scene: Move OffscreenQuickView painting to EffectsHandlerImpl

There's no any way to integrate OffscreenQuickView into the scene graph.
So make the EffectsHandlerImpl responsible for drawing quick views until
the corresponding item is introduced (requires a lot and a lot of
refactoring in effects) or the design of kwin changes so much that we
don't need this special code path.

src/effects.cpp

@@ -56,6 +56,7 @@
 
 #include <QDebug>
 #include <QMouseEvent>
+#include <QPainter>
 #include <QQmlEngine>
 #include <QQuickItem>
 #include <QQuickWindow>
@@ -1763,7 +1764,48 @@ void EffectsHandlerImpl::renderOffscreenQuickView(OffscreenQuickView *w) const
     if (!w->isVisible()) {
         return;
     }
-    scene()->paintOffscreenQuickView(w);
+    if (compositingType() == OpenGLCompositing) {
+        GLTexture *t = w->bufferAsTexture();
+        if (!t) {
+            return;
+        }
+
+        ShaderTraits traits = ShaderTrait::MapTexture;
+        const qreal a = w->opacity();
+        if (a != 1.0) {
+            traits |= ShaderTrait::Modulate;
+        }
+
+        GLShader *shader = ShaderManager::instance()->pushShader(traits);
+        const QRectF rect = scaledRect(w->geometry(), m_scene->renderer()->renderTargetScale());
+
+        QMatrix4x4 mvp(m_scene->renderer()->renderTargetProjectionMatrix());
+        mvp.translate(rect.x(), rect.y());
+        shader->setUniform(GLShader::ModelViewProjectionMatrix, mvp);
+
+        if (a != 1.0) {
+            shader->setUniform(GLShader::ModulationConstant, QVector4D(a, a, a, a));
+        }
+
+        glEnable(GL_BLEND);
+        glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+        t->bind();
+        t->render(w->geometry(), m_scene->renderer()->renderTargetScale());
+        t->unbind();
+        glDisable(GL_BLEND);
+
+        ShaderManager::instance()->popShader();
+    } else if (compositingType() == QPainterCompositing) {
+        QPainter *painter = effects->scenePainter();
+        const QImage buffer = w->bufferAsImage();
+        if (buffer.isNull()) {
+            return;
+        }
+        painter->save();
+        painter->setOpacity(w->opacity());
+        painter->drawImage(w->geometry(), buffer);
+        painter->restore();
+    }
 }
 
 SessionState EffectsHandlerImpl::sessionState() const

src/scene/scene.h

@@ -184,8 +184,6 @@ protected:
     // called after all effects had their drawWindow() called
     void finalDrawWindow(EffectWindowImpl *w, int mask, const QRegion &region, WindowPaintData &data);
 
-    virtual void paintOffscreenQuickView(OffscreenQuickView *w) = 0;
-
     // saved data for 2nd pass of optimized screen painting
     struct Phase2Data
     {

src/scene/scene_opengl.cpp

@@ -14,7 +14,6 @@
 #include "scene_opengl.h"
 
 #include <kwinglplatform.h>
-#include <kwinoffscreenquickview.h>
 
 #include "composite.h"
 #include "core/output.h"
@@ -56,40 +55,6 @@ SceneOpenGL::~SceneOpenGL()
     makeOpenGLContextCurrent();
 }
 
-void SceneOpenGL::paintOffscreenQuickView(OffscreenQuickView *w)
-{
-    GLTexture *t = w->bufferAsTexture();
-    if (!t) {
-        return;
-    }
-
-    ShaderTraits traits = ShaderTrait::MapTexture;
-    const qreal a = w->opacity();
-    if (a != 1.0) {
-        traits |= ShaderTrait::Modulate;
-    }
-
-    GLShader *shader = ShaderManager::instance()->pushShader(traits);
-    const QRectF rect = scaledRect(w->geometry(), renderer()->renderTargetScale());
-
-    QMatrix4x4 mvp(renderer()->renderTargetProjectionMatrix());
-    mvp.translate(rect.x(), rect.y());
-    shader->setUniform(GLShader::ModelViewProjectionMatrix, mvp);
-
-    if (a != 1.0) {
-        shader->setUniform(GLShader::ModulationConstant, QVector4D(a, a, a, a));
-    }
-
-    glEnable(GL_BLEND);
-    glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
-    t->bind();
-    t->render(w->geometry(), renderer()->renderTargetScale());
-    t->unbind();
-    glDisable(GL_BLEND);
-
-    ShaderManager::instance()->popShader();
-}
-
 bool SceneOpenGL::makeOpenGLContextCurrent()
 {
     return m_backend->makeCurrent();

src/scene/scene_opengl.h

@@ -48,9 +48,6 @@ public:
     QVector<QByteArray> openGLPlatformInterfaceExtensions() const override;
     std::shared_ptr<GLTexture> textureForOutput(Output *output) const override;
 
-protected:
-    void paintOffscreenQuickView(OffscreenQuickView *w) override;
-
 private:
     OpenGLBackend *m_backend;
     GLuint vao = 0;

src/scene/scene_qpainter.cpp

@@ -13,7 +13,6 @@
 #include "scene/surfaceitem.h"
 #include "window.h"
 
-#include <kwinoffscreenquickview.h>
 // Qt
 #include <KDecoration2/Decoration>
 #include <QDebug>
@@ -38,19 +37,6 @@ SceneQPainter::~SceneQPainter()
 {
 }
 
-void SceneQPainter::paintOffscreenQuickView(OffscreenQuickView *w)
-{
-    QPainter *painter = effects->scenePainter();
-    const QImage buffer = w->bufferAsImage();
-    if (buffer.isNull()) {
-        return;
-    }
-    painter->save();
-    painter->setOpacity(w->opacity());
-    painter->drawImage(w->geometry(), buffer);
-    painter->restore();
-}
-
 Shadow *SceneQPainter::createShadow(Window *window)
 {
     return new SceneQPainterShadow(window);

src/scene/scene_qpainter.h

@@ -40,9 +40,6 @@ public:
         return m_backend;
     }
 
-protected:
-    void paintOffscreenQuickView(OffscreenQuickView *w) override;
-
 private:
     QPainterBackend *m_backend;
 };