Refactored ScreenList into a true Pythonic singleton, though I sadly had to go with a "create" classmethod in order to retain the functionality of the previous constructor..

openlp/core/__init__.py

@@ -109,7 +109,7 @@ class OpenLP(QtGui.QApplication):
         QtCore.QObject.connect(Receiver.get_receiver(),
             QtCore.SIGNAL(u'cursor_normal'), self.setNormalCursor)
         # Decide how many screens we have and their size
-        screens = ScreenList(self.desktop())
+        screens = ScreenList.create(self.desktop())
         # First time checks in settings
         has_run_wizard = QtCore.QSettings().value(
             u'general/has run wizard', QtCore.QVariant(False)).toBool()

openlp/core/lib/dockwidget.py

@@ -52,7 +52,7 @@ class OpenLPDockWidget(QtGui.QDockWidget):
         if icon:
             self.setWindowIcon(build_icon(icon))
         # Sort out the minimum width.
-        screens = ScreenList.get_instance()
+        screens = ScreenList()
         mainwindow_docbars = screens.current[u'size'].width() / 5
         if mainwindow_docbars > 300:
             self.setMinimumWidth(300)

openlp/core/lib/imagemanager.py

@@ -163,7 +163,7 @@ class ImageManager(QtCore.QObject):
 
     def __init__(self):
         QtCore.QObject.__init__(self)
-        current_screen = ScreenList.get_instance().current
+        current_screen = ScreenList().current
         self.width = current_screen[u'size'].width()
         self.height = current_screen[u'size'].height()
         self._cache = {}
@@ -177,7 +177,7 @@ class ImageManager(QtCore.QObject):
         Screen has changed size so rebuild the cache to new size.
         """
         log.debug(u'update_display')
-        current_screen = ScreenList.get_instance().current
+        current_screen = ScreenList().current
         self.width = current_screen[u'size'].width()
         self.height = current_screen[u'size'].height()
         # Mark the images as dirty for a rebuild by setting the image and byte

openlp/core/lib/renderer.py

@@ -69,7 +69,7 @@ class Renderer(object):
         log.debug(u'Initialisation started')
         self.themeManager = themeManager
         self.imageManager = imageManager
-        self.screens = ScreenList.get_instance()
+        self.screens = ScreenList()
         self.service_theme = u''
         self.theme_level = u''
         self.override_background = None

openlp/core/ui/generaltab.py

@@ -42,7 +42,7 @@ class GeneralTab(SettingsTab):
         """
         Initialise the general settings tab
         """
-        self.screens = ScreenList.get_instance()
+        self.screens = ScreenList()
         self.iconPath = u':/icon/openlp-logo-16x16.png'
         generalTranslated = translate('OpenLP.GeneralTab', 'General')
         SettingsTab.__init__(self, parent, u'General', generalTranslated)

openlp/core/ui/maindisplay.py

@@ -119,7 +119,7 @@ class MainDisplay(Display):
     def __init__(self, parent, imageManager, live, controller):
         Display.__init__(self, parent, live, controller)
         self.imageManager = imageManager
-        self.screens = ScreenList.get_instance()
+        self.screens = ScreenList()
         self.plugins = PluginManager.get_instance().plugins
         self.rebuildCSS = False
         self.hideMode = None

openlp/core/ui/mainwindow.py

@@ -795,7 +795,7 @@ class MainWindow(QtGui.QMainWindow, Ui_MainWindow):
         if answer == QtGui.QMessageBox.No:
             return
         Receiver.send_message(u'cursor_busy')
-        screens = ScreenList.get_instance()
+        screens = ScreenList()
         FirstTimeForm(screens, self).exec_()
         self.firstTime()
         for plugin in self.pluginManager.plugins:

openlp/core/ui/screen.py

@@ -41,36 +41,40 @@ class ScreenList(object):
     """
     Wrapper to handle the parameters of the display screen.
 
-    To get access to the screen list call ``ScreenList.get_instance()``.
+    To get access to the screen list call ``ScreenList()``.
     """
     log.info(u'Screen loaded')
-    instance = None
+    __instance__ = None
 
-    @staticmethod
-    def get_instance():
-        return ScreenList.instance
+    def __new__(cls):
+        if not cls.__instance__:
+            cls.__instance__ = object.__new__(cls)
+        return cls.__instance__
 
-    def __init__(self, desktop):
+    @classmethod
+    def create(cls, desktop):
         """
         Initialise the screen list.
 
         ``desktop``
             A ``QDesktopWidget`` object.
         """
-        ScreenList.instance = self
-        self.desktop = desktop
-        self.preview = None
-        self.current = None
-        self.override = None
-        self.screen_list = []
-        self.display_count = 0
-        self.screen_count_changed()
-        self._load_screen_settings()
+        screen_list = cls()
+        screen_list.desktop = desktop
+        screen_list.preview = None
+        screen_list.current = None
+        screen_list.override = None
+        screen_list.screen_list = []
+        screen_list.display_count = 0
+        screen_list.screen_count_changed()
+        screen_list._load_screen_settings()
         QtCore.QObject.connect(desktop,
-            QtCore.SIGNAL(u'resized(int)'), self.screen_resolution_changed)
+            QtCore.SIGNAL(u'resized(int)'),
+            screen_list.screen_resolution_changed)
         QtCore.QObject.connect(desktop,
             QtCore.SIGNAL(u'screenCountChanged(int)'),
-            self.screen_count_changed)
+            screen_list.screen_count_changed)
+        return screen_list
 
     def screen_resolution_changed(self, number):
         """
@@ -233,8 +237,8 @@ class ScreenList(object):
         y = window.y() + (window.height() / 2)
         for screen in self.screen_list:
             size = screen[u'size']
-            if x >= size.x() and x <= (size.x() + size.width()) \
-                and y >= size.y() and y <= (size.y() + size.height()):
+            if x >= size.x() and x <= (size.x() + size.width()) and \
+                y >= size.y() and y <= (size.y() + size.height()):
                 return screen[u'number']
 
     def _load_screen_settings(self):

openlp/core/ui/slidecontroller.py

@@ -83,7 +83,7 @@ class SlideController(Controller):
         Set up the Slide Controller.
         """
         Controller.__init__(self, parent, isLive)
-        self.screens = ScreenList.get_instance()
+        self.screens = ScreenList()
         try:
             self.ratio = float(self.screens.current[u'size'].width()) / \
                 float(self.screens.current[u'size'].height())