From 53f6a337bf41a62588c971ba85ad0be1dbfb956f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Fl=C3=B6ser?= <mgraesslin@kde.org>
Date: Sun, 5 Nov 2017 11:07:04 +0100
Subject: [PATCH] Force Software QtQuick rendering when starting with QPainter
 compositor

Summary:
If KWin/Wayland starts up with the QPainter compositor we force software
rendering in QtQuick. It doesn't make sense to try to use the OpenGL
renderer as that normally just results in an abort when trying to create
the QOpenGLContext.

Test Plan:
Run KWin with KWIN_COMPOSE=Q, tried to quick tile a window and
used Alt+Tab. Worked fine, didn't crash anymore.

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D8663
---
 composite.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/composite.cpp b/composite.cpp
index 4d71bb5a5b..9cb2b389e0 100644
--- a/composite.cpp
+++ b/composite.cpp
@@ -50,6 +50,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QTimerEvent>
 #include <QDateTime>
 #include <QOpenGLContext>
+#include <QQuickWindow>
 #include <KGlobalAccel>
 #include <KLocalizedString>
 #include <KPluginLoader>
@@ -254,6 +255,12 @@ void Compositor::slotCompositingOptionsInitialized()
         }
         return;
     }
+
+    if (!Workspace::self() && m_scene && m_scene->compositingType() == QPainterCompositing) {
+        // Force Software QtQuick on first startup with QPainter
+        QQuickWindow::setSceneGraphBackend(QSGRendererInterface::Software);
+    }
+
     connect(m_scene, &Scene::resetCompositing, this, &Compositor::restart);
     emit sceneCreated();