Source/core/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 "core/platform/graphics/GraphicsContext3D.h"
#include "platform/geometry/IntSize.h"
#include "platform/graphics/GraphicsTypes3D.h"

#include "public/platform/WebExternalTextureLayerClient.h"
#include "public/platform/WebExternalTextureMailbox.h"
#include "wtf/Noncopyable.h"
#include "wtf/OwnPtr.h"
#include "wtf/PassOwnPtr.h"

namespace blink {
class WebExternalBitmap;
class WebExternalTextureLayer;
class WebGraphicsContext3D;
class WebLayer;
}

namespace WebCore {
class GraphicsContext3D;
class ImageData;

// Abstract interface to allow basic context eviction management
class ContextEvictionManager : public RefCounted<ContextEvictionManager> {
public:
    virtual ~ContextEvictionManager() {};

    virtual void forciblyLoseOldestContext(const String& reason) = 0;
    virtual IntSize oldestContextSize() = 0;
};

// Manages a rendering target (framebuffer + attachment) for a canvas.  Can publish its rendering
// results to a blink::WebLayer for compositing.
class DrawingBuffer : public RefCounted<DrawingBuffer>, public blink::WebExternalTextureLayerClient  {
    struct MailboxInfo : public RefCounted<MailboxInfo> {
        blink::WebExternalTextureMailbox mailbox;
        unsigned textureId;
        IntSize size;
    };
public:
    enum PreserveDrawingBuffer {
        Preserve,
        Discard
    };

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

    ~DrawingBuffer();

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

    // 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);

    // Given the desired buffer size, provides the largest dimensions that will fit in the pixel budget.
    IntSize adjustSize(const IntSize&);
    void reset(const IntSize&);
    void bind();
    IntSize size() const { return m_size; }
    bool isZeroSized() const { return m_size.isEmpty(); }

    // 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; }

    // 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;

    void markContentsChanged();

    blink::WebLayer* platformLayer();
    void paintCompositedResultsToCanvas(ImageBuffer*);

    // WebExternalTextureLayerClient implementation.
    virtual blink::WebGraphicsContext3D* context() OVERRIDE;
    virtual bool prepareMailbox(blink::WebExternalTextureMailbox*, blink::WebExternalBitmap*) OVERRIDE;
    virtual void mailboxReleased(const blink::WebExternalTextureMailbox&) OVERRIDE;

    bool copyToPlatformTexture(GraphicsContext3D&, Platform3DObject texture, GC3Denum internalFormat,
        GC3Denum destType, GC3Dint level, bool premultiplyAlpha, bool flipY);

private:
    DrawingBuffer(GraphicsContext3D*, const IntSize&, bool multisampleExtensionSupported,
                  bool packedDepthStencilExtensionSupported, PreserveDrawingBuffer, PassRefPtr<ContextEvictionManager>);

    void initialize(const IntSize&);

    Platform3DObject frontColorBuffer() const;
    Platform3DObject colorBuffer() const { return m_colorBuffer; }

    unsigned createColorTexture(const IntSize& size = IntSize());
    // Create the depth/stencil and multisample buffers, if needed.
    void createSecondaryBuffers();
    bool resizeFramebuffer(const IntSize&);
    bool resizeMultisampleFramebuffer(const IntSize&);
    void resizeDepthStencil(const IntSize&, int sampleCount);

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

    void clearPlatformLayer();

    PassRefPtr<MailboxInfo> recycledMailbox();
    PassRefPtr<MailboxInfo> createNewMailbox(unsigned);

    // Updates the current size of the buffer, ensuring that s_currentResourceUsePixels is updated.
    void setSize(const IntSize& size);

    // Calculates the difference in pixels between the current buffer size and the proposed size.
    int pixelDelta(const IntSize& size);

    // Given the desired buffer size, provides the largest dimensions that will fit in the pixel budget
    // Returns true if the buffer will only fit if the oldest WebGL context is forcibly lost
    IntSize adjustSizeWithContextEviction(const IntSize&, bool& evictContext);

    PreserveDrawingBuffer m_preserveDrawingBuffer;
    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;

    // 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;

    // True if commit() has been called since the last time markContentsChanged() had been called.
    bool m_contentsChangeCommitted;

    GraphicsContext3D::Attributes m_attributes;
    unsigned m_internalColorFormat;
    unsigned m_colorFormat;
    unsigned m_internalRenderbufferFormat;
    int m_maxTextureSize;

    OwnPtr<blink::WebExternalTextureLayer> m_layer;

    // All of the mailboxes that this DrawingBuffer has ever created.
    Vector<RefPtr<MailboxInfo> > m_textureMailboxes;
    // Mailboxes that were released by the compositor and can be used again by this DrawingBuffer.
    Vector<RefPtr<MailboxInfo> > m_recycledMailboxes;
    RefPtr<MailboxInfo> m_lastColorBuffer;

    RefPtr<ContextEvictionManager> m_contextEvictionManager;
};

} // namespace WebCore

#endif // DrawingBuffer_h