/memory.py
@@ -1,38 +1,44 @@
+# pylint: disable=C0111,R0903
+
+"""Displays available RAM, total amount of RAM and percentage available.
+
+Parameters:
+    * cpu.warning : Warning threshold in % of memory used (defaults to 80%)
+    * cpu.critical: Critical threshold in % of memory used (defaults to 90%)
+"""
+
 import psutil
-import bumblebee.module
+
 import bumblebee.util
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def description():
-    return "Shows available RAM, total amount of RAM and the percentage of available RAM."
-
-def parameters():
-    return [
-        "memory.warning: Warning threshold in % of memory used (defaults to 80%)",
-        "memory.critical: Critical threshold in % of memory used (defaults to 90%)",
-    ]
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-        self._mem = psutil.virtual_memory()
-
-        output.add_callback(module=self.instance(), button=1, cmd="gnome-system-monitor")
-
-    def widgets(self):
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.memory_usage)
+        )
         self._mem = psutil.virtual_memory()
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE,
+            cmd="gnome-system-monitor")
 
+    def memory_usage(self, widget):
         used = self._mem.total - self._mem.available
-
-        return bumblebee.output.Widget(self, "{}/{} ({:05.02f}%)".format(
+        return "{}/{} ({:05.02f}%)".format(
             bumblebee.util.bytefmt(used),
             bumblebee.util.bytefmt(self._mem.total),
-            self._mem.percent)
+            self._mem.percent
         )
 
-    def warning(self, widget):
-        return self._mem.percent > self._config.parameter("warning", 80)
+    def update(self, widgets):
+        self._mem = psutil.virtual_memory()
 
-    def critical(self, widget):
-        return self._mem.percent > self._config.parameter("critical", 90)
+    def state(self, widget):
+        if self._mem.percent > float(self.parameter("critical", 90)):
+            return "critical"
+        if self._mem.percent > float(self.parameter("warning", 80)):
+            return "warning"
+        return None
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/nic.py b/bumblebee/modules/nic.py
index 94f8bc4..bd94f94 100644
--- a/bumblebee/modules/nic.py
+++ b/bumblebee/modules/nic.py
@@ -1,24 +1,58 @@
+#pylint: disable=C0111,R0903
+
+"""Displays the name, IP address(es) and status of each available network interface.
+
+Parameters:
+    * nic.exclude: Comma-separated list of interface prefixes to exclude (defaults to "lo,virbr,docker,vboxnet,veth")
+"""
+
 import netifaces
-import bumblebee.module
 
-def description():
-    return "Displays the names, IP addresses and status of each available interface."
+import bumblebee.util
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def parameters():
-    return [
-            "nic.exclude: Comma-separated list of interface prefixes to exlude (defaults to: \"lo,virbr,docker,vboxnet,veth\")"
-    ]
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        widgets = []
+        super(Module, self).__init__(engine, config, widgets)
+        self._exclude = tuple(filter(len, self.parameter("exclude", "lo,virbr,docker,vboxnet,veth").split(",")))
+        self._update_widgets(widgets)
 
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-        self._exclude = tuple(filter(len, self._config.parameter("exclude", "lo,virbr,docker,vboxnet,veth").split(",")))
-        self._state = "down"
-        self._typecache = {}
+    def update(self, widgets):
+        self._update_widgets(widgets)
 
-    def widgets(self):
-        result = []
+    def state(self, widget):
+        states = []
+
+        if widget.get("state") == "down":
+            states.append("critical")
+        elif widget.get("state") != "up":
+            states.append("warning")
+
+        intf = widget.get("intf")
+        iftype = "wireless" if self._iswlan(intf) else "wired"
+        iftype = "tunnel" if self._istunnel(intf) else iftype
+
+        states.append("{}-{}".format(iftype, widget.get("state")))
+
+        return states
+
+    def _iswlan(self, intf):
+        # wifi, wlan, wlp, seems to work for me
+        if intf.startswith("w"): return True
+        return False
+
+    def _istunnel(self, intf):
+        return intf.startswith("tun")
+
+    def _update_widgets(self, widgets):
         interfaces = [ i for i in netifaces.interfaces() if not i.startswith(self._exclude) ]
+
+        for widget in widgets:
+            widget.set("visited", False)
+
         for intf in interfaces:
             addr = []
             state = "down"
@@ -30,37 +64,17 @@ class Module(bumblebee.module.Module):
                             state = "up"
             except Exception as e:
                 addr = []
-            widget = bumblebee.output.Widget(self, "{} {} {}".format(
-                intf, state, ", ".join(addr)
-            ))
+            widget = self.widget(intf)
+            if not widget:
+                widget = bumblebee.output.Widget(name=intf)
+                widgets.append(widget)
+            widget.full_text("{} {} {}".format(intf, state, ", ".join(addr)))
             widget.set("intf", intf)
             widget.set("state", state)
-            result.append(widget)
+            widget.set("visited", True)
 
-        return result
-
-    def _iswlan(self, intf):
-        # wifi, wlan, wlp, seems to work for me
-        if intf.startswith("w"): return True
-        return False
-
-    def _istunnel(self, intf):
-        return intf.startswith("tun")
-
-    def state(self, widget):
-        intf = widget.get("intf")
-
-        if not intf in self._typecache:
-            t = "wireless" if self._iswlan(intf) else "wired"
-            t = "tunnel" if self._istunnel(intf) else t
-            self._typecache[intf] = t
-
-        return "{}-{}".format(self._typecache[intf], widget.get("state"))
-
-    def warning(self, widget):
-        return widget.get("state") != "up"
-
-    def critical(self, widget):
-        return widget.get("state") == "down"
+        for widget in widgets:
+            if widget.get("visited") == False:
+                widgets.remove(widget)
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/pacman.py b/bumblebee/modules/pacman.py
index 66ece38..da3e66f 100644
--- a/bumblebee/modules/pacman.py
+++ b/bumblebee/modules/pacman.py
@@ -1,58 +1,60 @@
-import bumblebee.module
-import subprocess
+# pylint: disable=C0111,R0903
+
+"""Displays update information per repository for pacman."
+"""
+
 import os
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def description():
-    return "Displays available updates per repository for pacman."
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.updates)
+        )
         self._count = 0
+        self._out = ""
 
-    def widgets(self):
+    def updates(self, widget):
+        return self._out
+
+    def update(self, widgets):
         path = os.path.dirname(os.path.abspath(__file__))
         if self._count == 0:
             self._out = "?/?/?/?"
-            process = subprocess.Popen([ "{}/../../bin/customupdates".format(path) ], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-            
-            self._query, self._error = process.communicate()
-
-            if not process.returncode == 0:
-                self._out = "?/?/?/?"
-            else:
+            try:
+                result = bumblebee.util.execute("{}/../../bin/pacman-updates".format(path))
                 self._community = 0
                 self._core = 0
                 self._extra = 0
                 self._other = 0
 
-                for line in self._query.splitlines():
-                    if line.startswith(b'http'):
-                        if b"community" in line:
+                for line in result.splitlines():
+                    if line.startswith("http"):
+                        if "community" in line:
                             self._community += 1
                             continue
-                        if b"core" in line:
+                        if "core" in line:
                             self._core += 1;
                             continue
-                        if b"extra" in line:
+                        if "extra" in line:
                             self._extra += 1
                             continue
                         self._other += 1
                 self._out = str(self._core)+"/"+str(self._extra)+"/"+str(self._community)+"/"+str(self._other)
-            
+            except RuntimeError:
+                self._out = "?/?/?/?"
+ 
+        # TODO: improve this waiting mechanism a bit
         self._count += 1
         self._count = 0 if self._count > 300 else self._count
-        return bumblebee.output.Widget(self, "{}".format(self._out))
 
     def sumUpdates(self):
         return self._core + self._community + self._extra + self._other 
     
-    def critical(self, widget):
-        #return self._sumUpdates(self)
-        return self.sumUpdates() > 0
-
-
-
-
+    def state(self, widget):
+        if self.sumUpdates() > 0:
+            return "critical"
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/pasink.py b/bumblebee/modules/pasink.py
deleted file mode 120000
index 85ea20d..0000000
--- a/bumblebee/modules/pasink.py
+++ /dev/null
@@ -1 +0,0 @@
-pulseaudio.py
\ No newline at end of file
diff --git a/bumblebee/modules/pasource.py b/bumblebee/modules/pasource.py
deleted file mode 120000
index 85ea20d..0000000
--- a/bumblebee/modules/pasource.py
+++ /dev/null
@@ -1 +0,0 @@
-pulseaudio.py
\ No newline at end of file
diff --git a/bumblebee/modules/ping.py b/bumblebee/modules/ping.py
index 20fec39..6217438 100644
--- a/bumblebee/modules/ping.py
+++ b/bumblebee/modules/ping.py
@@ -1,97 +1,74 @@
-from __future__ import absolute_import
+# pylint: disable=C0111,R0903
+
+"""Periodically checks the RTT of a configurable host using ICMP echos
+
+Parameters:
+    * ping.interval: Time in seconds between two RTT checks (defaults to 60)
+    * ping.address : IP address to check
+    * ping.timeout : Timeout for waiting for a reply (defaults to 5.0)
+    * ping.probes  : Number of probes to send (defaults to 5)
+    * ping.warning : Threshold for warning state, in seconds (defaults to 1.0)
+    * ping.critical: Threshold for critical state, in seconds (defaults to 2.0)
+"""
 
 import re
 import time
-import shlex
 import threading
-import subprocess
 
-import bumblebee.module
-import bumblebee.util
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def description():
-    return "Periodically checks the RTT of a configurable IP"
+def get_rtt(module, widget):
+    try:
+        widget.set("rtt-unreachable", False)
+        res = bumblebee.util.execute("ping -n -q -c {} -W {} {}".format(
+            widget.get("rtt-probes"), widget.get("rtt-timeout"), widget.get("address")
+        ))
 
-def parameters():
-    return [
-        "ping.interval: Time in seconds between two RTT checks (defaults to 60)",
-        "ping.address: IP address to check",
-        "ping.warning: Threshold for warning state, in seconds (defaults to 1.0)",
-        "ping.critical: Threshold for critical state, in seconds (defaults to 2.0)",
-        "ping.timeout: Timeout for waiting for a reply (defaults to 5.0)",
-        "ping.probes: Number of probes to send (defaults to 5)",
-    ]
+        for line in res.split("\n"):
+            if not line.startswith("rtt"): continue
+            m = re.search(r'([0-9\.]+)/([0-9\.]+)/([0-9\.]+)/([0-9\.]+)\s+(\S+)', line)
 
-def get_rtt(obj):
-    loops = obj.get("interval")
+            widget.set("rtt-min", float(m.group(1)))
+            widget.set("rtt-avg", float(m.group(2)))
+            widget.set("rtt-max", float(m.group(3)))
+            widget.set("rtt-unit", m.group(5))
+    except Exception as e:
+        widget.set("rtt-unreachable", True)
 
-    for thread in threading.enumerate():
-        if thread.name == "MainThread":
-            main = thread
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        widget = bumblebee.output.Widget(full_text=self.rtt)
+        super(Module, self).__init__(engine, config, widget)
 
-    interval = obj.get("interval")
-    while main.is_alive():
-        loops += 1
-        if loops < interval:
-            time.sleep(1)
-            continue
+        widget.set("address", self.parameter("address", "8.8.8.8"))
+        widget.set("interval", self.parameter("interval", 60))
+        widget.set("rtt-probes", self.parameter("probes", 5))
+        widget.set("rtt-timeout", self.parameter("timeout", 5.0))
+        widget.set("rtt-avg", 0.0)
+        widget.set("rtt-unit", "")
 
-        loops = 0
-        try:
-            res = subprocess.check_output(shlex.split("ping -n -q -c {} -W {} {}".format(
-                obj.get("rtt-probes"), obj.get("rtt-timeout"), obj.get("address")
-            )))
-            obj.set("rtt-unreachable", False)
+        self._next_check = 0
 
-            for line in res.decode().split("\n"):
-                if not line.startswith("rtt"): continue
-                m = re.search(r'([0-9\.]+)/([0-9\.]+)/([0-9\.]+)/([0-9\.]+)\s+(\S+)', line)
-
-                obj.set("rtt-min", float(m.group(1)))
-                obj.set("rtt-avg", float(m.group(2)))
-                obj.set("rtt-max", float(m.group(3)))
-                obj.set("rtt-unit", m.group(5))
-        except Exception as e:
-            obj.set("rtt-unreachable", True)
-
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-
-        self._counter = {}
-
-        self.set("address", self._config.parameter("address", "8.8.8.8"))
-        self.set("interval", self._config.parameter("interval", 60))
-        self.set("rtt-probes", self._config.parameter("probes", 5))
-        self.set("rtt-timeout", self._config.parameter("timeout", 5.0))
-
-        self._thread = threading.Thread(target=get_rtt, args=(self,))
-        self._thread.start()
-
-    def set(self, what, value):
-        self._counter[what] = value
-
-    def get(self, what):
-        return self._counter.get(what, 0)
-
-    def widgets(self):
-        text = "{}: {:.1f}{}".format(
-            self.get("address"),
-            self.get("rtt-avg"),
-            self.get("rtt-unit")
+    def rtt(self, widget):
+        if widget.get("rtt-unreachable"):
+            return "{}: unreachable".format(widget.get("address"))
+        return "{}: {:.1f}{}".format(
+            widget.get("address"),
+            widget.get("rtt-avg"),
+            widget.get("rtt-unit")
         )
 
-        if self.get("rtt-unreachable"):
-            text = "{}: unreachable".format(self.get("address"))
+    def state(self, widget):
+        if widget.get("rtt-unreachable"): return ["critical"]
+        return self.threshold_state(widget.get("rtt-avg"), 1000.0, 2000.0)
 
-        return bumblebee.output.Widget(self, text)
-
-    def warning(self, widget):
-        return self.get("rtt-avg") > float(self._config.parameter("warning", 1.0))*1000.0
-
-    def critical(self, widget):
-        if self.get("rtt-unreachable"): return True
-        return self.get("rtt-avg") > float(self._config.parameter("critical", 2.0))*1000.0
+    def update(self, widgets):
+        if int(time.time()) < self._next_check:
+            return
+        thread = threading.Thread(target=get_rtt, args=(self,widgets[0],))
+        thread.start()
+        self._next_check = int(time.time()) + widgets[0].get("interval")
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/pulseaudio.py b/bumblebee/modules/pulseaudio.py
index a8cda45..b13eda3 100644
--- a/bumblebee/modules/pulseaudio.py
+++ b/bumblebee/modules/pulseaudio.py
@@ -1,60 +1,68 @@
+# pylint: disable=C0111,R0903
+
+"""Displays volume and mute status of PulseAudio devices.
+
+Aliases: pasink, pasource
+"""
+
 import re
-import shlex
-import subprocess
 
-import bumblebee.module
 import bumblebee.util
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-def description():
-    module = __name__.split(".")[-1]
-    if module == "pasink":
-        return "Shows volume and mute status of the default PulseAudio Sink."
-    if module == "pasource":
-        return "Shows volume and mute status of the default PulseAudio Source."
-    return "See 'pasource'."
+ALIASES = [ "pasink", "pasource" ]
 
-def parameters():
-    return [ "none" ]
-    
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.volume)
+        )
 
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-
-        self._module = self.__module__.split(".")[-1]
         self._left = 0
         self._right = 0
         self._mono = 0
         self._mute = False
-        channel = "sink" if self._module == "pasink" else "source"
+        channel = "sink" if self.name == "pasink" else "source"
 
-        output.add_callback(module=self.instance(), button=3,
-            cmd="pavucontrol")
-        output.add_callback(module=self.instance(), button=1,
+        engine.input.register_callback(self, button=bumblebee.input.RIGHT_MOUSE, cmd="pavucontrol")
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE,
             cmd="pactl set-{}-mute @DEFAULT_{}@ toggle".format(channel, channel.upper()))
-        output.add_callback(module=self.instance(), button=4,
+        engine.input.register_callback(self, button=bumblebee.input.WHEEL_UP,
             cmd="pactl set-{}-volume @DEFAULT_{}@ +2%".format(channel, channel.upper()))
-        output.add_callback(module=self.instance(), button=5,
+        engine.input.register_callback(self, button=bumblebee.input.WHEEL_DOWN,
             cmd="pactl set-{}-volume @DEFAULT_{}@ -2%".format(channel, channel.upper()))
 
-    def widgets(self):
-        res = subprocess.check_output(shlex.split("pactl info"))
-        channel = "sinks" if self._module == "pasink" else "sources"
-        name = None
-        for line in res.decode().split("\n"):
-            if line.startswith("Default Sink: ") and channel == "sinks":
-                name = line[14:]
-            if line.startswith("Default Source: ") and channel == "sources":
-                name = line[16:]
-        
-        res = subprocess.check_output(shlex.split("pactl list {}".format(channel)))
+    def _default_device(self):
+        output = bumblebee.util.execute("pactl info")
+        pattern = "Default Sink: " if self.name == "pasink" else "Default Source: "
+        for line in output.split("\n"):
+            if line.startswith(pattern):
+                return line.replace(pattern, "")
+        return "n/a"
 
+    def volume(self, widget):
+        if int(self._mono) > 0:
+            return "{}%".format(self._mono)
+        elif self._left == self._right:
+            return "{}%".format(self._left)
+        else:
+            return "{}%/{}%".format(self._left, self._right)
+        return "n/a"
+
+    def update(self, widgets):
+        channel = "sinks" if self.name == "pasink" else "sources"
+        device = self._default_device()
+
+        result = bumblebee.util.execute("pactl list {}".format(channel))
         found = False
-        for line in res.decode().split("\n"):
+        for line in result.split("\n"):
             if "Name:" in line and found == True:
                 break
-            if name in line:
+            if device in line:
                 found = True
+
             if "Mute:" in line and found == True:
                 self._mute = False if " no" in line.lower() else True
 
@@ -71,22 +79,10 @@ class Module(bumblebee.module.Module):
                 else:
                     self._left = m.group(1)
                     self._right = m.group(2)
-        result = ""
-        if int(self._mono) > 0:
-            result = "{}%".format(self._mono)
-        elif self._left == self._right:
-            result = "{}%".format(self._left)
-        else:
-            result="{}%/{}%".format(self._left, self._right)
-        return bumblebee.output.Widget(self, result)
 
     def state(self, widget):
-        return "muted" if self._mute is True else "unmuted"
-
-    def warning(self, widget):
-        return self._mute
-
-    def critical(self, widget):
-        return False
+        if self._mute:
+            return [ "warning", "muted" ]
+        return [ "unmuted" ]
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/spacer.py b/bumblebee/modules/spacer.py
index 798338e..b89c233 100644
--- a/bumblebee/modules/spacer.py
+++ b/bumblebee/modules/spacer.py
@@ -1,17 +1,23 @@
-import bumblebee.module
-import bumblebee.util
+# pylint: disable=C0111,R0903
 
-def description():
-    return "Draws a widget with configurable content."
+"""Draws a widget with configurable text content.
 
-def parameters():
-    return [ "spacer.text: Text to draw (defaults to '')" ]
+Parameters:
+    * spacer.text: Widget contents (defaults to empty string)
+"""
 
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
-    def widgets(self):
-        return bumblebee.output.Widget(self, self._config.parameter("text", ""))
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.text)
+        )
+        self._text = self.parameter("text", "")
+
+    def text(self, widget):
+        return self._text
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/test.py b/bumblebee/modules/test.py
new file mode 100644
index 0000000..9f7485f
--- /dev/null
+++ b/bumblebee/modules/test.py
@@ -0,0 +1,13 @@
+# pylint: disable=C0111,R0903
+
+"""Test module"""
+
+import bumblebee.engine
+
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text="test")
+        )
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/time.py b/bumblebee/modules/time.py
deleted file mode 100644
index 4a19649..0000000
--- a/bumblebee/modules/time.py
+++ /dev/null
@@ -1,34 +0,0 @@
-from __future__ import absolute_import
-
-import datetime
-import bumblebee.module
-
-def description():
-    return "Displays the current time, using the optional format string as input for strftime."
-
-def parameters():
-    module = __name__.split(".")[-1]
-    return [
-        "{}.format: strftime specification (defaults to {})".format(module, default_format(module))
-    ]
-
-def default_format(module):
-    default = "%x %X"
-    if module == "date":
-        default = "%x"
-    if module == "time":
-        default = "%X"
-    return default
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-
-        module = self.__module__.split(".")[-1]
-
-        self._fmt = self._config.parameter("format", default_format(module))
-
-    def widgets(self):
-        return bumblebee.output.Widget(self, datetime.datetime.now().strftime(self._fmt))
-
-# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/modules/xrandr.py b/bumblebee/modules/xrandr.py
index 51998a9..def9235 100644
--- a/bumblebee/modules/xrandr.py
+++ b/bumblebee/modules/xrandr.py
@@ -1,89 +1,72 @@
-import bumblebee.module
-import bumblebee.util
-import re
+# pylint: disable=C0111,R0903
+
+"""Shows a widget for each connected screen and allows the user to enable/disable screens.
+
+"""
+
 import os
+import re
 import sys
-import subprocess
 
-def description():
-    return "Shows all connected screens"
-
-def parameters():
-    return [
-    ]
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config, alias):
-        super(Module, self).__init__(output, config, alias)
-
-        self._widgets = []
-
-    def toggle(self, event, widget):
-        path = os.path.dirname(os.path.abspath(__file__))
-        toggle_cmd = "{}/../../bin/toggle-display.sh".format(path)
-
-        if widget.get("state") == "on":
-            bumblebee.util.execute("{} --output {} --off".format(toggle_cmd, widget.get("display")))
-        else:
-            neighbor = None
-            for w in self._widgets:
-                if w.get("state") == "on":
-                    neighbor = w
-                    if event.get("button") == 1:
-                        break
-    
-            if neighbor == None:
-                bumblebee.util.execute("{} --output {} --auto".format(toggle_cmd,
-                    widget.get("display")))
-            else:
-                bumblebee.util.execute("{} --output {} --auto --{}-of {}".format(toggle_cmd,
-                    widget.get("display"), "left" if event.get("button") == 1 else "right",
-                    neighbor.get("display")))
-
-    def widgets(self):
-        process = subprocess.Popen([ "xrandr", "-q" ], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-        output, error = process.communicate()
+import bumblebee.util
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
 
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
         widgets = []
+        self._engine = engine
+        super(Module, self).__init__(engine, config, widgets)
+        self.update_widgets(widgets)
 
-        for line in output.split("\n"):
+    def update_widgets(self, widgets):
+        new_widgets = []
+        for line in bumblebee.util.execute("xrandr -q").split("\n"):
             if not " connected" in line:
                 continue
             display = line.split(" ", 2)[0]
             m = re.search(r'\d+x\d+\+(\d+)\+\d+', line)
 
-            widget = bumblebee.output.Widget(self, display, instance=display)
-            widget.set("display", display)
-
-            # not optimal (add callback once per interval), but since
-            # add_callback() just returns if the callback has already
-            # been registered, it should be "ok"
-            self._output.add_callback(module=display, button=1,
-                cmd=self.toggle)
-            self._output.add_callback(module=display, button=3,
-                cmd=self.toggle)
-            if m:
-                widget.set("state", "on")
-                widget.set("pos", int(m.group(1)))
-            else:
-                widget.set("state", "off")
-                widget.set("pos", sys.maxint)
+            widget = self.widget(display)
+            if not widget:
+                widget = bumblebee.output.Widget(full_text=display, name=display)
+                self._engine.input.register_callback(widget, button=1, cmd=self._toggle)
+                self._engine.input.register_callback(widget, button=3, cmd=self._toggle)
+            new_widgets.append(widget)
+            widget.set("state", "on" if m else "off")
+            widget.set("pos", int(m.group(1)) if m else sys.maxint)
 
+        while len(widgets) > 0:
+            del widgets[0]
+        for widget in new_widgets:
             widgets.append(widget)
 
-        widgets.sort(key=lambda widget : widget.get("pos"))
-
-        self._widgets = widgets
-
-        return widgets
+    def update(self, widgets):
+        self.update_widgets(widgets)
 
     def state(self, widget):
         return widget.get("state", "off")
 
-    def warning(self, widget):
-        return False
+    def _toggle(self, event):
+        path = os.path.dirname(os.path.abspath(__file__))
+        toggle_cmd = "{}/../../bin/toggle-display.sh".format(path)
 
-    def critical(self, widget):
-        return False
+        widget = self.widget_by_id(event["instance"])
+
+        if widget.get("state") == "on":
+            bumblebee.util.execute("{} --output {} --off".format(toggle_cmd, widget.name))
+        else:
+            first_neighbor = next((widget for widget in self.widgets() if widget.get("state") == "on"), None)
+            last_neighbor = next((widget for widget in reversed(self.widgets()) if widget.get("state") == "on"), None)
+
+            neighbor = first_neighbor if event["button"] == bumblebee.input.LEFT_MOUSE else last_neighbor
+    
+            if neighbor == None:
+                bumblebee.util.execute("{} --output {} --auto".format(toggle_cmd, widget.name))
+            else:
+                bumblebee.util.execute("{} --output {} --auto --{}-of {}".format(toggle_cmd, widget.name,
+                    "left" if event.get("button") == bumblebee.input.LEFT_MOUSE else "right",
+                    neighbor.name))
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/output.py b/bumblebee/output.py
index 1f494ad..974e651 100644
--- a/bumblebee/output.py
+++ b/bumblebee/output.py
@@ -1,123 +1,105 @@
-import os
-import shlex
-import inspect
-import threading
-import subprocess
+# pylint: disable=R0201
 
-def output(args):
-    import bumblebee.outputs.i3
-    return bumblebee.outputs.i3.Output(args)
+"""Output classes"""
 
-class Widget(object):
-    def __init__(self, obj, text, instance=None):
-        self._obj = obj
-        self._text = text
-        self._store = {}
-        self._instance = instance
+import sys
+import json
+import uuid
 
-        obj._output.register_widget(self.instance(), self)
+import bumblebee.store
 
-    def set(self, key, value):
-        self._store[key] = value
+class Widget(bumblebee.store.Store):
+    """Represents a single visible block in the status bar"""
+    def __init__(self, full_text="", name=""):
+        super(Widget, self).__init__()
+        self._full_text = full_text
+        self.module = None
+        self._module = None
+        self.name = name
+        self.id = str(uuid.uuid4())
 
-    def get(self, key, default=None):
-        return self._store.get(key, default)
+    def link_module(self, module):
+        """Set the module that spawned this widget
+
+        This is done outside the constructor to avoid having to
+        pass in the module name in every concrete module implementation"""
+        self.module = module.name
+        self._module = module
 
     def state(self):
-        return self._obj.state(self)
+        """Return the widget's state"""
+        if self._module and hasattr(self._module, "state"):
+            states = self._module.state(self)
+            if not isinstance(states, list):
+                return [states]
+            return states
+        return []
 
-    def warning(self):
-        return self._obj.warning(self)
-
-    def critical(self):
-        return self._obj.critical(self)
-
-    def module(self):
-        return self._obj.__module__.split(".")[-1]
-
-    def instance(self):
-        return self._instance if self._instance else getattr(self._obj, "instance")(self)
-
-    def text(self):
-        return self._text
-
-class Command(object):
-    def __init__(self, command, event, widget):
-        self._command = command
-        self._event = event
-        self._widget = widget
-
-    def __call__(self, *args, **kwargs):
-        if not isinstance(self._command, list):
-            self._command = [ self._command ]
-
-        for cmd in self._command:
-            if not cmd: continue
-            if inspect.ismethod(cmd):
-                cmd(self._event, self._widget)
+    def full_text(self, value=None):
+        """Set or retrieve the full text to display in the widget"""
+        if value:
+            self._full_text = value
+        else:
+            if callable(self._full_text):
+                return self._full_text(self)
             else:
-                c = cmd.format(*args, **kwargs)
-                DEVNULL = open(os.devnull, 'wb')
-                subprocess.Popen(shlex.split(c), stdout=DEVNULL, stderr=DEVNULL)
+                return self._full_text
 
-class Output(object):
-    def __init__(self, config):
-        self._config = config
-        self._callbacks = {}
-        self._wait = threading.Condition()
-        self._wait.acquire()
-        self._widgets = {}
-
-    def register_widget(self, identity, widget):
-        self._widgets[identity] = widget
-
-    def redraw(self):
-        self._wait.acquire()
-        self._wait.notify()
-        self._wait.release()
-
-    def add_callback(self, cmd, button, module=None):
-        if module:
-            module = module.replace("bumblebee.modules.", "")
-
-        if self._callbacks.get((button, module)): return
-
-        self._callbacks[(
-            button,
-            module,
-        )] = cmd
-
-    def callback(self, event):
-        cb = self._callbacks.get((
-            event.get("button", -1),
-            None,
-        ), None)
-        cb = self._callbacks.get((
-            event.get("button", -1),
-            event.get("instance", event.get("module", None)),
-        ), cb)
-
-        identity = event.get("instance", event.get("module", None))
-        return Command(cb, event, self._widgets.get(identity, None))
-
-    def wait(self):
-        self._wait.wait(self._config.parameter("interval", 1))
+class I3BarOutput(object):
+    """Manage output according to the i3bar protocol"""
+    def __init__(self, theme):
+        self._theme = theme
+        self._widgets = []
 
     def start(self):
-        pass
-
-    def draw(self, widgets, theme):
-        if not type(widgets) is list:
-            widgets = [ widgets ]
-        self._draw(widgets, theme)
-
-    def _draw(self, widgets, theme):
-        pass
-
-    def flush(self):
-        pass
+        """Print start preamble for i3bar protocol"""
+        sys.stdout.write(json.dumps({"version": 1, "click_events": True}) + "[\n")
 
     def stop(self):
-        pass
+        """Finish i3bar protocol"""
+        sys.stdout.write("]\n")
+
+    def draw(self, widget, module=None, engine=None):
+        """Draw a single widget"""
+        full_text = widget.full_text()
+        padding = self._theme.padding(widget)
+        prefix = self._theme.prefix(widget, padding)
+        suffix = self._theme.suffix(widget, padding)
+        if prefix:
+            full_text = u"{}{}".format(prefix, full_text)
+        if suffix:
+            full_text = u"{}{}".format(full_text, suffix)
+        separator = self._theme.separator(widget)
+        if separator:
+            self._widgets.append({
+                u"full_text": separator,
+                "separator": False,
+                "color": self._theme.separator_fg(widget),
+                "background": self._theme.separator_bg(widget),
+                "separator_block_width": self._theme.separator_block_width(widget),
+            })
+        self._widgets.append({
+            u"full_text": full_text,
+            "color": self._theme.fg(widget),
+            "background": self._theme.bg(widget),
+            "separator_block_width": self._theme.separator_block_width(widget),
+            "separator": True if separator is None else False,
+            "instance": widget.id,
+            "name": module.id,
+        })
+
+    def begin(self):
+        """Start one output iteration"""
+        self._widgets = []
+        self._theme.reset()
+
+    def flush(self):
+        """Flushes output"""
+        sys.stdout.write(json.dumps(self._widgets))
+
+    def end(self):
+        """Finalizes output"""
+        sys.stdout.write(",\n")
+        sys.stdout.flush()
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/outputs/__init__.py b/bumblebee/outputs/__init__.py
deleted file mode 100644
index e69de29..0000000
diff --git a/bumblebee/outputs/i3.py b/bumblebee/outputs/i3.py
deleted file mode 100644
index c0800dd..0000000
--- a/bumblebee/outputs/i3.py
+++ /dev/null
@@ -1,82 +0,0 @@
-from __future__ import unicode_literals
-
-import os
-import sys
-import json
-import shlex
-import threading
-import subprocess
-import bumblebee.output
-
-def read_input(output):
-    while True:
-        line = sys.stdin.readline().strip(",").strip()
-        if line == "[": continue
-        if line == "]": break
-
-        DEVNULL = open(os.devnull, 'wb')
-
-        event = json.loads(line)
-        cb = output.callback(event)
-        if cb:
-            cb(
-                name=event.get("name", ""),
-                instance=event.get("instance", ""),
-                button=event.get("button", -1)
-            )
-        output.redraw()
-
-class Output(bumblebee.output.Output):
-    def __init__(self, args):
-        super(Output, self).__init__(args)
-        self._data = []
-
-        self.add_callback("i3-msg workspace prev_on_output", 4)
-        self.add_callback("i3-msg workspace next_on_output", 5)
-
-        self._thread = threading.Thread(target=read_input, args=(self,))
-        self._thread.start()
-
-    def start(self):
-        print(json.dumps({ "version": 1, "click_events": True }) + "[")
-
-    def _draw(self, widgets, theme):
-        for widget in widgets:
-            if theme.separator(widget):
-                self._data.append({
-                    u"full_text": theme.separator(widget),
-                    "color": theme.separator_color(widget),
-                    "background": theme.separator_background(widget),
-                    "separator": False,
-                    "separator_block_width": 0,
-                })
-
-            sep = theme.default_separators(widget)
-            sep = sep if sep else False
-            width = theme.separator_block_width(widget)
-            width = width if width else 0
-            self._data.append({
-                u"full_text": " {} {} {}".format(
-                    theme.prefix(widget),
-                    widget.text(),
-                    theme.suffix(widget)
-                ),
-                "color": theme.color(widget),
-                "background": theme.background(widget),
-                "name": widget.module(),
-                "instance": widget.instance(),
-                "separator": sep,
-                "separator_block_width": width,
-            })
-            theme.next_widget()
-
-    def flush(self):
-        data = json.dumps(self._data)
-        self._data = []
-        print(data + ",")
-        sys.stdout.flush()
-
-    def stop(self):
-        return "]"
-
-# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/store.py b/bumblebee/store.py
new file mode 100644
index 0000000..8fac71b
--- /dev/null
+++ b/bumblebee/store.py
@@ -0,0 +1,21 @@
+"""Store interface
+
+Allows arbitrary classes to offer a simple get/set
+store interface by deriving from the Store class in
+this module
+"""
+
+class Store(object):
+    """Interface for storing and retrieving simple values"""
+    def __init__(self):
+        self._data = {}
+
+    def set(self, key, value):
+        """Set 'key' to 'value', overwriting 'key' if it exists already"""
+        self._data[key] = value
+
+    def get(self, key, default=None):
+        """Return the current value of 'key', or 'default' if 'key' is not set"""
+        return self._data.get(key, default)
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/theme.py b/bumblebee/theme.py
index cd8d860..3486f70 100644
--- a/bumblebee/theme.py
+++ b/bumblebee/theme.py
@@ -1,46 +1,154 @@
+# pylint: disable=C0103
+
+"""Theme support"""
+
 import os
 import copy
 import json
-import yaml
-import glob
 
-def getpath():
+import bumblebee.error
+
+def theme_path():
+    """Return the path of the theme directory"""
     return os.path.dirname("{}/../themes/".format(os.path.dirname(os.path.realpath(__file__))))
 
-def themes():
-    d = getpath()
-    return [ os.path.basename(f).replace(".json", "") for f in glob.iglob("{}/*.json".format(d)) ]
+class Theme(object):
+    """Represents a collection of icons and colors"""
+    def __init__(self, name):
+        self._init(self.load(name))
+        self._widget = None
+        self._cycle_idx = 0
+        self._cycle = {}
+        self._prevbg = None
 
-class Theme:
-    def __init__(self, config):
-        self._config = config
+    def _init(self, data):
+        """Initialize theme from data structure"""
+        for iconset in data.get("icons", []):
+            self._merge(data, self._load_icons(iconset))
+        self._theme = data
+        self._defaults = data.get("defaults", {})
+        self._cycles = self._theme.get("cycle", [])
+        self.reset()
 
-        self._data = self.get_theme(config.theme())
+    def data(self):
+        """Return the raw theme data"""
+        return self._theme
 
-        for iconset in self._data.get("icons", []):
-            self.merge(self._data, self.get_theme(iconset))
+    def reset(self):
+        """Reset theme to initial state"""
+        self._cycle = self._cycles[0] if len(self._cycles) > 0 else {}
+        self._cycle_idx = 0
+        self._widget = None
+        self._prevbg = None
 
-        self._defaults = self._data.get("defaults", {})
-        self._cycles = self._defaults.get("cycle", [])
-        self.begin()
+    def padding(self, widget):
+        """Return padding for widget"""
+        return self._get(widget, "padding", "")
 
-    def get_theme(self, name):
-        for path in [ getpath(), "{}/icons/".format(getpath()) ]:
-            if os.path.isfile("{}/{}.yaml".format(path, name)):
-                with open("{}/{}.yaml".format(path, name)) as f:
-                    return yaml.load(f)
-            if os.path.isfile("{}/{}.json".format(path, name)):
-                with open("{}/{}.json".format(path, name)) as f:
-                    return json.load(f)
-        return None
+    def prefix(self, widget, default=None):
+        """Return the theme prefix for a widget's full text"""
+        padding = self.padding(widget)
+        pre = self._get(widget, "prefix", None)
+        return u"{}{}{}".format(padding, pre, padding) if pre else default
+
+    def suffix(self, widget, default=None):
+        """Return the theme suffix for a widget's full text"""
+        padding = self._get(widget, "padding", "")
+        suf = self._get(widget, "suffix", None)
+        return u"{}{}{}".format(padding, suf, padding) if suf else default
+
+    def fg(self, widget):
+        """Return the foreground color for this widget"""
+        return self._get(widget, "fg", None)
+
+    def bg(self, widget):
+        """Return the background color for this widget"""
+        return self._get(widget, "bg", None)
+
+    def separator(self, widget):
+        """Return the separator between widgets"""
+        return self._get(widget, "separator", None)
+
+    def separator_fg(self, widget):
+        """Return the separator's foreground/text color"""
+        return self.bg(widget)
+
+    def separator_bg(self, widget):
+        """Return the separator's background color"""
+        return self._prevbg
+
+    def separator_block_width(self, widget):
+        """Return the SBW"""
+        return self._get(widget, "separator-block-width", None)
+
+    def loads(self, data):
+        """Initialize the theme from a JSON string"""
+        theme = json.loads(data)
+        self._init(theme)
+
+    def _load_icons(self, name):
+        """Load icons for a theme"""
+        path = "{}/icons/".format(theme_path())
+        return self.load(name, path=path)
+
+    def load(self, name, path=theme_path()):
+        """Load and parse a theme file"""
+        themefile = "{}/{}.json".format(path, name)
+
+        if os.path.isfile(themefile):
+            try:
+                with open(themefile) as data:
+                    return json.load(data)
+            except ValueError as exception:
+                raise bumblebee.error.ThemeLoadError("JSON error: {}".format(exception))
+        else:
+            raise bumblebee.error.ThemeLoadError("no such theme: {}".format(name))
+
+    def _get(self, widget, name, default=None):
+        """Return the config value 'name' for 'widget'"""
+
+        if not self._widget:
+            self._widget = widget
+
+        if self._widget != widget:
+            self._prevbg = self.bg(self._widget)
+            self._widget = widget
+            if len(self._cycles) > 0:
+                self._cycle_idx = (self._cycle_idx + 1) % len(self._cycles)
+                self._cycle = self._cycles[self._cycle_idx]
+
+        module_theme = self._theme.get(widget.module, {})
+
+        state_themes = []
+        # avoid infinite recursion
+        states = widget.state()
+        if name not in states:
+            for state in states:
+                state_themes.append(self._get(widget, state, {}))
+
+        value = self._defaults.get(name, default)
+        value = self._cycle.get(name, value)
+        value = module_theme.get(name, value)
+
+        for theme in state_themes:
+            value = theme.get(name, value)
+
+        if isinstance(value, list):
+            key = "{}-idx".format(name)
+            idx = widget.get(key, 0)
+            widget.set(key, (idx + 1) % len(value))
+            value = value[idx]
+
+        return value
 
     # algorithm copied from
     # http://blog.impressiver.com/post/31434674390/deep-merge-multiple-python-dicts
     # nicely done :)
-    def merge(self, target, *args):
+    def _merge(self, target, *args):
+        """Merge two arbitrarily nested data structures"""
         if len(args) > 1:
             for item in args:
-                self.merge(item)
+                self._merge(item)
             return target
 
         item = args[0]
@@ -48,83 +156,9 @@ class Theme:
             return item
         for key, value in item.items():
             if key in target and isinstance(target[key], dict):
-                self.merge(target[key], value)
+                self._merge(target[key], value)
             else:
                 target[key] = copy.deepcopy(value)
         return target
 
-    def begin(self):
-        self._config.set("theme.cycleidx", 0)
-        self._cycle = self._cycles[0] if len(self._cycles) > 0 else {}
-        self._background = [ None, None ]
-
-    def next_widget(self):
-        self._background[1] = self._background[0]
-        idx = self._config.increase("theme.cycleidx", len(self._cycles), 0)
-        self._cycle = self._cycles[idx] if len(self._cycles) > idx else {}
-
-    def prefix(self, widget):
-        return self._get(widget, "prefix", "")
-
-    def suffix(self, widget):
-        return self._get(widget, "suffix", "")
-
-    def color(self, widget):
-        result = self._get(widget, "fg")
-        if widget.warning():
-            result = self._get(widget, "fg-warning")
-        if widget.critical():
-            result = self._get(widget, "fg-critical")
-        return result
-
-    def background(self, widget):
-        result = self._get(widget, "bg")
-        if widget.warning():
-            result = self._get(widget, "bg-warning")
-        if widget.critical():
-            result = self._get(widget, "bg-critical")
-        self._background[0] = result
-        return result
-
-    def separator(self, widget):
-        return self._get(widget, "separator")
-
-    def default_separators(self, widget):
-        return self._get(widget, "default-separators")
-
-    def separator_color(self, widget):
-        return self.background(widget)
-
-    def separator_background(self, widget):
-        return self._background[1]
-
-    def separator_block_width(self, widget):
-        return self._get(widget, "separator-block-width")
-
-    def _get(self, widget, name, default = None):
-        module = widget.module()
-        state = widget.state()
-        inst = widget.instance()
-        inst = inst.replace("{}.".format(module), "")
-        module_theme = self._data.get(module, {})
-        state_theme = module_theme.get("states", {}).get(state, {})
-        instance_theme = module_theme.get(inst, {})
-        instance_state_theme = instance_theme.get("states", {}).get(state, {})
-
-        value = None
-        value = self._defaults.get(name, value)
-        value = self._cycle.get(name, value)
-        value = module_theme.get(name, value)
-        value = state_theme.get(name, value)
-        value = instance_theme.get(name, value)
-        value = instance_state_theme.get(name, value)
-
-        if type(value) is list:
-            key = "{}{}".format(repr(widget), value)
-            idx = self._config.parameter(key, 0)
-            self._config.increase(key, len(value), 0)
-            value = value[idx]
-
-        return value if value else default
-
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/util.py b/bumblebee/util.py
index c38bb79..f35ce89 100644
--- a/bumblebee/util.py
+++ b/bumblebee/util.py
@@ -1,11 +1,23 @@
 import shlex
 import subprocess
+
 try:
     from exceptions import RuntimeError
 except ImportError:
     # Python3 doesn't require this anymore
     pass
 
+def execute(cmd, wait=True):
+    args = shlex.split(cmd)
+    proc = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+
+    if wait:
+        out, _ = proc.communicate()
+        if proc.returncode != 0:
+            raise RuntimeError("{} exited with {}".format(cmd, proc.returncode))
+        return out.decode("utf-8")
+    return None
+
 def bytefmt(num):
     for unit in [ "", "Ki", "Mi", "Gi" ]:
         if num < 1024.0:
@@ -21,12 +33,4 @@ def durationfmt(duration):
 
     return res
 
-def execute(cmd):
-    args = shlex.split(cmd)
-    p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-    out, err = p.communicate()
-
-    if p.returncode != 0:
-        raise RuntimeError("{} exited with {}".format(cmd, p.returncode))
-
-    return out.decode("utf-8")
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/runlint.sh b/runlint.sh
new file mode 100755
index 0000000..6902ce9
--- /dev/null
+++ b/runlint.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+find . -name "*.py"|xargs pylint --disable=R0903,R0201,C0330
diff --git a/runtests.sh b/runtests.sh
index 58521b5..cbc5a2a 100755
--- a/runtests.sh
+++ b/runtests.sh
@@ -1,3 +1,13 @@
 #!/bin/sh
 
-nosetests --rednose -v tests/
+test=$(which nosetests)
+
+echo "testing with $(python2 -V 2>&1)"
+python2 $test --rednose -v tests/
+
+if [ $? == 0 ]; then
+	echo
+
+	echo "testing with $(python3 -V 2>&1)"
+	python3 $test --rednose -v tests/
+fi
diff --git a/screenshots/cpu.png b/screenshots/cpu.png
index f160ba2..0b5527c 100644
Binary files a/screenshots/cpu.png and b/screenshots/cpu.png differ
diff --git a/testjson.sh b/testjson.sh
new file mode 100755
index 0000000..ce473ea
--- /dev/null
+++ b/testjson.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+find themes/ -name "*.json"|xargs cat|json_verify -s
diff --git a/tests/modules/test_battery.py b/tests/modules/test_battery.py
new file mode 100644
index 0000000..499a0fa
--- /dev/null
+++ b/tests/modules/test_battery.py
@@ -0,0 +1,68 @@
+# pylint: disable=C0103,C0111
+
+import sys
+import json
+import unittest
+import mock
+
+from contextlib import contextmanager
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.battery import Module
+from tests.util import MockEngine, MockConfig, assertPopen
+
+class MockOpen(object):
+    def __init__(self):
+        self._value = ""
+
+    def returns(self, value):
+        self._value = value
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, a, b, c):
+        pass
+
+    def read(self):
+        return self._value
+
+class TestBatteryModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.config = MockConfig()
+        self.module = Module(engine=self.engine, config={ "config": self.config })
+        for widget in self.module.widgets():
+            widget.link_module(self.module)
+
+    @mock.patch("sys.stdout")
+    def test_format(self, mock_output):
+        for widget in self.module.widgets():
+            self.assertEquals(len(widget.full_text()), len("100%"))
+
+    @mock.patch("os.path.exists")
+    @mock.patch("{}.open".format("__builtin__" if sys.version_info[0] < 3 else "builtins"))
+    @mock.patch("subprocess.Popen")
+    def test_critical(self, mock_output, mock_open, mock_exists):
+        mock_open.return_value = MockOpen()
+        mock_open.return_value.returns("19")
+        mock_exists.return_value = True
+        self.config.set("battery.critical", "20")
+        self.config.set("battery.warning", "25")
+        self.module.update(self.module.widgets())
+        self.assertTrue("critical" in self.module.widgets()[0].state())
+
+    @mock.patch("os.path.exists")
+    @mock.patch("{}.open".format("__builtin__" if sys.version_info[0] < 3 else "builtins"))
+    @mock.patch("subprocess.Popen")
+    def test_warning(self, mock_output, mock_open, mock_exists):
+        mock_open.return_value = MockOpen()
+        mock_exists.return_value = True
+        mock_open.return_value.returns("22")
+        self.config.set("battery.critical", "20")
+        self.config.set("battery.warning", "25")
+        self.module.update(self.module.widgets())
+        self.assertTrue("warning" in self.module.widgets()[0].state())
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/modules/test_brightness.py b/tests/modules/test_brightness.py
new file mode 100644
index 0000000..0594fc3
--- /dev/null
+++ b/tests/modules/test_brightness.py
@@ -0,0 +1,56 @@
+# pylint: disable=C0103,C0111
+
+import json
+import unittest
+import mock
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.brightness import Module
+from tests.util import MockEngine, MockConfig, assertPopen, assertMouseEvent
+
+class TestBrightnessModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.engine.input = I3BarInput()
+        self.engine.input.need_event = True
+        self.config = MockConfig()
+        self.module = Module(engine=self.engine, config={ "config": self.config })
+        for widget in self.module.widgets():
+            widget.link_module(self.module)
+
+    @mock.patch("sys.stdout")
+    def test_format(self, mock_output):
+        for widget in self.module.widgets():
+            self.assertEquals(len(widget.full_text()), len("100%"))
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_wheel_up(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.WHEEL_UP,
+            "xbacklight +2%"
+        )
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_wheel_down(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.WHEEL_DOWN,
+            "xbacklight -2%"
+        )
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_custom_step(self, mock_input, mock_output, mock_select):
+        self.config.set("brightness.step", "10")
+        module = Module(engine=self.engine, config={ "config": self.config })
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            module, bumblebee.input.WHEEL_DOWN,
+            "xbacklight -10%"
+        )
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/modules/test_caffeine.py b/tests/modules/test_caffeine.py
new file mode 100644
index 0000000..995eece
--- /dev/null
+++ b/tests/modules/test_caffeine.py
@@ -0,0 +1,21 @@
+# pylint: disable=C0103,C0111
+
+import json
+import unittest
+import mock
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.caffeine import Module
+from tests.util import MockEngine, MockConfig, assertPopen
+
+class TestCaffeineModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.engine.input = I3BarInput()
+        self.engine.input.need_event = True
+        self.engine.input.need_valid_event = True
+        self.config = MockConfig()
+        self.module = Module(engine=self.engine, config={ "config": self.config })
+        for widget in self.module.widgets():
+            widget.link_module(self.module)
diff --git a/tests/modules/test_cmus.py b/tests/modules/test_cmus.py
new file mode 100644
index 0000000..1bc8b67
--- /dev/null
+++ b/tests/modules/test_cmus.py
@@ -0,0 +1,57 @@
+# pylint: disable=C0103,C0111
+
+import json
+import unittest
+import mock
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.cmus import Module
+from tests.util import MockEngine, MockConfig, assertPopen
+
+class TestCmusModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.engine.input = I3BarInput()
+        self.engine.input.need_event = True
+        self.module = Module(engine=self.engine, config={"config": MockConfig()})
+
+    @mock.patch("subprocess.Popen")
+    def test_read_song(self, mock_output):
+        rv = mock.Mock()
+        rv.configure_mock(**{
+            "communicate.return_value": ("out", None)
+        })
+        mock_output.return_value = rv
+        self.module.update(self.module.widgets())
+        assertPopen(mock_output, "cmus-remote -Q")
+
+    def test_widgets(self):
+        self.assertTrue(len(self.module.widgets()), 5)
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_interaction(self, mock_input, mock_output, mock_select):
+        events = [
+            {"widget": "cmus.shuffle", "action": "cmus-remote -S"},
+            {"widget": "cmus.repeat", "action": "cmus-remote -R"},
+            {"widget": "cmus.next", "action": "cmus-remote -n"},
+            {"widget": "cmus.prev", "action": "cmus-remote -r"},
+            {"widget": "cmus.main", "action": "cmus-remote -u"},
+        ]
+
+        mock_select.return_value = (1,2,3)
+
+        for event in events:
+            mock_input.readline.return_value = json.dumps({
+                "name": self.module.id,
+                "button": bumblebee.input.LEFT_MOUSE,
+                "instance": self.module.widget(event["widget"]).id
+            })
+            self.engine.input.start()
+            self.engine.input.stop()
+            mock_input.readline.assert_any_call()
+            assertPopen(mock_output, event["action"])
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/modules/test_cpu.py b/tests/modules/test_cpu.py
index 3b3fa65..a00d2c2 100644
--- a/tests/modules/test_cpu.py
+++ b/tests/modules/test_cpu.py
@@ -1,26 +1,48 @@
+# pylint: disable=C0103,C0111
+
+import json
 import unittest
+import mock
 
-import bumblebee.config
-import bumblebee.modules.cpu
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.cpu import Module
+from tests.util import MockEngine, MockConfig, assertPopen, assertMouseEvent, assertStateContains
 
-class FakeOutput(object):
-    def add_callback(self, cmd, button, module=None):
-        pass
-
-class TestCpuModule(unittest.TestCase):
+class TestCPUModule(unittest.TestCase):
     def setUp(self):
-        output = FakeOutput()
-        config = bumblebee.config.Config(["-m", "cpu"])
-        self.cpu = bumblebee.modules.cpu.Module(output, config, None)
+        self.engine = MockEngine()
+        self.engine.input = I3BarInput()
+        self.engine.input.need_event = True
+        self.config = MockConfig()
+        self.module = Module(engine=self.engine, config={ "config": self.config })
 
-    def test_documentation(self):
-        self.assertTrue(hasattr(bumblebee.modules.cpu, "description"))
-        self.assertTrue(hasattr(bumblebee.modules.cpu, "parameters"))
+    @mock.patch("sys.stdout")
+    def test_format(self, mock_output):
+        for widget in self.module.widgets():
+            self.assertEquals(len(widget.full_text()), len("100.00%"))
 
-    def test_warning(self):
-        self.assertTrue(hasattr(self.cpu, "warning"))
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_leftclick(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.LEFT_MOUSE,
+            "gnome-system-monitor"
+        )
 
-    def test_critical(self):
-        self.assertTrue(hasattr(self.cpu, "critical"))
+    @mock.patch("psutil.cpu_percent")
+    def test_warning(self, mock_psutil):
+        self.config.set("cpu.critical", "20")
+        self.config.set("cpu.warning", "18")
+        mock_psutil.return_value = 19.0
+        assertStateContains(self, self.module, "warning")
+
+    @mock.patch("psutil.cpu_percent")
+    def test_critical(self, mock_psutil):
+        self.config.set("cpu.critical", "20")
+        self.config.set("cpu.warning", "19")
+        mock_psutil.return_value = 21.0
+        assertStateContains(self, self.module, "critical")
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/modules/test_disk.py b/tests/modules/test_disk.py
new file mode 100644
index 0000000..f8fee4f
--- /dev/null
+++ b/tests/modules/test_disk.py
@@ -0,0 +1,56 @@
+# pylint: disable=C0103,C0111
+
+import json
+import unittest
+import mock
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.disk import Module
+from tests.util import MockEngine, MockConfig, assertPopen, assertStateContains
+
+class MockVFS(object):
+    def __init__(self, perc):
+        self.f_blocks = 1024*1024
+        self.f_frsize = 1
+        self.f_bavail = self.f_blocks - self.f_blocks*(perc/100.0)
+
+class TestDiskModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.engine.input = I3BarInput()
+        self.engine.input.need_event = True
+        self.config = MockConfig()
+        self.config.set("disk.path", "somepath")
+        self.module = Module(engine=self.engine, config={"config": self.config})
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_leftclick(self, mock_input, mock_output, mock_select):
+        mock_input.readline.return_value = json.dumps({
+            "name": self.module.id,
+            "button": bumblebee.input.LEFT_MOUSE,
+            "instance": None
+        })
+        mock_select.return_value = (1,2,3)
+        self.engine.input.start()
+        self.engine.input.stop()
+        mock_input.readline.assert_any_call()
+        assertPopen(mock_output, "nautilus {}".format(self.module.parameter("path")))
+
+    @mock.patch("os.statvfs")
+    def test_warning(self, mock_stat):
+        self.config.set("disk.critical", "80")
+        self.config.set("disk.warning", "70")
+        mock_stat.return_value = MockVFS(75.0)
+        assertStateContains(self, self.module, "warning")
+
+    @mock.patch("os.statvfs")
+    def test_critical(self, mock_stat):
+        self.config.set("disk.critical", "80")
+        self.config.set("disk.warning", "70")
+        mock_stat.return_value = MockVFS(85.0)
+        assertStateContains(self, self.module, "critical")
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/modules/test_load.py b/tests/modules/test_load.py
new file mode 100644
index 0000000..d8120e2
--- /dev/null
+++ b/tests/modules/test_load.py
@@ -0,0 +1,47 @@
+# pylint: disable=C0103,C0111
+
+import json
+import unittest
+import mock
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.load import Module
+from tests.util import MockEngine, MockConfig, assertStateContains, assertMouseEvent
+
+class TestLoadModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.engine.input = I3BarInput()
+        self.engine.input.need_event = True
+        self.config = MockConfig()
+        self.module = Module(engine=self.engine, config={ "config": self.config })
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_leftclick(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.LEFT_MOUSE,
+            "gnome-system-monitor"
+        )
+
+    @mock.patch("multiprocessing.cpu_count")
+    @mock.patch("os.getloadavg")
+    def test_warning(self, mock_loadavg, mock_cpucount):
+        self.config.set("load.critical", "1")
+        self.config.set("load.warning", "0.8")
+        mock_cpucount.return_value = 1
+        mock_loadavg.return_value = [ 0.9, 0, 0 ]
+        assertStateContains(self, self.module, "warning")
+
+    @mock.patch("multiprocessing.cpu_count")
+    @mock.patch("os.getloadavg")
+    def test_critical(self, mock_loadavg, mock_cpucount):
+        self.config.set("load.critical", "1")
+        self.config.set("load.warning", "0.8")
+        mock_cpucount.return_value = 1
+        mock_loadavg.return_value = [ 1.1, 0, 0 ]
+        assertStateContains(self, self.module, "critical")
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/modules/test_memory.py b/tests/modules/test_memory.py
new file mode 100644
index 0000000..4533357
--- /dev/null
+++ b/tests/modules/test_memory.py
@@ -0,0 +1,47 @@
+# pylint: disable=C0103,C0111
+
+import json
+import unittest
+import mock
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.memory import Module
+from tests.util import MockEngine, MockConfig, assertPopen, assertMouseEvent, assertStateContains
+
+class VirtualMemory(object):
+    def __init__(self, percent):
+        self.percent = percent
+
+class TestMemoryModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.engine.input = I3BarInput()
+        self.engine.input.need_event = True
+        self.config = MockConfig()
+        self.module = Module(engine=self.engine, config={ "config": self.config })
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_leftclick(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.LEFT_MOUSE,
+            "gnome-system-monitor"
+        )
+
+    @mock.patch("psutil.virtual_memory")
+    def test_warning(self, mock_vmem):
+        self.config.set("memory.critical", "80")
+        self.config.set("memory.warning", "70")
+        mock_vmem.return_value = VirtualMemory(75)
+        assertStateContains(self, self.module, "warning")
+
+    @mock.patch("psutil.virtual_memory")
+    def test_critical(self, mock_vmem):
+        self.config.set("memory.critical", "80")
+        self.config.set("memory.warning", "70")
+        mock_vmem.return_value = VirtualMemory(85)
+        assertStateContains(self, self.module, "critical")
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/modules/test_modules.py b/tests/modules/test_modules.py
new file mode 100644
index 0000000..4c54a93
--- /dev/null
+++ b/tests/modules/test_modules.py
@@ -0,0 +1,57 @@
+# pylint: disable=C0103,C0111
+
+import unittest
+import importlib
+import mock
+
+from bumblebee.engine import all_modules
+from bumblebee.config import Config
+from tests.util import assertWidgetAttributes, MockEngine
+
+class MockCommunicate(object):
+    def __init__(self):
+        self.returncode = 0
+
+    def communicate(self):
+        return (str.encode("1"), "error")
+
+class TestGenericModules(unittest.TestCase):
+    @mock.patch("subprocess.Popen")
+    def setUp(self, mock_output):
+        mock_output.return_value = MockCommunicate()
+        engine = MockEngine()
+        config = Config()
+        self.objects = {}
+        for mod in all_modules():
+            cls = importlib.import_module("bumblebee.modules.{}".format(mod["name"]))
+            self.objects[mod["name"]] = getattr(cls, "Module")(engine, {"config": config})
+            for widget in self.objects[mod["name"]].widgets():
+                self.assertEquals(widget.get("variable", None), None)
+
+    @mock.patch("subprocess.Popen")
+    def test_widgets(self, mock_output):
+        mock_output.return_value = MockCommunicate()
+        for mod in self.objects:
+            widgets = self.objects[mod].widgets()
+            for widget in widgets:
+                widget.link_module(self.objects[mod])
+                self.assertEquals(widget.module, mod)
+                assertWidgetAttributes(self, widget)
+                widget.set("variable", "value")
+                self.assertEquals(widget.get("variable", None), "value")
+                self.assertTrue(isinstance(widget.full_text(), str))
+
+    @mock.patch("subprocess.Popen")
+    def test_update(self, mock_output):
+        mock_output.return_value = MockCommunicate()
+        rv = mock.Mock()
+        rv.configure_mock(**{
+            "communicate.return_value": ("out", None)
+        })
+        for mod in self.objects:
+            widgets = self.objects[mod].widgets()
+            self.objects[mod].update(widgets)
+            self.test_widgets()
+            self.assertEquals(widgets, self.objects[mod].widgets())
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/modules/test_pulseaudio.py b/tests/modules/test_pulseaudio.py
new file mode 100644
index 0000000..6515589
--- /dev/null
+++ b/tests/modules/test_pulseaudio.py
@@ -0,0 +1,56 @@
+# pylint: disable=C0103,C0111
+
+import json
+import unittest
+import mock
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.pulseaudio import Module
+from tests.util import MockEngine, MockConfig, assertPopen, assertMouseEvent, assertStateContains
+
+class TestPulseAudioModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.engine.input = I3BarInput()
+        self.engine.input.need_event = True
+        self.config = MockConfig()
+        self.module = Module(engine=self.engine, config={ "config": self.config })
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_leftclick(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.LEFT_MOUSE,
+            "pactl set-source-mute @DEFAULT_SOURCE@ toggle"
+        )
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_rightclick(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.RIGHT_MOUSE,
+            "pavucontrol"
+        )
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_wheelup(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.WHEEL_UP,
+            "pactl set-source-volume @DEFAULT_SOURCE@ +2%"
+        )
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_wheeldown(self, mock_input, mock_output, mock_select):
+        assertMouseEvent(mock_input, mock_output, mock_select, self.engine,
+            self.module, bumblebee.input.WHEEL_DOWN,
+            "pactl set-source-volume @DEFAULT_SOURCE@ -2%"
+        )
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/test_config.py b/tests/test_config.py
index 6891eab..90e9816 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -1,10 +1,28 @@
+# pylint: disable=C0103,C0111
 import unittest
 
-import bumblebee.config
+from bumblebee.config import Config
 
-class TestConfigCreation(unittest.TestCase):
+class TestConfig(unittest.TestCase):
     def setUp(self):
-        pass
+        self.defaultConfig = Config()
+        self.someSimpleModules = ["foo", "bar", "baz"]
+        self.someAliasModules = ["foo:a", "bar:b", "baz:c"]
 
+    def test_no_modules_by_default(self):
+        self.assertEquals(self.defaultConfig.modules(), [])
+
+    def test_simple_modules(self):
+        cfg = Config(["-m"] + self.someSimpleModules)
+        self.assertEquals(cfg.modules(), [{
+            "name": x, "module": x
+        } for x in self.someSimpleModules])
+
+    def test_alias_modules(self):
+        cfg = Config(["-m"] + self.someAliasModules)
+        self.assertEquals(cfg.modules(), [{
+            "module": x.split(":")[0],
+            "name": x.split(":")[1],
+        } for x in self.someAliasModules])
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/test_engine.py b/tests/test_engine.py
new file mode 100644
index 0000000..069a71d
--- /dev/null
+++ b/tests/test_engine.py
@@ -0,0 +1,55 @@
+# pylint: disable=C0103,C0111,W0703,W0212
+
+import unittest
+
+from bumblebee.error import ModuleLoadError
+from bumblebee.engine import Engine
+from bumblebee.config import Config
+
+from tests.util import MockOutput, MockInput
+
+class TestEngine(unittest.TestCase):
+    def setUp(self):
+        self.engine = Engine(config=Config(), output=MockOutput(), inp=MockInput())
+        self.singleWidgetModule = [{"module": "test", "name": "a"}]
+        self.testModule = "test"
+        self.invalidModule = "no-such-module"
+        self.testModuleSpec = "bumblebee.modules.{}".format(self.testModule)
+        self.testModules = [
+            {"module": "test", "name": "a"},
+            {"module": "test", "name": "b"},
+        ]
+
+    def test_stop(self):
+        self.assertTrue(self.engine.running())
+        self.engine.stop()
+        self.assertFalse(self.engine.running())
+
+    def test_load_module(self):
+        module = self.engine._load_module(self.testModule)
+        self.assertEquals(module.__module__, self.testModuleSpec)
+
+    def test_load_invalid_module(self):
+        with self.assertRaises(ModuleLoadError):
+            self.engine._load_module(self.invalidModule)
+
+    def test_load_none(self):
+        with self.assertRaises(ModuleLoadError):
+            self.engine._load_module(None)
+
+    def test_load_modules(self):
+        modules = self.engine.load_modules(self.testModules)
+        self.assertEquals(len(modules), len(self.testModules))
+        self.assertEquals(
+            [module.__module__ for module in modules],
+            [self.testModuleSpec for module in modules]
+        )
+
+    def test_run(self):
+        self.engine.load_modules(self.singleWidgetModule)
+        try:
+            self.engine.run()
+        except Exception as e:
+            self.fail(e)
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/test_i3barinput.py b/tests/test_i3barinput.py
new file mode 100644
index 0000000..e2758d6
--- /dev/null
+++ b/tests/test_i3barinput.py
@@ -0,0 +1,115 @@
+# pylint: disable=C0103,C0111
+
+import unittest
+import json
+import subprocess
+import mock
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from tests.util import MockWidget, MockModule, assertPopen, assertMouseEvent
+
+class TestI3BarInput(unittest.TestCase):
+    def setUp(self):
+        self.input = I3BarInput()
+        self.input.need_event = True
+        self.anyModule = MockModule()
+        self.anyWidget = MockWidget("test")
+        self.anyModule.id = "test-module"
+        self._called = 0
+
+    def callback(self, event):
+        self._called += 1
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_basic_read_event(self, mock_input, mock_select):
+        mock_select.return_value = (1,2,3)
+        mock_input.readline.return_value = ""
+        self.input.start()
+        self.input.stop()
+        mock_input.readline.assert_any_call()
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_ignore_invalid_data(self, mock_input, mock_select):
+        mock_select.return_value = (1,2,3)
+        mock_input.readline.return_value = "garbage"
+        self.input.start()
+        self.assertEquals(self.input.alive(), True)
+        self.assertEquals(self.input.stop(), True)
+        mock_input.readline.assert_any_call()
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_ignore_invalid_event(self, mock_input, mock_select):
+        mock_select.return_value = (1,2,3)
+        mock_input.readline.return_value = json.dumps({
+            "name": None,
+            "instance": None,
+            "button": None,
+        })
+        self.input.start()
+        self.assertEquals(self.input.alive(), True)
+        self.assertEquals(self.input.stop(), True)
+        mock_input.readline.assert_any_call()
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_global_callback(self, mock_input, mock_select):
+        self.input.register_callback(None, button=1, cmd=self.callback)
+        assertMouseEvent(mock_input, None, mock_select, self, None,
+            bumblebee.input.LEFT_MOUSE, None, "someinstance")
+        self.assertTrue(self._called > 0)
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_remove_global_callback(self, mock_input, mock_select):
+        self.input.register_callback(None, button=1, cmd=self.callback)
+        self.input.deregister_callbacks(None)
+        assertMouseEvent(mock_input, None, mock_select, self, None,
+            bumblebee.input.LEFT_MOUSE, None, "someinstance")
+        self.assertTrue(self._called == 0)
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_global_callback_button_missmatch(self, mock_input, mock_select):
+        self.input.register_callback(self.anyModule, button=1, cmd=self.callback)
+        assertMouseEvent(mock_input, None, mock_select, self, None,
+            bumblebee.input.RIGHT_MOUSE, None, "someinstance")
+        self.assertTrue(self._called == 0)
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_module_callback(self, mock_input, mock_select):
+        self.input.register_callback(self.anyModule, button=1, cmd=self.callback)
+        assertMouseEvent(mock_input, None, mock_select, self, self.anyModule,
+            bumblebee.input.LEFT_MOUSE, None)
+        self.assertTrue(self._called > 0)
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_remove_module_callback(self, mock_input, mock_select):
+        self.input.register_callback(self.anyModule, button=1, cmd=self.callback)
+        self.input.deregister_callbacks(self.anyModule)
+        assertMouseEvent(mock_input, None, mock_select, self, None,
+            bumblebee.input.LEFT_MOUSE, None, self.anyWidget.id)
+        self.assertTrue(self._called == 0)
+
+    @mock.patch("select.select")
+    @mock.patch("sys.stdin")
+    def test_widget_callback(self, mock_input, mock_select):
+        self.input.register_callback(self.anyWidget, button=1, cmd=self.callback)
+        assertMouseEvent(mock_input, None, mock_select, self, None,
+            bumblebee.input.LEFT_MOUSE, None, self.anyWidget.id)
+        self.assertTrue(self._called > 0)
+
+    @mock.patch("select.select")
+    @mock.patch("subprocess.Popen")
+    @mock.patch("sys.stdin")
+    def test_widget_cmd_callback(self, mock_input, mock_output, mock_select):
+        self.input.register_callback(self.anyWidget, button=1, cmd="echo")
+        assertMouseEvent(mock_input, mock_output, mock_select, self, None,
+            bumblebee.input.LEFT_MOUSE, "echo", self.anyWidget.id)
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/test_i3baroutput.py b/tests/test_i3baroutput.py
new file mode 100644
index 0000000..f4c4cca
--- /dev/null
+++ b/tests/test_i3baroutput.py
@@ -0,0 +1,104 @@
+# pylint: disable=C0103,C0111
+
+import json
+import unittest
+import mock
+try:
+    from StringIO import StringIO
+except ImportError:
+    from io import StringIO
+
+from bumblebee.output import I3BarOutput
+from tests.util import MockWidget, MockTheme, MockModule
+
+class TestI3BarOutput(unittest.TestCase):
+    def setUp(self):
+        self.theme = MockTheme()
+        self.output = I3BarOutput(self.theme)
+        self.expectedStart = json.dumps({"version": 1, "click_events": True}) + "[\n"
+        self.expectedStop = "]\n"
+        self.someWidget = MockWidget("foo bar baz")
+        self.anyModule = MockModule(None, None)
+        self.anyColor = "#ababab"
+        self.anotherColor = "#cccccc"
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_start(self, stdout):
+        self.output.start()
+        self.assertEquals(self.expectedStart, stdout.getvalue())
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_stop(self, stdout):
+        self.output.stop()
+        self.assertEquals(self.expectedStop, stdout.getvalue())
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_draw_single_widget(self, stdout):
+        self.output.draw(self.someWidget, self.anyModule)
+        self.output.flush()
+        result = json.loads(stdout.getvalue())[0]
+        self.assertEquals(result["full_text"], self.someWidget.full_text())
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_draw_multiple_widgets(self, stdout):
+        for widget in [self.someWidget, self.someWidget]:
+            self.output.draw(widget, self.anyModule)
+        self.output.flush()
+        result = json.loads(stdout.getvalue())
+        for res in result:
+            self.assertEquals(res["full_text"], self.someWidget.full_text())
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_begin(self, stdout):
+        self.output.begin()
+        self.assertEquals("", stdout.getvalue())
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_end(self, stdout):
+        self.output.end()
+        self.assertEquals(",\n", stdout.getvalue())
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_prefix(self, stdout):
+        self.theme.attr_prefix = " - "
+        self.output.draw(self.someWidget, self.anyModule)
+        self.output.flush()
+        result = json.loads(stdout.getvalue())[0]
+        self.assertEquals(result["full_text"], "{}{}".format(
+            self.theme.prefix(self.someWidget), self.someWidget.full_text())
+        )
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_suffix(self, stdout):
+        self.theme.attr_suffix = " - "
+        self.output.draw(self.someWidget, self.anyModule)
+        self.output.flush()
+        result = json.loads(stdout.getvalue())[0]
+        self.assertEquals(result["full_text"], "{}{}".format(
+            self.someWidget.full_text(), self.theme.suffix(self.someWidget))
+        )
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_bothfix(self, stdout):
+        self.theme.attr_suffix = " - "
+        self.theme.attr_prefix = " * "
+        self.output.draw(self.someWidget, self.anyModule)
+        self.output.flush()
+        result = json.loads(stdout.getvalue())[0]
+        self.assertEquals(result["full_text"], "{}{}{}".format(
+            self.theme.prefix(self.someWidget),
+            self.someWidget.full_text(),
+            self.theme.suffix(self.someWidget)
+        ))
+
+    @mock.patch("sys.stdout", new_callable=StringIO)
+    def test_colors(self, stdout):
+        self.theme.attr_fg = self.anyColor
+        self.theme.attr_bg = self.anotherColor
+        self.output.draw(self.someWidget, self.anyModule)
+        self.output.flush()
+        result = json.loads(stdout.getvalue())[0]
+        self.assertEquals(result["color"], self.anyColor)
+        self.assertEquals(result["background"], self.anotherColor)
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/test_module.py b/tests/test_module.py
new file mode 100644
index 0000000..0cc95ad
--- /dev/null
+++ b/tests/test_module.py
@@ -0,0 +1,50 @@
+# pylint: disable=C0103,C0111,W0703
+
+import unittest
+
+from bumblebee.engine import Module
+from bumblebee.config import Config
+from tests.util import MockWidget
+
+class TestModule(unittest.TestCase):
+    def setUp(self):
+        self.widget = MockWidget("foo")
+        self.config = Config()
+        self.moduleWithoutWidgets = Module(engine=None, widgets=None)
+        self.moduleWithOneWidget = Module(engine=None, widgets=self.widget)
+        self.moduleWithMultipleWidgets = Module(engine=None,
+            widgets=[self.widget, self.widget, self.widget]
+        )
+
+        self.anyConfigName = "cfg"
+        self.anotherConfigName = "cfg2"
+        self.anyModule = Module(engine=None, widgets=self.widget, config={
+            "name": self.anyConfigName, "config": self.config
+        })
+        self.anotherModule = Module(engine=None, widgets=self.widget, config={
+            "name": self.anotherConfigName, "config": self.config
+        })
+        self.anyKey = "some-parameter"
+        self.anyValue = "value"
+        self.anotherValue = "another-value"
+        self.emptyKey = "i-do-not-exist"
+        self.config.set("{}.{}".format(self.anyConfigName, self.anyKey), self.anyValue)
+        self.config.set("{}.{}".format(self.anotherConfigName, self.anyKey), self.anotherValue)
+
+    def test_empty_widgets(self):
+        self.assertEquals(self.moduleWithoutWidgets.widgets(), [])
+
+    def test_single_widget(self):
+        self.assertEquals(self.moduleWithOneWidget.widgets(), [self.widget])
+
+    def test_multiple_widgets(self):
+        for widget in self.moduleWithMultipleWidgets.widgets():
+            self.assertEquals(widget, self.widget)
+
+    def test_parameters(self):
+        self.assertEquals(self.anyModule.parameter(self.anyKey), self.anyValue)
+        self.assertEquals(self.anotherModule.parameter(self.anyKey), self.anotherValue)
+
+    def test_default_parameters(self):
+        self.assertEquals(self.anyModule.parameter(self.emptyKey), None)
+        self.assertEquals(self.anyModule.parameter(self.emptyKey, self.anyValue), self.anyValue)
diff --git a/tests/test_store.py b/tests/test_store.py
new file mode 100644
index 0000000..0b712f0
--- /dev/null
+++ b/tests/test_store.py
@@ -0,0 +1,24 @@
+# pylint: disable=C0103,C0111,W0703
+
+import unittest
+
+from bumblebee.store import Store
+
+class TestStore(unittest.TestCase):
+    def setUp(self):
+        self.store = Store()
+        self.anyKey = "some-key"
+        self.anyValue = "some-value"
+        self.unsetKey = "invalid-key"
+
+    def test_set_value(self):
+        self.store.set(self.anyKey, self.anyValue)
+        self.assertEquals(self.store.get(self.anyKey), self.anyValue)
+
+    def test_get_invalid_value(self):
+        result = self.store.get(self.unsetKey)
+        self.assertEquals(result, None)
+
+    def test_get_invalid_with_default_value(self):
+        result = self.store.get(self.unsetKey, self.anyValue)
+        self.assertEquals(result, self.anyValue)
diff --git a/tests/test_theme.py b/tests/test_theme.py
new file mode 100644
index 0000000..8d9dccc
--- /dev/null
+++ b/tests/test_theme.py
@@ -0,0 +1,115 @@
+# pylint: disable=C0103,C0111,W0703
+
+import unittest
+from bumblebee.theme import Theme
+from bumblebee.error import ThemeLoadError
+from tests.util import MockWidget
+
+class TestTheme(unittest.TestCase):
+    def setUp(self):
+        self.nonexistentThemeName = "no-such-theme"
+        self.invalidThemeName = "invalid"
+        self.validThemeName = "test"
+        self.themedWidget = MockWidget("bla")
+        self.theme = Theme(self.validThemeName)
+        self.cycleTheme = Theme("test_cycle")
+        self.anyWidget = MockWidget("bla")
+        self.anotherWidget = MockWidget("blub")
+
+        data = self.theme.data()
+        self.widgetTheme = "test-widget"
+        self.themedWidget.module = self.widgetTheme
+        self.defaultColor = data["defaults"]["fg"]
+        self.defaultBgColor = data["defaults"]["bg"]
+        self.widgetColor = data[self.widgetTheme]["fg"]
+        self.widgetBgColor = data[self.widgetTheme]["bg"]
+        self.defaultPrefix = data["defaults"]["prefix"]
+        self.defaultSuffix = data["defaults"]["suffix"]
+        self.widgetPrefix = data[self.widgetTheme]["prefix"]
+        self.widgetSuffix = data[self.widgetTheme]["suffix"]
+
+    def test_load_valid_theme(self):
+        try:
+            Theme(self.validThemeName)
+        except Exception as e:
+            self.fail(e)
+
+    def test_load_nonexistent_theme(self):
+        with self.assertRaises(ThemeLoadError):
+            Theme(self.nonexistentThemeName)
+
+    def test_load_invalid_theme(self):
+        with self.assertRaises(ThemeLoadError):
+            Theme(self.invalidThemeName)
+
+    def test_default_prefix(self):
+        self.assertEquals(self.theme.prefix(self.anyWidget), self.defaultPrefix)
+
+    def test_default_suffix(self):
+        self.assertEquals(self.theme.suffix(self.anyWidget), self.defaultSuffix)
+
+    def test_widget_prefix(self):
+        self.assertEquals(self.theme.prefix(self.themedWidget), self.widgetPrefix)
+
+    def test_widget_fg(self):
+        self.assertEquals(self.theme.fg(self.anyWidget), self.defaultColor)
+        self.anyWidget.module = self.widgetTheme
+        self.assertEquals(self.theme.fg(self.anyWidget), self.widgetColor)
+
+    def test_widget_bg(self):
+        self.assertEquals(self.theme.bg(self.anyWidget), self.defaultBgColor)
+        self.anyWidget.module = self.widgetTheme
+        self.assertEquals(self.theme.bg(self.anyWidget), self.widgetBgColor)
+
+    def test_absent_cycle(self):
+        theme = self.theme
+        try:
+            theme.fg(self.anyWidget)
+            theme.fg(self.anotherWidget)
+        except Exception as e:
+            self.fail(e)
+
+    def test_reset(self):
+        theme = self.cycleTheme
+        data = theme.data()
+        theme.reset()
+        self.assertEquals(theme.fg(self.anyWidget), data["cycle"][0]["fg"])
+        self.assertEquals(theme.fg(self.anotherWidget), data["cycle"][1]["fg"])
+        theme.reset()
+        self.assertEquals(theme.fg(self.anyWidget), data["cycle"][0]["fg"])
+
+    def test_separator_block_width(self):
+        theme = self.theme
+        data = theme.data()
+
+        self.assertEquals(theme.separator_block_width(self.anyWidget),
+            data["defaults"]["separator-block-width"]
+        )
+
+    def test_separator(self):
+        for theme in [self.theme, self.cycleTheme]:
+            theme.reset()
+            prev_bg = theme.bg(self.anyWidget)
+            theme.bg(self.anotherWidget)
+
+            self.assertEquals(theme.separator_fg(self.anotherWidget), theme.bg(self.anotherWidget))
+            self.assertEquals(theme.separator_bg(self.anotherWidget), prev_bg)
+
+    def test_state(self):
+        theme = self.theme
+        data = theme.data()
+
+        self.assertEquals(theme.fg(self.anyWidget), data["defaults"]["fg"])
+        self.assertEquals(theme.bg(self.anyWidget), data["defaults"]["bg"])
+
+        self.anyWidget.attr_state = ["critical"]
+        self.assertEquals(theme.fg(self.anyWidget), data["defaults"]["critical"]["fg"])
+        self.assertEquals(theme.bg(self.anyWidget), data["defaults"]["critical"]["bg"])
+
+        self.themedWidget.attr_state = ["critical"]
+        self.assertEquals(theme.fg(self.themedWidget), data[self.widgetTheme]["critical"]["fg"])
+        # if elements are missing in the state theme, they are taken from the
+        # widget theme instead (i.e. no fallback to a more general state theme)
+        self.assertEquals(theme.bg(self.themedWidget), data[self.widgetTheme]["bg"])
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/util.py b/tests/util.py
new file mode 100644
index 0000000..0b46d62
--- /dev/null
+++ b/tests/util.py
@@ -0,0 +1,138 @@
+# pylint: disable=C0103,C0111,W0613
+
+import json
+import shlex
+import subprocess
+
+from bumblebee.output import Widget
+
+def assertWidgetAttributes(test, widget):
+    test.assertTrue(isinstance(widget, Widget))
+    test.assertTrue(hasattr(widget, "full_text"))
+
+def assertPopen(output, cmd):
+    res = shlex.split(cmd)
+    output.assert_any_call(res,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT
+    )
+
+def assertStateContains(test, module, state):
+    for widget in module.widgets():
+        widget.link_module(module)
+    module.update(module.widgets())
+    test.assertTrue(state in module.widgets()[0].state())
+
+def assertMouseEvent(mock_input, mock_output, mock_select, engine, module, button, cmd, instance_id=None):
+        mock_input.readline.return_value = json.dumps({
+            "name": module.id if module else "test",
+            "button": button,
+            "instance": instance_id
+        })
+        mock_select.return_value = (1, 2, 3)
+        engine.input.start()
+        engine.input.stop()
+        mock_input.readline.assert_any_call()
+        if cmd:
+            assertPopen(mock_output, cmd)
+
+class MockInput(object):
+    def start(self):
+        pass
+
+    def stop(self):
+        pass
+
+    def register_callback(self, obj, button, cmd):
+        pass
+
+class MockEngine(object):
+    def __init__(self):
+        self.input = MockInput()
+
+class MockConfig(object):
+    def __init__(self):
+        self._data = {}
+
+    def get(self, name, default):
+        if name in self._data:
+            return self._data[name]
+        return default
+
+    def set(self, name, value):
+        self._data[name] = value
+
+class MockOutput(object):
+    def start(self):
+        pass
+
+    def stop(self):
+        pass
+
+    def draw(self, widget, engine, module):
+        engine.stop()
+
+    def begin(self):
+        pass
+
+    def flush(self):
+        pass
+
+    def end(self):
+        pass
+
+class MockModule(object):
+    def __init__(self, engine=None, config=None):
+        self.id = None
+
+class MockWidget(Widget):
+    def __init__(self, text):
+        super(MockWidget, self).__init__(text)
+        self._text = text
+        self.module = None
+        self.attr_state = ["state-default"]
+        self.id = "none"
+
+    def state(self):
+        return self.attr_state
+
+    def update(self, widgets):
+        pass
+
+    def full_text(self):
+        return self._text
+
+class MockTheme(object):
+    def __init__(self):
+        self.attr_prefix = None
+        self.attr_suffix = None
+        self.attr_fg = None
+        self.attr_bg = None
+        self.attr_separator = None
+        self.attr_separator_block_width = 0
+
+    def padding(self, widget):
+        return ""
+
+    def reset(self):
+        pass
+
+    def separator_block_width(self, widget):
+        return self.attr_separator_block_width
+
+    def separator(self, widget):
+        return self.attr_separator
+
+    def prefix(self, widget, default=None):
+        return self.attr_prefix
+
+    def suffix(self, widget, default=None):
+        return self.attr_suffix
+
+    def fg(self, widget):
+        return self.attr_fg
+
+    def bg(self, widget):
+        return self.attr_bg
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/themes/gruvbox-powerline.json b/themes/gruvbox-powerline.json
index f04bbc7..e8921c3 100644
--- a/themes/gruvbox-powerline.json
+++ b/themes/gruvbox-powerline.json
@@ -3,42 +3,41 @@
 	"defaults": {
 		"prefix": " ",
 		"suffix" : " ",
-		"cycle": [
-			{
-				"fg": "#ebdbb2",
-				"bg": "#1d2021"
-			},
-			{
-				"fg": "#fbf1c7",
-				"bg": "#282828"
-			}
-		],
-		"fg-critical": "#fbf1c7",
-		"bg-critical": "#cc241d",
-		"fg-warning": "#1d2021",
-		"bg-warning": "#d79921",
-
+		"warning": {
+			"fg": "#1d2021",
+			"bg": "#d79921"
+		},
+		"critical": {
+			"fg": "#fbf1c7",
+			"bg": "#cc241d"
+		},
 		"default-separators": false,
 		"separator-block-width": 0
 	},
+	"cycle": [
+		{
+			"fg": "#ebdbb2",
+			"bg": "#1d2021"
+		},
+		{
+			"fg": "#fbf1c7",
+			"bg": "#282828"
+		}
+	],
 	"dnf": {
-		"states": {
-			"good": {
-				"fg": "#002b36",
-				"bg": "#859900"
-			}
+		"good": {
+			"fg": "#002b36",
+			"bg": "#859900"
 		}
 	},
 	"battery": {
-		"states": {
-			"charged": {
-				"fg": "#1d2021",
-				"bg": "#b8bb26"
-			},
-			"AC": {
-				"fg": "#1d2021",
-				"bg": "#b8bb26"
-			}
+		"charged": {
+			"fg": "#1d2021",
+			"bg": "#b8bb26"
+		},
+		"AC": {
+			"fg": "#1d2021",
+			"bg": "#b8bb26"
 		}
 	}
 }
diff --git a/themes/icons/ascii.json b/themes/icons/ascii.json
index bd051ce..613f133 100644
--- a/themes/icons/ascii.json
+++ b/themes/icons/ascii.json
@@ -1,119 +1,56 @@
 {
-	"memory": {
-		"prefix": "ram"
-	},
-	"cpu": {
-		"prefix": "cpu"
-	},
-	"disk": {
-		"prefix": "hdd"
-	},
-	"dnf": {
-		"prefix": "dnf"
-	},
-	"brightness": {
-		"prefix": "o"
+	"defaults": {
+		"padding": " "
 	},
+	"memory": { "prefix": "ram" },
+	"cpu": { "prefix": "cpu" },
+	"disk": { "prefix": "hdd" },
+	"dnf": { "prefix": "dnf" },
+	"brightness": { "prefix": "o" },
 	"cmus": {
-		"states": {
-			"playing": {
-				"prefix": ">"
-			},
-			"paused": {
-				"prefix": "||"
-			},
-			"stopped": {
-				"prefix": "[]"
-			}
-		},
-		"prev": {
-			"prefix": "|<"
-		},
-		"next": {
-			"prefix": ">|"
-		},
-		"shuffle": {
-			"states": { "on": { "prefix": "S" }, "off": { "prefix": "[s]" } }
-		},
-		"repeat": {
-			"states": { "on": { "prefix": "R" }, "off": { "prefix": "[r]" } }
-		}
+		"playing": { "prefix": ">" },
+		"paused": { "prefix": "||" },
+		"stopped": { "prefix": "[]" },
+		"prev": { "prefix": "|<" },
+		"next": { "prefix": ">|" },
+		"shuffle-on": { "prefix": "S" },
+		"shuffle-off": { "prefix": "[s]" },
+		"repeat-on": { "prefix": "R" },
+		"repeat-off": { "prefix": "[r]" }
 	},
 	"pasink": {
-		"states": {
-			"muted": {
-				"prefix": "audio(mute)"
-			},
-			"unmuted": {
-				"prefix": "audio"
-			}
-		}
+		"muted": { "prefix": "audio(mute)" },
+		"unmuted": { "prefix": "audio" }
 	},
 	"pasource": {
-		"states": {
-			"muted": {
-				"prefix": "mic(mute)"
-			},
-			"unmuted": {
-				"prefix": "mic"
-			}
-		}
+		"muted": { "prefix": "mic(mute)" },
+		"unmuted": { "prefix": "mic" }
 	},
 	"nic": {
-		"states": {
-			"wireless-up": {
-				"prefix": "wifi"
-			},
-			"wireless-down": {
-				"prefix": "wifi"
-			},
-			"wired-up": {
-				"prefix": "lan"
-			},
-			"wired-down": {
-				"prefix": "lan"
-			},
-			"tunnel-up": {
-				"prefix": "tun"
-			},
-			"tunnel-down": {
-				"prefix": "tun"
-			}
-		}
+		"wireless-up": { "prefix": "wifi" },
+		"wireless-down": { "prefix": "wifi" },
+		"wired-up": { "prefix": "lan" },
+		"wired-down": { "prefix": "lan" },
+		"tunnel-up": { "prefix": "tun" },
+		"tunnel-down": { "prefix": "tun" }
 	},
 	"battery": {
-		"states": {
-			"charged": {
-				"suffix": "full"
-			},
-			"charging": {
-				"suffix": "chr"
-			},
-			"AC": {
-				"suffix": "ac"
-			},
-			"discharging-10": {
-				"prefix": "!",
-				"suffix": "dis"
-			},
-			"discharging-25": {
-				"suffix": "dis"
-			},
-			"discharging-50": {
-				"suffix": "dis"
-			},
-			"discharging-80": {
-				"suffix": "dis"
-			},
-			"discharging-100": {
-				"suffix": "dis"
-			}
-		}
+		"charged": { "suffix": "full" },
+		"charging": { "suffix": "chr" },
+		"AC": { "suffix": "ac" },
+		"discharging-10": {
+			"prefix": "!",
+			"suffix": "dis"
+		},
+		"discharging-25": { "suffix": "dis" },
+		"discharging-50": { "suffix": "dis" },
+		"discharging-80": { "suffix": "dis" },
+		"discharging-100": { "suffix": "dis" }
 	},
 	"caffeine": {
-		"states": { "activated": {"prefix": "caf-on" }, "deactivated": { "prefix": "caf-off " } }
+		"activated": {"prefix": "caf-on" }, "deactivated": { "prefix": "caf-off " }
 	},
 	"xrandr": {
-		"states": { "on": { "prefix": " off "}, "off": { "prefix": " on "} }
+		"on": { "prefix": " off "}, "off": { "prefix": " on "}
 	}
 }
diff --git a/themes/icons/awesome-fonts.json b/themes/icons/awesome-fonts.json
index 62d9294..b3784eb 100644
--- a/themes/icons/awesome-fonts.json
+++ b/themes/icons/awesome-fonts.json
@@ -1,134 +1,60 @@
 {
 	"defaults": {
-		"separator": ""
-	},
-	"date": {
-		"prefix": ""
-	},
-	"time": {
-		"prefix": ""
-	},
-	"memory": {
-		"prefix": ""
-	},
-	"cpu": {
-		"prefix": ""
-	},
-	"disk": {
-		"prefix": ""
-	},
-	"dnf": {
-		"prefix": ""
-	},
-	"brightness": {
-		"prefix": ""
+		"separator": "", "padding": " ",
+		"unknown": { "prefix": "" }
 	},
+	"date": { "prefix": ""	},
+	"time": { "prefix": "" },
+	"memory": { "prefix": "" },
+	"cpu": { "prefix": "" },
+	"disk": { "prefix": "" },
+	"dnf": { "prefix": "" },
+	"brightness": { "prefix": "" },
+	"load": { "prefix": "" },
 	"cmus": {
-		"states": {
-			"playing": {
-				"prefix": ""
-			},
-			"paused": {
-				"prefix": ""
-			},
-			"stopped": {
-				"prefix": ""
-			}
-		},
-		"prev": {
-			"prefix": ""
-		},
-		"next": {
-			"prefix": ""
-		},
-		"shuffle": {
-			"states": { "on": { "prefix": "" }, "off": { "prefix": "" } }
-		},
-		"repeat": {
-			"states": { "on": { "prefix": "" }, "off": { "prefix": "" } }
-		}
+		"playing": { "prefix": "" },
+		"paused": { "prefix": "" },
+		"stopped": { "prefix": "" },
+		"prev": { "prefix": "" },
+		"next": { "prefix": "" },
+		"shuffle-on": { "prefix": "" },
+		"shuffle-off": { "prefix": "" },
+		"repeat-on": { "prefix": "" },
+		"repeat-off": { "prefix": "" }
 	},
 	"pasink": {
-		"states": {
-			"muted": {
-				"prefix": ""
-			},
-			"unmuted": {
-				"prefix": ""
-			}
-		}
+		"muted": { "prefix": "" },
+		"unmuted": { "prefix": "" }
 	},
 	"pasource": {
-		"states": {
-			"muted": {
-				"prefix": ""
-			},
-			"unmuted": {
-				"prefix": ""
-			}
-		}
+		"muted": { "prefix": "" },
+		"unmuted": { "prefix": "" }
 	},
 	"nic": {
-		"states": {
-			"wireless-up": {
-				"prefix": ""
-			},
-			"wireless-down": {
-				"prefix": ""
-			},
-			"wired-up": {
-				"prefix": ""
-			},
-			"wired-down": {
-				"prefix": ""
-			},
-			"tunnel-up": {
-				"prefix": ""
-			},
-			"tunnel-down": {
-				"prefix": ""
-			}
-		}
+		"wireless-up": { "prefix": "" },
+		"wireless-down": { "prefix": "" },
+		"wired-up": { "prefix": "" },
+		"wired-down": { "prefix": "" },
+		"tunnel-up": { "prefix": "" },
+		"tunnel-down": { "prefix": "" }
 	},
 	"battery": {
-		"states": {
-			"charged": {
-				"prefix": "",
-				"suffix": ""
-			},
-			"AC": {
-				"suffix": ""
-			},
-			"charging": {
-				"prefix": [ "", "", "", "", "" ],
-				"suffix": ""
-			},
-			"discharging-10": {
-				"prefix": "",
-				"suffix": ""
-			},
-			"discharging-25": {
-				"prefix": "",
-				"suffix": ""
-			},
-			"discharging-50": {
-				"prefix": "",
-				"suffix": ""
-			},
-			"discharging-80": {
-				"prefix": "",
-				"suffix": ""
-			},
-			"discharging-100": {
-				"prefix": "",
-				"suffix": ""
-			}
-		}
+		"charged": { "prefix": "", "suffix": "" },
+		"AC": { "suffix": "" },
+		"charging": {
+			"prefix": [ "", "", "", "", "" ],
+			"suffix": ""
+		},
+		"discharging-10": { "prefix": "", "suffix": "" },
+		"discharging-25": { "prefix": "", "suffix": "" },
+		"discharging-50": { "prefix": "", "suffix": "" },
+		"discharging-80": { "prefix": "", "suffix": "" },
+		"discharging-100": { "prefix": "", "suffix": "" }
 	},
 	"caffeine": {
-		"states": { "activated": {"prefix": " " }, "deactivated": { "prefix": " " } }
+		"activated": {"prefix": " " }, "deactivated": { "prefix": " " }
 	},
 	"xrandr": {
-		"states": { "on": { "prefix": " "}, "off": { "prefix": " "} }
+		"on": { "prefix": " "}, "off": { "prefix": " "}
 	}
 }
diff --git a/themes/icons/test.json b/themes/icons/test.json
new file mode 100644
index 0000000..ad17178
--- /dev/null
+++ b/themes/icons/test.json
@@ -0,0 +1,6 @@
+{
+	"test-widget": {
+		"prefix": "widget-prefix",
+		"suffix": "widget-suffix"
+	}
+}
diff --git a/themes/invalid.json b/themes/invalid.json
new file mode 100644
index 0000000..d510f27
--- /dev/null
+++ b/themes/invalid.json
@@ -0,0 +1 @@
+this is really not json
diff --git a/themes/powerline.json b/themes/powerline.json
index bfec776..afea669 100644
--- a/themes/powerline.json
+++ b/themes/powerline.json
@@ -1,41 +1,40 @@
 {
 	"icons": [ "awesome-fonts" ],
 	"defaults": {
-		"cycle": [
-			{
-				"fg": "#ffd700",
-				"bg": "#d75f00"
-			},
-			{
-				"fg": "#ffffff",
-				"bg": "#0087af"
-			}
-		],
-		"fg-critical": "#ffffff",
-		"bg-critical": "#ff0000",
-		"fg-warning": "#d75f00",
-		"bg-warning": "#ffd700",
-
+		"critical": {
+			"fg": "#ffffff",
+			"bg": "#ff0000"
+		},
+		"warning": {
+			"fg": "#d75f00",
+			"bg": "#ffd700"
+		},
 		"default_separators": false
 	},
+	"cycle": [
+		{
+			"fg": "#ffd700",
+			"bg": "#d75f00"
+		},
+		{
+			"fg": "#ffffff",
+			"bg": "#0087af"
+		}
+	],
 	"dnf": {
-		"states": {
-			"good": {
-				"fg": "#494949",
-				"bg": "#41db00"
-			}
+		"good": {
+			"fg": "#494949",
+			"bg": "#41db00"
 		}
 	},
 	"battery": {
-		"states": {
-			"charged": {
-				"fg": "#494949",
-				"bg": "#41db00"
-			},
-			"AC": {
-				"fg": "#494949",
-				"bg": "#41db00"
-			}
+		"charged": {
+			"fg": "#494949",
+			"bg": "#41db00"
+		},
+		"AC": {
+			"fg": "#494949",
+			"bg": "#41db00"
 		}
 	}
 }
diff --git a/themes/solarized-powerline.json b/themes/solarized-powerline.json
index 998b7f4..cb9049b 100644
--- a/themes/solarized-powerline.json
+++ b/themes/solarized-powerline.json
@@ -1,42 +1,34 @@
 {
 	"icons": [ "awesome-fonts" ],
 	"defaults": {
-		"cycle": [
-			{
-				"fg": "#93a1a1",
-				"bg": "#002b36"
-			},
-			{
-				"fg": "#eee8d5",
-				"bg": "#586e75"
-			}
-		],
-		"fg-critical": "#002b36",
-		"bg-critical": "#dc322f",
-		"fg-warning": "#002b36",
-		"bg-warning": "#b58900",
-
-		"default-separators": false,
-		"separator-block-width": 0
+		"separator-block-width": 0,
+		"warning": {
+			"fg": "#002b36",
+			"bg": "#b58900"
+		},
+		"critical": {
+			"fg": "#002b36",
+			"bg": "#dc322f"
+		}
 	},
+	"cycle": [
+		{ "fg": "#93a1a1", "bg": "#002b36" },
+		{ "fg": "#eee8d5", "bg": "#586e75" }
+	],
 	"dnf": {
-		"states": {
-			"good": {
-				"fg": "#002b36",
-				"bg": "#859900"
-			}
+		"good": {
+			"fg": "#002b36",
+			"bg": "#859900"
 		}
 	},
 	"battery": {
-		"states": {
-			"charged": {
-				"fg": "#002b36",
-				"bg": "#859900"
-			},
-			"AC": {
-				"fg": "#002b36",
-				"bg": "#859900"
-			}
+		"charged": {
+			"fg": "#002b36",
+			"bg": "#859900"
+		},
+		"AC": {
+			"fg": "#002b36",
+			"bg": "#859900"
 		}
 	}
 }
diff --git a/themes/solarized.json b/themes/solarized.json
index 5cc8f86..2ea76c4 100644
--- a/themes/solarized.json
+++ b/themes/solarized.json
@@ -1,41 +1,41 @@
 {
 	"icons": [ "ascii" ],
 	"defaults": {
-		"cycle": [
-			{
-				"fg": "#93a1a1",
-				"bg": "#002b36"
-			},
-			{
-				"fg": "#eee8d5",
-				"bg": "#586e75"
-			}
-		],
-		"fg-critical": "#002b36",
-		"bg-critical": "#dc322f",
-		"fg-warning": "#002b36",
-		"bg-warning": "#b58900",
-
+		"critical": {
+			"fg": "#002b36",
+			"bg": "#dc322f"
+		},
+		"warning": {
+			"fg": "#002b36",
+			"bg": "#b58900"
+		},
 		"default_separators": false,
 		"separator": ""
 	},
+	"cycle": [
+		{
+			"fg": "#93a1a1",
+			"bg": "#002b36"
+		},
+		{
+			"fg": "#eee8d5",
+			"bg": "#586e75"
+		}
+	],
 	"dnf": {
-		"states": {
-			"good": {
-				"fg": "#002b36",
-				"bg": "#859900"
-			}
+		"good": {
+			"fg": "#002b36",
+			"bg": "#859900"
 		}
 	},
 	"battery": {
-		"states": {
-			"charged": {
-				"fg": "#002b36",
-				"bg": "#859900"
-			},
-			"AC": {
-				"fg": "#002b36",
-				"bg": "#859900"
-			}
+		"charged": {
+			"fg": "#002b36",
+			"bg": "#859900"
+		},
+		"AC": {
+			"fg": "#002b36",
+			"bg": "#859900"
+		}
 	}
 }
diff --git a/themes/test.json b/themes/test.json
new file mode 100644
index 0000000..401a234
--- /dev/null
+++ b/themes/test.json
@@ -0,0 +1,22 @@
+{
+	"icons": [ "test" ],
+	"defaults": {
+		"prefix": "default-prefix",
+		"suffix": "default-suffix",
+		"fg": "#000000",
+		"bg": "#111111",
+		"separator": " * ",
+		"separator-block-width": 10,
+		"critical": {
+			"fg": "#ffffff",
+			"bg": "#010101"
+		}
+	},
+	"test-widget": {
+		"fg": "#ababab",
+		"bg": "#222222",
+		"critical": {
+			"fg": "#bababa"
+		}
+	}
+}
diff --git a/themes/test_cycle.json b/themes/test_cycle.json
new file mode 100644
index 0000000..5fd7e1a
--- /dev/null
+++ b/themes/test_cycle.json
@@ -0,0 +1,18 @@
+{
+	"icons": [ "test" ],
+	"defaults": {
+		"prefix": "default-prefix",
+		"suffix": "default-suffix",
+		"fg": "#000000",
+		"bg": "#111111"
+	},
+	"cycle": [
+		{ "fg": "#aa0000" },
+		{ "fg": "#00aa00" },
+		{ "fg": "#0000aa" }
+	],
+	"test-widget": {
+		"fg": "#ababab",
+		"bg": "#222222"
+	}
+}