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diff --git a/src/core/compositor/compositor.h b/src/core/compositor/compositor.h
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+++ b/src/core/compositor/compositor.h
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+// Copyright (C) 2020 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef COMPOSITOR_H
+#define COMPOSITOR_H
+
+#include <QtWebEngineCore/private/qtwebenginecoreglobal_p.h>
+
+QT_BEGIN_NAMESPACE
+class QQuickWindow;
+class QSize;
+class QSGTexture;
+QT_END_NAMESPACE
+
+namespace viz {
+class FrameSinkId;
+} // namespace viz
+
+namespace QtWebEngineCore {
+
+// Produces composited frames for display.
+//
+// Used by quick/widgets libraries for accessing the frames and
+// controlling frame swapping.
+class Q_WEBENGINECORE_EXPORT Compositor
+{
+    struct Binding;
+
+public:
+    // Identifies the implementation type.
+    enum class Type {
+        Software,
+        OpenGL, // TODO: Legacy, remove it with DisplaySkiaOutputDevice!
+        Native
+    };
+
+    // Identifies a compositor.
+    //
+    // The purpose of assigning ids to compositors is to allow the
+    // corresponding observer to be registered before the compositor
+    // itself is created, which is necessary since the creation
+    // happens on a different thread in the depths of viz.
+    //
+    // (Maps to viz::FrameSinkId internally).
+    struct Id
+    {
+        quint32 client_id;
+        quint32 sink_id;
+
+        Id(viz::FrameSinkId);
+    };
+
+    // Pointer to Compositor or Observer that holds a lock to prevent
+    // either from being unbound and destroyed.
+    template<typename T>
+    class Handle
+    {
+    public:
+        Handle(std::nullptr_t) : m_data(nullptr) { }
+        Handle(T *data) : m_data(data) { }
+        Handle(Handle &&that) : m_data(that.m_data) { that.m_data = nullptr; }
+        ~Handle()
+        {
+            if (m_data)
+                Compositor::unlockBindings();
+        }
+        T *operator->() const { return m_data; }
+        T &operator*() const { return *m_data; }
+        explicit operator bool() const { return m_data; }
+
+    private:
+        T *m_data;
+    };
+
+    // Observes the compositor corresponding to the given id.
+    //
+    // Only one observer can exist per compositor.
+    class Q_WEBENGINECORE_EXPORT Observer
+    {
+    public:
+        // Binding to compositor
+        void bind(Id id);
+        void unbind();
+
+        // Compositor if bound
+        Handle<Compositor> compositor();
+
+        // There's a new frame ready, time to swapFrame().
+        virtual void readyToSwap() = 0;
+
+    protected:
+        Observer() = default;
+        ~Observer() { if (m_binding) unbind(); }
+
+    private:
+        Binding *m_binding = nullptr;
+    };
+
+    // Type determines which methods can be called.
+    Type type() const { return m_type; }
+
+    // Binding to observer.
+    void bind(Id id);
+    void unbind();
+
+    // Observer if bound.
+    Handle<Observer> observer();
+
+    // Update to next frame if possible.
+    virtual void swapFrame() = 0;
+
+    // Ratio of pixels to DIPs.
+    //
+    // Don't use the devicePixelRatio of QImage, it's always 1.
+    virtual float devicePixelRatio() = 0;
+
+    // Size of frame in pixels.
+    virtual QSize size() = 0;
+
+    // Whether frame needs an alpha channel.
+    virtual bool requiresAlphaChannel() = 0;
+
+    // Wait on texture to be ready aka. sync.
+    virtual void waitForTexture();
+
+    // Release any held texture resources
+    virtual void releaseTexture();
+
+    // QSGTexture of the frame.
+    virtual QSGTexture *texture(QQuickWindow *win, uint32_t textureOptions);
+
+    // Is the texture produced upside down?
+    virtual bool textureIsFlipped();
+
+    // Release resources created in texture()
+    virtual void releaseResources();
+
+protected:
+    Compositor(Type type) : m_type(type) { }
+    virtual ~Compositor() { if (m_binding) unbind(); }
+
+private:
+    template<typename T>
+    friend class Handle;
+
+    class BindingMap;
+    static void unlockBindings();
+
+    const Type m_type;
+    Binding *m_binding = nullptr;
+};
+
+} // namespace QtWebEngineCore
+
+#endif // !COMPOSITOR_H