Move scenegraph handling out of core

Replace Display{Producer,Consumer,FrameSink} with the new classes
Compositor and Compositor::Observer.

The Compositor subclasses are implemented by the OutputSurfaces,
replacing DisplayProducer in this role. Unlike DisplayProducer, the
new classes do not use QtQuick scenegraph types, but rather give
access to the software QImage or OpenGL texture directly.

The connection to the "other half" is simplified by replacing
DisplayConsumer with Compositor::Observer, which is no longer
implemented by RenderWidgetHostViewQt, but directly by its delegates
in the quick and widgets libraries. RenderWidgetHostViewQt now only
provides the delegate with a Compositor::Id which is used to connect
the corresponding Compositor and Observer.

The delegates are responsible for generating QtQuick scenegraph nodes
from the information provided by the Compositor subclasses.

Behavior with software and old OpenGL scenegraph backends is
unchanged: both continue to work. As for the RHI scenegraph backend,
the code here is correct but nonetheless not working: changes are
needed in qtbase to make RHI use the global share context for its
OpenGL context.

Fixes: QTBUG-78682
Change-Id: I837da8860a18ec366ed33f6ecc44c147245e1101
Reviewed-by: Michal Klocek <michal.klocek@qt.io>

1 files changed, 7 insertions, 6 deletions

diff --git a/src/webengine/render_widget_host_view_qt_delegate_quick.h b/src/webengine/render_widget_host_view_qt_delegate_quick.h
index feea10017..cb38ebd20 100644
--- a/src/webengine/render_widget_host_view_qt_delegate_quick.h
+++ b/src/webengine/render_widget_host_view_qt_delegate_quick.h
@@ -40,6 +40,7 @@
 #ifndef RENDER_WIDGET_HOST_VIEW_QT_DELEGATE_QUICK_H
 #define RENDER_WIDGET_HOST_VIEW_QT_DELEGATE_QUICK_H
 
+#include "compositor/compositor.h"
 #include "render_widget_host_view_qt_delegate.h"
 
 #include <QAccessibleObject>
@@ -55,7 +56,9 @@ namespace QtWebEngineCore {
 
 class RenderWidgetHostViewQtDelegateClient;
 
-class RenderWidgetHostViewQtDelegateQuick : public QQuickItem, public RenderWidgetHostViewQtDelegate
+class RenderWidgetHostViewQtDelegateQuick : public QQuickItem,
+                                            public RenderWidgetHostViewQtDelegate,
+                                            public Compositor::Observer
 {
     Q_OBJECT
 public:
@@ -73,11 +76,6 @@ public:
     void hide() override;
     bool isVisible() const override;
     QWindow* window() const override;
-    QSGTexture *createTextureFromImage(const QImage &) override;
-    QSGLayer *createLayer() override;
-    QSGImageNode *createImageNode() override;
-    QSGRectangleNode *createRectangleNode() override;
-    void update() override;
     void updateCursor(const QCursor &) override;
     void resize(int width, int height) override;
     void move(const QPoint&) override { }
@@ -87,6 +85,8 @@ public:
     void setClearColor(const QColor &) override { }
     bool copySurface(const QRect &rect, const QSize &size, QImage &image) override;
 
+    void readyToSwap() override;
+
 protected:
     bool event(QEvent *event) override;
     void focusInEvent(QFocusEvent *event) override;
@@ -107,6 +107,7 @@ protected:
     QSGNode *updatePaintNode(QSGNode *, UpdatePaintNodeData *) override;
 
 private slots:
+    void onBeforeRendering();
     void onWindowPosChanged();
     void onHide();