From a930e59fcf0f8f388d5b8168abf57d6061adda4c Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Tue, 18 Aug 2020 13:18:58 +0300
Subject: [PATCH] Revert "Don't flush in SurfaceInterface::frameRendered()"

This reverts commit 3cf004b68ef1df6e1d15f1746eafd779800b99d9.

Unfortunately, 3cf004b broke a couple of tests in kwin due to Qt not
emitting QAbstractEventDispatcher::aboutToBlock() signal when macros
such as QTRY_VERIFY() or QTRY_COMPARE() spin the event loop.
---
 src/wayland/surface_interface.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/wayland/surface_interface.cpp b/src/wayland/surface_interface.cpp
index 0a61f8ed6a..9587b1f382 100644
--- a/src/wayland/surface_interface.cpp
+++ b/src/wayland/surface_interface.cpp
@@ -426,6 +426,7 @@ QList<SurfaceInterface *> SurfaceInterface::surfaces()
 void SurfaceInterface::frameRendered(quint32 msec)
 {
     // notify all callbacks
+    const bool needsFlush = !d->current.frameCallbacks.isEmpty();
     while (!d->current.frameCallbacks.isEmpty()) {
         KWaylandFrameCallback *frameCallback = d->current.frameCallbacks.takeFirst();
         frameCallback->send_done(msec);
@@ -438,6 +439,9 @@ void SurfaceInterface::frameRendered(quint32 msec)
         }
         subSurface->d_func()->surface->frameRendered(msec);
     }
+    if (needsFlush)  {
+        client()->flush();
+    }
 }
 
 QMatrix4x4 SurfaceInterfacePrivate::buildSurfaceToBufferMatrix(const State *state)