xcb: Avoid repaint lags with DnD

The lags can be seen when dragged data is requested for a
MIME type. This leads to calling QXcbClipboard::waitForClipboardEvent()
which runs a loop in the GUI thread and processes events from
QXcbEventQueue. The loop ends when a corresponding event is
received, otherwise it makes a delay of 50 ms before the next
iteration.

Sync with QXcbEventQueue thread by QWaitCondition instead
of using the delay. This way the loop will end as soon as
possible and Expose events will be processed with minimal
delay.

Task-number: QTBUG-44849
Fixes: QTBUG-55442
Fixes: QTBUG-62344
Fixes: QTBUG-73253
Change-Id: Ie18d63b51a7260c83d53ffe1169b25e5135dd73b
Reviewed-by: Mikhail Svetkin <mikhail.svetkin@qt.io>
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

0 files changed, 0 insertions, 0 deletions