Fix shortcut to exit fullscreen mode (close #71)

Fix the shortcut for fullscreen mode to also exit it. Additionally fix
the shortcuts window to show the correct shortcut for fullscreen mode.

mcg/widgets.py

@@ -230,6 +230,10 @@ class Window():
         self._panel_action.set_enabled(False)
         self._panel_action.connect('change-state', self.on_menu_panel)
         self._appwindow.add_action(self._panel_action)
+        self._toggle_fullscreen_action = Gio.SimpleAction.new("toggle-fullscreen", None)
+        self._toggle_fullscreen_action.set_enabled(True)
+        self._toggle_fullscreen_action.connect('activate', self.on_menu_toggle_fullscreen)
+        self._appwindow.add_action(self._toggle_fullscreen_action)
 
 
     def get(self):
@@ -269,6 +273,14 @@ class Window():
         self._stack.set_visible_child(self._panels[int(value.get_string())].get())
 
 
+    def on_menu_toggle_fullscreen(self, action, value):
+        self._stack.set_visible_child(self._panels[Window._PANEL_INDEX_COVER].get())
+        if not self._state.get_property(WindowState.IS_FULLSCREENED):
+            self._appwindow.fullscreen()
+        else:
+            self._appwindow.unfullscreen()
+
+
     # HeaderBar callbacks
 
     def on_header_bar_stack_switched(self, widget):
@@ -1029,7 +1041,6 @@ class CoverPanel(GObject.GObject):
 
     def get_signal_handlers(self):
         return {
-            'on_cover-toolbar-fullscreen_clicked': self.on_fullscreen_clicked,
             'on_cover-box_button_press_event': self.on_cover_box_pressed,
             'on_cover-scroll_size_allocate': self.on_cover_size_allocate,
             'on_cover-songs_button_press_event': self.on_songs_start_change,
@@ -1037,10 +1048,6 @@ class CoverPanel(GObject.GObject):
         }
 
 
-    def on_fullscreen_clicked(self, widget):
-        self.emit('toggle-fullscreen')
-
-
     def on_cover_box_pressed(self, widget, event):
         if self._current_album and event.type == Gdk.EventType._2BUTTON_PRESS:
             self.emit('toggle-fullscreen')