Kill Toplevel::screenScale()

Tracking AbstractOutput properties in Toplevel is not extensible. Since
DecorationItem is the only one who needs Toplevel::screenScale(), make
it track the output device pixel ratio.

src/decorationitem.cpp

@@ -7,6 +7,7 @@
 
 #include "decorationitem.h"
 #include "abstract_client.h"
+#include "abstract_output.h"
 #include "composite.h"
 #include "decorations/decoratedclient.h"
 #include "deleted.h"
@@ -28,8 +29,6 @@ DecorationRenderer::DecorationRenderer(Decoration::DecoratedClientImpl *client)
     connect(client->decoration(), &KDecoration2::Decoration::damaged,
             this, &DecorationRenderer::addDamage);
 
-    connect(client->client(), &AbstractClient::screenScaleChanged,
-            this, &DecorationRenderer::invalidate);
     connect(client->decoration(), &KDecoration2::Decoration::bordersChanged,
             this, &DecorationRenderer::invalidate);
     connect(client->decoratedClient(), &KDecoration2::DecoratedClient::sizeChanged,
@@ -67,10 +66,22 @@ void DecorationRenderer::resetDamage()
     m_damage = QRegion();
 }
 
+qreal DecorationRenderer::devicePixelRatio() const
+{
+    return m_devicePixelRatio;
+}
+
+void DecorationRenderer::setDevicePixelRatio(qreal dpr)
+{
+    if (m_devicePixelRatio != dpr) {
+        m_devicePixelRatio = dpr;
+        invalidate();
+    }
+}
+
 QImage DecorationRenderer::renderToImage(const QRect &geo)
 {
     Q_ASSERT(m_client);
-    auto dpr = client()->client()->screenScale();
 
     // Guess the pixel format of the X pixmap into which the QImage will be copied.
     QImage::Format format;
@@ -89,8 +100,8 @@ QImage DecorationRenderer::renderToImage(const QRect &geo)
         break;
     };
 
-    QImage image(geo.width() * dpr, geo.height() * dpr, format);
-    image.setDevicePixelRatio(dpr);
+    QImage image(geo.width() * m_devicePixelRatio, geo.height() * m_devicePixelRatio, format);
+    image.setDevicePixelRatio(m_devicePixelRatio);
     image.fill(Qt::transparent);
     QPainter p(&image);
     p.setRenderHint(QPainter::Antialiasing);
@@ -115,9 +126,9 @@ DecorationItem::DecorationItem(KDecoration2::Decoration *decoration, AbstractCli
             this, &DecorationItem::handleFrameGeometryChanged);
     connect(window, &Toplevel::windowClosed,
             this, &DecorationItem::handleWindowClosed);
+    connect(window, &Toplevel::screenChanged,
+            this, &DecorationItem::handleOutputChanged);
 
-    connect(window, &Toplevel::screenScaleChanged,
-            this, &DecorationItem::discardQuads);
     connect(decoration, &KDecoration2::Decoration::bordersChanged,
             this, &DecorationItem::discardQuads);
 
@@ -125,6 +136,7 @@ DecorationItem::DecorationItem(KDecoration2::Decoration *decoration, AbstractCli
             this, &DecorationItem::scheduleRepaint);
 
     setSize(window->size());
+    handleOutputChanged();
 }
 
 void DecorationItem::preprocess()
@@ -136,6 +148,29 @@ void DecorationItem::preprocess()
     }
 }
 
+void DecorationItem::handleOutputChanged()
+{
+    if (m_output) {
+        disconnect(m_output, &AbstractOutput::scaleChanged, this, &DecorationItem::handleOutputScaleChanged);
+    }
+
+    m_output = m_window->output();
+
+    if (m_output) {
+        handleOutputScaleChanged();
+        connect(m_output, &AbstractOutput::scaleChanged, this, &DecorationItem::handleOutputScaleChanged);
+    }
+}
+
+void DecorationItem::handleOutputScaleChanged()
+{
+    const qreal dpr = m_output->scale();
+    if (m_renderer->devicePixelRatio() != dpr) {
+        m_renderer->setDevicePixelRatio(dpr);
+        discardQuads();
+    }
+}
+
 void DecorationItem::handleFrameGeometryChanged()
 {
     setSize(m_window->size());
@@ -169,7 +204,7 @@ WindowQuadList DecorationItem::buildQuads() const
         deleted->layoutDecorationRects(rects[0], rects[1], rects[2], rects[3]);
     }
 
-    const qreal textureScale = m_window->screenScale();
+    const qreal textureScale = m_renderer->devicePixelRatio();
     const int padding = 1;
 
     const QPoint topSpritePosition(padding, padding);

src/decorationitem.h

@@ -38,6 +38,9 @@ public:
     void addDamage(const QRegion &region);
     void resetDamage();
 
+    qreal devicePixelRatio() const;
+    void setDevicePixelRatio(qreal dpr);
+
 Q_SIGNALS:
     void damaged(const QRegion &region);
 
@@ -58,6 +61,7 @@ protected:
 private:
     QPointer<Decoration::DecoratedClientImpl> m_client;
     QRegion m_damage;
+    qreal m_devicePixelRatio = 1;
     bool m_imageSizesDirty;
 };
 
@@ -76,6 +80,8 @@ public:
 private Q_SLOTS:
     void handleFrameGeometryChanged();
     void handleWindowClosed(Toplevel *original, Deleted *deleted);
+    void handleOutputChanged();
+    void handleOutputScaleChanged();
 
 protected:
     void preprocess() override;
@@ -83,6 +89,7 @@ protected:
 
 private:
     Toplevel *m_window;
+    QPointer<AbstractOutput> m_output;
     QPointer<KDecoration2::Decoration> m_decoration;
     QScopedPointer<DecorationRenderer> m_renderer;
 };

src/scenes/opengl/scene_opengl.cpp

@@ -1661,22 +1661,21 @@ void SceneOpenGLDecorationRenderer::render(const QRegion &region)
         }
 
         QRect viewport = geo.translated(-rect.x(), -rect.y());
-        const qreal devicePixelRatio = client()->client()->screenScale();
 
-        QImage image(rect.size() * devicePixelRatio, QImage::Format_ARGB32_Premultiplied);
-        image.setDevicePixelRatio(devicePixelRatio);
+        QImage image(rect.size() * devicePixelRatio(), QImage::Format_ARGB32_Premultiplied);
+        image.setDevicePixelRatio(devicePixelRatio());
         image.fill(Qt::transparent);
 
         QPainter painter(&image);
         painter.setRenderHint(QPainter::Antialiasing);
-        painter.setViewport(QRect(viewport.topLeft(), viewport.size() * devicePixelRatio));
+        painter.setViewport(QRect(viewport.topLeft(), viewport.size() * devicePixelRatio()));
         painter.setWindow(QRect(geo.topLeft(), geo.size() * qPainterEffectiveDevicePixelRatio(&painter)));
         painter.setClipRect(geo);
         renderToPainter(&painter, geo);
         painter.end();
 
-        const QRect viewportScaled(viewport.topLeft() * devicePixelRatio, viewport.size() * devicePixelRatio);
-        const bool isIntegerScaling = qFuzzyCompare(devicePixelRatio, std::ceil(devicePixelRatio));
+        const QRect viewportScaled(viewport.topLeft() * devicePixelRatio(), viewport.size() * devicePixelRatio());
+        const bool isIntegerScaling = qFuzzyCompare(devicePixelRatio(), std::ceil(devicePixelRatio()));
         clamp(image, isIntegerScaling ? viewportScaled : viewportScaled.marginsRemoved({1, 1, 1, 1}));
 
         if (rotated) {
@@ -1725,7 +1724,7 @@ void SceneOpenGLDecorationRenderer::resizeTexture()
 
     size.rwidth() = align(size.width(), 128);
 
-    size *= client()->client()->screenScale();
+    size *= devicePixelRatio();
     if (m_texture && m_texture->size() == size)
         return;
 

src/scenes/qpainter/scene_qpainter.cpp

@@ -466,7 +466,7 @@ void SceneQPainterDecorationRenderer::resizeImages()
     client()->client()->layoutDecorationRects(left, top, right, bottom);
 
     auto checkAndCreate = [this](int index, const QSize &size) {
-        auto dpr = client()->client()->screenScale();
+        auto dpr = devicePixelRatio();
         if (m_images[index].size() != size * dpr ||
             m_images[index].devicePixelRatio() != dpr)
         {

src/toplevel.cpp

@@ -411,17 +411,6 @@ void Toplevel::setOutput(AbstractOutput *output)
         m_output = output;
         Q_EMIT screenChanged();
     }
-
-    qreal newScale = m_output->scale();
-    if (newScale != m_screenScale) {
-        m_screenScale = newScale;
-        Q_EMIT screenScaleChanged();
-    }
-}
-
-qreal Toplevel::screenScale() const
-{
-    return m_screenScale;
 }
 
 bool Toplevel::isOnActiveOutput() const

src/toplevel.h

@@ -344,12 +344,6 @@ public:
     int screen() const; // the screen where the center is
     AbstractOutput *output() const;
     void setOutput(AbstractOutput *output);
-    /**
-     * The scale of the screen this window is currently on
-     * @note The buffer scale can be different.
-     * @since 5.12
-     */
-    qreal screenScale() const; //
     virtual QPoint clientPos() const = 0; // inside of geometry()
     QSize clientSize() const;
     /**
@@ -616,13 +610,6 @@ Q_SIGNALS:
      */
     void surfaceChanged();
 
-    /*
-     * Emitted when the client's screen changes onto a screen of a different scale
-     * or the screen we're on changes
-     * @since 5.12
-     */
-    void screenScaleChanged();
-
     /**
      * Emitted whenever the client's shadow changes.
      * @since 5.15
@@ -717,7 +704,6 @@ private:
     quint32 m_pendingSurfaceId = 0;
     QPointer<KWaylandServer::SurfaceInterface> m_surface;
     // when adding new data members, check also copyToDeleted()
-    qreal m_screenScale = 1.0;
     qreal m_opacity = 1.0;
     int m_stackingOrder = 0;
 };