[core/theme] Better separator handling

Add a generic method to the theme to get the "previous" value of an
attribute.

core/output.py

@@ -44,7 +44,7 @@ class i3(object):
         return [{
             'full_text': self._theme.separator(),
             'color': self._theme.bg(widget),
-            'background': self._theme.prev_bg(widget),
+            'background': self._theme.bg('previous'),
             'separator': False,
             'separator_block_width': self._theme.separator_block_width(),
             'border_top': self._theme.border_top(),

core/theme.py

@@ -16,6 +16,8 @@ class Theme(object):
     def __init__(self, name='default', iconset='auto', raw_data=None):
         self.name = name
         self.__widget_count = 0
+        self.__previous = {}
+        self.__current = {}
         if raw_data:
             self.__data = raw_data
         else:
@@ -50,19 +52,20 @@ class Theme(object):
 
     def __start(self):
         self.__widget_count = 0
-
-    def prev_bg(self, widget):
-        if self.__widget_count == 0:
-            return None
-        self.__widget_count = self.__widget_count - 1
-        value = self.bg(widget)
-        self.__widget_count = self.__widget_count + 1
-        return value
+        self.__current.clear()
+        self.__previous.clear()
 
     def __next_widget(self):
         self.__widget_count = self.__widget_count + 1
+        self.__previous = dict(self.__current)
+        self.__current.clear()
 
     def __get(self, widget, key, default=None):
+        if widget and isinstance(widget, str):
+            # special handling
+            if widget == 'previous':
+                return self.__previous.get(key, None)
+
         value = default
 
         for option in ['defaults', 'cycle']:
@@ -71,6 +74,8 @@ class Theme(object):
                 if isinstance(tmp, list):
                     tmp = tmp[self.__widget_count % len(tmp)]
                 value = tmp.get(key, value)
+
+        self.__current[key] = value
         return value
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4

tests/core/test_theme.py

@@ -36,11 +36,11 @@ class theme(unittest.TestCase):
 
     def test_cycle(self):
         theme = core.theme.Theme(raw_data=self.cycleTheme)
-        self.assertEqual(None, theme.prev_bg(None))
+        self.assertEqual(None, theme.bg('previous'))
         self.assertEqual(self.cycleTheme['cycle'][0]['fg'], theme.fg())
         self.assertEqual(self.cycleTheme['cycle'][0]['bg'], theme.bg())
         core.event.trigger('next-widget')
-        self.assertEqual(self.cycleTheme['cycle'][0]['bg'], theme.prev_bg(None))
+        self.assertEqual(self.cycleTheme['cycle'][0]['bg'], theme.bg('previous'))
         core.event.trigger('next-widget')
         self.assertEqual(self.cycleTheme['cycle'][2]['fg'], theme.fg())
         self.assertEqual(self.cycleTheme['cycle'][2]['bg'], theme.bg())