QEventDispatcherWin32: retrieve PM_REMOVE value as a bit flag

Windows unexpectedly passes PM_NOYIELD flag in wParam parameter to the
hook procedure, if ::PeekMessage(..., PM_REMOVE | PM_NOYIELD) is called
from the event loop. So, to ignore undocumented flag, we should
interpret wParam as a bit field.

Thanks to Robin Lobel for research.

Pick-to: 5.15
Fixes: QTBUG-84562
Change-Id: Ib16d7d747aebc9a3628e4ee67478c4d3edeb96f1
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/corelib/kernel/qeventdispatcher_win.cpp b/src/corelib/kernel/qeventdispatcher_win.cpp
index d9b9d84e41..43872fd027 100644
--- a/src/corelib/kernel/qeventdispatcher_win.cpp
+++ b/src/corelib/kernel/qeventdispatcher_win.cpp
@@ -277,9 +277,13 @@ LRESULT QT_WIN_CALLBACK qt_GetMessageHook(int code, WPARAM wp, LPARAM lp)
     Q_ASSERT(q != 0);
     QEventDispatcherWin32Private *d = q->d_func();
     MSG *msg = reinterpret_cast<MSG *>(lp);
+    // Windows unexpectedly passes PM_NOYIELD flag to the hook procedure,
+    // if ::PeekMessage(..., PM_REMOVE | PM_NOYIELD) is called from the event loop.
+    // So, retrieve 'removed' tag as a bit field.
+    const bool messageRemoved = (wp & PM_REMOVE) != 0;
 
     if (msg->hwnd == d->internalHwnd && msg->message == WM_QT_SENDPOSTEDEVENTS
-        && wp == PM_REMOVE && d->sendPostedEventsTimerId == 0) {
+        && messageRemoved && d->sendPostedEventsTimerId == 0) {
         // Start a timer to deliver posted events when the message queue is emptied.
         d->sendPostedEventsTimerId = SetTimer(d->internalHwnd, SendPostedEventsTimerId,
                                               USER_TIMER_MINIMUM, NULL);