[modules/battery] Fix ac and unknown display

If the computer runs on AC, display that instead of showing "100%" in
the status.

Also, if reading the charging status fails for some reason (except the
computer being on AC), go into critical state and display "n/a".

see #23

bumblebee/modules/battery.py

@@ -19,11 +19,15 @@ class Module(bumblebee.engine.Module):
         super(Module, self).__init__(engine, config,
             bumblebee.output.Widget(full_text=self.capacity)
         )
-        battery = self.parameter("device", "BAT1")
+        battery = self.parameter("device", "BAT0")
         self._path = "/sys/class/power_supply/{}".format(battery)
         self._capacity = 100
 
     def capacity(self):
+        if self._ac:
+            return "ac"
+        if self._capacity == -1:
+            return "n/a"
         return "{:03d}%".format(self._capacity)
 
     def update(self, widgets):
@@ -31,16 +35,22 @@ class Module(bumblebee.engine.Module):
         self._ac = False
         if not os.path.exists(self._path):
             self._ac = True
+            self._capacity = 100
+            return
 
         try:
             with open(self._path + "/capacity") as f:
                 self._capacity = int(f.read())
         except IOError:
-            self._capacity = 100
+            self._capacity = -1
         self._capacity = self._capacity if self._capacity < 100 else 100
 
     def state(self, widget):
         state = []
+
+        if self._capacity < 0:
+            return ["critical", "unknown"]
+
         if self._capacity < int(self.parameter("critical", 10)):
             state.append("critical")
         elif self._capacity < int(self.parameter("warning", 20)):

bumblebee/theme.py

@@ -121,8 +121,9 @@ class Theme(object):
 
         state_themes = []
         # avoid infinite recursion
-        if name not in widget.state():
-            for state in widget.state():
+        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)

themes/icons/awesome-fonts.json

@@ -1,5 +1,8 @@
 {
-	"defaults": { "separator": "", "padding": " " },
+	"defaults": {
+		"separator": "", "padding": " ",
+		"unknown": { "prefix": "" }
+	},
 	"date": { "prefix": ""	},
 	"time": { "prefix": "" },
 	"memory": { "prefix": "" },