Revert "Client: Remove mWaitingForUpdateDelivery"

The reverted commit introduces a severe performance regression
when a client window is resized while a QtQuick renderthread
animation is running.

This reverts commit feb1a5c207c13d0bf87c0d8ad039279dbf8cee9e.

Fixes: QTBUG-101726
Change-Id: Ib5b52ce06efec8c86fada1623c2af82099e57fc6
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

2 files changed, 9 insertions, 3 deletions

diff --git a/src/client/qwaylandwindow.cpp b/src/client/qwaylandwindow.cpp
index 1ede38275..05e7160be 100644
--- a/src/client/qwaylandwindow.cpp
+++ b/src/client/qwaylandwindow.cpp
@@ -716,9 +716,12 @@ void QWaylandWindow::handleFrameCallback()
     mFrameCallbackElapsedTimer.invalidate();
 
     // The rest can wait until we can run it on the correct thread
-    // Queued connection, to make sure we don't call handleUpdate() from inside waitForFrameSync()
-    // in the single-threaded case.
-    QMetaObject::invokeMethod(this, &QWaylandWindow::doHandleFrameCallback, Qt::QueuedConnection);
+    if (!mWaitingForUpdateDelivery) {
+        // Queued connection, to make sure we don't call handleUpdate() from inside waitForFrameSync()
+        // in the single-threaded case.
+        mWaitingForUpdateDelivery = true;
+        QMetaObject::invokeMethod(this, &QWaylandWindow::doHandleFrameCallback, Qt::QueuedConnection);
+    }
 
     mFrameSyncWait.notify_all();
 }
@@ -731,6 +734,8 @@ void QWaylandWindow::doHandleFrameCallback()
         sendExposeEvent(QRect(QPoint(), geometry().size()));
     if (wasExposed && hasPendingUpdateRequest())
         deliverUpdateRequest();
+
+    mWaitingForUpdateDelivery = false;
 }
 
 bool QWaylandWindow::waitForFrameSync(int timeout)
diff --git a/src/client/qwaylandwindow_p.h b/src/client/qwaylandwindow_p.h
index 4bbcc93c3..d8eebb738 100644
--- a/src/client/qwaylandwindow_p.h
+++ b/src/client/qwaylandwindow_p.h
@@ -283,6 +283,7 @@ protected:
     WId mWindowId;
     bool mWaitingForFrameCallback = false;
     bool mFrameCallbackTimedOut = false; // Whether the frame callback has timed out
+    bool mWaitingForUpdateDelivery = false;
     int mFrameCallbackCheckIntervalTimerId = -1;
     QElapsedTimer mFrameCallbackElapsedTimer;
     struct ::wl_callback *mFrameCallback = nullptr;