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>

7 files changed, 102 insertions, 65 deletions

diff --git a/src/webengine/api/qquickwebengineview.cpp b/src/webengine/api/qquickwebengineview.cpp
index 7fddb16a9..8a426c887 100644
--- a/src/webengine/api/qquickwebengineview.cpp
+++ b/src/webengine/api/qquickwebengineview.cpp
@@ -482,11 +482,29 @@ void QQuickWebEngineViewPrivate::loadCommitted()
     m_history->reset();
 }
 
-void QQuickWebEngineViewPrivate::loadVisuallyCommitted()
+void QQuickWebEngineViewPrivate::didFirstVisuallyNonEmptyPaint()
 {
 #if QT_CONFIG(webengine_testsupport)
-    if (m_testSupport)
-        Q_EMIT m_testSupport->loadVisuallyCommitted();
+    if (m_loadVisuallyCommittedState == NotCommitted) {
+        m_loadVisuallyCommittedState = DidFirstVisuallyNonEmptyPaint;
+    } else if (m_loadVisuallyCommittedState == DidFirstCompositorFrameSwap) {
+        if (m_testSupport)
+            Q_EMIT m_testSupport->loadVisuallyCommitted();
+        m_loadVisuallyCommittedState = NotCommitted;
+    }
+#endif
+}
+
+void QQuickWebEngineViewPrivate::didCompositorFrameSwap()
+{
+#if QT_CONFIG(webengine_testsupport)
+    if (m_loadVisuallyCommittedState == NotCommitted) {
+        m_loadVisuallyCommittedState = DidFirstCompositorFrameSwap;
+    } else if (m_loadVisuallyCommittedState == DidFirstVisuallyNonEmptyPaint) {
+        if (m_testSupport)
+            Q_EMIT m_testSupport->loadVisuallyCommitted();
+        m_loadVisuallyCommittedState = NotCommitted;
+    }
 #endif
 }
 
diff --git a/src/webengine/api/qquickwebengineview_p.h b/src/webengine/api/qquickwebengineview_p.h
index 9dbb8cffc..86b7145db 100644
--- a/src/webengine/api/qquickwebengineview_p.h
+++ b/src/webengine/api/qquickwebengineview_p.h
@@ -59,6 +59,10 @@
 #include "qquickwebengineprofile.h"
 #include "qquickwebenginescript.h"
 
+namespace QtWebEngineCore {
+class RenderWidgetHostViewQtDelegateQuick;
+}
+
 QT_BEGIN_NAMESPACE
 
 class QQmlWebChannel;
@@ -603,6 +607,7 @@ private:
     Q_DECLARE_PRIVATE(QQuickWebEngineView)
     QScopedPointer<QQuickWebEngineViewPrivate> d_ptr;
 
+    friend class QtWebEngineCore::RenderWidgetHostViewQtDelegateQuick;
     friend class QQuickContextMenuBuilder;
     friend class QQuickWebEngineNewViewRequest;
     friend class QQuickWebEngineFaviconProvider;
diff --git a/src/webengine/api/qquickwebengineview_p_p.h b/src/webengine/api/qquickwebengineview_p_p.h
index 68d65410a..bfed75f45 100644
--- a/src/webengine/api/qquickwebengineview_p_p.h
+++ b/src/webengine/api/qquickwebengineview_p_p.h
@@ -115,7 +115,7 @@ public:
     QColor backgroundColor() const override;
     void loadStarted(const QUrl &provisionalUrl, bool isErrorPage = false) override;
     void loadCommitted() override;
-    void loadVisuallyCommitted() override;
+    void didFirstVisuallyNonEmptyPaint() override;
     void loadFinished(bool success, const QUrl &url, bool isErrorPage = false, int errorCode = 0, const QString &errorDescription = QString()) override;
     void focusContainer() override;
     void unhandledKeyEvent(QKeyEvent *event) override;
@@ -173,6 +173,8 @@ public:
     void widgetChanged(QtWebEngineCore::RenderWidgetHostViewQtDelegate *newWidgetBase) override;
     void findTextFinished(const QWebEngineFindTextResult &result) override;
 
+    void didCompositorFrameSwap();
+
     void updateAction(QQuickWebEngineView::WebAction) const;
     void adoptWebContents(QtWebEngineCore::WebContentsAdapter *webContents);
     void setProfile(QQuickWebEngineProfile *profile);
@@ -223,12 +225,19 @@ public:
     bool profileInitialized() const;
 
 private:
+    enum LoadVisuallyCommittedState {
+        NotCommitted,
+        DidFirstVisuallyNonEmptyPaint,
+        DidFirstCompositorFrameSwap
+    };
+
     QScopedPointer<QtWebEngineCore::UIDelegatesManager> m_uIDelegatesManager;
     QList<QQuickWebEngineScript *> m_userScripts;
     QColor m_backgroundColor;
     qreal m_zoomFactor;
     bool m_ui2Enabled;
     bool m_profileInitialized;
+    LoadVisuallyCommittedState m_loadVisuallyCommittedState = NotCommitted;
 };
 
 #ifndef QT_NO_ACCESSIBILITY
diff --git a/src/webengine/render_widget_host_view_qt_delegate_quick.cpp b/src/webengine/render_widget_host_view_qt_delegate_quick.cpp
index c0d4dd4a5..9ed660f2e 100644
--- a/src/webengine/render_widget_host_view_qt_delegate_quick.cpp
+++ b/src/webengine/render_widget_host_view_qt_delegate_quick.cpp
@@ -85,10 +85,12 @@ RenderWidgetHostViewQtDelegateQuick::RenderWidgetHostViewQtDelegateQuick(RenderW
     }
 #endif
 
+    bind(client->compositorId());
 }
 
 RenderWidgetHostViewQtDelegateQuick::~RenderWidgetHostViewQtDelegateQuick()
 {
+    unbind();
     QQuickWebEngineViewPrivate::bindViewAndWidget(nullptr, this);
 }
 
@@ -167,30 +169,10 @@ QWindow* RenderWidgetHostViewQtDelegateQuick::window() const
     return QQuickItem::window();
 }
 
-QSGTexture *RenderWidgetHostViewQtDelegateQuick::createTextureFromImage(const QImage &image)
+void RenderWidgetHostViewQtDelegateQuick::readyToSwap()
 {
-    return QQuickItem::window()->createTextureFromImage(image, QQuickWindow::TextureCanUseAtlas);
-}
-
-QSGLayer *RenderWidgetHostViewQtDelegateQuick::createLayer()
-{
-    QSGRenderContext *renderContext = QQuickWindowPrivate::get(QQuickItem::window())->context;
-    return renderContext->sceneGraphContext()->createLayer(renderContext);
-}
-
-QSGImageNode *RenderWidgetHostViewQtDelegateQuick::createImageNode()
-{
-    return QQuickItem::window()->createImageNode();
-}
-
-QSGRectangleNode *RenderWidgetHostViewQtDelegateQuick::createRectangleNode()
-{
-    return QQuickItem::window()->createRectangleNode();
-}
-
-void RenderWidgetHostViewQtDelegateQuick::update()
-{
-    QQuickItem::update();
+    // Call update() on UI thread.
+    QMetaObject::invokeMethod(this, &QQuickItem::update, Qt::QueuedConnection);
 }
 
 void RenderWidgetHostViewQtDelegateQuick::updateCursor(const QCursor &cursor)
@@ -345,6 +327,8 @@ void RenderWidgetHostViewQtDelegateQuick::itemChange(ItemChange change, const It
             disconnect(c);
         m_windowConnections.clear();
         if (value.window) {
+            m_windowConnections.append(connect(value.window, SIGNAL(beforeRendering()),
+                                               SLOT(onBeforeRendering()), Qt::DirectConnection));
             m_windowConnections.append(connect(value.window, SIGNAL(xChanged(int)), SLOT(onWindowPosChanged())));
             m_windowConnections.append(connect(value.window, SIGNAL(yChanged(int)), SLOT(onWindowPosChanged())));
             if (!m_isPopup)
@@ -359,7 +343,58 @@ void RenderWidgetHostViewQtDelegateQuick::itemChange(ItemChange change, const It
 
 QSGNode *RenderWidgetHostViewQtDelegateQuick::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
 {
-    return m_client->updatePaintNode(oldNode);
+    auto comp = compositor();
+    if (!comp)
+        return nullptr;
+
+    QQuickWindow *win = QQuickItem::window();
+
+    // Delete old node before swapFrame to decrement refcount of
+    // QImage in software mode.
+    delete oldNode;
+    QSGImageNode *node = win->createImageNode();
+    node->setOwnsTexture(true);
+
+    comp->swapFrame();
+
+    if (comp->type() == Compositor::Type::Software) {
+        QImage image = comp->image();
+        float pixPerDip = comp->devicePixelRatio();
+        QSizeF sizeInDips = QSizeF(image.size()) / pixPerDip;
+        node->setRect(QRectF(QPointF(0, 0), sizeInDips));
+        node->setTexture(win->createTextureFromImage(image));
+    } else if (comp->type() == Compositor::Type::OpenGL) {
+        QSize texSize = comp->textureSize();
+        float pixPerDip = comp->devicePixelRatio();
+        QSizeF sizeInDips = QSizeF(texSize) / pixPerDip;
+        node->setRect(QRectF(QPointF(0, 0), sizeInDips));
+        QQuickWindow::CreateTextureOptions texOpts;
+        if (comp->hasAlphaChannel())
+            texOpts.setFlag(QQuickWindow::TextureHasAlphaChannel);
+        int texId = comp->textureId();
+        node->setTexture(win->createTextureFromNativeObject(QQuickWindow::NativeObjectTexture,
+                                                            texId, 0, texSize, texOpts));
+        node->setTextureCoordinatesTransform(QSGImageNode::MirrorVertically);
+    } else {
+        Q_UNREACHABLE();
+    }
+
+#if QT_CONFIG(webengine_testsupport)
+    if (m_view)
+        QMetaObject::invokeMethod(
+                m_view, [view = m_view]() { view->d_ptr->didCompositorFrameSwap(); },
+                Qt::QueuedConnection);
+#endif
+
+    return node;
+}
+
+void RenderWidgetHostViewQtDelegateQuick::onBeforeRendering()
+{
+    auto comp = compositor();
+    if (!comp || comp->type() != Compositor::Type::OpenGL)
+        return;
+    comp->waitForTexture();
 }
 
 void RenderWidgetHostViewQtDelegateQuick::onWindowPosChanged()
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();
 
diff --git a/src/webengine/render_widget_host_view_qt_delegate_quickwindow.cpp b/src/webengine/render_widget_host_view_qt_delegate_quickwindow.cpp
index 1de4d8835..0b7e736ad 100644
--- a/src/webengine/render_widget_host_view_qt_delegate_quickwindow.cpp
+++ b/src/webengine/render_widget_host_view_qt_delegate_quickwindow.cpp
@@ -121,32 +121,6 @@ QWindow *RenderWidgetHostViewQtDelegateQuickWindow::window() const
     return const_cast<RenderWidgetHostViewQtDelegateQuickWindow*>(this);
 }
 
-QSGTexture *RenderWidgetHostViewQtDelegateQuickWindow::createTextureFromImage(const QImage &image)
-{
-    return m_realDelegate->createTextureFromImage(image);
-}
-
-QSGLayer *RenderWidgetHostViewQtDelegateQuickWindow::createLayer()
-{
-    return m_realDelegate->createLayer();
-}
-
-QSGImageNode *RenderWidgetHostViewQtDelegateQuickWindow::createImageNode()
-{
-    return m_realDelegate->createImageNode();
-}
-
-QSGRectangleNode *RenderWidgetHostViewQtDelegateQuickWindow::createRectangleNode()
-{
-    return m_realDelegate->createRectangleNode();
-}
-
-void RenderWidgetHostViewQtDelegateQuickWindow::update()
-{
-    QQuickWindow::update();
-    m_realDelegate->update();
-}
-
 void RenderWidgetHostViewQtDelegateQuickWindow::updateCursor(const QCursor &cursor)
 {
     setCursor(cursor);
diff --git a/src/webengine/render_widget_host_view_qt_delegate_quickwindow.h b/src/webengine/render_widget_host_view_qt_delegate_quickwindow.h
index bebbfa439..cff189d1c 100644
--- a/src/webengine/render_widget_host_view_qt_delegate_quickwindow.h
+++ b/src/webengine/render_widget_host_view_qt_delegate_quickwindow.h
@@ -66,11 +66,6 @@ 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 &screenPos) override;