Standard QT drag / drop event code to transfer data between widgets produces a combase error and causes GUI thread to stall. Reproducable in QT examples in both debug and release builds with MINGW and MSVC.
Reproducible when a drag event is in progress but it is not catageorized as one of the following:
In other words, if an item is dragged and mouse stops on the receiving widget.
Related QT forum post: