skins2: fix maximizing a window in a multi-screen context.

The current screen in a multi-screen config is chosen to
  maximize the window instead of the default main screen.

  This fixes trac #16500

modules/gui/skins2/src/window_manager.cpp

@@ -325,7 +325,11 @@ void WindowManager::maximize( TopWindow &rWindow )
                                rWindow.getLeft() + rWindow.getWidth(),
                                rWindow.getTop() + rWindow.getHeight() );
 
-    SkinsRect workArea = OSFactory::instance( getIntf() )->getWorkArea();
+    // maximise the window within the current screen (multiple screens allowed)
+    int x, y, width, height;
+    rWindow.getMonitorInfo( &x, &y, &width, &height );
+    SkinsRect workArea(x, y, x + width, y + height);
+
     // Move the window
     startMove( rWindow );
     move( rWindow, workArea.getLeft(), workArea.getTop() );