There seems to be a regression in 5.12.0 (or perhaps in 5.11.2 / 5.11.3) that causes DragEnterEvents to not be accepted as intended. My code accepts the QDragEnterEvent, but by the time it returns to the application my event is no longer accepted. As a result, my QWidget subclass rejects all drag events.

The regression seems to be in QWidgetWindow::handleDragMoveEvent() in Qt 5.12.0. It looks like the edits QWidgetWindow::handleDragEnterEvent() (called by forwardEvent()) modify the "event" object, which then gets overwritten in handleDragMoveEvent().

(see qt-5-12-0 attachment, especially the right-hand portion of the screenshot)

This seems to work as intended in Qt 5.11.1, which has similar code within the QWidgetWindow::handleDragEnterMoveEvent() function but the Accepted attribute was correctly attributed to the "translated" object, which then gets copied to the "Event" object.

(see qt-5-11-1 attachment, especially the right-hand portion of the screenshot)

I haven't tested 5.11.2 or 5.11.3 to verify whether this regression is present there.