scene: Split base Scene class from WorkspaceScene class

The main motivation behind this change is to share rendering code
between windows and the cursor, specifically the Item class which
requires a Scene.

Note that Scene subclasses are responsible for issuing
ItemRenderer::renderItem() calls. The main reason for that is the
current architecture of the effects system, specifically we need to call
some effects hooks before and after painting a window.

src/CMakeLists.txt

@@ -123,6 +123,7 @@ target_sources(kwin PRIVATE
     scene/itemrenderer.cpp
     scene/itemrenderer_opengl.cpp
     scene/itemrenderer_qpainter.cpp
+    scene/scene.cpp
     scene/shadowitem.cpp
     scene/surfaceitem.cpp
     scene/surfaceitem_internal.cpp

src/deleted.cpp

@@ -52,7 +52,7 @@ Deleted::~Deleted()
     deleteShadow();
 }
 
-WindowItem *Deleted::createItem(WorkspaceScene *scene)
+WindowItem *Deleted::createItem(Scene *scene)
 {
     Q_UNREACHABLE();
 }

src/deleted.h

@@ -104,7 +104,7 @@ public:
     { /* nothing to do */
         return geometry;
     }
-    WindowItem *createItem(WorkspaceScene *scene) override;
+    WindowItem *createItem(Scene *scene) override;
 
     /**
      * Returns whether the client was a popup.

src/internalwindow.cpp

@@ -67,7 +67,7 @@ InternalWindow::~InternalWindow()
 {
 }
 
-WindowItem *InternalWindow::createItem(WorkspaceScene *scene)
+WindowItem *InternalWindow::createItem(Scene *scene)
 {
     return new WindowItemInternal(this, scene);
 }

src/internalwindow.h

@@ -72,7 +72,7 @@ protected:
     void doInteractiveResizeSync(const QRectF &rect) override;
     void updateCaption() override;
     void moveResizeInternal(const QRectF &rect, MoveResizeMode mode) override;
-    WindowItem *createItem(WorkspaceScene *scene) override;
+    WindowItem *createItem(Scene *scene) override;
 
 private:
     void requestGeometry(const QRectF &rect);

src/plugins/screencast/windowscreencastsource.cpp

@@ -63,7 +63,7 @@ void WindowScreenCastSource::render(GLFramebuffer *target)
     GLFramebuffer::pushFramebuffer(target);
     glClearColor(0.0, 0.0, 0.0, 0.0);
     glClear(GL_COLOR_BUFFER_BIT);
-    Compositor::self()->scene()->renderer()->renderItem(m_window->windowItem(), WorkspaceScene::PAINT_WINDOW_TRANSFORMED, infiniteRegion(), data);
+    Compositor::self()->scene()->renderer()->renderItem(m_window->windowItem(), Scene::PAINT_WINDOW_TRANSFORMED, infiniteRegion(), data);
     GLFramebuffer::popFramebuffer();
 }
 

src/scene/decorationitem.cpp

@@ -124,7 +124,7 @@ void DecorationRenderer::renderToPainter(QPainter *painter, const QRect &rect)
     client()->decoration()->paint(painter, rect);
 }
 
-DecorationItem::DecorationItem(KDecoration2::Decoration *decoration, Window *window, WorkspaceScene *scene, Item *parent)
+DecorationItem::DecorationItem(KDecoration2::Decoration *decoration, Window *window, Scene *scene, Item *parent)
     : Item(scene, parent)
     , m_window(window)
 {

src/scene/decorationitem.h

@@ -79,7 +79,7 @@ class KWIN_EXPORT DecorationItem : public Item
     Q_OBJECT
 
 public:
-    explicit DecorationItem(KDecoration2::Decoration *decoration, Window *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit DecorationItem(KDecoration2::Decoration *decoration, Window *window, Scene *scene, Item *parent = nullptr);
 
     DecorationRenderer *renderer() const;
     Window *window() const;

src/scene/dndiconitem.cpp

@@ -12,7 +12,7 @@
 namespace KWin
 {
 
-DragAndDropIconItem::DragAndDropIconItem(KWaylandServer::DragAndDropIcon *icon, WorkspaceScene *scene, Item *parent)
+DragAndDropIconItem::DragAndDropIconItem(KWaylandServer::DragAndDropIcon *icon, Scene *scene, Item *parent)
     : Item(scene, parent)
 {
     m_surfaceItem = std::make_unique<SurfaceItemWayland>(icon->surface(), scene, this);

src/scene/dndiconitem.h

@@ -23,7 +23,7 @@ class DragAndDropIconItem : public Item
     Q_OBJECT
 
 public:
-    explicit DragAndDropIconItem(KWaylandServer::DragAndDropIcon *icon, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit DragAndDropIconItem(KWaylandServer::DragAndDropIcon *icon, Scene *scene, Item *parent = nullptr);
     ~DragAndDropIconItem() override;
 
     void frameRendered(quint32 timestamp);

src/scene/item.cpp

@@ -7,17 +7,17 @@
 #include "scene/item.h"
 #include "core/renderlayer.h"
 #include "core/renderloop.h"
-#include "scene/workspacescene.h"
+#include "scene/scene.h"
 #include "utils/common.h"
 
 namespace KWin
 {
 
-Item::Item(WorkspaceScene *scene, Item *parent)
+Item::Item(Scene *scene, Item *parent)
     : m_scene(scene)
 {
     setParentItem(parent);
-    connect(m_scene, &WorkspaceScene::delegateRemoved, this, &Item::removeRepaints);
+    connect(m_scene, &Scene::delegateRemoved, this, &Item::removeRepaints);
 }
 
 Item::~Item()
@@ -30,7 +30,7 @@ Item::~Item()
     }
 }
 
-WorkspaceScene *Item::scene() const
+Scene *Item::scene() const
 {
     return m_scene;
 }

src/scene/item.h

@@ -19,7 +19,7 @@ namespace KWin
 {
 
 class SceneDelegate;
-class WorkspaceScene;
+class Scene;
 
 /**
  * The Item class is the base class for items in the scene.
@@ -29,10 +29,10 @@ class KWIN_EXPORT Item : public QObject
     Q_OBJECT
 
 public:
-    explicit Item(WorkspaceScene *scene, Item *parent = nullptr);
+    explicit Item(Scene *scene, Item *parent = nullptr);
     ~Item() override;
 
-    WorkspaceScene *scene() const;
+    Scene *scene() const;
 
     qreal opacity() const;
     void setOpacity(qreal opacity);
@@ -142,7 +142,7 @@ private:
     void updateEffectiveVisibility();
     void removeRepaints(SceneDelegate *delegate);
 
-    WorkspaceScene *m_scene;
+    Scene *m_scene;
     QPointer<Item> m_parentItem;
     QList<Item *> m_childItems;
     QMatrix4x4 m_transform;

src/scene/itemrenderer_opengl.cpp

@@ -252,7 +252,7 @@ void ItemRendererOpenGL::renderItem(Item *item, int mask, const QRegion &region,
 
     RenderContext renderContext{
         .clip = region,
-        .hardwareClipping = region != infiniteRegion() && ((mask & WorkspaceScene::PAINT_WINDOW_TRANSFORMED) || (mask & WorkspaceScene::PAINT_SCREEN_TRANSFORMED)),
+        .hardwareClipping = region != infiniteRegion() && ((mask & Scene::PAINT_WINDOW_TRANSFORMED) || (mask & Scene::PAINT_SCREEN_TRANSFORMED)),
         .renderTargetScale = data.renderTargetScale().value_or(renderTargetScale()),
     };
 

src/scene/itemrenderer_qpainter.cpp

@@ -53,7 +53,7 @@ void ItemRendererQPainter::renderItem(Item *item, int mask, const QRegion &_regi
     QRegion region = _region;
 
     const QRect boundingRect = item->mapToGlobal(item->boundingRect()).toAlignedRect();
-    if (!(mask & (WorkspaceScene::PAINT_WINDOW_TRANSFORMED | WorkspaceScene::PAINT_SCREEN_TRANSFORMED))) {
+    if (!(mask & (Scene::PAINT_WINDOW_TRANSFORMED | Scene::PAINT_SCREEN_TRANSFORMED))) {
         region &= boundingRect;
     }
 
@@ -66,7 +66,7 @@ void ItemRendererQPainter::renderItem(Item *item, int mask, const QRegion &_regi
     m_painter->setClipping(true);
     m_painter->setOpacity(data.opacity());
 
-    if (mask & WorkspaceScene::PAINT_WINDOW_TRANSFORMED) {
+    if (mask & Scene::PAINT_WINDOW_TRANSFORMED) {
         m_painter->translate(data.xTranslation(), data.yTranslation());
         m_painter->scale(data.xScale(), data.yScale());
     }

src/scene/scene.cpp

@@ -0,0 +1,143 @@
+/*
+    SPDX-FileCopyrightText: 2022 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+
+#include "scene/scene.h"
+#include "core/output.h"
+#include "core/renderlayer.h"
+#include "scene/itemrenderer.h"
+
+namespace KWin
+{
+
+SceneDelegate::SceneDelegate(Scene *scene)
+    : m_scene(scene)
+{
+    m_scene->addDelegate(this);
+}
+
+SceneDelegate::SceneDelegate(Scene *scene, Output *output)
+    : m_scene(scene)
+    , m_output(output)
+{
+    m_scene->addDelegate(this);
+}
+
+SceneDelegate::~SceneDelegate()
+{
+    m_scene->removeDelegate(this);
+}
+
+QRegion SceneDelegate::repaints() const
+{
+    return m_scene->damage().translated(-viewport().topLeft());
+}
+
+SurfaceItem *SceneDelegate::scanoutCandidate() const
+{
+    return m_scene->scanoutCandidate();
+}
+
+void SceneDelegate::prePaint()
+{
+    m_scene->prePaint(this);
+}
+
+void SceneDelegate::postPaint()
+{
+    m_scene->postPaint();
+}
+
+void SceneDelegate::paint(RenderTarget *renderTarget, const QRegion &region)
+{
+    m_scene->paint(renderTarget, region.translated(viewport().topLeft()));
+}
+
+Output *SceneDelegate::output() const
+{
+    return m_output;
+}
+
+QRect SceneDelegate::viewport() const
+{
+    return m_output ? m_output->geometry() : m_scene->geometry();
+}
+
+Scene::Scene(std::unique_ptr<ItemRenderer> &&renderer)
+    : m_renderer(std::move(renderer))
+{
+}
+
+Scene::~Scene()
+{
+}
+
+ItemRenderer *Scene::renderer() const
+{
+    return m_renderer.get();
+}
+
+void Scene::addRepaintFull()
+{
+    addRepaint(geometry());
+}
+
+void Scene::addRepaint(int x, int y, int width, int height)
+{
+    addRepaint(QRegion(x, y, width, height));
+}
+
+void Scene::addRepaint(const QRegion &region)
+{
+    for (const auto &delegate : std::as_const(m_delegates)) {
+        const QRect viewport = delegate->viewport();
+        QRegion dirtyRegion = region & viewport;
+        dirtyRegion.translate(-viewport.topLeft());
+        if (!dirtyRegion.isEmpty()) {
+            delegate->layer()->addRepaint(dirtyRegion);
+        }
+    }
+}
+
+QRegion Scene::damage() const
+{
+    return QRegion();
+}
+
+QRect Scene::geometry() const
+{
+    return m_geometry;
+}
+
+void Scene::setGeometry(const QRect &rect)
+{
+    if (m_geometry != rect) {
+        m_geometry = rect;
+        addRepaintFull();
+    }
+}
+
+QList<SceneDelegate *> Scene::delegates() const
+{
+    return m_delegates;
+}
+
+void Scene::addDelegate(SceneDelegate *delegate)
+{
+    m_delegates.append(delegate);
+}
+
+void Scene::removeDelegate(SceneDelegate *delegate)
+{
+    m_delegates.removeOne(delegate);
+    Q_EMIT delegateRemoved(delegate);
+}
+
+SurfaceItem *Scene::scanoutCandidate() const
+{
+    return nullptr;
+}
+
+} // namespace KWin

src/scene/scene.h

@@ -0,0 +1,98 @@
+/*
+    SPDX-FileCopyrightText: 2022 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+
+#pragma once
+
+#include "core/renderlayerdelegate.h"
+
+#include <QObject>
+
+#include <memory>
+
+namespace KWin
+{
+
+class ItemRenderer;
+class Output;
+class Scene;
+
+class KWIN_EXPORT SceneDelegate : public RenderLayerDelegate
+{
+public:
+    explicit SceneDelegate(Scene *scene);
+    explicit SceneDelegate(Scene *scene, Output *output);
+    ~SceneDelegate() override;
+
+    Output *output() const;
+    QRect viewport() const;
+
+    QRegion repaints() const override;
+    SurfaceItem *scanoutCandidate() const override;
+    void prePaint() override;
+    void postPaint() override;
+    void paint(RenderTarget *renderTarget, const QRegion &region) override;
+
+private:
+    Scene *m_scene;
+    Output *m_output = nullptr;
+};
+
+class KWIN_EXPORT Scene : public QObject
+{
+    Q_OBJECT
+
+public:
+    // Flags controlling how painting is done.
+    enum {
+        // WindowItem (or at least part of it) will be painted opaque.
+        PAINT_WINDOW_OPAQUE = 1 << 0,
+        // WindowItem (or at least part of it) will be painted translucent.
+        PAINT_WINDOW_TRANSLUCENT = 1 << 1,
+        // WindowItem will be painted with transformed geometry.
+        PAINT_WINDOW_TRANSFORMED = 1 << 2,
+        // Paint only a region of the screen (can be optimized, cannot
+        // be used together with TRANSFORMED flags).
+        PAINT_SCREEN_REGION = 1 << 3,
+        // Whole screen will be painted with transformed geometry.
+        PAINT_SCREEN_TRANSFORMED = 1 << 4,
+        // At least one window will be painted with transformed geometry.
+        PAINT_SCREEN_WITH_TRANSFORMED_WINDOWS = 1 << 5,
+        // Clear whole background as the very first step, without optimizing it
+        PAINT_SCREEN_BACKGROUND_FIRST = 1 << 6,
+    };
+
+    explicit Scene(std::unique_ptr<ItemRenderer> &&renderer);
+    ~Scene() override;
+
+    ItemRenderer *renderer() const;
+
+    void addRepaint(const QRegion &region);
+    void addRepaint(int x, int y, int width, int height);
+    void addRepaintFull();
+    virtual QRegion damage() const;
+
+    QRect geometry() const;
+    void setGeometry(const QRect &rect);
+
+    QList<SceneDelegate *> delegates() const;
+    void addDelegate(SceneDelegate *delegate);
+    void removeDelegate(SceneDelegate *delegate);
+
+    virtual SurfaceItem *scanoutCandidate() const;
+    virtual void prePaint(SceneDelegate *delegate) = 0;
+    virtual void postPaint() = 0;
+    virtual void paint(RenderTarget *renderTarget, const QRegion &region) = 0;
+
+Q_SIGNALS:
+    void delegateRemoved(SceneDelegate *delegate);
+
+protected:
+    std::unique_ptr<ItemRenderer> m_renderer;
+    QList<SceneDelegate *> m_delegates;
+    QRect m_geometry;
+};
+
+} // namespace KWin

src/scene/shadowitem.cpp

@@ -11,7 +11,7 @@
 namespace KWin
 {
 
-ShadowItem::ShadowItem(Shadow *shadow, Window *window, WorkspaceScene *scene, Item *parent)
+ShadowItem::ShadowItem(Shadow *shadow, Window *window, Scene *scene, Item *parent)
     : Item(scene, parent)
     , m_window(window)
     , m_shadow(shadow)

src/scene/shadowitem.h

@@ -23,7 +23,7 @@ class KWIN_EXPORT ShadowItem : public Item
     Q_OBJECT
 
 public:
-    explicit ShadowItem(Shadow *shadow, Window *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit ShadowItem(Shadow *shadow, Window *window, Scene *scene, Item *parent = nullptr);
     ~ShadowItem() override;
 
     Shadow *shadow() const;

src/scene/surfaceitem.cpp

@@ -9,7 +9,7 @@
 namespace KWin
 {
 
-SurfaceItem::SurfaceItem(WorkspaceScene *scene, Item *parent)
+SurfaceItem::SurfaceItem(Scene *scene, Item *parent)
     : Item(scene, parent)
 {
 }

src/scene/surfaceitem.h

@@ -45,7 +45,7 @@ Q_SIGNALS:
     void damaged();
 
 protected:
-    explicit SurfaceItem(WorkspaceScene *scene, Item *parent = nullptr);
+    explicit SurfaceItem(Scene *scene, Item *parent = nullptr);
 
     virtual std::unique_ptr<SurfacePixmap> createPixmap() = 0;
     void preprocess() override;

src/scene/surfaceitem_internal.cpp

@@ -15,7 +15,7 @@
 namespace KWin
 {
 
-SurfaceItemInternal::SurfaceItemInternal(InternalWindow *window, WorkspaceScene *scene, Item *parent)
+SurfaceItemInternal::SurfaceItemInternal(InternalWindow *window, Scene *scene, Item *parent)
     : SurfaceItem(scene, parent)
     , m_window(window)
 {

src/scene/surfaceitem_internal.h

@@ -24,7 +24,7 @@ class KWIN_EXPORT SurfaceItemInternal : public SurfaceItem
     Q_OBJECT
 
 public:
-    explicit SurfaceItemInternal(InternalWindow *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit SurfaceItemInternal(InternalWindow *window, Scene *scene, Item *parent = nullptr);
 
     Window *window() const;
 

src/scene/surfaceitem_wayland.cpp

@@ -15,7 +15,7 @@
 namespace KWin
 {
 
-SurfaceItemWayland::SurfaceItemWayland(KWaylandServer::SurfaceInterface *surface, WorkspaceScene *scene, Item *parent)
+SurfaceItemWayland::SurfaceItemWayland(KWaylandServer::SurfaceInterface *surface, Scene *scene, Item *parent)
     : SurfaceItem(scene, parent)
     , m_surface(surface)
 {
@@ -202,7 +202,7 @@ void SurfacePixmapWayland::setBuffer(KWaylandServer::ClientBuffer *buffer)
     }
 }
 
-SurfaceItemXwayland::SurfaceItemXwayland(Window *window, WorkspaceScene *scene, Item *parent)
+SurfaceItemXwayland::SurfaceItemXwayland(Window *window, Scene *scene, Item *parent)
     : SurfaceItemWayland(window->surface(), scene, parent)
     , m_window(window)
 {

src/scene/surfaceitem_wayland.h

@@ -28,7 +28,7 @@ class KWIN_EXPORT SurfaceItemWayland : public SurfaceItem
     Q_OBJECT
 
 public:
-    explicit SurfaceItemWayland(KWaylandServer::SurfaceInterface *surface, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit SurfaceItemWayland(KWaylandServer::SurfaceInterface *surface, Scene *scene, Item *parent = nullptr);
 
     QVector<QRectF> shape() const override;
     QRegion opaque() const override;
@@ -87,7 +87,7 @@ class KWIN_EXPORT SurfaceItemXwayland : public SurfaceItemWayland
     Q_OBJECT
 
 public:
-    explicit SurfaceItemXwayland(Window *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit SurfaceItemXwayland(Window *window, Scene *scene, Item *parent = nullptr);
 
     QVector<QRectF> shape() const override;
 

src/scene/surfaceitem_x11.cpp

@@ -13,7 +13,7 @@
 namespace KWin
 {
 
-SurfaceItemX11::SurfaceItemX11(Window *window, WorkspaceScene *scene, Item *parent)
+SurfaceItemX11::SurfaceItemX11(Window *window, Scene *scene, Item *parent)
     : SurfaceItem(scene, parent)
     , m_window(window)
 {

src/scene/surfaceitem_x11.h

@@ -24,7 +24,7 @@ class KWIN_EXPORT SurfaceItemX11 : public SurfaceItem
     Q_OBJECT
 
 public:
-    explicit SurfaceItemX11(Window *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit SurfaceItemX11(Window *window, Scene *scene, Item *parent = nullptr);
     ~SurfaceItemX11() override;
 
     Window *window() const;

src/scene/windowitem.cpp

@@ -19,7 +19,7 @@
 namespace KWin
 {
 
-WindowItem::WindowItem(Window *window, WorkspaceScene *scene, Item *parent)
+WindowItem::WindowItem(Window *window, Scene *scene, Item *parent)
     : Item(scene, parent)
     , m_window(window)
 {
@@ -248,7 +248,7 @@ void WindowItem::markDamaged()
     Q_EMIT m_window->damaged(m_window);
 }
 
-WindowItemX11::WindowItemX11(Window *window, WorkspaceScene *scene, Item *parent)
+WindowItemX11::WindowItemX11(Window *window, Scene *scene, Item *parent)
     : WindowItem(window, scene, parent)
 {
     initialize();
@@ -275,13 +275,13 @@ void WindowItemX11::initialize()
     }
 }
 
-WindowItemWayland::WindowItemWayland(Window *window, WorkspaceScene *scene, Item *parent)
+WindowItemWayland::WindowItemWayland(Window *window, Scene *scene, Item *parent)
     : WindowItem(window, scene, parent)
 {
     updateSurfaceItem(new SurfaceItemWayland(window->surface(), scene, this));
 }
 
-WindowItemInternal::WindowItemInternal(InternalWindow *window, WorkspaceScene *scene, Item *parent)
+WindowItemInternal::WindowItemInternal(InternalWindow *window, Scene *scene, Item *parent)
     : WindowItem(window, scene, parent)
 {
     updateSurfaceItem(new SurfaceItemInternal(window, scene, this));

src/scene/windowitem.h

@@ -53,7 +53,7 @@ public:
     void unrefVisible(int reason);
 
 protected:
-    explicit WindowItem(Window *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit WindowItem(Window *window, Scene *scene, Item *parent = nullptr);
     void updateSurfaceItem(SurfaceItem *surfaceItem);
 
 private Q_SLOTS:
@@ -92,7 +92,7 @@ class KWIN_EXPORT WindowItemX11 : public WindowItem
     Q_OBJECT
 
 public:
-    explicit WindowItemX11(Window *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit WindowItemX11(Window *window, Scene *scene, Item *parent = nullptr);
 
 private Q_SLOTS:
     void initialize();
@@ -106,7 +106,7 @@ class KWIN_EXPORT WindowItemWayland : public WindowItem
     Q_OBJECT
 
 public:
-    explicit WindowItemWayland(Window *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit WindowItemWayland(Window *window, Scene *scene, Item *parent = nullptr);
 };
 
 /**
@@ -118,7 +118,7 @@ class KWIN_EXPORT WindowItemInternal : public WindowItem
     Q_OBJECT
 
 public:
-    explicit WindowItemInternal(InternalWindow *window, WorkspaceScene *scene, Item *parent = nullptr);
+    explicit WindowItemInternal(InternalWindow *window, Scene *scene, Item *parent = nullptr);
 };
 
 } // namespace KWin

src/scene/workspacescene.cpp

@@ -79,65 +79,12 @@
 namespace KWin
 {
 
-SceneDelegate::SceneDelegate(WorkspaceScene *scene)
-    : m_scene(scene)
-{
-    m_scene->addDelegate(this);
-}
-
-SceneDelegate::SceneDelegate(WorkspaceScene *scene, Output *output)
-    : m_scene(scene)
-    , m_output(output)
-{
-    m_scene->addDelegate(this);
-}
-
-SceneDelegate::~SceneDelegate()
-{
-    m_scene->removeDelegate(this);
-}
-
-QRegion SceneDelegate::repaints() const
-{
-    return m_scene->damage().translated(-viewport().topLeft());
-}
-
-SurfaceItem *SceneDelegate::scanoutCandidate() const
-{
-    return m_scene->scanoutCandidate();
-}
-
-void SceneDelegate::prePaint()
-{
-    m_scene->prePaint(this);
-}
-
-void SceneDelegate::postPaint()
-{
-    m_scene->postPaint();
-}
-
-void SceneDelegate::paint(RenderTarget *renderTarget, const QRegion &region)
-{
-    m_scene->paint(renderTarget, region.translated(viewport().topLeft()));
-}
-
-Output *SceneDelegate::output() const
-{
-    return m_output;
-}
-
-QRect SceneDelegate::viewport() const
-{
-    return m_output ? m_output->geometry() : m_scene->geometry();
-}
-
 //****************************************
 // Scene
 //****************************************
 
 WorkspaceScene::WorkspaceScene(std::unique_ptr<ItemRenderer> renderer)
-    : m_renderer(std::move(renderer))
+    : Scene(std::move(renderer))
 {
 }
 
@@ -185,62 +132,11 @@ void WorkspaceScene::destroyDndIconItem()
     m_dndIcon.reset();
 }
 
-void WorkspaceScene::addRepaintFull()
-{
-    addRepaint(geometry());
-}
-
-void WorkspaceScene::addRepaint(int x, int y, int width, int height)
-{
-    addRepaint(QRegion(x, y, width, height));
-}
-
-void WorkspaceScene::addRepaint(const QRegion &region)
-{
-    for (const auto &delegate : std::as_const(m_delegates)) {
-        const QRect viewport = delegate->viewport();
-        QRegion dirtyRegion = region & viewport;
-        dirtyRegion.translate(-viewport.topLeft());
-        if (!dirtyRegion.isEmpty()) {
-            delegate->layer()->addRepaint(dirtyRegion);
-        }
-    }
-}
-
 QRegion WorkspaceScene::damage() const
 {
     return m_paintContext.damage;
 }
 
-QRect WorkspaceScene::geometry() const
-{
-    return m_geometry;
-}
-
-void WorkspaceScene::setGeometry(const QRect &rect)
-{
-    if (m_geometry != rect) {
-        m_geometry = rect;
-        addRepaintFull();
-    }
-}
-
-QList<SceneDelegate *> WorkspaceScene::delegates() const
-{
-    return m_delegates;
-}
-
-void WorkspaceScene::addDelegate(SceneDelegate *delegate)
-{
-    m_delegates.append(delegate);
-}
-
-void WorkspaceScene::removeDelegate(SceneDelegate *delegate)
-{
-    m_delegates.removeOne(delegate);
-    Q_EMIT delegateRemoved(delegate);
-}
-
 static SurfaceItem *findTopMostSurface(SurfaceItem *item)
 {
     const QList<Item *> children = item->childItems();
@@ -470,11 +366,6 @@ void WorkspaceScene::paint(RenderTarget *renderTarget, const QRegion &region)
     m_renderer->endFrame();
 }
 
-ItemRenderer *WorkspaceScene::renderer() const
-{
-    return m_renderer.get();
-}
-
 // the function that'll be eventually called by paintScreen() above
 void WorkspaceScene::finalPaintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {

src/scene/workspacescene.h

@@ -9,7 +9,8 @@
 
 #pragma once
 
-#include "core/renderlayerdelegate.h"
+#include "scene/scene.h"
+
 #include "kwineffects.h"
 #include "utils/common.h"
 #include "window.h"
@@ -27,8 +28,6 @@ namespace Decoration
 class DecoratedClientImpl;
 }
 
-class ItemRenderer;
-class Output;
 class DecorationRenderer;
 class Deleted;
 class DragAndDropIconItem;
@@ -42,28 +41,7 @@ class ShadowItem;
 class SurfaceItem;
 class WindowItem;
 
-class SceneDelegate : public RenderLayerDelegate
-{
-public:
-    explicit SceneDelegate(WorkspaceScene *scene);
-    explicit SceneDelegate(WorkspaceScene *scene, Output *output);
-    ~SceneDelegate() override;
-
-    Output *output() const;
-    QRect viewport() const;
-
-    QRegion repaints() const override;
-    SurfaceItem *scanoutCandidate() const override;
-    void prePaint() override;
-    void postPaint() override;
-    void paint(RenderTarget *renderTarget, const QRegion &region) override;
-
-private:
-    WorkspaceScene *m_scene;
-    Output *m_output = nullptr;
-};
-
-class KWIN_EXPORT WorkspaceScene : public QObject
+class KWIN_EXPORT WorkspaceScene : public Scene
 {
     Q_OBJECT
 
@@ -73,25 +51,11 @@ public:
 
     void initialize();
 
-    /**
-     * Schedules a repaint for the specified @a region.
-     */
-    void addRepaint(const QRegion &region);
-    void addRepaint(int x, int y, int width, int height);
-    void addRepaintFull();
-    QRegion damage() const;
-
-    QRect geometry() const;
-    void setGeometry(const QRect &rect);
-
-    QList<SceneDelegate *> delegates() const;
-    void addDelegate(SceneDelegate *delegate);
-    void removeDelegate(SceneDelegate *delegate);
-
-    SurfaceItem *scanoutCandidate() const;
-    void prePaint(SceneDelegate *delegate);
-    void postPaint();
-    void paint(RenderTarget *renderTarget, const QRegion &region);
+    QRegion damage() const override;
+    SurfaceItem *scanoutCandidate() const override;
+    void prePaint(SceneDelegate *delegate) override;
+    void postPaint() override;
+    void paint(RenderTarget *renderTarget, const QRegion &region) override;
 
     /**
      * @brief Creates the Scene specific Shadow subclass.
@@ -102,24 +66,6 @@ public:
      * @param window The Window for which the Shadow needs to be created.
      */
     virtual Shadow *createShadow(Window *window) = 0;
-    // Flags controlling how painting is done.
-    enum {
-        // WindowItem (or at least part of it) will be painted opaque.
-        PAINT_WINDOW_OPAQUE = 1 << 0,
-        // WindowItem (or at least part of it) will be painted translucent.
-        PAINT_WINDOW_TRANSLUCENT = 1 << 1,
-        // WindowItem will be painted with transformed geometry.
-        PAINT_WINDOW_TRANSFORMED = 1 << 2,
-        // Paint only a region of the screen (can be optimized, cannot
-        // be used together with TRANSFORMED flags).
-        PAINT_SCREEN_REGION = 1 << 3,
-        // Whole screen will be painted with transformed geometry.
-        PAINT_SCREEN_TRANSFORMED = 1 << 4,
-        // At least one window will be painted with transformed geometry.
-        PAINT_SCREEN_WITH_TRANSFORMED_WINDOWS = 1 << 5,
-        // Clear whole background as the very first step, without optimizing it
-        PAINT_SCREEN_BACKGROUND_FIRST = 1 << 6,
-    };
 
     virtual bool makeOpenGLContextCurrent();
     virtual void doneOpenGLContextCurrent();
@@ -140,12 +86,9 @@ public:
         return {};
     }
 
-    ItemRenderer *renderer() const;
-
 Q_SIGNALS:
     void preFrameRender();
     void frameRendered();
-    void delegateRemoved(SceneDelegate *delegate);
 
 protected:
     void createStackingOrder();
@@ -194,10 +137,7 @@ private:
     void createDndIconItem();
     void destroyDndIconItem();
 
-    std::unique_ptr<ItemRenderer> m_renderer;
     std::chrono::milliseconds m_expectedPresentTimestamp = std::chrono::milliseconds::zero();
-    QList<SceneDelegate *> m_delegates;
-    QRect m_geometry;
     // how many times finalPaintScreen() has been called
     int m_paintScreenCount = 0;
     PaintContext m_paintContext;

src/scripting/windowthumbnailitem.cpp

@@ -443,7 +443,7 @@ void WindowThumbnailItem::updateOffscreenTexture()
     // The thumbnail must be rendered using kwin's opengl context as VAOs are not
     // shared across contexts. Unfortunately, this also introduces a latency of 1
     // frame, which is not ideal, but it is acceptable for things such as thumbnails.
-    const int mask = WorkspaceScene::PAINT_WINDOW_TRANSFORMED;
+    const int mask = Scene::PAINT_WINDOW_TRANSFORMED;
     Compositor::self()->scene()->renderer()->renderItem(m_client->windowItem(), mask, infiniteRegion(), data);
     GLFramebuffer::popFramebuffer();
 

src/unmanaged.cpp

@@ -71,7 +71,7 @@ Unmanaged::~Unmanaged()
 {
 }
 
-WindowItem *Unmanaged::createItem(WorkspaceScene *scene)
+WindowItem *Unmanaged::createItem(Scene *scene)
 {
     return new WindowItemX11(this, scene);
 }

src/unmanaged.h

@@ -59,7 +59,7 @@ public:
     { /* nothing to do */
         return geometry;
     }
-    WindowItem *createItem(WorkspaceScene *scene) override;
+    WindowItem *createItem(Scene *scene) override;
 
 public Q_SLOTS:
     void release(ReleaseReason releaseReason = ReleaseReason::Release);

src/waylandwindow.cpp

@@ -53,7 +53,7 @@ WaylandWindow::WaylandWindow(SurfaceInterface *surface)
     updateIcon();
 }
 
-WindowItem *WaylandWindow::createItem(WorkspaceScene *scene)
+WindowItem *WaylandWindow::createItem(Scene *scene)
 {
     return new WindowItemWayland(this, scene);
 }

src/waylandwindow.h

@@ -44,7 +44,7 @@ protected:
     bool belongsToDesktop() const override;
     void doSetActive() override;
     void updateCaption() override;
-    WindowItem *createItem(WorkspaceScene *scene) override;
+    WindowItem *createItem(Scene *scene) override;
 
     void cleanGrouping();
     void updateGeometry(const QRectF &rect);

src/window.h

@@ -51,6 +51,7 @@ class ClientMachine;
 class Deleted;
 class EffectWindowImpl;
 class Tile;
+class Scene;
 class Shadow;
 class SurfaceItem;
 class VirtualDesktop;
@@ -1579,7 +1580,7 @@ protected:
     void getWmOpaqueRegion();
     void discardShapeRegion();
 
-    virtual WindowItem *createItem(WorkspaceScene *scene) = 0;
+    virtual WindowItem *createItem(Scene *scene) = 0;
     void deleteItem();
 
     void getResourceClass();

src/x11window.cpp

@@ -316,7 +316,7 @@ X11Window::~X11Window()
     Q_ASSERT(!check_active_modal);
 }
 
-WindowItem *X11Window::createItem(WorkspaceScene *scene)
+WindowItem *X11Window::createItem(Scene *scene)
 {
     return new WindowItemX11(this, scene);
 }

src/x11window.h

@@ -357,7 +357,7 @@ protected:
     QSizeF resizeIncrements() const override;
     bool acceptsFocus() const override;
     void moveResizeInternal(const QRectF &rect, MoveResizeMode mode) override;
-    WindowItem *createItem(WorkspaceScene *scene) override;
+    WindowItem *createItem(Scene *scene) override;
 
     // Signals for the scripting interface
     // Signals make an excellent way for communication