Fix getting last main window when it was closed.

Fixes #242.

qutebrowser/app.py

@@ -231,8 +231,8 @@ class Application(QApplication):
             window_to_raise = window
         else:
             try:
-                window = objreg.get('last-main-window')
-            except KeyError:
+                window = objreg.last_window()
+            except objreg.NoWindow:
                 # We can't display an error here because... duh, there is no
                 # window.
                 log.ipc.error("No main window found!")

qutebrowser/utils/objreg.py

@@ -45,6 +45,11 @@ class RegistryUnavailableError(Exception):
     pass
 
 
+class NoWindow(Exception):
+
+    """Exception raised by last_window if no window is available."""
+
+
 _UNSET = UnsetObject()
 
 
@@ -141,8 +146,8 @@ def _get_window_registry(window):
             win = get('last-focused-main-window')
         except KeyError:
             try:
-                win = get('last-main-window')
-            except KeyError:
+                win = last_window()
+            except NoWindow:
                 raise RegistryUnavailableError('window')
         assert hasattr(win, 'registry')
     else:
@@ -238,3 +243,12 @@ def dump_objects():
         for line in data:
             lines.append("    {}".format(line))
     return lines
+
+
+def last_window():
+    """Get the last opened window object."""
+    if not window_registry:
+        raise NoWindow()
+    else:
+        key = sorted(window_registry)[-1]
+        return window_registry[key]

qutebrowser/widgets/mainwindow.py

@@ -62,7 +62,6 @@ class MainWindow(QWidget):
         self.registry = objreg.ObjectRegistry()
         objreg.window_registry[win_id] = self
         objreg.register('main-window', self, scope='window', window=win_id)
-        objreg.register('last-main-window', self, update=True)
         tab_registry = objreg.ObjectRegistry()
         objreg.register('tab-registry', tab_registry, scope='window',
                         window=win_id)