From 2e1880b85a02c716f4b1714fc800404c74b0b56b Mon Sep 17 00:00:00 2001
From: Aleix Pol <aleixpol@kde.org>
Date: Fri, 29 Mar 2019 18:43:43 +0100
Subject: [PATCH] Fix crash when using kwin on windowed mode

Summary:
Used to get:
`kwin_wayland: kwin/composite.cpp:646: void KWin::Compositor::aboutToSwapBuffers(): Assertion "!m_bufferSwapPending' failed."`

Test Plan: Ran `kwin_wayland --socket dave --output-count 2 konsole`

Reviewers: #kwin, zzag

Reviewed By: #kwin, zzag

Subscribers: zzag, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D20056
---
 plugins/platforms/wayland/egl_wayland_backend.cpp | 6 +++++-
 plugins/platforms/wayland/egl_wayland_backend.h   | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/plugins/platforms/wayland/egl_wayland_backend.cpp b/plugins/platforms/wayland/egl_wayland_backend.cpp
index 9113a96f33..74f285bfb1 100644
--- a/plugins/platforms/wayland/egl_wayland_backend.cpp
+++ b/plugins/platforms/wayland/egl_wayland_backend.cpp
@@ -289,7 +289,10 @@ void EglWaylandBackend::present()
 void EglWaylandBackend::presentOnSurface(EglWaylandOutput *output)
 {
     output->m_waylandOutput->surface()->setupFrameCallback();
-    Compositor::self()->aboutToSwapBuffers();
+    if (!m_swapping) {
+        m_swapping = true;
+        Compositor::self()->aboutToSwapBuffers();
+    }
 
     if (supportsBufferAge()) {
         eglSwapBuffers(eglDisplay(), output->m_eglSurface);
@@ -321,6 +324,7 @@ QRegion EglWaylandBackend::prepareRenderingFrame()
 {
     eglWaitNative(EGL_CORE_NATIVE_ENGINE);
     startRenderTimer();
+    m_swapping = false;
     return QRegion();
 }
 
diff --git a/plugins/platforms/wayland/egl_wayland_backend.h b/plugins/platforms/wayland/egl_wayland_backend.h
index 86b5c74e54..98a31b64c0 100644
--- a/plugins/platforms/wayland/egl_wayland_backend.h
+++ b/plugins/platforms/wayland/egl_wayland_backend.h
@@ -109,6 +109,7 @@ private:
     WaylandBackend *m_backend;
     QVector<EglWaylandOutput*> m_outputs;
     bool m_havePlatformBase;
+    bool m_swapping = false;
     friend class EglWaylandTexture;
 };