QXcbConnection::getTimestamp: do not return stale timestamp
requested to merge asturmlechner/qtbase:asturmlechner/QTBUG-56595-QXcbConnection-getTimestamp-no-stale-timestamp into kde/5.15
The problem is PropertyNotify event generated by
xcb_delete_property() at return could be reported as an actual
timestamp at next call due to a missing state filter.
Because PropertyNotify is generated even if an unchanged property
value is set we can get rid of this delete event easily.
This issue causes observable problems in kwin_x11 (KDE project) too.
Fixes: QTBUG-56595 Pick-to: 5.15 6.2 6.4 6.5 Change-Id: Ice6cfa934e3769d86e9f7264e369dc5918c8542a Reviewed-by: Giuseppe D'Angelo giuseppe.dangelo@kdab.com Reviewed-by: Liang Qi liang.qi@qt.io Reviewed-by: JiDe Zhang zhangjide@uniontech.com (cherry picked from commit 03ac8c73)