From 809f383d4477df754058085a3b626333c4c2fd6e Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Tue, 5 Apr 2022 17:15:57 +0300
Subject: [PATCH] Take layer-local damage regions

Using the global coordinate system when specifying output layer damage
regions would be very confusing. In order to make the coordinate system
comprehensible, use the layer-local coordinate system.

The infinite region is used to tell the Compositor when it needs to
repaint the entire layer.
---
 src/abstract_output.cpp                       |  5 ++++
 src/abstract_output.h                         |  5 ++++
 src/backends/drm/drm_abstract_output.cpp      |  2 +-
 src/backends/drm/drm_qpainter_layer.cpp       |  2 +-
 src/backends/drm/dumb_swapchain.cpp           |  5 ++--
 src/backends/drm/dumb_swapchain.h             |  2 +-
 src/backends/drm/egl_gbm_layer.cpp            | 21 ++++-------------
 src/backends/drm/gbm_surface.cpp              |  7 +++---
 src/backends/drm/gbm_surface.h                |  2 +-
 src/backends/drm/virtual_egl_gbm_layer.cpp    |  2 +-
 src/backends/virtual/egl_gbm_backend.cpp      |  2 +-
 src/backends/wayland/egl_wayland_backend.cpp  |  4 ++--
 .../scene_qpainter_wayland_backend.cpp        | 10 +++-----
 .../wayland/scene_qpainter_wayland_backend.h  |  1 -
 src/backends/x11/standalone/eglbackend.cpp    |  2 +-
 src/backends/x11/standalone/glxbackend.cpp    |  2 +-
 src/backends/x11/windowed/egl_x11_backend.cpp |  2 +-
 .../windowed/scene_qpainter_x11_backend.cpp   |  2 +-
 src/composite.cpp                             | 10 ++++----
 src/plugins/screencast/screencastmanager.cpp  |  2 +-
 src/scene.cpp                                 | 23 +++++++++++--------
 src/scene.h                                   |  2 ++
 22 files changed, 58 insertions(+), 57 deletions(-)

diff --git a/src/abstract_output.cpp b/src/abstract_output.cpp
index 6ea73ad065..4595e9a159 100644
--- a/src/abstract_output.cpp
+++ b/src/abstract_output.cpp
@@ -173,4 +173,9 @@ bool AbstractOutput::usesSoftwareCursor() const
     return true;
 }
 
+QRect AbstractOutput::mapFromGlobal(const QRect &rect) const
+{
+    return rect.translated(-geometry().topLeft());
+}
+
 } // namespace KWin
diff --git a/src/abstract_output.h b/src/abstract_output.h
index 3c65b6dee6..a8f759c0c4 100644
--- a/src/abstract_output.h
+++ b/src/abstract_output.h
@@ -94,6 +94,11 @@ public:
     explicit AbstractOutput(QObject *parent = nullptr);
     ~AbstractOutput() override;
 
+    /**
+     * Maps the specified @a rect from the global coordinate system to the output-local coords.
+     */
+    QRect mapFromGlobal(const QRect &rect) const;
+
     /**
      * Returns a dummy OutputLayer corresponding to the primary plane.
      *
diff --git a/src/backends/drm/drm_abstract_output.cpp b/src/backends/drm/drm_abstract_output.cpp
index 017852c034..81690b1445 100644
--- a/src/backends/drm/drm_abstract_output.cpp
+++ b/src/backends/drm/drm_abstract_output.cpp
@@ -39,7 +39,7 @@ void DrmAbstractOutput::pageFlipped(std::chrono::nanoseconds timestamp) const
 QVector<int32_t> DrmAbstractOutput::regionToRects(const QRegion &region) const
 {
     const int height = pixelSize().height();
-    const QMatrix4x4 matrix = AbstractWaylandOutput::logicalToNativeMatrix(geometry(), scale(), transform());
+    const QMatrix4x4 matrix = AbstractWaylandOutput::logicalToNativeMatrix(QRect(QPoint(0, 0), geometry().size()), scale(), transform());
     QVector<EGLint> rects;
     rects.reserve(region.rectCount() * 4);
     for (const QRect &_rect : region) {
diff --git a/src/backends/drm/drm_qpainter_layer.cpp b/src/backends/drm/drm_qpainter_layer.cpp
index cc66350a1e..0289ee315a 100644
--- a/src/backends/drm/drm_qpainter_layer.cpp
+++ b/src/backends/drm/drm_qpainter_layer.cpp
@@ -36,7 +36,7 @@ std::optional<QRegion> DrmQPainterLayer::startRendering()
         m_swapchain = QSharedPointer<DumbSwapchain>::create(m_pipeline->gpu(), m_pipeline->sourceSize(), DRM_FORMAT_XRGB8888);
     }
     QRegion needsRepaint;
-    if (!m_swapchain->acquireBuffer(m_pipeline->output()->geometry(), &needsRepaint)) {
+    if (!m_swapchain->acquireBuffer(&needsRepaint)) {
         return std::optional<QRegion>();
     }
     return needsRepaint;
diff --git a/src/backends/drm/dumb_swapchain.cpp b/src/backends/drm/dumb_swapchain.cpp
index e2d3f1d788..df5d032fc2 100644
--- a/src/backends/drm/dumb_swapchain.cpp
+++ b/src/backends/drm/dumb_swapchain.cpp
@@ -10,6 +10,7 @@
 #include "dumb_swapchain.h"
 #include "drm_buffer.h"
 #include "drm_gpu.h"
+#include "kwineffects.h"
 #include "logging.h"
 
 namespace KWin
@@ -40,14 +41,14 @@ DumbSwapchain::DumbSwapchain(DrmGpu *gpu, const QSize &size, uint32_t drmFormat,
     }
 }
 
-QSharedPointer<DrmDumbBuffer> DumbSwapchain::acquireBuffer(const QRect &geometry, QRegion *needsRepaint)
+QSharedPointer<DrmDumbBuffer> DumbSwapchain::acquireBuffer(QRegion *needsRepaint)
 {
     if (m_slots.isEmpty()) {
         return {};
     }
     index = (index + 1) % m_slots.count();
     if (needsRepaint) {
-        *needsRepaint = m_damageJournal.accumulate(m_slots[index].age, geometry);
+        *needsRepaint = m_damageJournal.accumulate(m_slots[index].age, infiniteRegion());
     }
     return m_slots[index].buffer;
 }
diff --git a/src/backends/drm/dumb_swapchain.h b/src/backends/drm/dumb_swapchain.h
index c1b5173ce5..c0f035ff78 100644
--- a/src/backends/drm/dumb_swapchain.h
+++ b/src/backends/drm/dumb_swapchain.h
@@ -27,7 +27,7 @@ class DumbSwapchain
 public:
     DumbSwapchain(DrmGpu *gpu, const QSize &size, uint32_t drmFormat, QImage::Format imageFormat = QImage::Format_RGB32);
 
-    QSharedPointer<DrmDumbBuffer> acquireBuffer(const QRect &geometry = {}, QRegion *needsRepaint = nullptr);
+    QSharedPointer<DrmDumbBuffer> acquireBuffer(QRegion *needsRepaint = nullptr);
     QSharedPointer<DrmDumbBuffer> currentBuffer() const;
     void releaseBuffer(QSharedPointer<DrmDumbBuffer> buffer, const QRegion &damage = {});
 
diff --git a/src/backends/drm/egl_gbm_layer.cpp b/src/backends/drm/egl_gbm_layer.cpp
index 37ddeb435c..d68a3c3dc5 100644
--- a/src/backends/drm/egl_gbm_layer.cpp
+++ b/src/backends/drm/egl_gbm_layer.cpp
@@ -90,7 +90,7 @@ std::optional<QRegion> EglGbmLayer::startRendering()
     if (!m_gbmSurface->makeContextCurrent()) {
         return std::optional<QRegion>();
     }
-    auto repaintRegion = m_gbmSurface->repaintRegion(m_pipeline->output()->geometry());
+    auto repaintRegion = m_gbmSurface->repaintRegion();
 
     // shadow buffer
     if (doesShadowBufferFit(m_shadowBuffer.data())) {
@@ -185,7 +185,7 @@ bool EglGbmLayer::renderTestBuffer()
         return false;
     }
     glClear(GL_COLOR_BUFFER_BIT);
-    if (!endRendering(m_pipeline->output()->geometry())) {
+    if (!endRendering(infiniteRegion())) {
         return false;
     }
     return true;
@@ -441,22 +441,11 @@ bool EglGbmLayer::scanout(SurfaceItem *surfaceItem)
         m_scanoutBuffer.reset();
         return false;
     }
-    // damage tracking for screen casting
-    QRegion damage;
-    if (m_scanoutCandidate.surface == item->surface()) {
-        QRegion trackedDamage = surfaceItem->damage();
-        surfaceItem->resetDamage();
-        for (const auto &rect : trackedDamage) {
-            auto damageRect = QRect(rect);
-            damageRect.translate(m_pipeline->output()->geometry().topLeft());
-            damage |= damageRect;
-        }
-    } else {
-        damage = m_pipeline->output()->geometry();
-    }
+
     if (m_pipeline->testScanout()) {
         m_currentBuffer = m_scanoutBuffer;
-        m_currentDamage = damage;
+        m_currentDamage = surfaceItem->damage();
+        surfaceItem->resetDamage();
         return true;
     } else {
         m_scanoutBuffer.reset();
diff --git a/src/backends/drm/gbm_surface.cpp b/src/backends/drm/gbm_surface.cpp
index 7a7f6169a2..9399206764 100644
--- a/src/backends/drm/gbm_surface.cpp
+++ b/src/backends/drm/gbm_surface.cpp
@@ -14,6 +14,7 @@
 #include "drm_backend.h"
 #include "drm_gpu.h"
 #include "egl_gbm_backend.h"
+#include "kwineffects.h"
 #include "kwineglutils_p.h"
 #include "kwinglplatform.h"
 #include "logging.h"
@@ -178,12 +179,12 @@ int GbmSurface::bufferAge() const
     return m_bufferAge;
 }
 
-QRegion GbmSurface::repaintRegion(const QRect &geometry) const
+QRegion GbmSurface::repaintRegion() const
 {
     if (m_eglBackend->supportsBufferAge()) {
-        return m_damageJournal.accumulate(m_bufferAge, geometry);
+        return m_damageJournal.accumulate(m_bufferAge, infiniteRegion());
     } else {
-        return geometry;
+        return infiniteRegion();
     }
 }
 
diff --git a/src/backends/drm/gbm_surface.h b/src/backends/drm/gbm_surface.h
index 1e57ece5fd..c80f8a6833 100644
--- a/src/backends/drm/gbm_surface.h
+++ b/src/backends/drm/gbm_surface.h
@@ -49,7 +49,7 @@ public:
     uint32_t format() const;
     QVector<uint64_t> modifiers() const;
     int bufferAge() const;
-    QRegion repaintRegion(const QRect &geometry) const;
+    QRegion repaintRegion() const;
 
 private:
     gbm_surface *m_surface;
diff --git a/src/backends/drm/virtual_egl_gbm_layer.cpp b/src/backends/drm/virtual_egl_gbm_layer.cpp
index 21f0284914..4618a4a96f 100644
--- a/src/backends/drm/virtual_egl_gbm_layer.cpp
+++ b/src/backends/drm/virtual_egl_gbm_layer.cpp
@@ -79,7 +79,7 @@ std::optional<QRegion> VirtualEglGbmLayer::startRendering()
         return std::optional<QRegion>();
     }
     GLRenderTarget::pushRenderTarget(m_gbmSurface->renderTarget());
-    return m_gbmSurface->repaintRegion(m_output->geometry());
+    return m_gbmSurface->repaintRegion();
 }
 
 bool VirtualEglGbmLayer::endRendering(const QRegion &damagedRegion)
diff --git a/src/backends/virtual/egl_gbm_backend.cpp b/src/backends/virtual/egl_gbm_backend.cpp
index cccd9fd318..e017831db6 100644
--- a/src/backends/virtual/egl_gbm_backend.cpp
+++ b/src/backends/virtual/egl_gbm_backend.cpp
@@ -164,7 +164,7 @@ QRegion EglGbmBackend::beginFrame(AbstractOutput *output)
     if (!GLRenderTarget::currentRenderTarget()) {
         GLRenderTarget::pushRenderTarget(m_fbo);
     }
-    return QRegion(0, 0, screens()->size().width(), screens()->size().height());
+    return infiniteRegion();
 }
 
 static void convertFromGLImage(QImage &img, int w, int h)
diff --git a/src/backends/wayland/egl_wayland_backend.cpp b/src/backends/wayland/egl_wayland_backend.cpp
index 0a7d1ebd0c..bea12a69c8 100644
--- a/src/backends/wayland/egl_wayland_backend.cpp
+++ b/src/backends/wayland/egl_wayland_backend.cpp
@@ -297,7 +297,7 @@ bool EglWaylandBackend::initBufferConfigs()
 static QVector<EGLint> regionToRects(const QRegion &region, AbstractWaylandOutput *output)
 {
     const int height = output->modeSize().height();
-    const QMatrix4x4 matrix = WaylandOutput::logicalToNativeMatrix(output->geometry(),
+    const QMatrix4x4 matrix = WaylandOutput::logicalToNativeMatrix(QRect(QPoint(0, 0), output->geometry().size()),
                                                                    output->scale(),
                                                                    output->transform());
 
@@ -385,7 +385,7 @@ QRegion EglWaylandBackend::beginFrame(AbstractOutput *output)
     GLRenderTarget::pushRenderTarget(eglOutput->renderTarget());
 
     if (supportsBufferAge()) {
-        return eglOutput->m_damageJournal.accumulate(eglOutput->m_bufferAge, eglOutput->m_waylandOutput->geometry());
+        return eglOutput->m_damageJournal.accumulate(eglOutput->m_bufferAge, infiniteRegion());
     }
 
     return QRegion();
diff --git a/src/backends/wayland/scene_qpainter_wayland_backend.cpp b/src/backends/wayland/scene_qpainter_wayland_backend.cpp
index 77f4c8ec2c..764873754f 100644
--- a/src/backends/wayland/scene_qpainter_wayland_backend.cpp
+++ b/src/backends/wayland/scene_qpainter_wayland_backend.cpp
@@ -12,6 +12,7 @@
 #include "wayland_output.h"
 
 #include "composite.h"
+#include "kwineffects.h"
 #include "logging.h"
 
 #include <KWayland/Client/buffer.h>
@@ -127,12 +128,7 @@ WaylandQPainterBufferSlot *WaylandQPainterOutput::acquire()
 
 QRegion WaylandQPainterOutput::accumulateDamage(int bufferAge) const
 {
-    return m_damageJournal.accumulate(bufferAge, m_waylandOutput->geometry());
-}
-
-QRegion WaylandQPainterOutput::mapToLocal(const QRegion &region) const
-{
-    return region.translated(-m_waylandOutput->geometry().topLeft());
+    return m_damageJournal.accumulate(bufferAge, infiniteRegion());
 }
 
 WaylandQPainterBackend::WaylandQPainterBackend(Wayland::WaylandBackend *b)
@@ -174,7 +170,7 @@ void WaylandQPainterBackend::endFrame(AbstractOutput *output, const QRegion &ren
     WaylandQPainterOutput *rendererOutput = m_outputs[output];
     Q_ASSERT(rendererOutput);
 
-    rendererOutput->present(rendererOutput->mapToLocal(damagedRegion));
+    rendererOutput->present(damagedRegion);
 }
 
 QImage *WaylandQPainterBackend::bufferForScreen(AbstractOutput *output)
diff --git a/src/backends/wayland/scene_qpainter_wayland_backend.h b/src/backends/wayland/scene_qpainter_wayland_backend.h
index 0c5504085f..9fecb4b5de 100644
--- a/src/backends/wayland/scene_qpainter_wayland_backend.h
+++ b/src/backends/wayland/scene_qpainter_wayland_backend.h
@@ -63,7 +63,6 @@ public:
     void present(const QRegion &damage);
 
     QRegion accumulateDamage(int bufferAge) const;
-    QRegion mapToLocal(const QRegion &region) const;
 
 private:
     WaylandOutput *m_waylandOutput;
diff --git a/src/backends/x11/standalone/eglbackend.cpp b/src/backends/x11/standalone/eglbackend.cpp
index c715104a2a..d3ba25ae07 100644
--- a/src/backends/x11/standalone/eglbackend.cpp
+++ b/src/backends/x11/standalone/eglbackend.cpp
@@ -112,7 +112,7 @@ QRegion EglBackend::beginFrame(AbstractOutput *output)
 
     QRegion repaint;
     if (supportsBufferAge()) {
-        repaint = m_damageJournal.accumulate(m_bufferAge, screens()->geometry());
+        repaint = m_damageJournal.accumulate(m_bufferAge, infiniteRegion());
     }
 
     eglWaitNative(EGL_CORE_NATIVE_ENGINE);
diff --git a/src/backends/x11/standalone/glxbackend.cpp b/src/backends/x11/standalone/glxbackend.cpp
index 3ceb27c51e..8a5d0a8a5d 100644
--- a/src/backends/x11/standalone/glxbackend.cpp
+++ b/src/backends/x11/standalone/glxbackend.cpp
@@ -772,7 +772,7 @@ QRegion GlxBackend::beginFrame(AbstractOutput *output)
 
     GLRenderTarget::pushRenderTarget(m_renderTarget.data());
     if (supportsBufferAge()) {
-        repaint = m_damageJournal.accumulate(m_bufferAge, screens()->geometry());
+        repaint = m_damageJournal.accumulate(m_bufferAge, infiniteRegion());
     }
 
     glXWaitX();
diff --git a/src/backends/x11/windowed/egl_x11_backend.cpp b/src/backends/x11/windowed/egl_x11_backend.cpp
index d5e31eb645..bef3170d8a 100644
--- a/src/backends/x11/windowed/egl_x11_backend.cpp
+++ b/src/backends/x11/windowed/egl_x11_backend.cpp
@@ -71,7 +71,7 @@ QRegion EglX11Backend::beginFrame(AbstractOutput *output)
     const EglX11Output *rendererOutput = m_outputs[output];
     makeContextCurrent(rendererOutput->m_eglSurface);
     GLRenderTarget::pushRenderTarget(rendererOutput->m_renderTarget.data());
-    return output->geometry();
+    return QRect(QPoint(0, 0), output->geometry().size());
 }
 
 void EglX11Backend::endFrame(AbstractOutput *output, const QRegion &renderedRegion, const QRegion &damagedRegion)
diff --git a/src/backends/x11/windowed/scene_qpainter_x11_backend.cpp b/src/backends/x11/windowed/scene_qpainter_x11_backend.cpp
index ce66627ae9..b981405f1b 100644
--- a/src/backends/x11/windowed/scene_qpainter_x11_backend.cpp
+++ b/src/backends/x11/windowed/scene_qpainter_x11_backend.cpp
@@ -52,7 +52,7 @@ QImage *X11WindowedQPainterBackend::bufferForScreen(AbstractOutput *output)
 
 QRegion X11WindowedQPainterBackend::beginFrame(AbstractOutput *output)
 {
-    return output->geometry();
+    return QRect(QPoint(0, 0), output->geometry().size());
 }
 
 void X11WindowedQPainterBackend::endFrame(AbstractOutput *output, const QRegion &renderedRegion, const QRegion &damagedRegion)
diff --git a/src/composite.cpp b/src/composite.cpp
index 25e3adf78e..b7ae35c26b 100644
--- a/src/composite.cpp
+++ b/src/composite.cpp
@@ -434,9 +434,9 @@ void Compositor::addOutput(AbstractOutput *output)
 
     auto workspaceLayer = new RenderLayer(output->renderLoop());
     workspaceLayer->setDelegate(new SceneDelegate(m_scene, output));
-    workspaceLayer->setGeometry(output->geometry());
+    workspaceLayer->setGeometry(QRect(QPoint(0, 0), output->geometry().size()));
     connect(output, &AbstractOutput::geometryChanged, workspaceLayer, [output, workspaceLayer]() {
-        workspaceLayer->setGeometry(output->geometry());
+        workspaceLayer->setGeometry(QRect(QPoint(0, 0), output->geometry().size()));
     });
 
     auto cursorLayer = new RenderLayer(output->renderLoop());
@@ -445,10 +445,10 @@ void Compositor::addOutput(AbstractOutput *output)
     cursorLayer->setParent(workspaceLayer);
     cursorLayer->setSuperlayer(workspaceLayer);
 
-    auto updateCursorLayer = [output, workspaceLayer, cursorLayer]() {
+    auto updateCursorLayer = [output, cursorLayer]() {
         const Cursor *cursor = Cursors::self()->currentCursor();
         cursorLayer->setVisible(cursor->isOnOutput(output) && output->usesSoftwareCursor());
-        cursorLayer->setGeometry(workspaceLayer->mapFromGlobal(cursor->geometry()));
+        cursorLayer->setGeometry(output->mapFromGlobal(cursor->geometry()));
         cursorLayer->addRepaintFull();
     };
     updateCursorLayer();
@@ -682,7 +682,7 @@ void Compositor::composite(RenderLoop *renderLoop)
         preparePaintPass(superLayer, &surfaceDamage);
 
         const QRegion repair = m_backend->beginFrame(output);
-        const QRegion bufferDamage = surfaceDamage.united(repair);
+        const QRegion bufferDamage = surfaceDamage.united(repair).intersected(superLayer->rect());
         m_backend->aboutToStartPainting(output, bufferDamage);
 
         paintPass(superLayer, bufferDamage);
diff --git a/src/plugins/screencast/screencastmanager.cpp b/src/plugins/screencast/screencastmanager.cpp
index 6b8eb9a55e..eddfd19b38 100644
--- a/src/plugins/screencast/screencastmanager.cpp
+++ b/src/plugins/screencast/screencastmanager.cpp
@@ -139,7 +139,7 @@ void ScreencastManager::streamOutput(KWaylandServer::ScreencastStreamV1Interface
         }
 
         const QRect frame({}, streamOutput->modeSize());
-        const QRegion region = streamOutput->pixelSize() != streamOutput->modeSize() ? frame : damagedRegion.translated(-streamOutput->geometry().topLeft()).intersected(frame);
+        const QRegion region = streamOutput->pixelSize() != streamOutput->modeSize() ? frame : damagedRegion;
         stream->recordFrame(region);
     };
     connect(stream, &ScreenCastStream::startStreaming, waylandStream, [streamOutput, stream, bufferToStream] {
diff --git a/src/scene.cpp b/src/scene.cpp
index 8275105df8..e653c849c7 100644
--- a/src/scene.cpp
+++ b/src/scene.cpp
@@ -104,7 +104,7 @@ SceneDelegate::~SceneDelegate()
 
 QRegion SceneDelegate::repaints() const
 {
-    return m_scene->damage();
+    return m_scene->damage().translated(-viewport().topLeft());
 }
 
 SurfaceItem *SceneDelegate::scanoutCandidate() const
@@ -124,7 +124,12 @@ void SceneDelegate::postPaint()
 
 void SceneDelegate::paint(const QRegion &region)
 {
-    m_scene->paint(region);
+    m_scene->paint(region.translated(viewport().topLeft()));
+}
+
+QRect SceneDelegate::viewport() const
+{
+    return m_output ? m_output->geometry() : m_scene->geometry();
 }
 
 //****************************************
@@ -168,9 +173,11 @@ void Scene::addRepaint(int x, int y, int width, int height)
 void Scene::addRepaint(const QRegion &region)
 {
     for (const auto &delegate : std::as_const(m_delegates)) {
-        const QRegion dirtyRegion = region & delegate->layer()->geometry();
+        const QRect viewport = delegate->viewport();
+        QRegion dirtyRegion = region & viewport;
+        dirtyRegion.translate(-viewport.topLeft());
         if (!dirtyRegion.isEmpty()) {
-            delegate->layer()->addRepaint(delegate->layer()->mapFromGlobal(dirtyRegion));
+            delegate->layer()->addRepaint(dirtyRegion);
         }
     }
 }
@@ -347,7 +354,7 @@ void Scene::preparePaintGenericScreen()
         }
     }
 
-    m_paintContext.damage = QRect(QPoint(0, 0), renderTargetRect().size());
+    m_paintContext.damage = renderTargetRect();
 }
 
 void Scene::preparePaintSimpleScreen()
@@ -384,18 +391,14 @@ void Scene::preparePaintSimpleScreen()
     }
 
     // Perform an occlusion cull pass, remove surface damage occluded by opaque windows.
-    QRegion surfaceDamage;
     QRegion opaque;
     for (int i = m_paintContext.phase2Data.size() - 1; i >= 0; --i) {
         const auto &paintData = m_paintContext.phase2Data.at(i);
-        surfaceDamage += paintData.region - opaque;
+        m_paintContext.damage += paintData.region - opaque;
         if (!(paintData.mask & (PAINT_WINDOW_TRANSLUCENT | PAINT_WINDOW_TRANSFORMED))) {
             opaque += paintData.opaque;
         }
     }
-
-    m_paintContext.damage += surfaceDamage & renderTargetRect();
-    m_paintContext.damage.translate(-renderTargetRect().topLeft());
 }
 
 void Scene::postPaint()
diff --git a/src/scene.h b/src/scene.h
index 0c27a67d64..684c28c561 100644
--- a/src/scene.h
+++ b/src/scene.h
@@ -53,6 +53,8 @@ public:
     explicit SceneDelegate(Scene *scene, AbstractOutput *output, QObject *parent = nullptr);
     ~SceneDelegate() override;
 
+    QRect viewport() const;
+
     QRegion repaints() const override;
     SurfaceItem *scanoutCandidate() const override;
     void prePaint() override;