[modules/disk] Re-enable disk usage module

Add a module that shows the disk usage for various paths and opens
nautilus on that path whenever it is clicked.

see #23

bumblebee/modules/disk.py

@@ -0,0 +1,50 @@
+# 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.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.diskspace)
+        )
+        self._path = self.parameter("path", "/")
+        self._perc = 0
+
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE,
+            cmd="nautilus {}".format(self._path))
+
+    def diskspace(self):
+        st = os.statvfs(self._path)
+        size = st.f_frsize*st.f_blocks
+        used = size - st.f_frsize*st.f_bavail
+        self._perc = 100.0*used/size
+
+        return "{} {}/{} ({:05.02f}%)".format(self._path,
+            bumblebee.util.bytefmt(used),
+            bumblebee.util.bytefmt(size), self._perc
+        )
+
+    def update(self, widgets):
+        pass
+
+    def state(self, widget):
+        pass
+    def warning(self, widget):
+        return self._perc > self._config.parameter("warning", 80)
+
+    def critical(self, widget):
+        return self._perc > self._config.parameter("critical", 90)
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4