Source/WebCore/platform/graphics/gpu/DrawingBuffer.h

/*
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 * modification, are permitted provided that the following conditions are
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 *
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 * in the documentation and/or other materials provided with the
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#ifndef DrawingBuffer_h
#define DrawingBuffer_h

#include "GraphicsContext3D.h"
#include "GraphicsTypes3D.h"
#include "IntSize.h"
#include "PlatformLayer.h"

#include <wtf/Noncopyable.h>
#include <wtf/OwnPtr.h>
#include <wtf/PassOwnPtr.h>
#if PLATFORM(MAC)
#include <wtf/RetainPtr.h>
#endif

namespace WebCore {
class GraphicsContext3D;

// Manages a rendering target (framebuffer + attachment) for a canvas.  Can publish its rendering
// results to a PlatformLayer for compositing.
class DrawingBuffer : public RefCounted<DrawingBuffer> {
public:
    enum PreserveDrawingBuffer {
        Preserve,
        Discard
    };

    enum AlphaRequirement {
        Alpha,
        Opaque
    };

    static PassRefPtr<DrawingBuffer> create(GraphicsContext3D*, const IntSize&, PreserveDrawingBuffer, AlphaRequirement);
    friend class GraphicsContext3D;

    ~DrawingBuffer();

    // Issues a glClear() on all framebuffers associated with this DrawingBuffer. The caller is responsible for
    // making the context current and setting the clear values and masks. Modifies the framebuffer binding.
    void clearFramebuffers(GC3Dbitfield clearMask);

    // Returns true if the buffer was successfully resized.
    bool reset(const IntSize&);
    void bind();
    IntSize size() const { return m_size; }
    Platform3DObject colorBuffer() const { return m_colorBuffer; }

    // Clear all resources from this object, as well as context. Called when context is destroyed
    // to prevent invalid accesses to the resources.
    void clear();

    // Create the depth/stencil and multisample buffers, if needed.
    void createSecondaryBuffers();
    
    void resizeDepthStencil(int sampleCount);

    // Copies the multisample color buffer to the normal color buffer and leaves m_fbo bound
    void commit(long x = 0, long y = 0, long width = -1, long height = -1);

    // commit should copy the full multisample buffer, and not respect the
    // current scissor bounds. Track the state of the scissor test so that it
    // can be disabled during calls to commit.
    void setScissorEnabled(bool scissorEnabled) { m_scissorEnabled = scissorEnabled; }

    // The DrawingBuffer needs to track the texture bound to texture unit 0.
    // The bound texture is tracked to avoid costly queries during rendering.
    void setTexture2DBinding(Platform3DObject texture) { m_texture2DBinding = texture; }

    // The DrawingBuffer needs to track the currently bound framebuffer so it
    // restore the binding when needed.
    void setFramebufferBinding(Platform3DObject fbo) { m_framebufferBinding = fbo; }

    // Bind to the m_framebufferBinding if it's not 0.
    void restoreFramebufferBinding();

    // Track the currently active texture unit. Texture unit 0 is used as host for a scratch
    // texture.
    void setActiveTextureUnit(GC3Dint textureUnit) { m_activeTextureUnit = textureUnit; }

    bool multisample() const;

    Platform3DObject framebuffer() const;

    // Immediately releases ownership of all resources. Call upon loss of the
    // graphics context to prevent freeing invalid resources.
    void discardResources();

    void markContentsChanged() { m_contentsChanged = true; }

    PlatformLayer* platformLayer();
    unsigned frontColorBuffer() const;
    void paintCompositedResultsToCanvas(ImageBuffer*);

    GraphicsContext3D* graphicsContext3D() const { return m_context.get(); }

private:
    DrawingBuffer(GraphicsContext3D*, const IntSize&, bool multisampleExtensionSupported,
                  bool packedDepthStencilExtensionSupported, PreserveDrawingBuffer, AlphaRequirement);

    void initialize(const IntSize&);

    bool checkBufferIntegrity();

    PreserveDrawingBuffer m_preserveDrawingBuffer;
    AlphaRequirement m_alpha;
    bool m_scissorEnabled;
    Platform3DObject m_texture2DBinding;
    Platform3DObject m_framebufferBinding;
    GC3Denum m_activeTextureUnit;

    RefPtr<GraphicsContext3D> m_context;
    IntSize m_size;
    bool m_multisampleExtensionSupported;
    bool m_packedDepthStencilExtensionSupported;
    Platform3DObject m_fbo;
    Platform3DObject m_colorBuffer;
    Platform3DObject m_frontColorBuffer;
    bool m_separateFrontTexture;

    // This is used when we have OES_packed_depth_stencil.
    Platform3DObject m_depthStencilBuffer;

    // These are used when we don't.
    Platform3DObject m_depthBuffer;
    Platform3DObject m_stencilBuffer;

    // For multisampling
    Platform3DObject m_multisampleFBO;
    Platform3DObject m_multisampleColorBuffer;

    // True if our contents have been modified since the last presentation of this buffer.
    bool m_contentsChanged;

#if PLATFORM(MAC)
    RetainPtr<WebGLLayer> m_platformLayer;
#endif
};

} // namespace WebCore

#endif // DrawingBuffer_h