Hi,

The drag of a tab isn't correctly handle in your patch :
You have to call startDragging() directly in mouseMoveEvent() instead
of leaveEvent(). To achieve that, you have to store the position of
the click (in mousePressEvent) in a QPoint.
Then, you compare the difference between the old and the new position
(in mouseMoveEvent). If it's greater than QApplication::dragDistance()
you can start the drag.

For more information, you can look the dragging code in the
BookmarkToolBar class. (line 400)

After modifying that, every drag is successfully dropped (in the BK
toolbar and the webview). Then for change the tab order inside the
QListWidget, I think you have to reimplement
QListWidget::dropMimeData(...) instead of dropEvent.

Regards.