1. Have a project running some animation a QmlApplicationViewer. I attached an example.
2. Compile, link, run. See the animation moving.
3. Drag the lower right corner of the window to resize. Quickly move the mouse to the lower right corner of the screen and release the mouse button while moving. Maybe you'll have to try it several times.

The Animation will stop. An event filter installed on the QmlApplicationViewer will not show any new events. When the mouse pointer enters the window the animation and the events will start moving again.