Done in version 0.1.22: Changelog: * Added BackgroundUpdateIntervalSeconds setting to DateTime widget. If set the widget is updated every x seconds also when the lockscreen isn't visible, so that the time you see when you click the power button isn't too "old". As said in the changelog add Code: BackgroundUpdateIntervalSeconds=60 to your DateTime widget to let it update in background.
BackgroundUpdateIntervalSeconds=60
When does this happen (double buffering is enabled by default in QGraphicsView)?