UIKit changes the run-loop mode during scrolling to UITrackingMode, which presumably prioritizes touch events and other sources related to a smooth scrolling experience. It signals this change by interrupting the current run-loop pass, and the outer loop is responsible for re-entering the run-loop in the new mode. Failing to enter the run-loop with this new mode results in UIScrollViews losing their kinetic feel when flicking. This can be observed by e.g. bringing up the Emoji keyboard and scrolling it horizontally. We keep track of the current run-loop mode by listening for push and pop notifications on the UIApplication object. The current mode is then used in our Q_FOREVER-loop when re-entering CFRunLoopRunInMode. For now we don't add our posted event source or timer source to the new modes, under the assumption that the system prefers to limit the number of sources that will fire during scrolling. If this turns out to give a bad user-experience for Qt applications we should consider changing it. Change-Id: I3a612b3cfc77c74b658963057732dc4d61684df8 Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>