diff --git a/scene.cpp b/scene.cpp
index 550e114f4..c8f449031 100644
--- a/scene.cpp
+++ b/scene.cpp
@@ -1,1145 +1,1147 @@
 /********************************************************************
  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/>.
 *********************************************************************/
 
 /*
  The base class for compositing, implementing shared functionality
  between the OpenGL and XRender backends.
 
  Design:
 
  When compositing is turned on, XComposite extension is used to redirect
  drawing of windows to pixmaps and XDamage extension is used to get informed
  about damage (changes) to window contents. This code is mostly in composite.cpp .
 
  Compositor::performCompositing() starts one painting pass. Painting is done
  by painting the screen, which in turn paints every window. Painting can be affected
  using effects, which are chained. E.g. painting a screen means that actually
  paintScreen() of the first effect is called, which possibly does modifications
  and calls next effect's paintScreen() and so on, until Scene::finalPaintScreen()
  is called.
 
  There are 3 phases of every paint (not necessarily done together):
  The pre-paint phase, the paint phase and the post-paint phase.
 
  The pre-paint phase is used to find out about how the painting will be actually
  done (i.e. what the effects will do). For example when only a part of the screen
  needs to be updated and no effect will do any transformation it is possible to use
  an optimized paint function. How the painting will be done is controlled
  by the mask argument, see PAINT_WINDOW_* and PAINT_SCREEN_* flags in scene.h .
  For example an effect that decides to paint a normal windows as translucent
  will need to modify the mask in its prePaintWindow() to include
  the PAINT_WINDOW_TRANSLUCENT flag. The paintWindow() function will then get
  the mask with this flag turned on and will also paint using transparency.
 
  The paint pass does the actual painting, based on the information collected
  using the pre-paint pass. After running through the effects' paintScreen()
  either paintGenericScreen() or optimized paintSimpleScreen() are called.
  Those call paintWindow() on windows (not necessarily all), possibly using
  clipping to optimize performance and calling paintWindow() first with only
  PAINT_WINDOW_OPAQUE to paint the opaque parts and then later
  with PAINT_WINDOW_TRANSLUCENT to paint the transparent parts. Function
  paintWindow() again goes through effects' paintWindow() until
  finalPaintWindow() is called, which calls the window's performPaint() to
  do the actual painting.
 
  The post-paint can be used for cleanups and is also used for scheduling
  repaints during the next painting pass for animations. Effects wanting to
  repaint certain parts can manually damage them during post-paint and repaint
  of these parts will be done during the next paint pass.
 
 */
 
 #include "scene.h"
 
 #include <QQuickWindow>
 #include <QVector2D>
 
 #include "x11client.h"
 #include "deleted.h"
 #include "effects.h"
 #include "overlaywindow.h"
 #include "screens.h"
 #include "shadow.h"
 #include "wayland_server.h"
 
 #include "thumbnailitem.h"
 
 #include <KWayland/Server/buffer_interface.h>
 #include <KWayland/Server/subcompositor_interface.h>
 #include <KWayland/Server/surface_interface.h>
 
 namespace KWin
 {
 
 //****************************************
 // Scene
 //****************************************
 
 Scene::Scene(QObject *parent)
     : QObject(parent)
 {
     last_time.invalidate(); // Initialize the timer
 }
 
 Scene::~Scene()
 {
     Q_ASSERT(m_windows.isEmpty());
 }
 
 // returns mask and possibly modified region
 void Scene::paintScreen(int* mask, const QRegion &damage, const QRegion &repaint,
                         QRegion *updateRegion, QRegion *validRegion, const QMatrix4x4 &projection, const QRect &outputGeometry)
 {
     const QSize &screenSize = screens()->size();
     const QRegion displayRegion(0, 0, screenSize.width(), screenSize.height());
     *mask = (damage == displayRegion) ? 0 : PAINT_SCREEN_REGION;
 
     updateTimeDiff();
     // preparation step
     static_cast<EffectsHandlerImpl*>(effects)->startPaint();
 
     QRegion region = damage;
 
     ScreenPrePaintData pdata;
     pdata.mask = *mask;
     pdata.paint = region;
 
     effects->prePaintScreen(pdata, time_diff);
     *mask = pdata.mask;
     region = pdata.paint;
 
     if (*mask & (PAINT_SCREEN_TRANSFORMED | PAINT_SCREEN_WITH_TRANSFORMED_WINDOWS)) {
         // Region painting is not possible with transformations,
         // because screen damage doesn't match transformed positions.
         *mask &= ~PAINT_SCREEN_REGION;
         region = infiniteRegion();
     } else if (*mask & PAINT_SCREEN_REGION) {
         // make sure not to go outside visible screen
         region &= displayRegion;
     } else {
         // whole screen, not transformed, force region to be full
         region = displayRegion;
     }
 
     painted_region = region;
     repaint_region = repaint;
 
     if (*mask & PAINT_SCREEN_BACKGROUND_FIRST) {
         paintBackground(region);
     }
 
     ScreenPaintData data(projection, outputGeometry);
     effects->paintScreen(*mask, region, data);
 
     foreach (Window *w, stacking_order) {
         effects->postPaintWindow(effectWindow(w));
     }
 
     effects->postPaintScreen();
 
     // make sure not to go outside of the screen area
     *updateRegion = damaged_region;
     *validRegion = (region | painted_region) & displayRegion;
 
     repaint_region = QRegion();
     damaged_region = QRegion();
 
     // make sure all clipping is restored
     Q_ASSERT(!PaintClipper::clip());
 }
 
 // Compute time since the last painting pass.
 void Scene::updateTimeDiff()
 {
     if (!last_time.isValid()) {
         // Painting has been idle (optimized out) for some time,
         // which means time_diff would be huge and would break animations.
         // Simply set it to one (zero would mean no change at all and could
         // cause problems).
         time_diff = 1;
         last_time.start();
     } else
 
     time_diff = last_time.restart();
 
     if (time_diff < 0)   // check time rollback
         time_diff = 1;
 }
 
 // Painting pass is optimized away.
 void Scene::idle()
 {
     // Don't break time since last paint for the next pass.
     last_time.invalidate();
 }
 
 // the function that'll be eventually called by paintScreen() above
 void Scene::finalPaintScreen(int mask, QRegion region, ScreenPaintData& data)
 {
     if (mask & (PAINT_SCREEN_TRANSFORMED | PAINT_SCREEN_WITH_TRANSFORMED_WINDOWS))
         paintGenericScreen(mask, data);
     else
         paintSimpleScreen(mask, region);
 }
 
 // The generic painting code that can handle even transformations.
 // It simply paints bottom-to-top.
 void Scene::paintGenericScreen(int orig_mask, ScreenPaintData)
 {
     if (!(orig_mask & PAINT_SCREEN_BACKGROUND_FIRST)) {
         paintBackground(infiniteRegion());
     }
     QVector<Phase2Data> phase2;
     phase2.reserve(stacking_order.size());
     foreach (Window * w, stacking_order) { // bottom to top
         Toplevel* topw = w->window();
 
         // Reset the repaint_region.
         // This has to be done here because many effects schedule a repaint for
         // the next frame within Effects::prePaintWindow.
         topw->resetRepaints();
 
         WindowPrePaintData data;
         data.mask = orig_mask | (w->isOpaque() ? PAINT_WINDOW_OPAQUE : PAINT_WINDOW_TRANSLUCENT);
         w->resetPaintingEnabled();
         data.paint = infiniteRegion(); // no clipping, so doesn't really matter
         data.clip = QRegion();
         data.quads = w->buildQuads();
         // preparation step
         effects->prePaintWindow(effectWindow(w), data, time_diff);
 #if !defined(QT_NO_DEBUG)
         if (data.quads.isTransformed()) {
             qFatal("Pre-paint calls are not allowed to transform quads!");
         }
 #endif
         if (!w->isPaintingEnabled()) {
             continue;
         }
         phase2.append({w, infiniteRegion(), data.clip, data.mask, data.quads});
     }
 
     foreach (const Phase2Data & d, phase2) {
         paintWindow(d.window, d.mask, d.region, d.quads);
     }
 
     const QSize &screenSize = screens()->size();
     damaged_region = QRegion(0, 0, screenSize.width(), screenSize.height());
 }
 
 // The optimized case without any transformations at all.
 // It can paint only the requested region and can use clipping
 // to reduce painting and improve performance.
 void Scene::paintSimpleScreen(int orig_mask, QRegion region)
 {
     Q_ASSERT((orig_mask & (PAINT_SCREEN_TRANSFORMED
                          | PAINT_SCREEN_WITH_TRANSFORMED_WINDOWS)) == 0);
     QVector<Phase2Data> phase2data;
     phase2data.reserve(stacking_order.size());
 
     QRegion dirtyArea = region;
-    bool opaqueFullscreen(false);
-    for (int i = 0;  // do prePaintWindow bottom to top
-            i < stacking_order.count();
-            ++i) {
-        Window* w = stacking_order[ i ];
-        Toplevel* topw = w->window();
+    bool opaqueFullscreen = false;
+
+    // Traverse the scene windows from bottom to top.
+    for (int i = 0; i < stacking_order.count(); ++i) {
+        Window *window = stacking_order[i];
+        Toplevel *toplevel = window->window();
         WindowPrePaintData data;
-        data.mask = orig_mask | (w->isOpaque() ? PAINT_WINDOW_OPAQUE : PAINT_WINDOW_TRANSLUCENT);
-        w->resetPaintingEnabled();
+        data.mask = orig_mask | (window->isOpaque() ? PAINT_WINDOW_OPAQUE : PAINT_WINDOW_TRANSLUCENT);
+        window->resetPaintingEnabled();
         data.paint = region;
-        data.paint |= topw->repaints();
+        data.paint |= toplevel->repaints();
 
         // Reset the repaint_region.
         // This has to be done here because many effects schedule a repaint for
         // the next frame within Effects::prePaintWindow.
-        topw->resetRepaints();
+        toplevel->resetRepaints();
 
         // Clip out the decoration for opaque windows; the decoration is drawn in the second pass
         opaqueFullscreen = false; // TODO: do we care about unmanged windows here (maybe input windows?)
-        if (w->isOpaque()) {
-            AbstractClient *c = dynamic_cast<AbstractClient*>(topw);
-            if (c) {
-                opaqueFullscreen = c->isFullScreen();
+        if (window->isOpaque()) {
+            AbstractClient *client = dynamic_cast<AbstractClient *>(toplevel);
+            if (client) {
+                opaqueFullscreen = client->isFullScreen();
             }
-            X11Client *cc = dynamic_cast<X11Client *>(c);
+            X11Client *cc = dynamic_cast<X11Client *>(client);
             // the window is fully opaque
             if (cc && cc->decorationHasAlpha()) {
                 // decoration uses alpha channel, so we may not exclude it in clipping
-                data.clip = w->clientShape().translated(w->x(), w->y());
+                data.clip = window->clientShape().translated(window->x(), window->y());
             } else {
                 // decoration is fully opaque
-                if (c && c->isShade()) {
+                if (client && client->isShade()) {
                     data.clip = QRegion();
                 } else {
-                    data.clip = w->shape().translated(w->x(), w->y());
+                    data.clip = window->shape().translated(window->x(), window->y());
                 }
             }
-        } else if (topw->hasAlpha() && topw->opacity() == 1.0) {
+        } else if (toplevel->hasAlpha() && toplevel->opacity() == 1.0) {
             // the window is partially opaque
-            data.clip = (w->clientShape() & topw->opaqueRegion().translated(topw->clientPos())).translated(w->x(), w->y());
+            data.clip = (window->clientShape() & toplevel->opaqueRegion().translated(toplevel->clientPos())).translated(window->x(), window->y());
         } else {
             data.clip = QRegion();
         }
-        data.quads = w->buildQuads();
+        data.quads = window->buildQuads();
         // preparation step
-        effects->prePaintWindow(effectWindow(w), data, time_diff);
+        effects->prePaintWindow(effectWindow(window), data, time_diff);
 #if !defined(QT_NO_DEBUG)
         if (data.quads.isTransformed()) {
             qFatal("Pre-paint calls are not allowed to transform quads!");
         }
 #endif
-        if (!w->isPaintingEnabled()) {
+        if (!window->isPaintingEnabled()) {
             continue;
         }
         dirtyArea |= data.paint;
         // Schedule the window for painting
-        phase2data.append({w, data.paint, data.clip, data.mask, data.quads});
+        phase2data.append({ window, data.paint, data.clip, data.mask, data.quads });
     }
 
     // Save the part of the repaint region that's exclusively rendered to
     // bring a reused back buffer up to date. Then union the dirty region
     // with the repaint region.
     const QRegion repaintClip = repaint_region - dirtyArea;
     dirtyArea |= repaint_region;
 
     const QSize &screenSize = screens()->size();
     const QRegion displayRegion(0, 0, screenSize.width(), screenSize.height());
     bool fullRepaint(dirtyArea == displayRegion); // spare some expensive region operations
     if (!fullRepaint) {
         extendPaintRegion(dirtyArea, opaqueFullscreen);
         fullRepaint = (dirtyArea == displayRegion);
     }
 
     QRegion allclips, upperTranslucentDamage;
     upperTranslucentDamage = repaint_region;
 
     // This is the occlusion culling pass
     for (int i = phase2data.count() - 1; i >= 0; --i) {
         Phase2Data *data = &phase2data[i];
 
-        if (fullRepaint)
+        if (fullRepaint) {
             data->region = displayRegion;
-        else
+        } else {
             data->region |= upperTranslucentDamage;
+        }
 
         // subtract the parts which will possibly been drawn as part of
         // a higher opaque window
         data->region -= allclips;
 
         // Here we rely on WindowPrePaintData::setTranslucent() to remove
         // the clip if needed.
         if (!data->clip.isEmpty() && !(data->mask & PAINT_WINDOW_TRANSLUCENT)) {
             // clip away the opaque regions for all windows below this one
             allclips |= data->clip;
             // extend the translucent damage for windows below this by remaining (translucent) regions
-            if (!fullRepaint)
+            if (!fullRepaint) {
                 upperTranslucentDamage |= data->region - data->clip;
+            }
         } else if (!fullRepaint) {
             upperTranslucentDamage |= data->region;
         }
     }
 
     QRegion paintedArea;
     // Fill any areas of the root window not covered by opaque windows
     if (!(orig_mask & PAINT_SCREEN_BACKGROUND_FIRST)) {
         paintedArea = dirtyArea - allclips;
         paintBackground(paintedArea);
     }
 
     // Now walk the list bottom to top and draw the windows.
     for (int i = 0; i < phase2data.count(); ++i) {
         Phase2Data *data = &phase2data[i];
 
         // add all regions which have been drawn so far
         paintedArea |= data->region;
         data->region = paintedArea;
 
         paintWindow(data->window, data->mask, data->region, data->quads);
     }
 
     if (fullRepaint) {
         painted_region = displayRegion;
         damaged_region = displayRegion;
     } else {
         painted_region |= paintedArea;
 
         // Clip the repainted region from the damaged region.
         // It's important that we don't add the union of the damaged region
         // and the repainted region to the damage history. Otherwise the
         // repaint region will grow with every frame until it eventually
         // covers the whole back buffer, at which point we're always doing
         // full repaints.
         damaged_region = paintedArea - repaintClip;
     }
 }
 
 void Scene::addToplevel(Toplevel *c)
 {
     Q_ASSERT(!m_windows.contains(c));
     Scene::Window *w = createWindow(c);
     m_windows[ c ] = w;
     connect(c, SIGNAL(geometryShapeChanged(KWin::Toplevel*,QRect)), SLOT(windowGeometryShapeChanged(KWin::Toplevel*)));
     connect(c, SIGNAL(windowClosed(KWin::Toplevel*,KWin::Deleted*)), SLOT(windowClosed(KWin::Toplevel*,KWin::Deleted*)));
     //A change of scale won't affect the geometry in compositor co-ordinates, but will affect the window quads.
     if (c->surface()) {
         connect(c->surface(), &KWayland::Server::SurfaceInterface::scaleChanged, this, std::bind(&Scene::windowGeometryShapeChanged, this, c));
     }
     connect(c, &Toplevel::screenScaleChanged, this,
         [this, c] {
             windowGeometryShapeChanged(c);
         }
     );
     c->effectWindow()->setSceneWindow(w);
     c->updateShadow();
     w->updateShadow(c->shadow());
     connect(c, &Toplevel::shadowChanged, this,
         [w] {
             w->invalidateQuadsCache();
         }
     );
 }
 
 void Scene::removeToplevel(Toplevel *toplevel)
 {
     Q_ASSERT(m_windows.contains(toplevel));
     delete m_windows.take(toplevel);
     toplevel->effectWindow()->setSceneWindow(nullptr);
 }
 
 void Scene::windowClosed(Toplevel *toplevel, Deleted *deleted)
 {
     if (!deleted) {
         removeToplevel(toplevel);
         return;
     }
 
     Q_ASSERT(m_windows.contains(toplevel));
     Window *window = m_windows.take(toplevel);
     window->updateToplevel(deleted);
     if (window->shadow()) {
         window->shadow()->setToplevel(deleted);
     }
     m_windows[deleted] = window;
 }
 
 void Scene::windowGeometryShapeChanged(Toplevel *c)
 {
     if (!m_windows.contains(c))    // this is ok, shape is not valid by default
         return;
     Window *w = m_windows[ c ];
     w->discardShape();
 }
 
 void Scene::createStackingOrder(ToplevelList toplevels)
 {
     // TODO: cache the stacking_order in case it has not changed
     foreach (Toplevel *c, toplevels) {
         Q_ASSERT(m_windows.contains(c));
         stacking_order.append(m_windows[ c ]);
     }
 }
 
 void Scene::clearStackingOrder()
 {
     stacking_order.clear();
 }
 
 static Scene::Window *s_recursionCheck = nullptr;
 
 void Scene::paintWindow(Window* w, int mask, QRegion region, WindowQuadList quads)
 {
     // no painting outside visible screen (and no transformations)
     const QSize &screenSize = screens()->size();
     region &= QRect(0, 0, screenSize.width(), screenSize.height());
     if (region.isEmpty())  // completely clipped
         return;
     if (w->window()->isDeleted() && w->window()->skipsCloseAnimation()) {
         // should not get painted
         return;
     }
 
     if (s_recursionCheck == w) {
         return;
     }
 
     WindowPaintData data(w->window()->effectWindow(), screenProjectionMatrix());
     data.quads = quads;
     effects->paintWindow(effectWindow(w), mask, region, data);
     // paint thumbnails on top of window
     paintWindowThumbnails(w, region, data.opacity(), data.brightness(), data.saturation());
     // and desktop thumbnails
     paintDesktopThumbnails(w);
 }
 
 static void adjustClipRegion(AbstractThumbnailItem *item, QRegion &clippingRegion)
 {
     if (item->clip() && item->clipTo()) {
         // the x/y positions of the parent item are not correct. The margins are added, though the size seems fine
         // that's why we have to get the offset by inspecting the anchors properties
         QQuickItem *parentItem = item->clipTo();
         QPointF offset;
         QVariant anchors = parentItem->property("anchors");
         if (anchors.isValid()) {
             if (QObject *anchorsObject = anchors.value<QObject*>()) {
                 offset.setX(anchorsObject->property("leftMargin").toReal());
                 offset.setY(anchorsObject->property("topMargin").toReal());
             }
         }
         QRectF rect = QRectF(parentItem->position() - offset, QSizeF(parentItem->width(), parentItem->height()));
         if (QQuickItem *p = parentItem->parentItem()) {
             rect = p->mapRectToScene(rect);
         }
         clippingRegion &= rect.adjusted(0,0,-1,-1).translated(item->window()->position()).toRect();
     }
 }
 
 void Scene::paintWindowThumbnails(Scene::Window *w, QRegion region, qreal opacity, qreal brightness, qreal saturation)
 {
     EffectWindowImpl *wImpl = static_cast<EffectWindowImpl*>(effectWindow(w));
     for (QHash<WindowThumbnailItem*, QPointer<EffectWindowImpl> >::const_iterator it = wImpl->thumbnails().constBegin();
             it != wImpl->thumbnails().constEnd();
             ++it) {
         if (it.value().isNull()) {
             continue;
         }
         WindowThumbnailItem *item = it.key();
         if (!item->isVisible()) {
             continue;
         }
         EffectWindowImpl *thumb = it.value().data();
         WindowPaintData thumbData(thumb, screenProjectionMatrix());
         thumbData.setOpacity(opacity);
         thumbData.setBrightness(brightness * item->brightness());
         thumbData.setSaturation(saturation * item->saturation());
 
         const QRect visualThumbRect(thumb->expandedGeometry());
 
         QSizeF size = QSizeF(visualThumbRect.size());
         size.scale(QSizeF(item->width(), item->height()), Qt::KeepAspectRatio);
         if (size.width() > visualThumbRect.width() || size.height() > visualThumbRect.height()) {
             size = QSizeF(visualThumbRect.size());
         }
         thumbData.setXScale(size.width() / static_cast<qreal>(visualThumbRect.width()));
         thumbData.setYScale(size.height() / static_cast<qreal>(visualThumbRect.height()));
 
         if (!item->window()) {
             continue;
         }
         const QPointF point = item->mapToScene(item->position());
         qreal x = point.x() + w->x() + (item->width() - size.width())/2;
         qreal y = point.y() + w->y() + (item->height() - size.height()) / 2;
         x -= thumb->x();
         y -= thumb->y();
         // compensate shadow topleft padding
         x += (thumb->x()-visualThumbRect.x())*thumbData.xScale();
         y += (thumb->y()-visualThumbRect.y())*thumbData.yScale();
         thumbData.setXTranslation(x);
         thumbData.setYTranslation(y);
         int thumbMask = PAINT_WINDOW_TRANSFORMED | PAINT_WINDOW_LANCZOS;
         if (thumbData.opacity() == 1.0) {
             thumbMask |= PAINT_WINDOW_OPAQUE;
         } else {
             thumbMask |= PAINT_WINDOW_TRANSLUCENT;
         }
         QRegion clippingRegion = region;
         clippingRegion &= QRegion(wImpl->x(), wImpl->y(), wImpl->width(), wImpl->height());
         adjustClipRegion(item, clippingRegion);
         effects->drawWindow(thumb, thumbMask, clippingRegion, thumbData);
     }
 }
 
 void Scene::paintDesktopThumbnails(Scene::Window *w)
 {
     EffectWindowImpl *wImpl = static_cast<EffectWindowImpl*>(effectWindow(w));
     for (QList<DesktopThumbnailItem*>::const_iterator it = wImpl->desktopThumbnails().constBegin();
             it != wImpl->desktopThumbnails().constEnd();
             ++it) {
         DesktopThumbnailItem *item = *it;
         if (!item->isVisible()) {
             continue;
         }
         if (!item->window()) {
             continue;
         }
         s_recursionCheck = w;
 
         ScreenPaintData data;
         const QSize &screenSize = screens()->size();
         QSize size = screenSize;
 
         size.scale(item->width(), item->height(), Qt::KeepAspectRatio);
         data *= QVector2D(size.width() / double(screenSize.width()),
                           size.height() / double(screenSize.height()));
         const QPointF point = item->mapToScene(item->position());
         const qreal x = point.x() + w->x() + (item->width() - size.width())/2;
         const qreal y = point.y() + w->y() + (item->height() - size.height()) / 2;
         const QRect region = QRect(x, y, item->width(), item->height());
         QRegion clippingRegion = region;
         clippingRegion &= QRegion(wImpl->x(), wImpl->y(), wImpl->width(), wImpl->height());
         adjustClipRegion(item, clippingRegion);
         data += QPointF(x, y);
         const int desktopMask = PAINT_SCREEN_TRANSFORMED | PAINT_WINDOW_TRANSFORMED | PAINT_SCREEN_BACKGROUND_FIRST;
         paintDesktop(item->desktop(), desktopMask, clippingRegion, data);
         s_recursionCheck = nullptr;
     }
 }
 
 void Scene::paintDesktop(int desktop, int mask, const QRegion &region, ScreenPaintData &data)
 {
     static_cast<EffectsHandlerImpl*>(effects)->paintDesktop(desktop, mask, region, data);
 }
 
 // the function that'll be eventually called by paintWindow() above
 void Scene::finalPaintWindow(EffectWindowImpl* w, int mask, QRegion region, WindowPaintData& data)
 {
     effects->drawWindow(w, mask, region, data);
 }
 
 // will be eventually called from drawWindow()
 void Scene::finalDrawWindow(EffectWindowImpl* w, int mask, QRegion region, WindowPaintData& data)
 {
     if (waylandServer() && waylandServer()->isScreenLocked() && !w->window()->isLockScreen() && !w->window()->isInputMethod()) {
         return;
     }
     w->sceneWindow()->performPaint(mask, region, data);
 }
 
 void Scene::extendPaintRegion(QRegion &region, bool opaqueFullscreen)
 {
     Q_UNUSED(region);
     Q_UNUSED(opaqueFullscreen);
 }
 
 void Scene::screenGeometryChanged(const QSize &size)
 {
     if (!overlayWindow()) {
         return;
     }
     overlayWindow()->resize(size);
 }
 
 bool Scene::makeOpenGLContextCurrent()
 {
     return false;
 }
 
 void Scene::doneOpenGLContextCurrent()
 {
 }
 
 void Scene::triggerFence()
 {
 }
 
 QMatrix4x4 Scene::screenProjectionMatrix() const
 {
     return QMatrix4x4();
 }
 
 xcb_render_picture_t Scene::xrenderBufferPicture() const
 {
     return XCB_RENDER_PICTURE_NONE;
 }
 
 QPainter *Scene::scenePainter() const
 {
     return nullptr;
 }
 
 QImage *Scene::qpainterRenderBuffer() const
 {
     return nullptr;
 }
 
 QVector<QByteArray> Scene::openGLPlatformInterfaceExtensions() const
 {
     return QVector<QByteArray>{};
 }
 
 //****************************************
 // Scene::Window
 //****************************************
 
 Scene::Window::Window(Toplevel * c)
     : toplevel(c)
     , filter(ImageFilterFast)
     , m_shadow(nullptr)
     , m_currentPixmap()
     , m_previousPixmap()
     , m_referencePixmapCounter(0)
     , disable_painting(0)
     , shape_valid(false)
     , cached_quad_list(nullptr)
 {
 }
 
 Scene::Window::~Window()
 {
     delete m_shadow;
 }
 
 void Scene::Window::referencePreviousPixmap()
 {
     if (!m_previousPixmap.isNull() && m_previousPixmap->isDiscarded()) {
         m_referencePixmapCounter++;
     }
 }
 
 void Scene::Window::unreferencePreviousPixmap()
 {
     if (m_previousPixmap.isNull() || !m_previousPixmap->isDiscarded()) {
         return;
     }
     m_referencePixmapCounter--;
     if (m_referencePixmapCounter == 0) {
         m_previousPixmap.reset();
     }
 }
 
 void Scene::Window::pixmapDiscarded()
 {
     if (!m_currentPixmap.isNull()) {
         if (m_currentPixmap->isValid()) {
             m_previousPixmap.reset(m_currentPixmap.take());
             m_previousPixmap->markAsDiscarded();
         } else {
             m_currentPixmap.reset();
         }
     }
 }
 
 void Scene::Window::discardShape()
 {
     // it is created on-demand and cached, simply
     // reset the flag
     shape_valid = false;
     invalidateQuadsCache();
 }
 
 // Find out the shape of the window using the XShape extension
 // or if shape is not set then simply it's the window geometry.
 const QRegion &Scene::Window::shape() const
 {
     if (!shape_valid) {
         if (toplevel->shape()) {
             auto cookie = xcb_shape_get_rectangles_unchecked(connection(), toplevel->frameId(), XCB_SHAPE_SK_BOUNDING);
             ScopedCPointer<xcb_shape_get_rectangles_reply_t> reply(xcb_shape_get_rectangles_reply(connection(), cookie, nullptr));
             if (!reply.isNull()) {
                 shape_region = QRegion();
                 auto *rects = xcb_shape_get_rectangles_rectangles(reply.data());
                 for (int i = 0;
                         i < xcb_shape_get_rectangles_rectangles_length(reply.data());
                         ++i)
                     shape_region += QRegion(rects[ i ].x, rects[ i ].y,
                                             rects[ i ].width, rects[ i ].height);
                 // make sure the shape is sane (X is async, maybe even XShape is broken)
                 shape_region &= QRegion(0, 0, width(), height());
             } else
                 shape_region = QRegion();
         } else
             shape_region = QRegion(0, 0, width(), height());
         shape_valid = true;
     }
     return shape_region;
 }
 
 QRegion Scene::Window::clientShape() const
 {
     if (AbstractClient *c = dynamic_cast< AbstractClient * > (toplevel)) {
         if (c->isShade())
             return QRegion();
     }
 
     // TODO: cache
     const QRegion r = shape() & QRect(toplevel->clientPos(), toplevel->clientSize());
     return r.isEmpty() ? QRegion() : r;
 }
 
 bool Scene::Window::isVisible() const
 {
     if (toplevel->isDeleted())
         return false;
     if (!toplevel->isOnCurrentDesktop())
         return false;
     if (!toplevel->isOnCurrentActivity())
         return false;
     if (AbstractClient *c = dynamic_cast<AbstractClient*>(toplevel))
         return c->isShown(true);
     return true; // Unmanaged is always visible
 }
 
 bool Scene::Window::isOpaque() const
 {
     return toplevel->opacity() == 1.0 && !toplevel->hasAlpha();
 }
 
 bool Scene::Window::isPaintingEnabled() const
 {
     return !disable_painting;
 }
 
 void Scene::Window::resetPaintingEnabled()
 {
     disable_painting = 0;
     if (toplevel->isDeleted())
         disable_painting |= PAINT_DISABLED_BY_DELETE;
     if (static_cast<EffectsHandlerImpl*>(effects)->isDesktopRendering()) {
         if (!toplevel->isOnDesktop(static_cast<EffectsHandlerImpl*>(effects)->currentRenderedDesktop())) {
             disable_painting |= PAINT_DISABLED_BY_DESKTOP;
         }
     } else {
         if (!toplevel->isOnCurrentDesktop())
             disable_painting |= PAINT_DISABLED_BY_DESKTOP;
     }
     if (!toplevel->isOnCurrentActivity())
         disable_painting |= PAINT_DISABLED_BY_ACTIVITY;
     if (AbstractClient *c = dynamic_cast<AbstractClient*>(toplevel)) {
         if (c->isMinimized())
             disable_painting |= PAINT_DISABLED_BY_MINIMIZE;
         if (c->isHiddenInternal()) {
             disable_painting |= PAINT_DISABLED;
         }
     }
 }
 
 void Scene::Window::enablePainting(int reason)
 {
     disable_painting &= ~reason;
 }
 
 void Scene::Window::disablePainting(int reason)
 {
     disable_painting |= reason;
 }
 
 WindowQuadList Scene::Window::buildQuads(bool force) const
 {
     if (cached_quad_list != nullptr && !force)
         return *cached_quad_list;
     WindowQuadList ret;
 
     const qreal scale = toplevel->bufferScale();
 
     if (toplevel->clientPos() == QPoint(0, 0) && toplevel->clientSize() == toplevel->decorationRect().size())
         ret = makeQuads(WindowQuadContents, shape(), QPoint(0,0), scale);  // has no decoration
     else {
         AbstractClient *client = dynamic_cast<AbstractClient*>(toplevel);
         QRegion contents = clientShape();
         QRegion center = toplevel->transparentRect();
         QRegion decoration = (client ? QRegion(client->decorationRect()) : shape()) - center;
         qreal decorationScale = 1.0;
         ret = makeQuads(WindowQuadContents, contents, toplevel->clientContentPos(), scale);
 
         QRect rects[4];
         bool isShadedClient = false;
 
         if (client) {
             client->layoutDecorationRects(rects[0], rects[1], rects[2], rects[3]);
             decorationScale = client->screenScale();
             isShadedClient = client->isShade() || center.isEmpty();
         }
 
         if (isShadedClient) {
             const QRect bounding = rects[0] | rects[1] | rects[2] | rects[3];
             ret += makeDecorationQuads(rects, bounding, decorationScale);
         } else {
             ret += makeDecorationQuads(rects, decoration, decorationScale);
         }
 
     }
     if (m_shadow && toplevel->wantsShadowToBeRendered()) {
         ret << m_shadow->shadowQuads();
     }
     effects->buildQuads(toplevel->effectWindow(), ret);
     cached_quad_list.reset(new WindowQuadList(ret));
     return ret;
 }
 
 WindowQuadList Scene::Window::makeDecorationQuads(const QRect *rects, const QRegion &region, qreal textureScale) const
 {
     WindowQuadList list;
 
     const QPoint offsets[4] = {
         QPoint(-rects[0].x() + rects[1].height() + rects[3].height() + 2, -rects[0].y()),                    // Left
         QPoint(-rects[1].x(), -rects[1].y()),                                                                // Top
         QPoint(-rects[2].x() + rects[1].height() + rects[3].height() + rects[0].width() + 3, -rects[2].y()), // Right
         QPoint(-rects[3].x(), -rects[3].y() + rects[1].height() + 1)                                         // Bottom
     };
 
     const Qt::Orientation orientations[4] = {
         Qt::Vertical,   // Left
         Qt::Horizontal, // Top
         Qt::Vertical,   // Right
         Qt::Horizontal, // Bottom
     };
 
     for (int i = 0; i < 4; i++) {
         const QRegion intersectedRegion = (region & rects[i]);
         for (const QRect &r : intersectedRegion) {
             if (!r.isValid())
                 continue;
 
             const bool swap = orientations[i] == Qt::Vertical;
 
             const int x0 = r.x();
             const int y0 = r.y();
             const int x1 = r.x() + r.width();
             const int y1 = r.y() + r.height();
 
             const int u0 = (x0 + offsets[i].x()) * textureScale;
             const int v0 = (y0 + offsets[i].y()) * textureScale;
             const int u1 = (x1 + offsets[i].x()) * textureScale;
             const int v1 = (y1 + offsets[i].y()) * textureScale;
 
             WindowQuad quad(WindowQuadDecoration);
             quad.setUVAxisSwapped(swap);
 
             if (swap) {
                 quad[0] = WindowVertex(x0, y0, v0, u0); // Top-left
                 quad[1] = WindowVertex(x1, y0, v0, u1); // Top-right
                 quad[2] = WindowVertex(x1, y1, v1, u1); // Bottom-right
                 quad[3] = WindowVertex(x0, y1, v1, u0); // Bottom-left
             } else {
                 quad[0] = WindowVertex(x0, y0, u0, v0); // Top-left
                 quad[1] = WindowVertex(x1, y0, u1, v0); // Top-right
                 quad[2] = WindowVertex(x1, y1, u1, v1); // Bottom-right
                 quad[3] = WindowVertex(x0, y1, u0, v1); // Bottom-left
             }
 
             list.append(quad);
         }
     }
 
     return list;
 }
 
 void Scene::Window::invalidateQuadsCache()
 {
     cached_quad_list.reset();
 }
 
 WindowQuadList Scene::Window::makeQuads(WindowQuadType type, const QRegion& reg, const QPoint &textureOffset, qreal scale) const
 {
     WindowQuadList ret;
     ret.reserve(reg.rectCount());
     for (const QRect &r : reg) {
         WindowQuad quad(type);
         // TODO asi mam spatne pravy dolni roh - bud tady, nebo v jinych castech
         quad[ 0 ] = WindowVertex(QPointF(r.x(), r.y()),
                                  QPointF(r.x() + textureOffset.x(), r.y() + textureOffset.y()) * scale);
         quad[ 1 ] = WindowVertex(QPointF(r.x() + r.width(), r.y()),
                                  QPointF(r.x() + r.width() + textureOffset.x(), r.y() + textureOffset.y()) * scale);
         quad[ 2 ] = WindowVertex(QPointF(r.x() + r.width(), r.y() + r.height()),
                                  QPointF(r.x() + r.width() + textureOffset.x(), r.y() + r.height() + textureOffset.y()) * scale);
         quad[ 3 ] = WindowVertex(QPointF(r.x(), r.y() + r.height()),
                                  QPointF(r.x() + textureOffset.x(), r.y() + r.height() + textureOffset.y()) * scale);
 
         ret.append(quad);
     }
     return ret;
 }
 
 void Scene::Window::updateShadow(Shadow* shadow)
 {
     if (m_shadow == shadow) {
         return;
     }
     delete m_shadow;
     m_shadow = shadow;
 }
 
 //****************************************
 // WindowPixmap
 //****************************************
 WindowPixmap::WindowPixmap(Scene::Window *window)
     : m_window(window)
     , m_pixmap(XCB_PIXMAP_NONE)
     , m_discarded(false)
 {
 }
 
 WindowPixmap::WindowPixmap(const QPointer<KWayland::Server::SubSurfaceInterface> &subSurface, WindowPixmap *parent)
     : m_window(parent->m_window)
     , m_pixmap(XCB_PIXMAP_NONE)
     , m_discarded(false)
     , m_parent(parent)
     , m_subSurface(subSurface)
 {
 }
 
 WindowPixmap::~WindowPixmap()
 {
     if (m_pixmap != XCB_WINDOW_NONE) {
         xcb_free_pixmap(connection(), m_pixmap);
     }
     if (m_buffer) {
         using namespace KWayland::Server;
         QObject::disconnect(m_buffer.data(), &BufferInterface::aboutToBeDestroyed, m_buffer.data(), &BufferInterface::unref);
         m_buffer->unref();
     }
 }
 
 void WindowPixmap::create()
 {
     if (isValid() || toplevel()->isDeleted()) {
         return;
     }
     // always update from Buffer on Wayland, don't try using XPixmap
     if (kwinApp()->shouldUseWaylandForCompositing()) {
         // use Buffer
         updateBuffer();
         if ((m_buffer || !m_fbo.isNull()) && m_subSurface.isNull()) {
             m_window->unreferencePreviousPixmap();
         }
         return;
     }
     XServerGrabber grabber;
     xcb_pixmap_t pix = xcb_generate_id(connection());
     xcb_void_cookie_t namePixmapCookie = xcb_composite_name_window_pixmap_checked(connection(), toplevel()->frameId(), pix);
     Xcb::WindowAttributes windowAttributes(toplevel()->frameId());
     Xcb::WindowGeometry windowGeometry(toplevel()->frameId());
     if (xcb_generic_error_t *error = xcb_request_check(connection(), namePixmapCookie)) {
         qCDebug(KWIN_CORE) << "Creating window pixmap failed: " << error->error_code;
         free(error);
         return;
     }
     // check that the received pixmap is valid and actually matches what we
     // know about the window (i.e. size)
     if (!windowAttributes || windowAttributes->map_state != XCB_MAP_STATE_VIEWABLE) {
         qCDebug(KWIN_CORE) << "Creating window pixmap failed: " << this;
         xcb_free_pixmap(connection(), pix);
         return;
     }
     if (!windowGeometry ||
         windowGeometry->width != toplevel()->width() || windowGeometry->height != toplevel()->height()) {
         qCDebug(KWIN_CORE) << "Creating window pixmap failed: " << this;
         xcb_free_pixmap(connection(), pix);
         return;
     }
     m_pixmap = pix;
     m_pixmapSize = QSize(toplevel()->width(), toplevel()->height());
     m_contentsRect = QRect(toplevel()->clientPos(), toplevel()->clientSize());
     m_window->unreferencePreviousPixmap();
 }
 
 WindowPixmap *WindowPixmap::createChild(const QPointer<KWayland::Server::SubSurfaceInterface> &subSurface)
 {
     Q_UNUSED(subSurface)
     return nullptr;
 }
 
 bool WindowPixmap::isValid() const
 {
     if (!m_buffer.isNull() || !m_fbo.isNull() || !m_internalImage.isNull()) {
         return true;
     }
     return m_pixmap != XCB_PIXMAP_NONE;
 }
 
 void WindowPixmap::updateBuffer()
 {
     using namespace KWayland::Server;
     if (SurfaceInterface *s = surface()) {
         QVector<WindowPixmap*> oldTree = m_children;
         QVector<WindowPixmap*> children;
         using namespace KWayland::Server;
         const auto subSurfaces = s->childSubSurfaces();
         for (const auto &subSurface : subSurfaces) {
             if (subSurface.isNull()) {
                 continue;
             }
             auto it = std::find_if(oldTree.begin(), oldTree.end(), [subSurface] (WindowPixmap *p) { return p->m_subSurface == subSurface; });
             if (it != oldTree.end()) {
                 children << *it;
                 (*it)->updateBuffer();
                 oldTree.erase(it);
             } else {
                 WindowPixmap *p = createChild(subSurface);
                 if (p) {
                     p->create();
                     children << p;
                 }
             }
         }
         setChildren(children);
         qDeleteAll(oldTree);
         if (auto b = s->buffer()) {
             if (b == m_buffer) {
                 // no change
                 return;
             }
             if (m_buffer) {
                 QObject::disconnect(m_buffer.data(), &BufferInterface::aboutToBeDestroyed, m_buffer.data(), &BufferInterface::unref);
                 m_buffer->unref();
             }
             m_buffer = b;
             m_buffer->ref();
             QObject::connect(m_buffer.data(), &BufferInterface::aboutToBeDestroyed, m_buffer.data(), &BufferInterface::unref);
         } else if (m_subSurface) {
             if (m_buffer) {
                 QObject::disconnect(m_buffer.data(), &BufferInterface::aboutToBeDestroyed, m_buffer.data(), &BufferInterface::unref);
                 m_buffer->unref();
                 m_buffer.clear();
             }
         }
     } else if (toplevel()->internalFramebufferObject()) {
         m_fbo = toplevel()->internalFramebufferObject();
     } else if (!toplevel()->internalImageObject().isNull()) {
         m_internalImage = toplevel()->internalImageObject();
     } else {
         if (m_buffer) {
             QObject::disconnect(m_buffer.data(), &BufferInterface::aboutToBeDestroyed, m_buffer.data(), &BufferInterface::unref);
             m_buffer->unref();
             m_buffer.clear();
         }
     }
 }
 
 KWayland::Server::SurfaceInterface *WindowPixmap::surface() const
 {
     if (!m_subSurface.isNull()) {
         return m_subSurface->surface().data();
     } else {
         return toplevel()->surface();
     }
 }
 
 //****************************************
 // Scene::EffectFrame
 //****************************************
 Scene::EffectFrame::EffectFrame(EffectFrameImpl* frame)
     : m_effectFrame(frame)
 {
 }
 
 Scene::EffectFrame::~EffectFrame()
 {
 }
 
 SceneFactory::SceneFactory(QObject *parent)
     : QObject(parent)
 {
 }
 
 SceneFactory::~SceneFactory()
 {
 }
 
 } // namespace