qWaitFor: Prevent being stuck in QCoreApplication::processEvents

When using the overload of QCoreApplication::processEvents that takes a
maxtime argument, the function will keep processing events until there
are no more events, or until it times out.

The problem is that the function doesn't distinguish between events that
were on the event queue when the function was called, and events generated
by processing events as part of its own execution. If for example a widget
calls update() in its paintEvent, the function will spin for the entire
duration of maxtime.

That doesn't work for qWaitFor, where we need to check the predicate
between each pass, so we use the overload of processEvents that doesn't
take a maxtime. That's fine, as we have our own timeout logic.

Change-Id: I9738d7d0187c36d4a5ddfcd3fd075b0bd84583c4
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 1 insertions, 0 deletions

diff --git a/tests/auto/widgets/effects/qgraphicseffect/tst_qgraphicseffect.cpp b/tests/auto/widgets/effects/qgraphicseffect/tst_qgraphicseffect.cpp
index 95662a49a0..c4b6e22c37 100644
--- a/tests/auto/widgets/effects/qgraphicseffect/tst_qgraphicseffect.cpp
+++ b/tests/auto/widgets/effects/qgraphicseffect/tst_qgraphicseffect.cpp
@@ -313,6 +313,7 @@ void tst_QGraphicsEffect::draw()
     view.show();
     QVERIFY(QTest::qWaitForWindowActive(&view));
     QTRY_VERIFY(item->numRepaints > 0);
+    QCoreApplication::processEvents(); // Process all queued paint events
     item->reset();
 
     // Make sure installing the effect triggers a repaint.