AnimatedSprite stops updating after it was hidden, even if it subsequently becomes visible.

AnimatedSprite stops updating after it was (indirectly, effectively) hidden, even if it subsequently becomes visible.

The change in dtdeclarative@f5e2783, which fixed QTBUG-55935, has also caused a regression. Once AnimatedSprite stops updating due to its effectiveVisible becoming false (e.g. parent component being hidden), it then doesn't resume updating even after effectiveVisible becomes true (e.g. parent component becoming visible).

Cause/Analysis

As far as I understood the code, the animation "loop" is driven by a call to QQuickAnimatedSprite::update, which results in QQuickAnimatedSprite::updatePaintNode being called on the next update. QQuickAnimatedSprite::updatePaintNode in turn calls QQuickAnimatedSprite::update, starting the next iteration.

The above fix replaced most calls to QQuickAnimatedSprite::update with QQuickAnimatedSprite::maybeUpdate, which only dispatches to update if the item is effectiveVisible.

When effectiveVisible becomes false, the update/updatePaintNode "loop" stops. However, when later effectiveVisible becomes true, there is no provision to restart it.

Patch

I have a patch in hand (attached to this ticket) that observes changes to ItemVisibleHasChange, and restarts the update loop. The patch was developed for v5.8.0-derived code for our embedded platform, but the same fix applies cleanly to 5.9 and 5.10.

I am more than happy to rebase and submit a pull request, and would appreciate quick direction as to which branch this should go into.
 

Workaround

In case anyone finds this bug and wants a silly (but reliable) workaround, this code in your AnimatedSprite does the trick:

    AnimatedSprite {
        ...
        onVisibleChanged: {
            // Workaround for a regression in f5e2783 (QTBUG-55935)
            // This restarts the update loop and resumes the animation
            if (visible) {
                paused = !paused;
                paused = !paused;
            }
        }
    }