simple image slide show using property animations

[stevieC]

Thanks - d_stanz:
Rewrote the code as per your suggestion (much better) and although it made no difference to the operation of the animation your suggestion set me on the path to finding the issue. I then switched to debugging in visual studio code on windows (deploying to the pi later) rather than directly on the Raspberry pi. This showed that the animation was running in a separate thread second time around -- as result of using apscheduler and pydispatch to manage the timed image change. Worked perfectly when I got it running on the main thread. The apscheduler and pydispatch mechanism was carried over from a previous development of message Queue based sensor stations that don't have GUI components. Will now remove pydispatch and use signals /slots.
Thanks again

[d_stranz]

In Qt (at least the C++ implementation, which I am sure the Python implementation is just layered on top of), all GUI activity has to occur in the main thread (the one that holds the QApplication instance). You can do other Qt things in threads (like manipulate images and such) but when it comes to displaying them, that has to happen in the main thread.

[stevieC]

What was interesting this time was there was no exception raised, as has been true on the other occasions I have tried to update the ui from a different thread. That's why I thought it was my understanding rather than a problem with my code. Thanks