diff --git a/autotests/integration/generic_scene_opengl_test.cpp b/autotests/integration/generic_scene_opengl_test.cpp
index ff13007b8..33a9cf48d 100644
--- a/autotests/integration/generic_scene_opengl_test.cpp
+++ b/autotests/integration/generic_scene_opengl_test.cpp
@@ -1,118 +1,120 @@
 /********************************************************************
 KWin - the KDE window manager
 This file is part of the KDE project.
 
 Copyright (C) 2016 Martin Gräßlin <mgraesslin@kde.org>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #include "generic_scene_opengl_test.h"
 #include "composite.h"
 #include "effectloader.h"
 #include "cursor.h"
 #include "platform.h"
 #include "scene.h"
 #include "shell_client.h"
 #include "wayland_server.h"
 #include "effect_builtins.h"
 
 #include <KConfigGroup>
 
 using namespace KWin;
 static const QString s_socketName = QStringLiteral("wayland_test_kwin_scene_opengl-0");
 
 GenericSceneOpenGLTest::GenericSceneOpenGLTest(const QByteArray &envVariable)
     : QObject()
     , m_envVariable(envVariable)
 {
 }
 
 GenericSceneOpenGLTest::~GenericSceneOpenGLTest()
 {
 }
 
 void GenericSceneOpenGLTest::cleanup()
 {
     Test::destroyWaylandConnection();
 }
 
 void GenericSceneOpenGLTest::initTestCase()
 {
     qRegisterMetaType<KWin::ShellClient*>();
     qRegisterMetaType<KWin::AbstractClient*>();
     QSignalSpy workspaceCreatedSpy(kwinApp(), &Application::workspaceCreated);
     QVERIFY(workspaceCreatedSpy.isValid());
     kwinApp()->platform()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName.toLocal8Bit()));
 
     // disable all effects - we don't want to have it interact with the rendering
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup plugins(config, QStringLiteral("Plugins"));
     ScriptedEffectLoader loader;
     const auto builtinNames = BuiltInEffects::availableEffectNames() << loader.listOfKnownEffects();
     for (QString name : builtinNames) {
         plugins.writeEntry(name + QStringLiteral("Enabled"), false);
     }
 
     config->sync();
     kwinApp()->setConfig(config);
 
     qputenv("XCURSOR_THEME", QByteArrayLiteral("DMZ-White"));
     qputenv("XCURSOR_SIZE", QByteArrayLiteral("24"));
     qputenv("KWIN_COMPOSE", m_envVariable);
 
     kwinApp()->start();
     QVERIFY(workspaceCreatedSpy.wait());
     QVERIFY(Compositor::self());
 
     auto scene = KWin::Compositor::self()->scene();
     QVERIFY(scene);
     QCOMPARE(scene->compositingType(), KWin::OpenGL2Compositing);
+    QCOMPARE(kwinApp()->platform()->selectedCompositor(), KWin::OpenGLCompositing);
 }
 
 void GenericSceneOpenGLTest::testRestart_data()
 {
     QTest::addColumn<bool>("core");
 
     QTest::newRow("GLCore") << true;
     QTest::newRow("Legacy") << false;
 }
 
 void GenericSceneOpenGLTest::testRestart()
 {
     // simple restart of the OpenGL compositor without any windows being shown
 
     // setup opengl compositing options
     auto compositingGroup = kwinApp()->config()->group("Compositing");
     QFETCH(bool, core);
     compositingGroup.writeEntry("GLCore", core);
     compositingGroup.sync();
 
     QSignalSpy sceneCreatedSpy(KWin::Compositor::self(), &Compositor::sceneCreated);
     QVERIFY(sceneCreatedSpy.isValid());
     KWin::Compositor::self()->slotReinitialize();
     if (sceneCreatedSpy.isEmpty()) {
         QVERIFY(sceneCreatedSpy.wait());
     }
     QCOMPARE(sceneCreatedSpy.count(), 1);
     auto scene = KWin::Compositor::self()->scene();
     QVERIFY(scene);
     QCOMPARE(scene->compositingType(), KWin::OpenGL2Compositing);
+    QCOMPARE(kwinApp()->platform()->selectedCompositor(), KWin::OpenGLCompositing);
 
     // trigger a repaint
     KWin::Compositor::self()->addRepaintFull();
     // and wait 100 msec to ensure it's rendered
     // TODO: introduce frameRendered signal in SceneOpenGL
     QTest::qWait(100);
 }
diff --git a/autotests/integration/scene_qpainter_test.cpp b/autotests/integration/scene_qpainter_test.cpp
index a887fe1ca..61ff40e0c 100644
--- a/autotests/integration/scene_qpainter_test.cpp
+++ b/autotests/integration/scene_qpainter_test.cpp
@@ -1,396 +1,397 @@
 /********************************************************************
 KWin - the KDE window manager
 This file is part of the KDE project.
 
 Copyright (C) 2016 Martin Gräßlin <mgraesslin@kde.org>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #include "kwin_wayland_test.h"
 #include "composite.h"
 #include "effectloader.h"
 #include "client.h"
 #include "cursor.h"
 #include "effects.h"
 #include "platform.h"
 #include "shell_client.h"
 #include "wayland_server.h"
 #include "effect_builtins.h"
 #include "workspace.h"
 
 #include <KConfigGroup>
 
 #include <KWayland/Client/seat.h>
 #include <KWayland/Client/shell.h>
 #include <KWayland/Client/surface.h>
 #include <KWayland/Client/pointer.h>
 #include <KWayland/Server/buffer_interface.h>
 #include <KWayland/Server/surface_interface.h>
 
 #include <QPainter>
 
 #include <netwm.h>
 #include <xcb/xcb_icccm.h>
 
 using namespace KWin;
 static const QString s_socketName = QStringLiteral("wayland_test_kwin_scene_qpainter-0");
 
 class SceneQPainterTest : public QObject
 {
 Q_OBJECT
 private Q_SLOTS:
     void initTestCase();
     void cleanup();
     void testStartFrame();
     void testCursorMoving();
     void testWindow_data();
     void testWindow();
     void testWindowScaled();
     void testCompositorRestart_data();
     void testCompositorRestart();
     void testX11Window();
 };
 
 void SceneQPainterTest::cleanup()
 {
     Test::destroyWaylandConnection();
 }
 
 void SceneQPainterTest::initTestCase()
 {
     qRegisterMetaType<KWin::ShellClient*>();
     qRegisterMetaType<KWin::AbstractClient*>();
     QSignalSpy workspaceCreatedSpy(kwinApp(), &Application::workspaceCreated);
     QVERIFY(workspaceCreatedSpy.isValid());
     kwinApp()->platform()->setInitialWindowSize(QSize(1280, 1024));
     QVERIFY(waylandServer()->init(s_socketName.toLocal8Bit()));
 
     // disable all effects - we don't want to have it interact with the rendering
     auto config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
     KConfigGroup plugins(config, QStringLiteral("Plugins"));
     ScriptedEffectLoader loader;
     const auto builtinNames = BuiltInEffects::availableEffectNames() << loader.listOfKnownEffects();
     for (QString name : builtinNames) {
         plugins.writeEntry(name + QStringLiteral("Enabled"), false);
     }
 
     config->sync();
     kwinApp()->setConfig(config);
 
     if (!QStandardPaths::locateAll(QStandardPaths::GenericDataLocation, QStringLiteral("icons/DMZ-White/index.theme")).isEmpty()) {
         qputenv("XCURSOR_THEME", QByteArrayLiteral("DMZ-White"));
     } else {
         // might be vanilla-dmz (e.g. Arch, FreeBSD)
         qputenv("XCURSOR_THEME", QByteArrayLiteral("Vanilla-DMZ"));
     }
     qputenv("XCURSOR_SIZE", QByteArrayLiteral("24"));
     qputenv("KWIN_COMPOSE", QByteArrayLiteral("Q"));
 
     kwinApp()->start();
     QVERIFY(workspaceCreatedSpy.wait());
     QVERIFY(Compositor::self());
 }
 
 void SceneQPainterTest::testStartFrame()
 {
     // this test verifies that the initial rendering is correct
     Compositor::self()->addRepaintFull();
     auto scene = Compositor::self()->scene();
     QVERIFY(scene);
+    QCOMPARE(kwinApp()->platform()->selectedCompositor(), QPainterCompositing);
     QSignalSpy frameRenderedSpy(scene, &Scene::frameRendered);
     QVERIFY(frameRenderedSpy.isValid());
     QVERIFY(frameRenderedSpy.wait());
     // now let's render a reference image for comparison
     QImage referenceImage(QSize(1280, 1024), QImage::Format_RGB32);
     referenceImage.fill(Qt::black);
     QPainter p(&referenceImage);
     const QImage cursorImage = kwinApp()->platform()->softwareCursor();
     QVERIFY(!cursorImage.isNull());
     p.drawImage(KWin::Cursor::pos() - kwinApp()->platform()->softwareCursorHotspot(), cursorImage);
     QCOMPARE(referenceImage, *scene->qpainterRenderBuffer());
 }
 
 void SceneQPainterTest::testCursorMoving()
 {
     // this test verifies that rendering is correct also after moving the cursor a few times
     auto scene = Compositor::self()->scene();
     QVERIFY(scene);
     QSignalSpy frameRenderedSpy(scene, &Scene::frameRendered);
     QVERIFY(frameRenderedSpy.isValid());
     KWin::Cursor::setPos(0, 0);
     QVERIFY(frameRenderedSpy.wait());
     KWin::Cursor::setPos(10, 0);
     QVERIFY(frameRenderedSpy.wait());
     KWin::Cursor::setPos(10, 12);
     QVERIFY(frameRenderedSpy.wait());
     KWin::Cursor::setPos(12, 14);
     QVERIFY(frameRenderedSpy.wait());
     KWin::Cursor::setPos(50, 60);
     QVERIFY(frameRenderedSpy.wait());
     KWin::Cursor::setPos(45, 45);
     QVERIFY(frameRenderedSpy.wait());
     // now let's render a reference image for comparison
     QImage referenceImage(QSize(1280, 1024), QImage::Format_RGB32);
     referenceImage.fill(Qt::black);
     QPainter p(&referenceImage);
     const QImage cursorImage = kwinApp()->platform()->softwareCursor();
     QVERIFY(!cursorImage.isNull());
     p.drawImage(QPoint(45, 45) - kwinApp()->platform()->softwareCursorHotspot(), cursorImage);
     QCOMPARE(referenceImage, *scene->qpainterRenderBuffer());
 }
 
 void SceneQPainterTest::testWindow_data()
 {
     QTest::addColumn<Test::ShellSurfaceType>("type");
 
     QTest::newRow("wlShell") << Test::ShellSurfaceType::WlShell;
     QTest::newRow("xdgShellV5") << Test::ShellSurfaceType::XdgShellV5;
     QTest::newRow("xdgShellV6") << Test::ShellSurfaceType::XdgShellV6;
     QTest::newRow("xdgWmBase") << Test::ShellSurfaceType::XdgShellStable;
 }
 
 void SceneQPainterTest::testWindow()
 {
     KWin::Cursor::setPos(45, 45);
     // this test verifies that a window is rendered correctly
     using namespace KWayland::Client;
     QVERIFY(Test::setupWaylandConnection(Test::AdditionalWaylandInterface::Seat));
     QVERIFY(Test::waitForWaylandPointer());
     QScopedPointer<Surface> s(Test::createSurface());
     QFETCH(Test::ShellSurfaceType, type);
     QScopedPointer<QObject> ss(Test::createShellSurface(type, s.data()));
     QScopedPointer<Pointer> p(Test::waylandSeat()->createPointer());
 
     auto scene = KWin::Compositor::self()->scene();
     QVERIFY(scene);
     QSignalSpy frameRenderedSpy(scene, &Scene::frameRendered);
     QVERIFY(frameRenderedSpy.isValid());
 
     // now let's map the window
     QVERIFY(Test::renderAndWaitForShown(s.data(), QSize(200, 300), Qt::blue));
     // which should trigger a frame
     if (frameRenderedSpy.isEmpty()) {
         QVERIFY(frameRenderedSpy.wait());
     }
     // we didn't set a cursor image on the surface yet, so it should be just black + window and previous cursor
     QImage referenceImage(QSize(1280, 1024), QImage::Format_RGB32);
     referenceImage.fill(Qt::black);
     QPainter painter(&referenceImage);
     painter.fillRect(0, 0, 200, 300, Qt::blue);
 
     // now let's set a cursor image
     QScopedPointer<Surface> cs(Test::createSurface());
     QVERIFY(!cs.isNull());
     Test::render(cs.data(), QSize(10, 10), Qt::red);
     p->setCursor(cs.data(), QPoint(5, 5));
     QVERIFY(frameRenderedSpy.wait());
     painter.fillRect(KWin::Cursor::pos().x() - 5, KWin::Cursor::pos().y() - 5, 10, 10, Qt::red);
     QCOMPARE(referenceImage, *scene->qpainterRenderBuffer());
     // let's move the cursor again
     KWin::Cursor::setPos(10, 10);
     QVERIFY(frameRenderedSpy.wait());
     painter.fillRect(0, 0, 200, 300, Qt::blue);
     painter.fillRect(5, 5, 10, 10, Qt::red);
     QCOMPARE(referenceImage, *scene->qpainterRenderBuffer());
 }
 
 void SceneQPainterTest::testWindowScaled()
 {
     KWin::Cursor::setPos(10, 10);
     // this test verifies that a window is rendered correctly
     using namespace KWayland::Client;
     QVERIFY(Test::setupWaylandConnection(Test::AdditionalWaylandInterface::Seat));
     QVERIFY(Test::waitForWaylandPointer());
     QScopedPointer<Surface> s(Test::createSurface());
     QScopedPointer<ShellSurface> ss(Test::createShellSurface(s.data()));
     QScopedPointer<Pointer> p(Test::waylandSeat()->createPointer());
     QSignalSpy pointerEnteredSpy(p.data(), &Pointer::entered);
     QVERIFY(pointerEnteredSpy.isValid());
 
     auto scene = KWin::Compositor::self()->scene();
     QVERIFY(scene);
     QSignalSpy frameRenderedSpy(scene, &Scene::frameRendered);
     QVERIFY(frameRenderedSpy.isValid());
 
     // now let's set a cursor image
     QScopedPointer<Surface> cs(Test::createSurface());
     QVERIFY(!cs.isNull());
     Test::render(cs.data(), QSize(10, 10), Qt::red);
 
     // now let's map the window
     s->setScale(2);
 
     //draw a blue square@400x600 with red rectangle@200x200 in the middle
     const QSize size(400,600);
     QImage img(size, QImage::Format_ARGB32_Premultiplied);
     img.fill(Qt::blue);
     QPainter surfacePainter(&img);
     surfacePainter.fillRect(200,300,200,200, Qt::red);
 
     //add buffer
     Test::render(s.data(), img);
     QVERIFY(pointerEnteredSpy.wait());
     p->setCursor(cs.data(), QPoint(5, 5));
 
     // which should trigger a frame
     QVERIFY(frameRenderedSpy.wait());
     QImage referenceImage(QSize(1280, 1024), QImage::Format_RGB32);
     referenceImage.fill(Qt::black);
     QPainter painter(&referenceImage);
     painter.fillRect(0, 0, 200, 300, Qt::blue);
     painter.fillRect(100, 150, 100, 100, Qt::red);
     painter.fillRect(5, 5, 10, 10, Qt::red); //cursor
 
     QCOMPARE(referenceImage, *scene->qpainterRenderBuffer());
 }
 
 void SceneQPainterTest::testCompositorRestart_data()
 {
     QTest::addColumn<Test::ShellSurfaceType>("type");
 
     QTest::newRow("wlShell") << Test::ShellSurfaceType::WlShell;
     QTest::newRow("xdgShellV5") << Test::ShellSurfaceType::XdgShellV5;
     QTest::newRow("xdgShellV6") << Test::ShellSurfaceType::XdgShellV6;
 }
 
 void SceneQPainterTest::testCompositorRestart()
 {
     // this test verifies that the compositor/SceneQPainter survive a restart of the compositor and still render correctly
     KWin::Cursor::setPos(400, 400);
 
     // first create a window
     using namespace KWayland::Client;
     QVERIFY(Test::setupWaylandConnection());
     QScopedPointer<Surface> s(Test::createSurface());
     QFETCH(Test::ShellSurfaceType, type);
     QScopedPointer<QObject> ss(Test::createShellSurface(type, s.data()));
     QVERIFY(Test::renderAndWaitForShown(s.data(), QSize(200, 300), Qt::blue));
 
     // now let's try to reinitialize the compositing scene
     auto oldScene = KWin::Compositor::self()->scene();
     QVERIFY(oldScene);
     QSignalSpy sceneCreatedSpy(KWin::Compositor::self(), &KWin::Compositor::sceneCreated);
     QVERIFY(sceneCreatedSpy.isValid());
     KWin::Compositor::self()->slotReinitialize();
     if (sceneCreatedSpy.isEmpty()) {
         QVERIFY(sceneCreatedSpy.wait());
     }
     QCOMPARE(sceneCreatedSpy.count(), 1);
     auto scene = KWin::Compositor::self()->scene();
     QVERIFY(scene);
 
     // this should directly trigger a frame
     KWin::Compositor::self()->addRepaintFull();
     QSignalSpy frameRenderedSpy(scene, &Scene::frameRendered);
     QVERIFY(frameRenderedSpy.isValid());
     QVERIFY(frameRenderedSpy.wait());
 
     // render reference image
     QImage referenceImage(QSize(1280, 1024), QImage::Format_RGB32);
     referenceImage.fill(Qt::black);
     QPainter painter(&referenceImage);
     painter.fillRect(0, 0, 200, 300, Qt::blue);
     const QImage cursorImage = kwinApp()->platform()->softwareCursor();
     QVERIFY(!cursorImage.isNull());
     painter.drawImage(QPoint(400, 400) - kwinApp()->platform()->softwareCursorHotspot(), cursorImage);
     QCOMPARE(referenceImage, *scene->qpainterRenderBuffer());
 }
 
 struct XcbConnectionDeleter
 {
     static inline void cleanup(xcb_connection_t *pointer)
     {
         xcb_disconnect(pointer);
     }
 };
 
 void SceneQPainterTest::testX11Window()
 {
     // this test verifies the condition of BUG: 382748
 
     // create X11 window
     QSignalSpy windowAddedSpy(effects, &EffectsHandler::windowAdded);
     QVERIFY(windowAddedSpy.isValid());
 
     // create an xcb window
     QScopedPointer<xcb_connection_t, XcbConnectionDeleter> c(xcb_connect(nullptr, nullptr));
     QVERIFY(!xcb_connection_has_error(c.data()));
     const QRect windowGeometry(0, 0, 100, 200);
     xcb_window_t w = xcb_generate_id(c.data());
     uint32_t value = defaultScreen()->white_pixel;
     xcb_create_window(c.data(), XCB_COPY_FROM_PARENT, w, rootWindow(),
                       windowGeometry.x(),
                       windowGeometry.y(),
                       windowGeometry.width(),
                       windowGeometry.height(),
                       0, XCB_WINDOW_CLASS_INPUT_OUTPUT, XCB_COPY_FROM_PARENT, XCB_CW_BACK_PIXEL, &value);
     xcb_size_hints_t hints;
     memset(&hints, 0, sizeof(hints));
     xcb_icccm_size_hints_set_position(&hints, 1, windowGeometry.x(), windowGeometry.y());
     xcb_icccm_size_hints_set_size(&hints, 1, windowGeometry.width(), windowGeometry.height());
     xcb_icccm_set_wm_normal_hints(c.data(), w, &hints);
     xcb_map_window(c.data(), w);
     xcb_flush(c.data());
 
 
     // we should get a client for it
     QSignalSpy windowCreatedSpy(workspace(), &Workspace::clientAdded);
     QVERIFY(windowCreatedSpy.isValid());
     QVERIFY(windowCreatedSpy.wait());
     Client *client = windowCreatedSpy.first().first().value<Client*>();
     QVERIFY(client);
     QCOMPARE(client->window(), w);
     QCOMPARE(client->clientSize(), QSize(100, 200));
     if (!client->surface()) {
         // wait for surface
         QSignalSpy surfaceChangedSpy(client, &Toplevel::surfaceChanged);
         QVERIFY(surfaceChangedSpy.isValid());
         QVERIFY(surfaceChangedSpy.wait());
     }
     QVERIFY(client->surface());
     QTRY_VERIFY(client->surface()->buffer());
     QTRY_COMPARE(client->surface()->buffer()->data().size(), client->geometry().size());
     QImage compareImage(client->clientSize(), QImage::Format_RGB32);
     compareImage.fill(Qt::white);
     QCOMPARE(client->surface()->buffer()->data().copy(QRect(client->clientPos(), client->clientSize())), compareImage);
 
     // enough time for rendering the window
     QTest::qWait(100);
 
     auto scene = KWin::Compositor::self()->scene();
     QVERIFY(scene);
 
     // this should directly trigger a frame
     KWin::Compositor::self()->addRepaintFull();
     QSignalSpy frameRenderedSpy(scene, &Scene::frameRendered);
     QVERIFY(frameRenderedSpy.isValid());
     QVERIFY(frameRenderedSpy.wait());
 
     const QPoint startPos = client->pos() + client->clientPos();
     auto image = scene->qpainterRenderBuffer();
     QCOMPARE(image->copy(QRect(startPos, client->clientSize())), compareImage);
 
     // and destroy the window again
     xcb_unmap_window(c.data(), w);
     xcb_flush(c.data());
 
     QSignalSpy windowClosedSpy(client, &Client::windowClosed);
     QVERIFY(windowClosedSpy.isValid());
     QVERIFY(windowClosedSpy.wait());
     xcb_destroy_window(c.data(), w);
     c.reset();
 }
 
 WAYLANDTEST_MAIN(SceneQPainterTest)
 #include "scene_qpainter_test.moc"
diff --git a/composite.cpp b/composite.cpp
index 5fd3a3106..ab096a4ed 100644
--- a/composite.cpp
+++ b/composite.cpp
@@ -1,1213 +1,1215 @@
 /********************************************************************
  KWin - the KDE window manager
  This file is part of the KDE project.
 
 Copyright (C) 2006 Lubos Lunak <l.lunak@kde.org>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #include "composite.h"
 
 #include "dbusinterface.h"
 #include "utils.h"
 #include <QTextStream>
 #include "workspace.h"
 #include "client.h"
 #include "unmanaged.h"
 #include "deleted.h"
 #include "effects.h"
 #include "overlaywindow.h"
 #include "scene.h"
 #include "screens.h"
 #include "shadow.h"
 #include "useractions.h"
 #include "xcbutils.h"
 #include "platform.h"
 #include "shell_client.h"
 #include "wayland_server.h"
 #include "decorations/decoratedclient.h"
 
 #include <kwingltexture.h>
 
 #include <KWayland/Server/surface_interface.h>
 
 #include <stdio.h>
 
 #include <QtConcurrentRun>
 #include <QFutureWatcher>
 #include <QMenu>
 #include <QTimerEvent>
 #include <QDateTime>
 #include <QOpenGLContext>
 #include <QQuickWindow>
 #include <KGlobalAccel>
 #include <KLocalizedString>
 #include <KPluginLoader>
 #include <KPluginMetaData>
 #include <KNotification>
 #include <KSelectionWatcher>
 
 #include <xcb/composite.h>
 #include <xcb/damage.h>
 
 Q_DECLARE_METATYPE(KWin::Compositor::SuspendReason)
 
 namespace KWin
 {
 
 extern int currentRefreshRate();
 
 CompositorSelectionOwner::CompositorSelectionOwner(const char *selection) : KSelectionOwner(selection, connection(), rootWindow()), owning(false)
 {
     connect (this, SIGNAL(lostOwnership()), SLOT(looseOwnership()));
 }
 
 void CompositorSelectionOwner::looseOwnership()
 {
     owning = false;
 }
 
 KWIN_SINGLETON_FACTORY_VARIABLE(Compositor, s_compositor)
 
 static inline qint64 milliToNano(int milli) { return qint64(milli) * 1000 * 1000; }
 static inline qint64 nanoToMilli(int nano) { return nano / (1000*1000); }
 
 Compositor::Compositor(QObject* workspace)
     : QObject(workspace)
     , m_suspended(options->isUseCompositing() ? NoReasonSuspend : UserSuspend)
     , cm_selection(NULL)
     , vBlankInterval(0)
     , fpsInterval(0)
     , m_xrrRefreshRate(0)
     , m_finishing(false)
     , m_starting(false)
     , m_timeSinceLastVBlank(0)
     , m_scene(NULL)
     , m_bufferSwapPending(false)
     , m_composeAtSwapCompletion(false)
 {
     qRegisterMetaType<Compositor::SuspendReason>("Compositor::SuspendReason");
     connect(&compositeResetTimer, SIGNAL(timeout()), SLOT(restart()));
     connect(options, &Options::configChanged, this, &Compositor::slotConfigChanged);
     compositeResetTimer.setSingleShot(true);
     nextPaintReference.invalidate(); // Initialize the timer
 
     // 2 sec which should be enough to restart the compositor
     static const int compositorLostMessageDelay = 2000;
 
     m_releaseSelectionTimer.setSingleShot(true);
     m_releaseSelectionTimer.setInterval(compositorLostMessageDelay);
     connect(&m_releaseSelectionTimer, SIGNAL(timeout()), SLOT(releaseCompositorSelection()));
 
     m_unusedSupportPropertyTimer.setInterval(compositorLostMessageDelay);
     m_unusedSupportPropertyTimer.setSingleShot(true);
     connect(&m_unusedSupportPropertyTimer, SIGNAL(timeout()), SLOT(deleteUnusedSupportProperties()));
 
     // delay the call to setup by one event cycle
     // The ctor of this class is invoked from the Workspace ctor, that means before
     // Workspace is completely constructed, so calling Workspace::self() would result
     // in undefined behavior. This is fixed by using a delayed invocation.
     if (kwinApp()->platform()->isReady()) {
         QMetaObject::invokeMethod(this, "setup", Qt::QueuedConnection);
     }
     connect(kwinApp()->platform(), &Platform::readyChanged, this,
         [this] (bool ready) {
             if (ready) {
                 setup();
             } else {
                 finish();
             }
         }, Qt::QueuedConnection
     );
     connect(kwinApp(), &Application::x11ConnectionAboutToBeDestroyed, this,
         [this] {
             delete cm_selection;
             cm_selection = nullptr;
         }
     );
 
     if (qEnvironmentVariableIsSet("KWIN_MAX_FRAMES_TESTED"))
        m_framesToTestForSafety = qEnvironmentVariableIntValue("KWIN_MAX_FRAMES_TESTED");
 
     // register DBus
     new CompositorDBusInterface(this);
 }
 
 Compositor::~Compositor()
 {
     emit aboutToDestroy();
     finish();
     deleteUnusedSupportProperties();
     delete cm_selection;
     s_compositor = NULL;
 }
 
 
 void Compositor::setup()
 {
     if (kwinApp()->isTerminating()) {
         // don't setup while KWin is terminating. An event to restart might be lingering in the event queue due to graphics reset
         return;
     }
     if (hasScene())
         return;
     if (m_suspended) {
         QStringList reasons;
         if (m_suspended & UserSuspend) {
             reasons << QStringLiteral("Disabled by User");
         }
         if (m_suspended & BlockRuleSuspend) {
             reasons << QStringLiteral("Disabled by Window");
         }
         if (m_suspended & ScriptSuspend) {
             reasons << QStringLiteral("Disabled by Script");
         }
         qCDebug(KWIN_CORE) << "Compositing is suspended, reason:" << reasons;
         return;
     } else if (!kwinApp()->platform()->compositingPossible()) {
         qCCritical(KWIN_CORE) << "Compositing is not possible";
         return;
     }
     m_starting = true;
 
     if (!options->isCompositingInitialized()) {
         options->reloadCompositingSettings(true);
     }
     slotCompositingOptionsInitialized();
 }
 
 extern int screen_number; // main.cpp
 extern bool is_multihead;
 
 void Compositor::slotCompositingOptionsInitialized()
 {
     setupX11Support();
 
     // There might still be a deleted around, needs to be cleared before creating the scene (BUG 333275)
     if (Workspace::self()) {
         while (!Workspace::self()->deletedList().isEmpty()) {
             Workspace::self()->deletedList().first()->discard();
         }
     }
 
     emit aboutToToggleCompositing();
 
     auto supportedCompositors = kwinApp()->platform()->supportedCompositors();
     const auto userConfigIt = std::find(supportedCompositors.begin(), supportedCompositors.end(), options->compositingMode());
     if (userConfigIt != supportedCompositors.end()) {
         supportedCompositors.erase(userConfigIt);
         supportedCompositors.prepend(options->compositingMode());
     } else {
         qCWarning(KWIN_CORE) << "Configured compositor not supported by Platform. Falling back to defaults";
     }
 
     const auto availablePlugins = KPluginLoader::findPlugins(QStringLiteral("org.kde.kwin.scenes"));
 
     for (auto type : qAsConst(supportedCompositors)) {
         const auto pluginIt = std::find_if(availablePlugins.begin(), availablePlugins.end(),
             [type] (const auto &plugin) {
                 const auto &metaData = plugin.rawData();
                 auto it = metaData.find(QStringLiteral("CompositingType"));
                 if (it != metaData.end()) {
                     if ((*it).toInt() == int{type}) {
                         return true;
                     }
                 }
                 return false;
             });
         if (pluginIt != availablePlugins.end()) {
             std::unique_ptr<SceneFactory> factory{qobject_cast<SceneFactory*>(pluginIt->instantiate())};
             if (factory) {
                 m_scene = factory->create(this);
                 if (m_scene) {
                     if (!m_scene->initFailed()) {
                         qCDebug(KWIN_CORE) << "Instantiated compositing plugin:" << pluginIt->name();
                         break;
                     } else {
                         delete m_scene;
                         m_scene = nullptr;
                     }
                 }
             }
         }
     }
 
     if (m_scene == NULL || m_scene->initFailed()) {
         qCCritical(KWIN_CORE) << "Failed to initialize compositing, compositing disabled";
         delete m_scene;
         m_scene = NULL;
         m_starting = false;
         if (cm_selection) {
             cm_selection->owning = false;
             cm_selection->release();
         }
         if (!supportedCompositors.contains(NoCompositing)) {
             qCCritical(KWIN_CORE) << "The used windowing system requires compositing";
             qCCritical(KWIN_CORE) << "We are going to quit KWin now as it is broken";
             qApp->quit();
         }
         return;
     }
 
+    kwinApp()->platform()->setSelectedCompositor(m_scene->compositingType() & OpenGLCompositing ? OpenGLCompositing : m_scene->compositingType());
+
     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();
 
     if (Workspace::self()) {
         startupWithWorkspace();
     } else {
         connect(kwinApp(), &Application::workspaceCreated, this, &Compositor::startupWithWorkspace);
     }
 }
 
 void Compositor::claimCompositorSelection()
 {
     if (!cm_selection) {
         char selection_name[ 100 ];
         sprintf(selection_name, "_NET_WM_CM_S%d", Application::x11ScreenNumber());
         cm_selection = new CompositorSelectionOwner(selection_name);
         connect(cm_selection, SIGNAL(lostOwnership()), SLOT(finish()));
     }
 
     if (!cm_selection) // no X11 yet
         return;
 
     if (!cm_selection->owning) {
         cm_selection->claim(true);   // force claiming
         cm_selection->owning = true;
     }
 }
 
 void Compositor::setupX11Support()
 {
     auto c = kwinApp()->x11Connection();
     if (!c) {
         delete cm_selection;
         cm_selection = nullptr;
         return;
     }
     claimCompositorSelection();
     xcb_composite_redirect_subwindows(c, kwinApp()->x11RootWindow(), XCB_COMPOSITE_REDIRECT_MANUAL);
 }
 
 void Compositor::startupWithWorkspace()
 {
     if (!m_starting) {
         return;
     }
     connect(kwinApp(), &Application::x11ConnectionChanged, this, &Compositor::setupX11Support, Qt::UniqueConnection);
     Workspace::self()->markXStackingOrderAsDirty();
     Q_ASSERT(m_scene);
     connect(workspace(), &Workspace::destroyed, this, [this] { compositeTimer.stop(); });
     setupX11Support();
     m_xrrRefreshRate = KWin::currentRefreshRate();
     fpsInterval = options->maxFpsInterval();
     if (m_scene->syncsToVBlank()) {  // if we do vsync, set the fps to the next multiple of the vblank rate
         vBlankInterval = milliToNano(1000) / m_xrrRefreshRate;
         fpsInterval = qMax((fpsInterval / vBlankInterval) * vBlankInterval, vBlankInterval);
     } else
         vBlankInterval = milliToNano(1); // no sync - DO NOT set "0", would cause div-by-zero segfaults.
     m_timeSinceLastVBlank = fpsInterval - (options->vBlankTime() + 1); // means "start now" - we don't have even a slight idea when the first vsync will occur
     scheduleRepaint();
     kwinApp()->platform()->createEffectsHandler(this, m_scene);   // sets also the 'effects' pointer
     connect(Workspace::self(), &Workspace::deletedRemoved, m_scene, &Scene::removeToplevel);
     connect(effects, SIGNAL(screenGeometryChanged(QSize)), SLOT(addRepaintFull()));
     addRepaintFull();
     foreach (Client * c, Workspace::self()->clientList()) {
         c->setupCompositing();
         c->getShadow();
     }
     foreach (Client * c,  Workspace::self()->desktopList())
         c->setupCompositing();
     foreach (Unmanaged * c, Workspace::self()->unmanagedList()) {
         c->setupCompositing();
         c->getShadow();
     }
     if (auto w = waylandServer()) {
         const auto clients = w->clients();
         for (auto c : clients) {
             c->setupCompositing();
             c->getShadow();
         }
         const auto internalClients = w->internalClients();
         for (auto c : internalClients) {
             c->setupCompositing();
             c->getShadow();
         }
     }
 
     emit compositingToggled(true);
 
     m_starting = false;
     if (m_releaseSelectionTimer.isActive()) {
         m_releaseSelectionTimer.stop();
     }
 
     // render at least once
     performCompositing();
 }
 
 void Compositor::scheduleRepaint()
 {
     if (!compositeTimer.isActive())
         setCompositeTimer();
 }
 
 void Compositor::finish()
 {
     if (!hasScene())
         return;
     m_finishing = true;
     m_releaseSelectionTimer.start();
 
     emit aboutToToggleCompositing();
 
     // Some effects might need access to effect windows when they are about to
     // be destroyed, for example to unreference deleted windows, so we have to
     // make sure that effect windows outlive effects.
     delete effects;
     effects = nullptr;
 
     if (Workspace::self()) {
         foreach (Client * c, Workspace::self()->clientList())
             m_scene->removeToplevel(c);
         foreach (Client * c, Workspace::self()->desktopList())
             m_scene->removeToplevel(c);
         foreach (Unmanaged * c, Workspace::self()->unmanagedList())
             m_scene->removeToplevel(c);
         foreach (Deleted * c, Workspace::self()->deletedList())
             m_scene->removeToplevel(c);
         foreach (Client * c, Workspace::self()->clientList())
         c->finishCompositing();
         foreach (Client * c, Workspace::self()->desktopList())
         c->finishCompositing();
         foreach (Unmanaged * c, Workspace::self()->unmanagedList())
         c->finishCompositing();
         foreach (Deleted * c, Workspace::self()->deletedList())
         c->finishCompositing();
         if (auto c = kwinApp()->x11Connection()) {
             xcb_composite_unredirect_subwindows(c, kwinApp()->x11RootWindow(), XCB_COMPOSITE_REDIRECT_MANUAL);
         }
     }
     if (waylandServer()) {
         foreach (ShellClient *c, waylandServer()->clients()) {
             m_scene->removeToplevel(c);
         }
         foreach (ShellClient *c, waylandServer()->internalClients()) {
             m_scene->removeToplevel(c);
         }
         foreach (ShellClient *c, waylandServer()->clients()) {
             c->finishCompositing();
         }
         foreach (ShellClient *c, waylandServer()->internalClients()) {
             c->finishCompositing();
         }
     }
     delete m_scene;
     m_scene = NULL;
     compositeTimer.stop();
     repaints_region = QRegion();
     if (Workspace::self()) {
         for (ClientList::ConstIterator it = Workspace::self()->clientList().constBegin();
                 it != Workspace::self()->clientList().constEnd();
                 ++it) {
             // forward all opacity values to the frame in case there'll be other CM running
             if ((*it)->opacity() != 1.0) {
                 NETWinInfo i(connection(), (*it)->frameId(), rootWindow(), 0, 0);
                 i.setOpacity(static_cast< unsigned long >((*it)->opacity() * 0xffffffff));
             }
         }
         // discard all Deleted windows (#152914)
         while (!Workspace::self()->deletedList().isEmpty())
             Workspace::self()->deletedList().first()->discard();
     }
     m_finishing = false;
     emit compositingToggled(false);
 }
 
 void Compositor::releaseCompositorSelection()
 {
     if (hasScene() && !m_finishing) {
         // compositor is up and running again, no need to release the selection
         return;
     }
     if (m_starting) {
         // currently still starting the compositor, it might fail, so restart the timer to test again
         m_releaseSelectionTimer.start();
         return;
     }
 
     if (m_finishing) {
         // still shutting down, a restart might follow, so restart the timer to test again
         m_releaseSelectionTimer.start();
         return;
     }
     qCDebug(KWIN_CORE) << "Releasing compositor selection";
     if (cm_selection) {
         cm_selection->owning = false;
         cm_selection->release();
     }
 }
 
 void Compositor::keepSupportProperty(xcb_atom_t atom)
 {
     m_unusedSupportProperties.removeAll(atom);
 }
 
 void Compositor::removeSupportProperty(xcb_atom_t atom)
 {
     m_unusedSupportProperties << atom;
     m_unusedSupportPropertyTimer.start();
 }
 
 void Compositor::deleteUnusedSupportProperties()
 {
     if (m_starting) {
         // currently still starting the compositor
         m_unusedSupportPropertyTimer.start();
         return;
     }
     if (m_finishing) {
         // still shutting down, a restart might follow
         m_unusedSupportPropertyTimer.start();
         return;
     }
     if (const auto c = kwinApp()->x11Connection()) {
         foreach (const xcb_atom_t &atom, m_unusedSupportProperties) {
             // remove property from root window
             xcb_delete_property(c, kwinApp()->x11RootWindow(), atom);
         }
     }
 }
 
 void Compositor::slotConfigChanged()
 {
     if (!m_suspended) {
         setup();
         if (effects)   // setupCompositing() may fail
             effects->reconfigure();
         addRepaintFull();
     } else
         finish();
 }
 
 void Compositor::slotReinitialize()
 {
     // Reparse config. Config options will be reloaded by setup()
     kwinApp()->config()->reparseConfiguration();
 
     // Restart compositing
     finish();
     // resume compositing if suspended
     m_suspended = NoReasonSuspend;
     options->setCompositingInitialized(false);
     setup();
 
     if (effects) { // setup() may fail
         effects->reconfigure();
     }
 }
 
 // for the shortcut
 void Compositor::slotToggleCompositing()
 {
     if (kwinApp()->platform()->requiresCompositing()) {
         // we are not allowed to turn on/off compositing
         return;
     }
     if (m_suspended) { // direct user call; clear all bits
         resume(AllReasonSuspend);
     } else { // but only set the user one (sufficient to suspend)
         suspend(UserSuspend);
     }
 }
 
 void Compositor::updateCompositeBlocking()
 {
     updateCompositeBlocking(NULL);
 }
 
 void Compositor::updateCompositeBlocking(Client *c)
 {
     if (kwinApp()->platform()->requiresCompositing()) {
         return;
     }
     if (c) { // if c == 0 we just check if we can resume
         if (c->isBlockingCompositing()) {
             if (!(m_suspended & BlockRuleSuspend)) // do NOT attempt to call suspend(true); from within the eventchain!
                 QMetaObject::invokeMethod(this, "suspend", Qt::QueuedConnection, Q_ARG(Compositor::SuspendReason, BlockRuleSuspend));
         }
     }
     else if (m_suspended & BlockRuleSuspend) {  // lost a client and we're blocked - can we resume?
         bool resume = true;
         for (ClientList::ConstIterator it = Workspace::self()->clientList().constBegin(); it != Workspace::self()->clientList().constEnd(); ++it) {
             if ((*it)->isBlockingCompositing()) {
                 resume = false;
                 break;
             }
         }
         if (resume) { // do NOT attempt to call suspend(false); from within the eventchain!
             QMetaObject::invokeMethod(this, "resume", Qt::QueuedConnection, Q_ARG(Compositor::SuspendReason, BlockRuleSuspend));
         }
     }
 }
 
 void Compositor::suspend(Compositor::SuspendReason reason)
 {
     if (kwinApp()->platform()->requiresCompositing()) {
         return;
     }
     Q_ASSERT(reason != NoReasonSuspend);
     m_suspended |= reason;
     if (reason & KWin::Compositor::ScriptSuspend) {
         // when disabled show a shortcut how the user can get back compositing
         const auto shortcuts = KGlobalAccel::self()->shortcut(workspace()->findChild<QAction*>(QStringLiteral("Suspend Compositing")));
         if (!shortcuts.isEmpty()) {
             // display notification only if there is the shortcut
             const QString message = i18n("Desktop effects have been suspended by another application.<br/>"
                                          "You can resume using the '%1' shortcut.", shortcuts.first().toString(QKeySequence::NativeText));
             KNotification::event(QStringLiteral("compositingsuspendeddbus"), message);
         }
     }
     finish();
 }
 
 void Compositor::resume(Compositor::SuspendReason reason)
 {
     Q_ASSERT(reason != NoReasonSuspend);
     m_suspended &= ~reason;
     setup(); // signal "toggled" is eventually emitted from within setup
 }
 
 void Compositor::restart()
 {
     if (hasScene()) {
         finish();
         QTimer::singleShot(0, this, SLOT(setup()));
     }
 }
 
 void Compositor::addRepaint(int x, int y, int w, int h)
 {
     if (!hasScene())
         return;
     repaints_region += QRegion(x, y, w, h);
     scheduleRepaint();
 }
 
 void Compositor::addRepaint(const QRect& r)
 {
     if (!hasScene())
         return;
     repaints_region += r;
     scheduleRepaint();
 }
 
 void Compositor::addRepaint(const QRegion& r)
 {
     if (!hasScene())
         return;
     repaints_region += r;
     scheduleRepaint();
 }
 
 void Compositor::addRepaintFull()
 {
     if (!hasScene())
         return;
     const QSize &s = screens()->size();
     repaints_region = QRegion(0, 0, s.width(), s.height());
     scheduleRepaint();
 }
 
 void Compositor::timerEvent(QTimerEvent *te)
 {
     if (te->timerId() == compositeTimer.timerId()) {
         performCompositing();
     } else
         QObject::timerEvent(te);
 }
 
 void Compositor::aboutToSwapBuffers()
 {
     assert(!m_bufferSwapPending);
 
     m_bufferSwapPending = true;
 }
 
 void Compositor::bufferSwapComplete()
 {
     assert(m_bufferSwapPending);
     m_bufferSwapPending = false;
 
     emit bufferSwapCompleted();
 
     if (m_composeAtSwapCompletion) {
         m_composeAtSwapCompletion = false;
         performCompositing();
     }
 }
 
 void Compositor::performCompositing()
 {
     if (m_scene->usesOverlayWindow() && !isOverlayWindowVisible())
         return; // nothing is visible anyway
 
     // If a buffer swap is still pending, we return to the event loop and
     // continue processing events until the swap has completed.
     if (m_bufferSwapPending) {
         m_composeAtSwapCompletion = true;
         compositeTimer.stop();
         return;
     }
 
     // If outputs are disabled, we return to the event loop and
     // continue processing events until the outputs are enabled again
     if (!kwinApp()->platform()->areOutputsEnabled()) {
         compositeTimer.stop();
         return;
     }
 
     // Create a list of all windows in the stacking order
     ToplevelList windows = Workspace::self()->xStackingOrder();
     ToplevelList damaged;
 
     // Reset the damage state of each window and fetch the damage region
     // without waiting for a reply
     foreach (Toplevel *win, windows) {
         if (win->resetAndFetchDamage())
             damaged << win;
     }
 
     if (damaged.count() > 0) {
         m_scene->triggerFence();
         if (auto c = kwinApp()->x11Connection()) {
             xcb_flush(c);
         }
     }
 
     // Move elevated windows to the top of the stacking order
     foreach (EffectWindow *c, static_cast<EffectsHandlerImpl *>(effects)->elevatedWindows()) {
         Toplevel* t = static_cast< EffectWindowImpl* >(c)->window();
         windows.removeAll(t);
         windows.append(t);
     }
 
     // Get the replies
     foreach (Toplevel *win, damaged) {
         // Discard the cached lanczos texture
         if (win->effectWindow()) {
             const QVariant texture = win->effectWindow()->data(LanczosCacheRole);
             if (texture.isValid()) {
                 delete static_cast<GLTexture *>(texture.value<void*>());
                 win->effectWindow()->setData(LanczosCacheRole, QVariant());
             }
         }
 
         win->getDamageRegionReply();
     }
 
     if (repaints_region.isEmpty() && !windowRepaintsPending()) {
         m_scene->idle();
         m_timeSinceLastVBlank = fpsInterval - (options->vBlankTime() + 1); // means "start now"
         m_timeSinceStart += m_timeSinceLastVBlank;
         // Note: It would seem here we should undo suspended unredirect, but when scenes need
         // it for some reason, e.g. transformations or translucency, the next pass that does not
         // need this anymore and paints normally will also reset the suspended unredirect.
         // Otherwise the window would not be painted normally anyway.
         compositeTimer.stop();
         return;
     }
 
     // skip windows that are not yet ready for being painted and if screen is locked skip windows that are
     // neither lockscreen nor inputmethod windows
     // TODO ?
     // this cannot be used so carelessly - needs protections against broken clients, the window
     // should not get focus before it's displayed, handle unredirected windows properly and so on.
     foreach (Toplevel *t, windows) {
         if (!t->readyForPainting()) {
             windows.removeAll(t);
         }
         if (waylandServer() && waylandServer()->isScreenLocked()) {
             if(!t->isLockScreen() && !t->isInputMethod()) {
                 windows.removeAll(t);
             }
         }
     }
 
     QRegion repaints = repaints_region;
     // clear all repaints, so that post-pass can add repaints for the next repaint
     repaints_region = QRegion();
 
     if (m_framesToTestForSafety > 0 && (m_scene->compositingType() & OpenGLCompositing)) {
         kwinApp()->platform()->createOpenGLSafePoint(Platform::OpenGLSafePoint::PreFrame);
     }
     m_timeSinceLastVBlank = m_scene->paint(repaints, windows);
     if (m_framesToTestForSafety > 0) {
         if (m_scene->compositingType() & OpenGLCompositing) {
             kwinApp()->platform()->createOpenGLSafePoint(Platform::OpenGLSafePoint::PostFrame);
         }
         m_framesToTestForSafety--;
         if (m_framesToTestForSafety == 0 && (m_scene->compositingType() & OpenGLCompositing)) {
             kwinApp()->platform()->createOpenGLSafePoint(Platform::OpenGLSafePoint::PostLastGuardedFrame);
         }
     }
     m_timeSinceStart += m_timeSinceLastVBlank;
 
     if (waylandServer()) {
         for (Toplevel *win : qAsConst(windows)) {
             if (auto surface = win->surface()) {
                 surface->frameRendered(m_timeSinceStart);
             }
         }
     }
 
     compositeTimer.stop(); // stop here to ensure *we* cause the next repaint schedule - not some effect through m_scene->paint()
 
     // Trigger at least one more pass even if there would be nothing to paint, so that scene->idle()
     // is called the next time. If there would be nothing pending, it will not restart the timer and
     // scheduleRepaint() would restart it again somewhen later, called from functions that
     // would again add something pending.
     if (m_bufferSwapPending && m_scene->syncsToVBlank()) {
         m_composeAtSwapCompletion = true;
     } else {
         scheduleRepaint();
     }
 }
 
 template <class T>
 static bool repaintsPending(const QList<T*> &windows)
 {
     return std::any_of(windows.begin(), windows.end(), [] (T *t) { return !t->repaints().isEmpty(); });
 }
 
 bool Compositor::windowRepaintsPending() const
 {
     if (repaintsPending(Workspace::self()->clientList())) {
         return true;
     }
     if (repaintsPending(Workspace::self()->desktopList())) {
         return true;
     }
     if (repaintsPending(Workspace::self()->unmanagedList())) {
         return true;
     }
     if (repaintsPending(Workspace::self()->deletedList())) {
         return true;
     }
     if (auto w = waylandServer()) {
         const auto &clients = w->clients();
         auto test = [] (ShellClient *c) {
             return c->readyForPainting() && !c->repaints().isEmpty();
         };
         if (std::any_of(clients.begin(), clients.end(), test)) {
             return true;
         }
         const auto &internalClients = w->internalClients();
         auto internalTest = [] (ShellClient *c) {
             return c->isShown(true) && !c->repaints().isEmpty();
         };
         if (std::any_of(internalClients.begin(), internalClients.end(), internalTest)) {
             return true;
         }
     }
     return false;
 }
 
 void Compositor::setCompositeResetTimer(int msecs)
 {
     compositeResetTimer.start(msecs);
 }
 
 void Compositor::setCompositeTimer()
 {
     if (!hasScene())  // should not really happen, but there may be e.g. some damage events still pending
         return;
     if (m_starting || !Workspace::self()) {
         return;
     }
 
     // Don't start the timer if we're waiting for a swap event
     if (m_bufferSwapPending && m_composeAtSwapCompletion)
         return;
 
     // Don't start the timer if all outputs are disabled
     if (!kwinApp()->platform()->areOutputsEnabled()) {
         return;
     }
 
     uint waitTime = 1;
 
     if (m_scene->blocksForRetrace()) {
 
         // TODO: make vBlankTime dynamic?!
         // It's required because glXWaitVideoSync will *likely* block a full frame if one enters
         // a retrace pass which can last a variable amount of time, depending on the actual screen
         // Now, my ooold 19" CRT can do such retrace so that 2ms are entirely sufficient,
         // while another ooold 15" TFT requires about 6ms
 
         qint64 padding = m_timeSinceLastVBlank;
         if (padding > fpsInterval) {
             // we're at low repaints or spent more time in painting than the user wanted to wait for that frame
             padding = vBlankInterval - (padding%vBlankInterval); // -> align to next vblank
         } else {  // -> align to the next maxFps tick
             padding = ((vBlankInterval - padding%vBlankInterval) + (fpsInterval/vBlankInterval-1)*vBlankInterval);
             //               "remaining time of the first vsync" + "time for the other vsyncs of the frame"
         }
 
         if (padding < options->vBlankTime()) { // we'll likely miss this frame
             waitTime = nanoToMilli(padding + vBlankInterval - options->vBlankTime()); // so we add one
         } else {
             waitTime = nanoToMilli(padding - options->vBlankTime());
         }
     }
     else { // w/o blocking vsync we just jump to the next demanded tick
         if (fpsInterval > m_timeSinceLastVBlank) {
             waitTime = nanoToMilli(fpsInterval - m_timeSinceLastVBlank);
             if (!waitTime) {
                 waitTime = 1; // will ensure we don't block out the eventloop - the system's just not faster ...
             }
         }/* else if (m_scene->syncsToVBlank() && m_timeSinceLastVBlank - fpsInterval < (vBlankInterval<<1)) {
             // NOTICE - "for later" ------------------------------------------------------------------
             // It can happen that we push two frames within one refresh cycle.
             // Swapping will then block even with triple buffering when the GPU does not discard but
             // queues frames
             // now here's the mean part: if we take that as "OMG, we're late - next frame ASAP",
             // there'll immediately be 2 frames in the pipe, swapping will block, we think we're
             // late ... ewww
             // so instead we pad to the clock again and add 2ms safety to ensure the pipe is really
             // free
             // NOTICE: obviously m_timeSinceLastVBlank can be too big because we're too slow as well
             // So if this code was enabled, we'd needlessly half the framerate once more (15 instead of 30)
             waitTime = nanoToMilli(vBlankInterval - (m_timeSinceLastVBlank - fpsInterval)%vBlankInterval) + 2;
         }*/ else {
             waitTime = 1; // ... "0" would be sufficient, but the compositor isn't the WMs only task
         }
     }
     compositeTimer.start(qMin(waitTime, 250u), this); // force 4fps minimum
 }
 
 bool Compositor::isActive()
 {
     return !m_finishing && hasScene();
 }
 
 bool Compositor::checkForOverlayWindow(WId w) const
 {
     if (!hasScene()) {
         // no scene, so it cannot be the overlay window
         return false;
     }
     if (!m_scene->overlayWindow()) {
         // no overlay window, it cannot be the overlay
         return false;
     }
     // and compare the window ID's
     return w == m_scene->overlayWindow()->window();
 }
 
 bool Compositor::isOverlayWindowVisible() const
 {
     if (!hasScene()) {
         return false;
     }
     if (!m_scene->overlayWindow()) {
         return false;
     }
     return m_scene->overlayWindow()->isVisible();
 }
 
 /*****************************************************
  * Workspace
  ****************************************************/
 
 bool Workspace::compositing() const
 {
     return m_compositor && m_compositor->hasScene();
 }
 
 //****************************************
 // Toplevel
 //****************************************
 
 bool Toplevel::setupCompositing()
 {
     if (!compositing())
         return false;
 
     if (damage_handle != XCB_NONE)
         return false;
 
     if (kwinApp()->operationMode() == Application::OperationModeX11 && !surface()) {
         damage_handle = xcb_generate_id(connection());
         xcb_damage_create(connection(), damage_handle, frameId(), XCB_DAMAGE_REPORT_LEVEL_NON_EMPTY);
     }
 
     damage_region = QRegion(0, 0, width(), height());
     effect_window = new EffectWindowImpl(this);
 
     Compositor::self()->scene()->addToplevel(this);
 
     // With unmanaged windows there is a race condition between the client painting the window
     // and us setting up damage tracking.  If the client wins we won't get a damage event even
     // though the window has been painted.  To avoid this we mark the whole window as damaged
     // and schedule a repaint immediately after creating the damage object.
     if (dynamic_cast<Unmanaged*>(this))
         addDamageFull();
 
     return true;
 }
 
 void Toplevel::finishCompositing(ReleaseReason releaseReason)
 {
     if (kwinApp()->operationMode() == Application::OperationModeX11 && damage_handle == XCB_NONE)
         return;
     if (effect_window->window() == this) { // otherwise it's already passed to Deleted, don't free data
         discardWindowPixmap();
         delete effect_window;
     }
 
     if (damage_handle != XCB_NONE &&
             releaseReason != ReleaseReason::Destroyed) {
         xcb_damage_destroy(connection(), damage_handle);
     }
 
     damage_handle = XCB_NONE;
     damage_region = QRegion();
     repaints_region = QRegion();
     effect_window = NULL;
 }
 
 void Toplevel::discardWindowPixmap()
 {
     addDamageFull();
     if (effectWindow() != NULL && effectWindow()->sceneWindow() != NULL)
         effectWindow()->sceneWindow()->pixmapDiscarded();
 }
 
 void Toplevel::damageNotifyEvent()
 {
     m_isDamaged = true;
 
     // Note: The rect is supposed to specify the damage extents,
     //       but we don't know it at this point. No one who connects
     //       to this signal uses the rect however.
     emit damaged(this, QRect());
 }
 
 bool Toplevel::compositing() const
 {
     if (!Workspace::self()) {
         return false;
     }
     return Workspace::self()->compositing();
 }
 
 void Client::damageNotifyEvent()
 {
     if (syncRequest.isPending && isResize()) {
         emit damaged(this, QRect());
         m_isDamaged = true;
         return;
     }
 
     if (!ready_for_painting) { // avoid "setReadyForPainting()" function calling overhead
         if (syncRequest.counter == XCB_NONE) {  // cannot detect complete redraw, consider done now
             setReadyForPainting();
             setupWindowManagementInterface();
         }
     }
 
     Toplevel::damageNotifyEvent();
 }
 
 bool Toplevel::resetAndFetchDamage()
 {
     if (!m_isDamaged)
         return false;
 
     if (damage_handle == XCB_NONE) {
         m_isDamaged = false;
         return true;
     }
 
     xcb_connection_t *conn = connection();
 
     // Create a new region and copy the damage region to it,
     // resetting the damaged state.
     xcb_xfixes_region_t region = xcb_generate_id(conn);
     xcb_xfixes_create_region(conn, region, 0, 0);
     xcb_damage_subtract(conn, damage_handle, 0, region);
 
     // Send a fetch-region request and destroy the region
     m_regionCookie = xcb_xfixes_fetch_region_unchecked(conn, region);
     xcb_xfixes_destroy_region(conn, region);
 
     m_isDamaged = false;
     m_damageReplyPending = true;
 
     return m_damageReplyPending;
 }
 
 void Toplevel::getDamageRegionReply()
 {
     if (!m_damageReplyPending)
         return;
 
     m_damageReplyPending = false;
 
     // Get the fetch-region reply
     xcb_xfixes_fetch_region_reply_t *reply =
             xcb_xfixes_fetch_region_reply(connection(), m_regionCookie, 0);
 
     if (!reply)
         return;
 
     // Convert the reply to a QRegion
     int count = xcb_xfixes_fetch_region_rectangles_length(reply);
     QRegion region;
 
     if (count > 1 && count < 16) {
         xcb_rectangle_t *rects = xcb_xfixes_fetch_region_rectangles(reply);
 
         QVector<QRect> qrects;
         qrects.reserve(count);
 
         for (int i = 0; i < count; i++)
             qrects << QRect(rects[i].x, rects[i].y, rects[i].width, rects[i].height);
 
         region.setRects(qrects.constData(), count);
     } else
         region += QRect(reply->extents.x, reply->extents.y,
                         reply->extents.width, reply->extents.height);
 
     damage_region += region;
     repaints_region += region;
 
     free(reply);
 }
 
 void Toplevel::addDamageFull()
 {
     if (!compositing())
         return;
 
     damage_region = rect();
     repaints_region |= rect();
 
     emit damaged(this, rect());
 }
 
 void Toplevel::resetDamage()
 {
     damage_region = QRegion();
 }
 
 void Toplevel::addRepaint(const QRect& r)
 {
     if (!compositing()) {
         return;
     }
     repaints_region += r;
     emit needsRepaint();
 }
 
 void Toplevel::addRepaint(int x, int y, int w, int h)
 {
     QRect r(x, y, w, h);
     addRepaint(r);
 }
 
 void Toplevel::addRepaint(const QRegion& r)
 {
     if (!compositing()) {
         return;
     }
     repaints_region += r;
     emit needsRepaint();
 }
 
 void Toplevel::addLayerRepaint(const QRect& r)
 {
     if (!compositing()) {
         return;
     }
     layer_repaints_region += r;
     emit needsRepaint();
 }
 
 void Toplevel::addLayerRepaint(int x, int y, int w, int h)
 {
     QRect r(x, y, w, h);
     addLayerRepaint(r);
 }
 
 void Toplevel::addLayerRepaint(const QRegion& r)
 {
     if (!compositing())
         return;
     layer_repaints_region += r;
     emit needsRepaint();
 }
 
 void Toplevel::addRepaintFull()
 {
     repaints_region = visibleRect().translated(-pos());
     emit needsRepaint();
 }
 
 void Toplevel::resetRepaints()
 {
     repaints_region = QRegion();
     layer_repaints_region = QRegion();
 }
 
 void Toplevel::addWorkspaceRepaint(int x, int y, int w, int h)
 {
     addWorkspaceRepaint(QRect(x, y, w, h));
 }
 
 void Toplevel::addWorkspaceRepaint(const QRect& r2)
 {
     if (!compositing())
         return;
     Compositor::self()->addRepaint(r2);
 }
 
 //****************************************
 // Client
 //****************************************
 
 bool Client::setupCompositing()
 {
     if (!Toplevel::setupCompositing()){
         return false;
     }
     updateVisibility(); // for internalKeep()
     return true;
 }
 
 void Client::finishCompositing(ReleaseReason releaseReason)
 {
     Toplevel::finishCompositing(releaseReason);
     updateVisibility();
     // for safety in case KWin is just resizing the window
     resetHaveResizeEffect();
 }
 
 } // namespace
diff --git a/platform.h b/platform.h
index 765d16794..e2fdc00cb 100644
--- a/platform.h
+++ b/platform.h
@@ -1,540 +1,560 @@
 /********************************************************************
  KWin - the KDE window manager
  This file is part of the KDE project.
 
 Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #ifndef KWIN_PLATFORM_H
 #define KWIN_PLATFORM_H
 #include <kwin_export.h>
 #include <kwinglobals.h>
 #include <epoxy/egl.h>
 #include "fixqopengl.h"
 
 #include <fixx11h.h>
 #include <QImage>
 #include <QObject>
 
 #include <functional>
 
 class QAction;
 
 namespace KWayland {
     namespace Server {
         class OutputConfigurationInterface;
     }
 }
 
 namespace KWin
 {
 namespace ColorCorrect {
 class Manager;
 }
 
 class AbstractOutput;
 class Edge;
 class Compositor;
 class OverlayWindow;
 class OpenGLBackend;
 class Outline;
 class OutlineVisual;
 class QPainterBackend;
 class Scene;
 class Screens;
 class ScreenEdges;
 class Toplevel;
 class WaylandCursorTheme;
 
 namespace Decoration
 {
 class Renderer;
 class DecoratedClientImpl;
 }
 
 class KWIN_EXPORT Outputs : public QVector<AbstractOutput*>
 {
 public:
     Outputs(){};
     template <typename T>
     Outputs(const QVector<T> &other) {
         resize(other.size());
         std::copy(other.constBegin(), other.constEnd(), begin());
     }
 };
 
 class KWIN_EXPORT Platform : public QObject
 {
     Q_OBJECT
 public:
     virtual ~Platform();
 
     virtual void init() = 0;
     virtual Screens *createScreens(QObject *parent = nullptr);
     virtual OpenGLBackend *createOpenGLBackend();
     virtual QPainterBackend *createQPainterBackend();
     /**
      * Allows the platform to create a platform specific screen edge.
      * The default implementation creates a Edge.
      **/
     virtual Edge *createScreenEdge(ScreenEdges *parent);
     /**
      * Allows the platform to create a platform specific Cursor.
      * The default implementation creates an InputRedirectionCursor.
      **/
     virtual void createPlatformCursor(QObject *parent = nullptr);
     virtual void warpPointer(const QPointF &globalPos);
     /**
      * Whether our Compositing EGL display allows a surface less context
      * so that a sharing context could be created.
      **/
     virtual bool supportsQpaContext() const;
     /**
      * The EGLDisplay used by the compositing scene.
      **/
     EGLDisplay sceneEglDisplay() const;
     void setSceneEglDisplay(EGLDisplay display);
     /**
      * The EGLContext used by the compositing scene.
      **/
     virtual EGLContext sceneEglContext() const {
         return m_context;
     }
     /**
      * Sets the @p context used by the compositing scene.
      **/
     void setSceneEglContext(EGLContext context) {
         m_context = context;
     }
     /**
      * The first (in case of multiple) EGLSurface used by the compositing scene.
      **/
     EGLSurface sceneEglSurface() const {
         return m_surface;
     }
     /**
      * Sets the first @p surface used by the compositing scene.
      * @see sceneEglSurface
      **/
     void setSceneEglSurface(EGLSurface surface) {
         m_surface = surface;
     }
 
     /**
      * The EglConfig used by the compositing scene.
      **/
     EGLConfig sceneEglConfig() const {
         return m_eglConfig;
     }
     /**
      * Sets the @p config used by the compositing scene.
      * @see sceneEglConfig
      **/
     void setSceneEglConfig(EGLConfig config) {
         m_eglConfig = config;
     }
 
     /**
      * Implementing subclasses should provide a size in case the backend represents
      * a basic screen and uses the BasicScreens.
      *
      * Base implementation returns an invalid size.
      **/
     virtual QSize screenSize() const;
     /**
      * Implementing subclasses should provide all geometries in case the backend represents
      * a basic screen and uses the BasicScreens.
      *
      * Base implementation returns one QRect positioned at 0/0 with screenSize() as size.
      **/
     virtual QVector<QRect> screenGeometries() const;
 
     /**
      * Implementing subclasses should provide all geometries in case the backend represents
      * a basic screen and uses the BasicScreens.
      *
      * Base implementation returns a screen with a scale of 1.
      **/
     virtual QVector<qreal> screenScales() const;
     /**
      * Implement this method to receive configuration change requests through KWayland's
      * OutputManagement interface.
      *
      * Base implementation warns that the current backend does not implement this
      * functionality.
      **/
     virtual void configurationChangeRequested(KWayland::Server::OutputConfigurationInterface *config);
 
     /**
      * Whether the Platform requires compositing for rendering.
      * Default implementation returns @c true. If the implementing Platform allows to be used
      * without compositing (e.g. rendering is done by the windowing system), re-implement this method.
      **/
     virtual bool requiresCompositing() const;
     /**
      * Whether Compositing is possible in the Platform.
      * Returning @c false in this method makes only sense if requiresCompositing returns @c false.
      *
      * The default implementation returns @c true.
      * @see requiresCompositing
      **/
     virtual bool compositingPossible() const;
     /**
      * Returns a user facing text explaining why compositing is not possible in case
      * compositingPossible returns @c false.
      *
      * The default implementation returns an empty string.
      * @see compositingPossible
      **/
     virtual QString compositingNotPossibleReason() const;
     /**
      * Whether OpenGL compositing is broken.
      * The Platform can implement this method if it is able to detect whether OpenGL compositing
      * broke (e.g. triggered a crash in a previous run).
      *
      * Default implementation returns @c false.
      * @see createOpenGLSafePoint
      **/
     virtual bool openGLCompositingIsBroken() const;
     enum class OpenGLSafePoint {
         PreInit,
         PostInit,
         PreFrame,
         PostFrame,
         PostLastGuardedFrame
     };
     /**
      * This method is invoked before and after creating the OpenGL rendering Scene.
      * An implementing Platform can use it to detect crashes triggered by the OpenGL implementation.
      * This can be used for openGLCompositingIsBroken.
      *
      * The default implementation does nothing.
      * @see openGLCompositingIsBroken.
      **/
     virtual void createOpenGLSafePoint(OpenGLSafePoint safePoint);
 
     /**
      * Starts an interactive window selection process.
      *
      * Once the user selected a window the @p callback is invoked with the selected Toplevel as
      * argument. In case the user cancels the interactive window selection or selecting a window is currently
      * not possible (e.g. screen locked) the @p callback is invoked with a @c nullptr argument.
      *
      * During the interactive window selection the cursor is turned into a crosshair cursor unless
      * @p cursorName is provided. The argument @p cursorName is a QByteArray instead of Qt::CursorShape
      * to support the "pirate" cursor for kill window which is not wrapped by Qt::CursorShape.
      *
      * The default implementation forwards to InputRedirection.
      *
      * @param callback The function to invoke once the interactive window selection ends
      * @param cursorName The optional name of the cursor shape to use, default is crosshair
      **/
     virtual void startInteractiveWindowSelection(std::function<void(KWin::Toplevel*)> callback, const QByteArray &cursorName = QByteArray());
 
     /**
      * Starts an interactive position selection process.
      *
      * Once the user selected a position on the screen the @p callback is invoked with
      * the selected point as argument. In case the user cancels the interactive position selection
      * or selecting a position is currently not possible (e.g. screen locked) the @p callback
      * is invoked with a point at @c -1 as x and y argument.
      *
      * During the interactive window selection the cursor is turned into a crosshair cursor.
      *
      * The default implementation forwards to InputRedirection.
      *
      * @param callback The function to invoke once the interactive position selection ends
      **/
     virtual void startInteractivePositionSelection(std::function<void(const QPoint &)> callback);
 
     /**
      * Platform specific preparation for an @p action which is used for KGlobalAccel.
      *
      * A platform might need to do preparation for an @p action before
      * it can be used with KGlobalAccel.
      *
      * Code using KGlobalAccel should invoke this method for the @p action
      * prior to setting up any shortcuts and connections.
      *
      * The default implementation does nothing.
      *
      * @param action The action which will be used with KGlobalAccel.
      * @since 5.10
      **/
     virtual void setupActionForGlobalAccel(QAction *action);
 
     bool usesSoftwareCursor() const {
         return m_softWareCursor;
     }
     QImage softwareCursor() const;
     QPoint softwareCursorHotspot() const;
     void markCursorAsRendered();
 
     /**
      * Returns a PlatformCursorImage. By default this is created by softwareCursor and
      * softwareCursorHotspot. An implementing subclass can use this to provide a better
      * suited PlatformCursorImage.
      *
      * @see softwareCursor
      * @see softwareCursorHotspot
      * @since 5.9
      **/
     virtual PlatformCursorImage cursorImage() const;
 
     /**
      * The Platform cursor image should be hidden.
      * @see showCursor
      * @see doHideCursor
      * @see isCursorHidden
      * @since 5.9
      **/
     void hideCursor();
 
     /**
      * The Platform cursor image should be shown again.
      * @see hideCursor
      * @see doShowCursor
      * @see isCursorHidden
      * @since 5.9
      **/
     void showCursor();
 
     /**
      * Whether the cursor is currently hidden.
      * @see showCursor
      * @see hideCursor
      * @since 5.9
      **/
     bool isCursorHidden() const {
         return m_hideCursorCounter > 0;
     }
 
     bool handlesOutputs() const {
         return m_handlesOutputs;
     }
     bool isReady() const {
         return m_ready;
     }
     void setInitialWindowSize(const QSize &size) {
         m_initialWindowSize = size;
     }
     void setDeviceIdentifier(const QByteArray &identifier) {
         m_deviceIdentifier = identifier;
     }
     bool supportsPointerWarping() const {
         return m_pointerWarping;
     }
     bool areOutputsEnabled() const {
         return m_outputsEnabled;
     }
     void setOutputsEnabled(bool enabled) {
         m_outputsEnabled = enabled;
     }
     int initialOutputCount() const {
         return m_initialOutputCount;
     }
     void setInitialOutputCount(int count) {
         m_initialOutputCount = count;
     }
     qreal initialOutputScale() const {
         return m_initialOutputScale;
     }
     void setInitialOutputScale(qreal scale) {
         m_initialOutputScale = scale;
     }
 
     /**
      * Creates the OverlayWindow required for X11 based compositors.
      * Default implementation returns @c nullptr.
      **/
     virtual OverlayWindow *createOverlayWindow();
 
     /**
      * Allows a platform to update the X11 timestamp.
      * Mostly for the X11 standalone platform to interact with QX11Info.
      *
      * Default implementation does nothing. This means code relying on the X timestamp being up to date,
      * might not be working. E.g. synced X11 window resizing
      **/
     virtual void updateXTime();
 
     /**
      * Creates the OutlineVisual for the given @p outline.
      * Default implementation creates an OutlineVisual suited for composited usage.
      **/
     virtual OutlineVisual *createOutline(Outline *outline);
 
     /**
      * Creates the Decoration::Renderer for the given @p client.
      *
      * The default implementation creates a Renderer suited for the Compositor, @c nullptr if there is no Compositor.
      **/
     virtual Decoration::Renderer *createDecorationRenderer(Decoration::DecoratedClientImpl *client);
 
     /**
      * Platform specific way to invert the screen.
      * Default implementation invokes the invert effect
      **/
     virtual void invertScreen();
 
     /**
      * Default implementation creates an EffectsHandlerImp;
      **/
     virtual void createEffectsHandler(Compositor *compositor, Scene *scene);
     /**
      * The CompositingTypes supported by the Platform.
      * The first item should be the most preferred one.
      * @since 5.11
      **/
     virtual QVector<CompositingType> supportedCompositors() const = 0;
 
     /**
      * Whether gamma control is supported by the backend.
      * @since 5.12
      **/
     bool supportsGammaControl() const {
         return m_supportsGammaControl;
     }
 
     ColorCorrect::Manager *colorCorrectManager() {
         return m_colorCorrect;
     }
 
     // outputs with connections (org_kde_kwin_outputdevice)
     virtual Outputs outputs() const {
         return Outputs();
     }
     // actively compositing outputs (wl_output)
     virtual Outputs enabledOutputs() const {
         return Outputs();
     }
 
     /**
      * A string of information to include in kwin debug output
      * It should not be translated.
      *
      * The base implementation prints the name.
      * @since 5.12
      **/
     virtual QString supportInformation() const;
 
+    /**
+     * The compositor plugin which got selected from @link{supportedCompositors}.
+     * Prior to selecting a compositor this returns @c NoCompositing.
+     *
+     * This method allows the platforms to limit the offerings in @link{supportedCompositors}
+     * in case they do not support runtime compositor switching
+     **/
+    CompositingType selectedCompositor() const
+    {
+        return m_selectedCompositor;
+    }
+    /**
+     * Used by Compositor to set the used compositor.
+     **/
+    void setSelectedCompositor(CompositingType type)
+    {
+        m_selectedCompositor = type;
+    }
+
 public Q_SLOTS:
     void pointerMotion(const QPointF &position, quint32 time);
     void pointerButtonPressed(quint32 button, quint32 time);
     void pointerButtonReleased(quint32 button, quint32 time);
     void pointerAxisHorizontal(qreal delta, quint32 time);
     void pointerAxisVertical(qreal delta, quint32 time);
     void keyboardKeyPressed(quint32 key, quint32 time);
     void keyboardKeyReleased(quint32 key, quint32 time);
     void keyboardModifiers(uint32_t modsDepressed, uint32_t modsLatched, uint32_t modsLocked, uint32_t group);
     void keymapChange(int fd, uint32_t size);
     void touchDown(qint32 id, const QPointF &pos, quint32 time);
     void touchUp(qint32 id, quint32 time);
     void touchMotion(qint32 id, const QPointF &pos, quint32 time);
     void touchCancel();
     void touchFrame();
 
     void processSwipeGestureBegin(int fingerCount, quint32 time);
     void processSwipeGestureUpdate(const QSizeF &delta, quint32 time);
     void processSwipeGestureEnd(quint32 time);
     void processSwipeGestureCancelled(quint32 time);
     void processPinchGestureBegin(int fingerCount, quint32 time);
     void processPinchGestureUpdate(qreal scale, qreal angleDelta, const QSizeF &delta, quint32 time);
     void processPinchGestureEnd(quint32 time);
     void processPinchGestureCancelled(quint32 time);
 
 Q_SIGNALS:
     void screensQueried();
     void initFailed();
     void cursorChanged();
     void readyChanged(bool);
     /**
      * Emitted by backends using a one screen (nested window) approach and when the size of that changes.
      **/
     void screenSizeChanged();
 
 protected:
     explicit Platform(QObject *parent = nullptr);
     void setSoftWareCursor(bool set);
     void handleOutputs() {
         m_handlesOutputs = true;
     }
     void repaint(const QRect &rect);
     void setReady(bool ready);
     QSize initialWindowSize() const {
         return m_initialWindowSize;
     }
     QByteArray deviceIdentifier() const {
         return m_deviceIdentifier;
     }
     void setSupportsPointerWarping(bool set) {
         m_pointerWarping = set;
     }
     void setSupportsGammaControl(bool set) {
         m_supportsGammaControl = set;
     }
 
     /**
      * Actual platform specific way to hide the cursor.
      * Sub-classes need to implement if they support hiding the cursor.
      *
      * This method is invoked by hideCursor if the cursor needs to be hidden.
      * The default implementation does nothing.
      *
      * @see doShowCursor
      * @see hideCursor
      * @see showCursor
      **/
     virtual void doHideCursor();
     /**
      * Actual platform specific way to show the cursor.
      * Sub-classes need to implement if they support showing the cursor.
      *
      * This method is invoked by showCursor if the cursor needs to be shown again.
      *
      * @see doShowCursor
      * @see hideCursor
      * @see showCursor
      **/
     virtual void doShowCursor();
 
 private:
     void triggerCursorRepaint();
     bool m_softWareCursor = false;
     struct {
         QRect lastRenderedGeometry;
     } m_cursor;
     bool m_handlesOutputs = false;
     bool m_ready = false;
     QSize m_initialWindowSize;
     QByteArray m_deviceIdentifier;
     bool m_pointerWarping = false;
     bool m_outputsEnabled = true;
     int m_initialOutputCount = 1;
     qreal m_initialOutputScale = 1;
     EGLDisplay m_eglDisplay;
     EGLConfig m_eglConfig = nullptr;
     EGLContext m_context = EGL_NO_CONTEXT;
     EGLSurface m_surface = EGL_NO_SURFACE;
     int m_hideCursorCounter = 0;
     ColorCorrect::Manager *m_colorCorrect = nullptr;
     bool m_supportsGammaControl = false;
+    CompositingType m_selectedCompositor = NoCompositing;
 };
 
 }
 
 Q_DECLARE_INTERFACE(KWin::Platform, "org.kde.kwin.Platform")
 
 #endif
diff --git a/plugins/platforms/drm/drm_backend.cpp b/plugins/platforms/drm/drm_backend.cpp
index 0ae0a7069..34c7c386a 100644
--- a/plugins/platforms/drm/drm_backend.cpp
+++ b/plugins/platforms/drm/drm_backend.cpp
@@ -1,790 +1,793 @@
 /********************************************************************
  KWin - the KDE window manager
  This file is part of the KDE project.
 
 Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #include "drm_backend.h"
 #include "drm_output.h"
 #include "drm_object_connector.h"
 #include "drm_object_crtc.h"
 #include "drm_object_plane.h"
 #include "composite.h"
 #include "cursor.h"
 #include "logging.h"
 #include "logind.h"
 #include "main.h"
 #include "scene_qpainter_drm_backend.h"
 #include "screens_drm.h"
 #include "udev.h"
 #include "wayland_server.h"
 #if HAVE_GBM
 #include "egl_gbm_backend.h"
 #include <gbm.h>
 #endif
 // KWayland
 #include <KWayland/Server/seat_interface.h>
 #include <KWayland/Server/outputconfiguration_interface.h>
 // KF5
 #include <KConfigGroup>
 #include <KCoreAddons>
 #include <KLocalizedString>
 #include <KSharedConfig>
 // Qt
 #include <QCryptographicHash>
 #include <QSocketNotifier>
 #include <QPainter>
 // system
 #include <algorithm>
 #include <unistd.h>
 // drm
 #include <xf86drm.h>
 #include <xf86drmMode.h>
 #include <libdrm/drm_mode.h>
 
 #ifndef DRM_CAP_CURSOR_WIDTH
 #define DRM_CAP_CURSOR_WIDTH 0x8
 #endif
 
 #ifndef DRM_CAP_CURSOR_HEIGHT
 #define DRM_CAP_CURSOR_HEIGHT 0x9
 #endif
 
 #define KWIN_DRM_EVENT_CONTEXT_VERSION 2
 
 namespace KWin
 {
 
 DrmBackend::DrmBackend(QObject *parent)
     : Platform(parent)
     , m_udev(new Udev)
     , m_udevMonitor(m_udev->monitor())
     , m_dpmsFilter()
 {
     setSupportsGammaControl(true);
     handleOutputs();
 }
 
 DrmBackend::~DrmBackend()
 {
 #if HAVE_GBM
     if (m_gbmDevice) {
         gbm_device_destroy(m_gbmDevice);
     }
 #endif
     if (m_fd >= 0) {
         // wait for pageflips
         while (m_pageFlipsPending != 0) {
             QCoreApplication::processEvents(QEventLoop::WaitForMoreEvents);
         }
         // we need to first remove all outputs
         qDeleteAll(m_outputs);
         m_outputs.clear();
         m_enabledOutputs.clear();
 
         qDeleteAll(m_planes);
         qDeleteAll(m_crtcs);
         qDeleteAll(m_connectors);
         close(m_fd);
     }
 }
 
 void DrmBackend::init()
 {
     LogindIntegration *logind = LogindIntegration::self();
     auto takeControl = [logind, this]() {
         if (logind->hasSessionControl()) {
             openDrm();
         } else {
             logind->takeControl();
             connect(logind, &LogindIntegration::hasSessionControlChanged, this, &DrmBackend::openDrm);
         }
     };
     if (logind->isConnected()) {
         takeControl();
     } else {
         connect(logind, &LogindIntegration::connectedChanged, this, takeControl);
     }
 }
 
 Outputs DrmBackend::outputs() const
 {
     return m_outputs;
 }
 
 Outputs DrmBackend::enabledOutputs() const
 {
     return m_enabledOutputs;
 }
 
 void DrmBackend::outputWentOff()
 {
     if (!m_dpmsFilter.isNull()) {
         // already another output is off
         return;
     }
     m_dpmsFilter.reset(new DpmsInputEventFilter(this));
     input()->prependInputEventFilter(m_dpmsFilter.data());
 }
 
 void DrmBackend::turnOutputsOn()
 {
     m_dpmsFilter.reset();
     for (auto it = m_enabledOutputs.constBegin(), end = m_enabledOutputs.constEnd(); it != end; it++) {
         (*it)->updateDpms(KWayland::Server::OutputInterface::DpmsMode::On);
     }
 }
 
 void DrmBackend::checkOutputsAreOn()
 {
     if (m_dpmsFilter.isNull()) {
         // already disabled, all outputs are on
         return;
     }
     for (auto it = m_enabledOutputs.constBegin(), end = m_enabledOutputs.constEnd(); it != end; it++) {
         if (!(*it)->isDpmsEnabled()) {
             // dpms still disabled, need to keep the filter
             return;
         }
     }
     // all outputs are on, disable the filter
     m_dpmsFilter.reset();
 }
 
 void DrmBackend::activate(bool active)
 {
     if (active) {
         qCDebug(KWIN_DRM) << "Activating session.";
         reactivate();
     } else {
         qCDebug(KWIN_DRM) << "Deactivating session.";
         deactivate();
     }
 }
 
 void DrmBackend::reactivate()
 {
     if (m_active) {
         return;
     }
     m_active = true;
     if (!usesSoftwareCursor()) {
         const QPoint cp = Cursor::pos() - softwareCursorHotspot();
         for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {
             DrmOutput *o = *it;
             // only relevant in atomic mode
             o->m_modesetRequested = true;
             o->pageFlipped();   // TODO: Do we really need this?
             o->m_crtc->blank();
             o->showCursor();
             o->moveCursor(cp);
         }
     }
     // restart compositor
     m_pageFlipsPending = 0;
     if (Compositor *compositor = Compositor::self()) {
         compositor->bufferSwapComplete();
         compositor->addRepaintFull();
     }
 }
 
 void DrmBackend::deactivate()
 {
     if (!m_active) {
         return;
     }
     // block compositor
     if (m_pageFlipsPending == 0 && Compositor::self()) {
         Compositor::self()->aboutToSwapBuffers();
     }
     // hide cursor and disable
     for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {
         DrmOutput *o = *it;
         o->hideCursor();
     }
     m_active = false;
 }
 
 void DrmBackend::pageFlipHandler(int fd, unsigned int frame, unsigned int sec, unsigned int usec, void *data)
 {
     Q_UNUSED(fd)
     Q_UNUSED(frame)
     Q_UNUSED(sec)
     Q_UNUSED(usec)
     auto output = reinterpret_cast<DrmOutput*>(data);
     output->pageFlipped();
     output->m_backend->m_pageFlipsPending--;
     if (output->m_backend->m_pageFlipsPending == 0) {
         // TODO: improve, this currently means we wait for all page flips or all outputs.
         // It would be better to driver the repaint per output
 
         if (output->m_dpmsAtomicOffPending) {
             output->m_modesetRequested = true;
             output->dpmsAtomicOff();
         }
 
         if (Compositor::self()) {
             Compositor::self()->bufferSwapComplete();
         }
     }
 }
 
 void DrmBackend::openDrm()
 {
     connect(LogindIntegration::self(), &LogindIntegration::sessionActiveChanged, this, &DrmBackend::activate);
     UdevDevice::Ptr device = m_udev->primaryGpu();
     if (!device) {
         qCWarning(KWIN_DRM) << "Did not find a GPU";
         return;
     }
     int fd = LogindIntegration::self()->takeDevice(device->devNode());
     if (fd < 0) {
         qCWarning(KWIN_DRM) << "failed to open drm device at" << device->devNode();
         return;
     }
     m_fd = fd;
     m_active = true;
     QSocketNotifier *notifier = new QSocketNotifier(m_fd, QSocketNotifier::Read, this);
     connect(notifier, &QSocketNotifier::activated, this,
         [this] {
             if (!LogindIntegration::self()->isActiveSession()) {
                 return;
             }
             drmEventContext e;
             memset(&e, 0, sizeof e);
             e.version = KWIN_DRM_EVENT_CONTEXT_VERSION;
             e.page_flip_handler = pageFlipHandler;
             drmHandleEvent(m_fd, &e);
         }
     );
     m_drmId = device->sysNum();
 
     // trying to activate Atomic Mode Setting (this means also Universal Planes)
     if (!qEnvironmentVariableIsSet("KWIN_DRM_NO_AMS")) {
         if (drmSetClientCap(m_fd, DRM_CLIENT_CAP_ATOMIC, 1) == 0) {
             qCDebug(KWIN_DRM) << "Using Atomic Mode Setting.";
             m_atomicModeSetting = true;
 
             ScopedDrmPointer<drmModePlaneRes, &drmModeFreePlaneResources> planeResources(drmModeGetPlaneResources(m_fd));
             if (!planeResources) {
                 qCWarning(KWIN_DRM) << "Failed to get plane resources. Falling back to legacy mode";
                 m_atomicModeSetting = false;
             }
 
             if (m_atomicModeSetting) {
                 qCDebug(KWIN_DRM) << "Number of planes:" << planeResources->count_planes;
 
                 // create the plane objects
                 for (unsigned int i = 0; i < planeResources->count_planes; ++i) {
                     drmModePlane *kplane = drmModeGetPlane(m_fd, planeResources->planes[i]);
                     DrmPlane *p = new DrmPlane(kplane->plane_id, m_fd);
                     if (p->atomicInit()) {
                         m_planes << p;
                         if (p->type() == DrmPlane::TypeIndex::Overlay) {
                             m_overlayPlanes << p;
                         }
                     } else {
                         delete p;
                     }
                 }
 
                 if (m_planes.isEmpty()) {
                     qCWarning(KWIN_DRM) << "Failed to create any plane. Falling back to legacy mode";
                     m_atomicModeSetting = false;
                 }
             }
         } else {
             qCWarning(KWIN_DRM) << "drmSetClientCap for Atomic Mode Setting failed. Using legacy mode.";
         }
     }
 
     ScopedDrmPointer<_drmModeRes, &drmModeFreeResources> resources(drmModeGetResources(m_fd));
     drmModeRes *res = resources.data();
     if (!resources) {
         qCWarning(KWIN_DRM) << "drmModeGetResources failed";
         return;
     }
 
     for (int i = 0; i < res->count_connectors; ++i) {
         m_connectors << new DrmConnector(res->connectors[i], m_fd);
     }
     for (int i = 0; i < res->count_crtcs; ++i) {
         m_crtcs << new DrmCrtc(res->crtcs[i], this, i);
     }
 
     if (m_atomicModeSetting) {
         auto tryAtomicInit = [] (DrmObject *obj) -> bool {
             if (obj->atomicInit()) {
                 return false;
             } else {
                 delete obj;
                 return true;
             }
         };
         m_connectors.erase(std::remove_if(m_connectors.begin(), m_connectors.end(), tryAtomicInit), m_connectors.end());
         m_crtcs.erase(std::remove_if(m_crtcs.begin(), m_crtcs.end(), tryAtomicInit), m_crtcs.end());
     }
 
     initCursor();
     updateOutputs();
 
     if (m_outputs.isEmpty()) {
         qCWarning(KWIN_DRM) << "No outputs, cannot render, will terminate now";
         emit initFailed();
         return;
     }
 
     // setup udevMonitor
     if (m_udevMonitor) {
         m_udevMonitor->filterSubsystemDevType("drm");
         const int fd = m_udevMonitor->fd();
         if (fd != -1) {
             QSocketNotifier *notifier = new QSocketNotifier(fd, QSocketNotifier::Read, this);
             connect(notifier, &QSocketNotifier::activated, this,
                 [this] {
                     auto device = m_udevMonitor->getDevice();
                     if (!device) {
                         return;
                     }
                     if (device->sysNum() != m_drmId) {
                         return;
                     }
                     if (device->hasProperty("HOTPLUG", "1")) {
                         qCDebug(KWIN_DRM) << "Received hot plug event for monitored drm device";
                         updateOutputs();
                         updateCursor();
                     }
                 }
             );
             m_udevMonitor->enable();
         }
     }
     setReady(true);
 }
 
 void DrmBackend::updateOutputs()
 {
     if (m_fd < 0) {
         return;
     }
 
     ScopedDrmPointer<_drmModeRes, &drmModeFreeResources> resources(drmModeGetResources(m_fd));
     if (!resources) {
         qCWarning(KWIN_DRM) << "drmModeGetResources failed";
         return;
     }
 
     QVector<DrmOutput*> connectedOutputs;
     QVector<DrmConnector*> pendingConnectors;
 
     // split up connected connectors in already or not yet assigned ones
     for (DrmConnector *con : qAsConst(m_connectors)) {
         if (!con->isConnected()) {
             continue;
         }
 
         if (DrmOutput *o = findOutput(con->id())) {
             connectedOutputs << o;
         } else {
             pendingConnectors << con;
         }
     }
 
     // check for outputs which got removed
     auto it = m_outputs.begin();
     while (it != m_outputs.end()) {
         if (connectedOutputs.contains(*it)) {
             it++;
             continue;
         }
         DrmOutput *removed = *it;
         it = m_outputs.erase(it);
         m_enabledOutputs.removeOne(removed);
         emit outputRemoved(removed);
         removed->teardown();
     }
 
     // now check new connections
     for (DrmConnector *con : qAsConst(pendingConnectors)) {
         ScopedDrmPointer<_drmModeConnector, &drmModeFreeConnector> connector(drmModeGetConnector(m_fd, con->id()));
         if (!connector) {
             continue;
         }
         if (connector->count_modes == 0) {
             continue;
         }
         bool outputDone = false;
 
         QVector<uint32_t> encoders = con->encoders();
         for (auto encId : qAsConst(encoders)) {
             ScopedDrmPointer<_drmModeEncoder, &drmModeFreeEncoder> encoder(drmModeGetEncoder(m_fd, encId));
             if (!encoder) {
                 continue;
             }
             for (DrmCrtc *crtc : qAsConst(m_crtcs)) {
                 if (!(encoder->possible_crtcs & (1 << crtc->resIndex()))) {
                         continue;
                 }
 
                 // check if crtc isn't used yet -- currently we don't allow multiple outputs on one crtc (cloned mode)
                 auto it = std::find_if(connectedOutputs.constBegin(), connectedOutputs.constEnd(),
                     [crtc] (DrmOutput *o) {
                         return o->m_crtc == crtc;
                     }
                 );
                 if (it != connectedOutputs.constEnd()) {
                     continue;
                 }
 
                 // we found a suitable encoder+crtc
                 // TODO: we could avoid these lib drm calls if we store all struct data in DrmCrtc and DrmConnector in the beginning
                 ScopedDrmPointer<_drmModeCrtc, &drmModeFreeCrtc> modeCrtc(drmModeGetCrtc(m_fd, crtc->id()));
                 if (!modeCrtc) {
                     continue;
                 }
 
                 DrmOutput *output = new DrmOutput(this);
                 con->setOutput(output);
                 output->m_conn = con;
                 crtc->setOutput(output);
                 output->m_crtc = crtc;
                 connect(output, &DrmOutput::dpmsChanged, this, &DrmBackend::outputDpmsChanged);
 
                 if (modeCrtc->mode_valid) {
                     output->m_mode = modeCrtc->mode;
                 } else {
                     output->m_mode = connector->modes[0];
                 }
                 qCDebug(KWIN_DRM) << "For new output use mode " << output->m_mode.name;
 
                 if (!output->init(connector.data())) {
                     qCWarning(KWIN_DRM) << "Failed to create output for connector " << con->id();
                     delete output;
                     continue;
                 }
                 if (!output->initCursor(m_cursorSize)) {
                     setSoftWareCursor(true);
                 }
                 qCDebug(KWIN_DRM) << "Found new output with uuid" << output->uuid();
 
                 connectedOutputs << output;
                 emit outputAdded(output);
                 outputDone = true;
                 break;
             }
             if (outputDone) {
                 break;
             }
         }
     }
     std::sort(connectedOutputs.begin(), connectedOutputs.end(), [] (DrmOutput *a, DrmOutput *b) { return a->m_conn->id() < b->m_conn->id(); });
     m_outputs = connectedOutputs;
     m_enabledOutputs = connectedOutputs;
     readOutputsConfiguration();
     if (!m_outputs.isEmpty()) {
         emit screensQueried();
     }
 }
 
 void DrmBackend::readOutputsConfiguration()
 {
     if (m_outputs.isEmpty()) {
         return;
     }
     const QByteArray uuid = generateOutputConfigurationUuid();
     const auto outputGroup = kwinApp()->config()->group("DrmOutputs");
     const auto configGroup = outputGroup.group(uuid);
     // default position goes from left to right
     QPoint pos(0, 0);
     for (auto it = m_outputs.begin(); it != m_outputs.end(); ++it) {
         qCDebug(KWIN_DRM) << "Reading output configuration for [" << uuid << "] ["<< (*it)->uuid() << "]";
         const auto outputConfig = configGroup.group((*it)->uuid());
         (*it)->setGlobalPos(outputConfig.readEntry<QPoint>("Position", pos));
         // TODO: add mode
         (*it)->setScale(outputConfig.readEntry("Scale", 1.0));
         pos.setX(pos.x() + (*it)->geometry().width());
     }
 }
 
 QByteArray DrmBackend::generateOutputConfigurationUuid() const
 {
     auto it = m_outputs.constBegin();
     if (m_outputs.size() == 1) {
         // special case: one output
         return (*it)->uuid();
     }
     QCryptographicHash hash(QCryptographicHash::Md5);
     for (; it != m_outputs.constEnd(); ++it) {
         hash.addData((*it)->uuid());
     }
     return hash.result().toHex().left(10);
 }
 
 void DrmBackend::configurationChangeRequested(KWayland::Server::OutputConfigurationInterface *config)
 {
     const auto changes = config->changes();
     bool countChanged = false;
 
     //process all non-disabling changes
     for (auto it = changes.begin(); it != changes.end(); it++) {
         KWayland::Server::OutputChangeSet *changeset = it.value();
 
         auto drmoutput = findOutput(it.key()->uuid());
         if (drmoutput == nullptr) {
             qCWarning(KWIN_DRM) << "Could NOT find DrmOutput matching " << it.key()->uuid();
             continue;
         }
         if (changeset->enabledChanged() && changeset->enabled() == KWayland::Server::OutputDeviceInterface::Enablement::Enabled) {
             drmoutput->setEnabled(true);
             m_enabledOutputs << drmoutput;
             emit outputAdded(drmoutput);
             countChanged = true;
         }
         drmoutput->setChanges(changeset);
     }
     //process any disable requests
     for (auto it = changes.begin(); it != changes.end(); it++) {
         KWayland::Server::OutputChangeSet *changeset = it.value();
         if (changeset->enabledChanged() && changeset->enabled() == KWayland::Server::OutputDeviceInterface::Enablement::Disabled) {
             if (m_enabledOutputs.count() == 1) {
                 qCWarning(KWIN_DRM) << "Not disabling final screen" << it.key()->uuid();
                 continue;
             }
             auto drmoutput = findOutput(it.key()->uuid());
             if (drmoutput == nullptr) {
                 qCWarning(KWIN_DRM) << "Could NOT find DrmOutput matching " << it.key()->uuid();
                 continue;
             }
             drmoutput->setEnabled(false);
             m_enabledOutputs.removeOne(drmoutput);
             emit outputRemoved(drmoutput);
             countChanged = true;
         }
     }
 
     if (countChanged) {
         emit screensQueried();
     } else {
         emit screens()->changed();
     }
     config->setApplied();
 }
 
 DrmOutput *DrmBackend::findOutput(quint32 connector)
 {
     auto it = std::find_if(m_outputs.constBegin(), m_outputs.constEnd(), [connector] (DrmOutput *o) {
         return o->m_conn->id() == connector;
     });
     if (it != m_outputs.constEnd()) {
         return *it;
     }
     return nullptr;
 }
 
 DrmOutput *DrmBackend::findOutput(const QByteArray &uuid)
 {
     auto it = std::find_if(m_outputs.constBegin(), m_outputs.constEnd(), [uuid] (DrmOutput *o) {
         return o->m_uuid == uuid;
     });
     if (it != m_outputs.constEnd()) {
         return *it;
     }
     return nullptr;
 }
 
 void DrmBackend::present(DrmBuffer *buffer, DrmOutput *output)
 {
     if (!buffer || buffer->bufferId() == 0) {
         if (m_deleteBufferAfterPageFlip) {
             delete buffer;
         }
         return;
     }
 
     if (output->present(buffer)) {
         m_pageFlipsPending++;
         if (m_pageFlipsPending == 1 && Compositor::self()) {
             Compositor::self()->aboutToSwapBuffers();
         }
     } else if (m_deleteBufferAfterPageFlip) {
         delete buffer;
     }
 }
 
 void DrmBackend::initCursor()
 {
     m_cursorEnabled = waylandServer()->seat()->hasPointer();
     connect(waylandServer()->seat(), &KWayland::Server::SeatInterface::hasPointerChanged, this,
         [this] {
             m_cursorEnabled = waylandServer()->seat()->hasPointer();
             if (usesSoftwareCursor()) {
                 return;
             }
             for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {
                 if (m_cursorEnabled) {
                     if (!(*it)->showCursor()) {
                         setSoftWareCursor(true);
                     }
                 } else {
                     (*it)->hideCursor();
                 }
             }
         }
     );
     uint64_t capability = 0;
     QSize cursorSize;
     if (drmGetCap(m_fd, DRM_CAP_CURSOR_WIDTH, &capability) == 0) {
         cursorSize.setWidth(capability);
     } else {
         cursorSize.setWidth(64);
     }
     if (drmGetCap(m_fd, DRM_CAP_CURSOR_HEIGHT, &capability) == 0) {
         cursorSize.setHeight(capability);
     } else {
         cursorSize.setHeight(64);
     }
     m_cursorSize = cursorSize;
     // now we have screens and can set cursors, so start tracking
     connect(this, &DrmBackend::cursorChanged, this, &DrmBackend::updateCursor);
     connect(Cursor::self(), &Cursor::posChanged, this, &DrmBackend::moveCursor);
 }
 
 void DrmBackend::setCursor()
 {
     if (m_cursorEnabled) {
         for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {
             if (!(*it)->showCursor()) {
                 setSoftWareCursor(true);
             }
         }
     }
     markCursorAsRendered();
 }
 
 void DrmBackend::updateCursor()
 {
     if (usesSoftwareCursor()) {
         return;
     }
     if (isCursorHidden()) {
         return;
     }
     const QImage &cursorImage = softwareCursor();
     if (cursorImage.isNull()) {
         doHideCursor();
         return;
     }
     for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {
         (*it)->updateCursor();
     }
 
     setCursor();
     moveCursor();
 }
 
 void DrmBackend::doShowCursor()
 {
     updateCursor();
 }
 
 void DrmBackend::doHideCursor()
 {
     if (!m_cursorEnabled) {
         return;
     }
     for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {
         (*it)->hideCursor();
     }
 }
 
 void DrmBackend::moveCursor()
 {
     if (!m_cursorEnabled || isCursorHidden()) {
         return;
     }
     for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {
         (*it)->moveCursor(Cursor::pos());
     }
 }
 
 Screens *DrmBackend::createScreens(QObject *parent)
 {
     return new DrmScreens(this, parent);
 }
 
 QPainterBackend *DrmBackend::createQPainterBackend()
 {
     m_deleteBufferAfterPageFlip = false;
     return new DrmQPainterBackend(this);
 }
 
 OpenGLBackend *DrmBackend::createOpenGLBackend()
 {
 #if HAVE_GBM
     m_deleteBufferAfterPageFlip = true;
     return new EglGbmBackend(this);
 #else
     return Platform::createOpenGLBackend();
 #endif
 }
 
 DrmDumbBuffer *DrmBackend::createBuffer(const QSize &size)
 {
     DrmDumbBuffer *b = new DrmDumbBuffer(m_fd, size);
     return b;
 }
 
 #if HAVE_GBM
 DrmSurfaceBuffer *DrmBackend::createBuffer(const std::shared_ptr<GbmSurface> &surface)
 {
     DrmSurfaceBuffer *b = new DrmSurfaceBuffer(m_fd, surface);
     return b;
 }
 #endif
 
 void DrmBackend::outputDpmsChanged()
 {
     if (m_enabledOutputs.isEmpty()) {
         return;
     }
     bool enabled = false;
     for (auto it = m_enabledOutputs.constBegin(); it != m_enabledOutputs.constEnd(); ++it) {
         enabled = enabled || (*it)->isDpmsEnabled();
     }
     setOutputsEnabled(enabled);
 }
 
 QVector<CompositingType> DrmBackend::supportedCompositors() const
 {
+    if (selectedCompositor() != NoCompositing) {
+        return {selectedCompositor()};
+    }
 #if HAVE_GBM
     return QVector<CompositingType>{OpenGLCompositing, QPainterCompositing};
 #else
     return QVector<CompositingType>{QPainterCompositing};
 #endif
 }
 
 QString DrmBackend::supportInformation() const
 {
     QString supportInfo;
     QDebug s(&supportInfo);
     s.nospace();
     s << "Name: " << "DRM" << endl;
     s << "Active: " << m_active << endl;
     s << "Atomic Mode Setting: " << m_atomicModeSetting << endl;
     return supportInfo;
 }
 
 }
diff --git a/plugins/platforms/virtual/virtual_backend.h b/plugins/platforms/virtual/virtual_backend.h
index b22f4b3fa..458dee57d 100644
--- a/plugins/platforms/virtual/virtual_backend.h
+++ b/plugins/platforms/virtual/virtual_backend.h
@@ -1,76 +1,79 @@
 /********************************************************************
  KWin - the KDE window manager
  This file is part of the KDE project.
 
 Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #ifndef KWIN_VIRTUAL_BACKEND_H
 #define KWIN_VIRTUAL_BACKEND_H
 #include "platform.h"
 
 #include <kwin_export.h>
 
 #include <QObject>
 #include <QRect>
 
 class QTemporaryDir;
 
 namespace KWin
 {
 class VirtualOutput;
 
 class KWIN_EXPORT VirtualBackend : public Platform
 {
     Q_OBJECT
     Q_INTERFACES(KWin::Platform)
     Q_PLUGIN_METADATA(IID "org.kde.kwin.Platform" FILE "virtual.json")
 
 public:
     VirtualBackend(QObject *parent = nullptr);
     virtual ~VirtualBackend();
     void init() override;
 
     bool saveFrames() const {
         return !m_screenshotDir.isNull();
     }
     QString screenshotDirPath() const;
 
     Screens *createScreens(QObject *parent = nullptr) override;
     QPainterBackend* createQPainterBackend() override;
     OpenGLBackend *createOpenGLBackend() override;
 
     Q_INVOKABLE void setVirtualOutputs(int count, QVector<QRect> geometries = QVector<QRect>(), QVector<int> scales = QVector<int>());
 
     Outputs outputs() const override;
     Outputs enabledOutputs() const override;
 
     QVector<CompositingType> supportedCompositors() const override {
+        if (selectedCompositor() != NoCompositing) {
+            return {selectedCompositor()};
+        }
         return QVector<CompositingType>{OpenGLCompositing, QPainterCompositing};
     }
 
 Q_SIGNALS:
     void virtualOutputsSet(bool countChanged);
 
 private:
     QVector<VirtualOutput*> m_outputs;
     QVector<VirtualOutput*> m_enabledOutputs;
 
     QScopedPointer<QTemporaryDir> m_screenshotDir;
 };
 
 }
 
 #endif
diff --git a/plugins/platforms/wayland/wayland_backend.cpp b/plugins/platforms/wayland/wayland_backend.cpp
index e06881f09..71e95e96c 100644
--- a/plugins/platforms/wayland/wayland_backend.cpp
+++ b/plugins/platforms/wayland/wayland_backend.cpp
@@ -1,668 +1,671 @@
 /********************************************************************
  KWin - the KDE window manager
  This file is part of the KDE project.
 
 Copyright (C) 2013 Martin Gräßlin <mgraesslin@kde.org>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 // own
 #include "wayland_backend.h"
 #include <config-kwin.h>
 // KWin
 #include "cursor.h"
 #include "logging.h"
 #include "main.h"
 #include "scene_qpainter_wayland_backend.h"
 #include "screens.h"
 #include "wayland_server.h"
 #include "wayland_cursor_theme.h"
 #if HAVE_WAYLAND_EGL
 #include "egl_wayland_backend.h"
 #endif
 #include <KWayland/Client/buffer.h>
 #include <KWayland/Client/compositor.h>
 #include <KWayland/Client/connection_thread.h>
 #include <KWayland/Client/event_queue.h>
 #include <KWayland/Client/keyboard.h>
 #include <KWayland/Client/pointer.h>
 #include <KWayland/Client/pointerconstraints.h>
 #include <KWayland/Client/pointergestures.h>
 #include <KWayland/Client/region.h>
 #include <KWayland/Client/registry.h>
 #include <KWayland/Client/seat.h>
 #include <KWayland/Client/server_decoration.h>
 #include <KWayland/Client/shell.h>
 #include <KWayland/Client/shm_pool.h>
 #include <KWayland/Client/surface.h>
 #include <KWayland/Client/touch.h>
 #include <KWayland/Client/xdgshell.h>
 #include <KWayland/Server/buffer_interface.h>
 #include <KWayland/Server/display.h>
 #include <KWayland/Server/seat_interface.h>
 #include <KWayland/Server/surface_interface.h>
 
 #include <KLocalizedString>
 // Qt
 #include <QMetaMethod>
 #include <QThread>
 // Wayland
 #include <wayland-cursor.h>
 
 #include <linux/input.h>
 
 namespace KWin
 {
 namespace Wayland
 {
 
 using namespace KWayland::Client;
 
 WaylandSeat::WaylandSeat(wl_seat *seat, WaylandBackend *backend)
     : QObject(NULL)
     , m_seat(new Seat(this))
     , m_pointer(NULL)
     , m_keyboard(NULL)
     , m_touch(nullptr)
     , m_cursor(NULL)
     , m_enteredSerial(0)
     , m_backend(backend)
     , m_installCursor(false)
 {
     m_seat->setup(seat);
     connect(m_seat, &Seat::hasKeyboardChanged, this,
         [this](bool hasKeyboard) {
             if (hasKeyboard) {
                 m_keyboard = m_seat->createKeyboard(this);
                 connect(m_keyboard, &Keyboard::keyChanged, this,
                     [this](quint32 key, Keyboard::KeyState state, quint32 time) {
                         switch (state) {
                         case Keyboard::KeyState::Pressed:
                             if (key == KEY_RIGHTCTRL) {
                                 m_backend->togglePointerConfinement();
                             }
                             m_backend->keyboardKeyPressed(key, time);
                             break;
                         case Keyboard::KeyState::Released:
                             m_backend->keyboardKeyReleased(key, time);
                             break;
                         default:
                             Q_UNREACHABLE();
                         }
                     }
                 );
                 connect(m_keyboard, &Keyboard::modifiersChanged, this,
                     [this](quint32 depressed, quint32 latched, quint32 locked, quint32 group) {
                         m_backend->keyboardModifiers(depressed, latched, locked, group);
                     }
                 );
                 connect(m_keyboard, &Keyboard::keymapChanged, this,
                     [this](int fd, quint32 size) {
                         m_backend->keymapChange(fd, size);
                     }
                 );
             } else {
                 destroyKeyboard();
             }
         }
     );
     connect(m_seat, &Seat::hasPointerChanged, this,
         [this](bool hasPointer) {
             if (hasPointer && !m_pointer) {
                 m_pointer = m_seat->createPointer(this);
                 setupPointerGestures();
                 connect(m_pointer, &Pointer::entered, this,
                     [this](quint32 serial) {
                         m_enteredSerial = serial;
                         if (!m_installCursor) {
                             // explicitly hide cursor
                             m_pointer->hideCursor();
                         }
                     }
                 );
                 connect(m_pointer, &Pointer::motion, this,
                     [this](const QPointF &relativeToSurface, quint32 time) {
                         m_backend->pointerMotion(relativeToSurface, time);
                     }
                 );
                 connect(m_pointer, &Pointer::buttonStateChanged, this,
                     [this](quint32 serial, quint32 time, quint32 button, Pointer::ButtonState state) {
                         Q_UNUSED(serial)
                         switch (state) {
                         case Pointer::ButtonState::Pressed:
                             m_backend->pointerButtonPressed(button, time);
                             break;
                         case Pointer::ButtonState::Released:
                             m_backend->pointerButtonReleased(button, time);
                             break;
                         default:
                             Q_UNREACHABLE();
                         }
                     }
                 );
                 connect(m_pointer, &Pointer::axisChanged, this,
                     [this](quint32 time, Pointer::Axis axis, qreal delta) {
                         switch (axis) {
                         case Pointer::Axis::Horizontal:
                             m_backend->pointerAxisHorizontal(delta, time);
                             break;
                         case Pointer::Axis::Vertical:
                             m_backend->pointerAxisVertical(delta, time);
                             break;
                         default:
                             Q_UNREACHABLE();
                         }
                     }
                 );
             } else {
                 destroyPointer();
             }
         }
     );
     connect(m_seat, &Seat::hasTouchChanged,
         [this] (bool hasTouch) {
             if (hasTouch && !m_touch) {
                 m_touch = m_seat->createTouch(this);
                 connect(m_touch, &Touch::sequenceCanceled, m_backend, &Platform::touchCancel);
                 connect(m_touch, &Touch::frameEnded, m_backend, &Platform::touchFrame);
                 connect(m_touch, &Touch::sequenceStarted, this,
                     [this] (TouchPoint *tp) {
                         m_backend->touchDown(tp->id(), tp->position(), tp->time());
                     }
                 );
                 connect(m_touch, &Touch::pointAdded, this,
                     [this] (TouchPoint *tp) {
                         m_backend->touchDown(tp->id(), tp->position(), tp->time());
                     }
                 );
                 connect(m_touch, &Touch::pointRemoved, this,
                     [this] (TouchPoint *tp) {
                         m_backend->touchUp(tp->id(), tp->time());
                     }
                 );
                 connect(m_touch, &Touch::pointMoved, this,
                     [this] (TouchPoint *tp) {
                         m_backend->touchMotion(tp->id(), tp->position(), tp->time());
                     }
                 );
             } else {
                 destroyTouch();
             }
         }
     );
     WaylandServer *server = waylandServer();
     if (server) {
         using namespace KWayland::Server;
         SeatInterface *si = server->seat();
         connect(m_seat, &Seat::hasKeyboardChanged, si, &SeatInterface::setHasKeyboard);
         connect(m_seat, &Seat::hasPointerChanged, si, &SeatInterface::setHasPointer);
         connect(m_seat, &Seat::hasTouchChanged, si, &SeatInterface::setHasTouch);
         connect(m_seat, &Seat::nameChanged, si, &SeatInterface::setName);
     }
 }
 
 WaylandSeat::~WaylandSeat()
 {
     destroyPointer();
     destroyKeyboard();
     destroyTouch();
 }
 
 void WaylandSeat::destroyPointer()
 {
     delete m_pinchGesture;
     m_pinchGesture = nullptr;
     delete m_swipeGesture;
     m_swipeGesture = nullptr;
     delete m_pointer;
     m_pointer = nullptr;
 }
 
 void WaylandSeat::destroyKeyboard()
 {
     delete m_keyboard;
     m_keyboard = nullptr;
 }
 
 void WaylandSeat::destroyTouch()
 {
     delete m_touch;
     m_touch = nullptr;
 }
 
 void WaylandSeat::installCursorImage(wl_buffer *image, const QSize &size, const QPoint &hotSpot)
 {
     if (!m_installCursor) {
         return;
     }
     if (!m_pointer || !m_pointer->isValid()) {
         return;
     }
     if (!m_cursor) {
         m_cursor = m_backend->compositor()->createSurface(this);
     }
     if (!m_cursor || !m_cursor->isValid()) {
         return;
     }
     m_pointer->setCursor(m_cursor, hotSpot);
     m_cursor->attachBuffer(image);
     m_cursor->damage(QRect(QPoint(0,0), size));
     m_cursor->commit(Surface::CommitFlag::None);
     m_backend->flush();
 }
 
 void WaylandSeat::installCursorImage(const QImage &image, const QPoint &hotSpot)
 {
     if (image.isNull()) {
         installCursorImage(nullptr, QSize(), QPoint());
         return;
     }
     installCursorImage(*(m_backend->shmPool()->createBuffer(image).data()), image.size(), hotSpot);
 }
 
 void WaylandSeat::setInstallCursor(bool install)
 {
     // TODO: remove, add?
     m_installCursor = install;
 }
 
 void WaylandSeat::setupPointerGestures()
 {
     if (!m_pointer || !m_gesturesInterface) {
         return;
     }
     if (m_pinchGesture || m_swipeGesture) {
         return;
     }
     m_pinchGesture = m_gesturesInterface->createPinchGesture(m_pointer, this);
     m_swipeGesture = m_gesturesInterface->createSwipeGesture(m_pointer, this);
     connect(m_pinchGesture, &PointerPinchGesture::started, m_backend,
         [this] (quint32 serial, quint32 time) {
             Q_UNUSED(serial);
             m_backend->processPinchGestureBegin(m_pinchGesture->fingerCount(), time);
         }
     );
     connect(m_pinchGesture, &PointerPinchGesture::updated, m_backend,
         [this] (const QSizeF &delta, qreal scale, qreal rotation, quint32 time) {
             m_backend->processPinchGestureUpdate(scale, rotation, delta, time);
         }
     );
     connect(m_pinchGesture, &PointerPinchGesture::ended, m_backend,
         [this] (quint32 serial, quint32 time) {
             Q_UNUSED(serial)
             m_backend->processPinchGestureEnd(time);
         }
     );
     connect(m_pinchGesture, &PointerPinchGesture::cancelled, m_backend,
         [this] (quint32 serial, quint32 time) {
             Q_UNUSED(serial)
             m_backend->processPinchGestureCancelled(time);
         }
     );
 
     connect(m_swipeGesture, &PointerSwipeGesture::started, m_backend,
         [this] (quint32 serial, quint32 time) {
             Q_UNUSED(serial)
             m_backend->processSwipeGestureBegin(m_swipeGesture->fingerCount(), time);
         }
     );
     connect(m_swipeGesture, &PointerSwipeGesture::updated, m_backend, &Platform::processSwipeGestureUpdate);
     connect(m_swipeGesture, &PointerSwipeGesture::ended, m_backend,
         [this] (quint32 serial, quint32 time) {
             Q_UNUSED(serial)
             m_backend->processSwipeGestureEnd(time);
         }
     );
     connect(m_swipeGesture, &PointerSwipeGesture::cancelled, m_backend,
         [this] (quint32 serial, quint32 time) {
             Q_UNUSED(serial)
             m_backend->processSwipeGestureCancelled(time);
         }
     );
 }
 
 WaylandBackend::WaylandBackend(QObject *parent)
     : Platform(parent)
     , m_display(nullptr)
     , m_eventQueue(new EventQueue(this))
     , m_registry(new Registry(this))
     , m_compositor(new KWayland::Client::Compositor(this))
     , m_shell(new Shell(this))
     , m_surface(nullptr)
     , m_shellSurface(NULL)
     , m_seat()
     , m_shm(new ShmPool(this))
     , m_connectionThreadObject(new ConnectionThread(nullptr))
     , m_connectionThread(nullptr)
 {
     connect(this, &WaylandBackend::connectionFailed, this, &WaylandBackend::initFailed);
     connect(this, &WaylandBackend::shellSurfaceSizeChanged, this, &WaylandBackend::screenSizeChanged);
 }
 
 WaylandBackend::~WaylandBackend()
 {
     if (m_pointerConstraints) {
         m_pointerConstraints->release();
     }
     if (m_xdgShellSurface) {
         m_xdgShellSurface->release();
     }
     if (m_shellSurface) {
         m_shellSurface->release();
     }
     if (m_surface) {
         m_surface->release();
     }
     if (m_xdgShell) {
         m_xdgShell->release();
     }
     m_shell->release();
     m_compositor->release();
     m_registry->release();
     m_seat.reset();
     m_shm->release();
     m_eventQueue->release();
 
     m_connectionThreadObject->deleteLater();
     m_connectionThread->quit();
     m_connectionThread->wait();
 
     qCDebug(KWIN_WAYLAND_BACKEND) << "Destroyed Wayland display";
 }
 
 void WaylandBackend::init()
 {
     connect(m_registry, &Registry::compositorAnnounced, this,
         [this](quint32 name) {
             m_compositor->setup(m_registry->bindCompositor(name, 1));
         }
     );
     connect(m_registry, &Registry::shellAnnounced, this,
         [this](quint32 name) {
             m_shell->setup(m_registry->bindShell(name, 1));
         }
     );
     connect(m_registry, &Registry::seatAnnounced, this,
         [this](quint32 name) {
             if (Application::usesLibinput()) {
                 return;
             }
             m_seat.reset(new WaylandSeat(m_registry->bindSeat(name, 2), this));
         }
     );
     connect(m_registry, &Registry::shmAnnounced, this,
         [this](quint32 name) {
             m_shm->setup(m_registry->bindShm(name, 1));
         }
     );
     connect(m_registry, &Registry::pointerConstraintsUnstableV1Announced, this,
         [this](quint32 name, quint32 version) {
             if (m_pointerConstraints) {
                 return;
             }
             m_pointerConstraints = m_registry->createPointerConstraints(name, version, this);
             updateWindowTitle();
         }
     );
     connect(m_registry, &Registry::interfacesAnnounced, this, &WaylandBackend::createSurface);
     connect(m_registry, &Registry::interfacesAnnounced, this,
         [this] {
             if (!m_seat) {
                 return;
             }
             const auto gi = m_registry->interface(Registry::Interface::PointerGesturesUnstableV1);
             if (gi.name == 0) {
                 return;
             }
             auto gesturesInterface = m_registry->createPointerGestures(gi.name, gi.version, m_seat.data());
             m_seat->installGesturesInterface(gesturesInterface);
         }
     );
     if (!deviceIdentifier().isEmpty()) {
         m_connectionThreadObject->setSocketName(deviceIdentifier());
     }
     connect(this, &WaylandBackend::cursorChanged, this,
         [this] {
             if (m_seat.isNull() || !m_seat->isInstallCursor()) {
                 return;
             }
             m_seat->installCursorImage(softwareCursor(), softwareCursorHotspot());
             markCursorAsRendered();
         }
     );
     initConnection();
 }
 
 void WaylandBackend::initConnection()
 {
     connect(m_connectionThreadObject, &ConnectionThread::connected, this,
         [this]() {
             // create the event queue for the main gui thread
             m_display = m_connectionThreadObject->display();
             m_eventQueue->setup(m_connectionThreadObject);
             m_registry->setEventQueue(m_eventQueue);
             // setup registry
             m_registry->create(m_display);
             m_registry->setup();
         },
         Qt::QueuedConnection);
     connect(m_connectionThreadObject, &ConnectionThread::connectionDied, this,
         [this]() {
             setReady(false);
             emit systemCompositorDied();
             m_seat.reset();
             m_shm->destroy();
             if (m_xdgShellSurface) {
                 m_xdgShellSurface->destroy();
                 delete m_xdgShellSurface;
                 m_xdgShellSurface = nullptr;
             }
             if (m_shellSurface) {
                 m_shellSurface->destroy();
                 delete m_shellSurface;
                 m_shellSurface = nullptr;
             }
             if (m_surface) {
                 m_surface->destroy();
                 delete m_surface;
                 m_surface = nullptr;
             }
             if (m_shell) {
                 m_shell->destroy();
             }
             if (m_xdgShell) {
                 m_xdgShell->destroy();
             }
             m_compositor->destroy();
             m_registry->destroy();
             m_eventQueue->destroy();
             if (m_display) {
                 m_display = nullptr;
             }
         },
         Qt::QueuedConnection);
     connect(m_connectionThreadObject, &ConnectionThread::failed, this, &WaylandBackend::connectionFailed, Qt::QueuedConnection);
 
     m_connectionThread = new QThread(this);
     m_connectionThreadObject->moveToThread(m_connectionThread);
     m_connectionThread->start();
 
     m_connectionThreadObject->initConnection();
 }
 
 void WaylandBackend::createSurface()
 {
     m_surface = m_compositor->createSurface(this);
     if (!m_surface || !m_surface->isValid()) {
         qCCritical(KWIN_WAYLAND_BACKEND) << "Creating Wayland Surface failed";
         return;
     }
     using namespace KWayland::Client;
     auto iface = m_registry->interface(Registry::Interface::ServerSideDecorationManager);
     if (iface.name != 0) {
         auto manager = m_registry->createServerSideDecorationManager(iface.name, iface.version, this);
         auto decoration = manager->create(m_surface, this);
         connect(decoration, &ServerSideDecoration::modeChanged, this,
             [this, decoration] {
                 if (decoration->mode() != ServerSideDecoration::Mode::Server) {
                     decoration->requestMode(ServerSideDecoration::Mode::Server);
                 }
             }
         );
     }
     if (m_seat) {
         m_seat->setInstallCursor(true);
     }
     // check for xdg shell
     auto xdgIface = m_registry->interface(Registry::Interface::XdgShellUnstableV6);
     if (xdgIface.name != 0) {
         m_xdgShell = m_registry->createXdgShell(xdgIface.name, xdgIface.version, this);
         if (m_xdgShell && m_xdgShell->isValid()) {
             m_xdgShellSurface = m_xdgShell->createSurface(m_surface, this);
             connect(m_xdgShellSurface, &XdgShellSurface::closeRequested, qApp, &QCoreApplication::quit);
             setupSurface(m_xdgShellSurface);
             return;
         }
     }
     if (m_shell->isValid()) {
         m_shellSurface = m_shell->createSurface(m_surface, this);
         setupSurface(m_shellSurface);
         m_shellSurface->setToplevel();
     }
 }
 
 template <class T>
 void WaylandBackend::setupSurface(T *surface)
 {
     connect(surface, &T::sizeChanged, this, &WaylandBackend::shellSurfaceSizeChanged);
     surface->setSize(initialWindowSize());
     updateWindowTitle();
     setReady(true);
     emit screensQueried();
 }
 
 QSize WaylandBackend::shellSurfaceSize() const
 {
     if (m_shellSurface) {
         return m_shellSurface->size();
     }
     if (m_xdgShellSurface) {
         return m_xdgShellSurface->size();
     }
     return QSize();
 }
 
 Screens *WaylandBackend::createScreens(QObject *parent)
 {
     return new BasicScreens(this, parent);
 }
 
 OpenGLBackend *WaylandBackend::createOpenGLBackend()
 {
 #if HAVE_WAYLAND_EGL
     return new EglWaylandBackend(this);
 #else
     return nullptr;
 #endif
 }
 
 QPainterBackend *WaylandBackend::createQPainterBackend()
 {
     return new WaylandQPainterBackend(this);
 }
 
 void WaylandBackend::flush()
 {
     if (m_connectionThreadObject) {
         m_connectionThreadObject->flush();
     }
 }
 
 void WaylandBackend::togglePointerConfinement()
 {
     if (!m_pointerConstraints) {
         return;
     }
     if (!m_seat) {
         return;
     }
     auto p = m_seat->pointer();
     if (!p) {
         return;
     }
     if (!m_surface) {
         return;
     }
     if (m_pointerConfinement && m_isPointerConfined) {
         delete m_pointerConfinement;
         m_pointerConfinement = nullptr;
         m_isPointerConfined = false;
         updateWindowTitle();
         flush();
         return;
     } else if (m_pointerConfinement) {
         return;
     }
     m_pointerConfinement = m_pointerConstraints->confinePointer(m_surface, p, nullptr, PointerConstraints::LifeTime::Persistent, this);
     connect(m_pointerConfinement, &ConfinedPointer::confined, this,
         [this] {
             m_isPointerConfined = true;
             updateWindowTitle();
         }
     );
     connect(m_pointerConfinement, &ConfinedPointer::unconfined, this,
         [this] {
             m_isPointerConfined = false;
             updateWindowTitle();
         }
     );
     updateWindowTitle();
     flush();
 }
 
 void WaylandBackend::updateWindowTitle()
 {
     if (!m_xdgShellSurface) {
         return;
     }
     QString grab;
     if (m_isPointerConfined) {
         grab = i18n("Press right control to ungrab pointer");
     } else {
         if (!m_pointerConfinement && m_pointerConstraints) {
             grab = i18n("Press right control key to grab pointer");
         }
     }
     const QString title = i18nc("Title of nested KWin Wayland with Wayland socket identifier as argument",
                                 "KDE Wayland Compositor (%1)", waylandServer()->display()->socketName());
     if (grab.isEmpty()) {
         m_xdgShellSurface->setTitle(title);
     } else {
         m_xdgShellSurface->setTitle(title + QStringLiteral(" - ") + grab);
     }
 }
 
 QVector<CompositingType> WaylandBackend::supportedCompositors() const
 {
+    if (selectedCompositor() != NoCompositing) {
+        return {selectedCompositor()};
+    }
 #if HAVE_WAYLAND_EGL
     return QVector<CompositingType>{OpenGLCompositing, QPainterCompositing};
 #else
     return QVector<CompositingType>{QPainterCompositing};
 #endif
 }
 
 
 }
 
 } // KWin
diff --git a/plugins/platforms/x11/windowed/x11windowed_backend.h b/plugins/platforms/x11/windowed/x11windowed_backend.h
index b34392cf9..b1df54573 100644
--- a/plugins/platforms/x11/windowed/x11windowed_backend.h
+++ b/plugins/platforms/x11/windowed/x11windowed_backend.h
@@ -1,120 +1,123 @@
 /********************************************************************
  KWin - the KDE window manager
  This file is part of the KDE project.
 
 Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 #ifndef KWIN_X11WINDOWED_BACKEND_H
 #define KWIN_X11WINDOWED_BACKEND_H
 #include "platform.h"
 
 #include <kwin_export.h>
 
 #include <QObject>
 #include <QSize>
 
 #include <xcb/xcb.h>
 
 struct _XDisplay;
 typedef struct _XDisplay Display;
 typedef struct _XCBKeySymbols xcb_key_symbols_t;
 class NETWinInfo;
 
 namespace KWin
 {
 
 class KWIN_EXPORT X11WindowedBackend : public Platform
 {
     Q_OBJECT
     Q_INTERFACES(KWin::Platform)
     Q_PLUGIN_METADATA(IID "org.kde.kwin.Platform" FILE "x11.json")
     Q_PROPERTY(QSize size READ screenSize NOTIFY sizeChanged)
 public:
     X11WindowedBackend(QObject *parent = nullptr);
     virtual ~X11WindowedBackend();
     void init() override;
     QVector<QRect> screenGeometries() const override;
     QVector<qreal> screenScales() const override;
 
     xcb_connection_t *connection() const {
         return m_connection;
     }
     int screenNumer() const {
         return m_screenNumber;
     }
     xcb_window_t window() const {
         return windowForScreen(0);
     }
     xcb_window_t windowForScreen(int screen) const;
     Display *display() const {
         return m_display;
     }
     xcb_window_t rootWindow() const;
 
     Screens *createScreens(QObject *parent = nullptr) override;
     OpenGLBackend *createOpenGLBackend() override;
     QPainterBackend* createQPainterBackend() override;
     void warpPointer(const QPointF &globalPos) override;
 
     QVector<CompositingType> supportedCompositors() const override {
+        if (selectedCompositor() != NoCompositing) {
+            return {selectedCompositor()};
+        }
         return QVector<CompositingType>{OpenGLCompositing, QPainterCompositing};
     }
 
 Q_SIGNALS:
     void sizeChanged();
 
 private:
     void createWindow();
     void startEventReading();
     void grabKeyboard(xcb_timestamp_t time);
     void updateWindowTitle();
     void handleEvent(xcb_generic_event_t *event);
     void handleClientMessage(xcb_client_message_event_t *event);
     void handleButtonPress(xcb_button_press_event_t *event);
     void handleExpose(xcb_expose_event_t *event);
     void updateSize(xcb_configure_notify_event_t *event);
     void createCursor(const QImage &img, const QPoint &hotspot);
     void initXInputForWindow(xcb_window_t window);
     void initXInput();
 
     xcb_connection_t *m_connection = nullptr;
     xcb_screen_t *m_screen = nullptr;
     xcb_key_symbols_t *m_keySymbols = nullptr;
     int m_screenNumber = 0;
     struct Output {
         xcb_window_t window = XCB_WINDOW_NONE;
         QSize size;
         qreal scale = 1;
         QPoint xPosition;
         QPoint internalPosition;
         NETWinInfo *winInfo = nullptr;
     };
     QVector<Output> m_windows;
     xcb_atom_t m_protocols = XCB_ATOM_NONE;
     xcb_atom_t m_deleteWindowProtocol = XCB_ATOM_NONE;
     xcb_cursor_t m_cursor = XCB_CURSOR_NONE;
     Display *m_display = nullptr;
     bool m_keyboardGrabbed = false;
 
     bool m_hasXInput = false;
     int m_xiOpcode = 0;
     int m_majorVersion = 0;
     int m_minorVersion = 0;
 };
 
 }
 
 #endif