third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h

/*
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 * modification, are permitted provided that the following conditions are
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#ifndef DrawingBuffer_h
#define DrawingBuffer_h

#include <memory>
#include "cc/layers/texture_layer_client.h"
#include "gpu/command_buffer/common/mailbox.h"
#include "gpu/command_buffer/common/sync_token.h"
#include "platform/PlatformExport.h"
#include "platform/geometry/IntSize.h"
#include "platform/graphics/GraphicsTypes3D.h"
#include "platform/graphics/gpu/WebGLImageConversion.h"
#include "platform/wtf/Deque.h"
#include "platform/wtf/Noncopyable.h"
#include "platform/wtf/RefCounted.h"
#include "platform/wtf/Vector.h"
#include "third_party/khronos/GLES2/gl2.h"
#include "third_party/skia/include/core/SkBitmap.h"
#include "ui/gfx/color_space.h"

namespace gfx {
class GpuMemoryBuffer;
}

namespace gpu {
namespace gles2 {
class GLES2Interface;
}
}

namespace viz {
class SharedBitmap;
}

namespace WTF {
class ArrayBufferContents;
}

namespace blink {
class CanvasColorParams;
class Extensions3DUtil;
class StaticBitmapImage;
class WebExternalTextureLayer;
class WebGraphicsContext3DProvider;
class WebGraphicsContext3DProviderWrapper;
class WebLayer;

// Manages a rendering target (framebuffer + attachment) for a canvas.  Can
// publish its rendering results to a WebLayer for compositing.
class PLATFORM_EXPORT DrawingBuffer
    : public NON_EXPORTED_BASE(cc::TextureLayerClient),
      public RefCounted<DrawingBuffer> {
  WTF_MAKE_NONCOPYABLE(DrawingBuffer);

 public:
  class Client {
   public:
    // Returns true if the DrawingBuffer is currently bound for draw.
    virtual bool DrawingBufferClientIsBoundForDraw() = 0;
    virtual void DrawingBufferClientRestoreScissorTest() = 0;
    // Restores the mask and clear value for color, depth, and stencil buffers.
    virtual void DrawingBufferClientRestoreMaskAndClearValues() = 0;
    // Assume client knows the GL/WebGL version and restore necessary params
    // accordingly.
    virtual void DrawingBufferClientRestorePixelPackParameters() = 0;
    // Restores the GL_TEXTURE_2D binding for the active texture unit only.
    virtual void DrawingBufferClientRestoreTexture2DBinding() = 0;
    virtual void DrawingBufferClientRestoreRenderbufferBinding() = 0;
    virtual void DrawingBufferClientRestoreFramebufferBinding() = 0;
    virtual void DrawingBufferClientRestorePixelUnpackBufferBinding() = 0;
    virtual void DrawingBufferClientRestorePixelPackBufferBinding() = 0;
  };

  enum PreserveDrawingBuffer {
    kPreserve,
    kDiscard,
  };
  enum WebGLVersion {
    kWebGL1,
    kWebGL2,
  };

  enum ChromiumImageUsage {
    kAllowChromiumImage,
    kDisallowChromiumImage,
  };

  static PassRefPtr<DrawingBuffer> Create(
      std::unique_ptr<WebGraphicsContext3DProvider>,
      Client*,
      const IntSize&,
      bool premultiplied_alpha,
      bool want_alpha_channel,
      bool want_depth_buffer,
      bool want_stencil_buffer,
      bool want_antialiasing,
      PreserveDrawingBuffer,
      WebGLVersion,
      ChromiumImageUsage,
      const CanvasColorParams&);
  static void ForceNextDrawingBufferCreationToFail();

  ~DrawingBuffer() override;

  // Destruction will be completed after all mailboxes are released.
  void BeginDestruction();

  // Issues a glClear() on all framebuffers associated with this DrawingBuffer.
  void ClearFramebuffers(GLbitfield clear_mask);

  // Indicates whether the DrawingBuffer internally allocated a packed
  // depth-stencil renderbuffer in the situation where the end user only asked
  // for a depth buffer. In this case, we need to upgrade clears of the depth
  // buffer to clears of the depth and stencil buffers in order to avoid
  // performance problems on some GPUs.
  bool HasImplicitStencilBuffer() const { return has_implicit_stencil_buffer_; }
  bool HasDepthBuffer() const { return !!depth_stencil_buffer_; }
  bool HasStencilBuffer() const { return !!depth_stencil_buffer_; }

  // Given the desired buffer size, provides the largest dimensions that will
  // fit in the pixel budget.
  static IntSize AdjustSize(const IntSize& desired_size,
                            const IntSize& cur_size,
                            int max_texture_size);

  // Resizes (or allocates if necessary) all buffers attached to the default
  // framebuffer. Returns whether the operation was successful.
  bool Resize(const IntSize&);

  // Bind the default framebuffer to |target|. |target| must be
  // GL_FRAMEBUFFER, GL_READ_FRAMEBUFFER, or GL_DRAW_FRAMEBUFFER.
  void Bind(GLenum target);
  IntSize Size() const { return size_; }

  // Resolves the multisample color buffer to the normal color buffer and leaves
  // the resolved color buffer bound to GL_READ_FRAMEBUFFER and
  // GL_DRAW_FRAMEBUFFER.
  void ResolveAndBindForReadAndDraw();

  bool Multisample() const;

  bool DiscardFramebufferSupported() const {
    return discard_framebuffer_supported_;
  }

  // Returns false if the contents had previously been marked as changed and
  // have not yet been resolved.
  bool MarkContentsChanged();
  void SetBufferClearNeeded(bool);
  bool BufferClearNeeded() const;
  void SetIsHidden(bool);
  void SetFilterQuality(SkFilterQuality);

  // Whether the target for draw operations has format GL_RGBA, but is
  // emulating format GL_RGB. When the target's storage is first
  // allocated, its alpha channel must be cleared to 1. All future drawing
  // operations must use a color mask with alpha=GL_FALSE.
  bool RequiresAlphaChannelToBePreserved();

  // Similar to requiresAlphaChannelToBePreserved(), but always targets the
  // default framebuffer.
  bool DefaultBufferRequiresAlphaChannelToBePreserved();

  WebLayer* PlatformLayer();

  gpu::gles2::GLES2Interface* ContextGL();
  WebGraphicsContext3DProvider* ContextProvider();

  // cc::TextureLayerClient implementation.
  bool PrepareTextureMailbox(viz::TextureMailbox* out_mailbox,
                             std::unique_ptr<cc::SingleReleaseCallback>*
                                 out_release_callback) override;

  // Returns a StaticBitmapImage backed by a texture containing the current
  // contents of the front buffer. This is done without any pixel copies. The
  // texture in the ImageBitmap is from the active ContextProvider on the
  // DrawingBuffer.
  PassRefPtr<StaticBitmapImage> TransferToStaticBitmapImage();

  bool CopyToPlatformTexture(gpu::gles2::GLES2Interface*,
                             GLenum target,
                             GLuint texture,
                             bool premultiply_alpha,
                             bool flip_y,
                             const IntPoint& dest_texture_offset,
                             const IntRect& source_sub_rectangle,
                             SourceDrawingBuffer);

  bool PaintRenderingResultsToImageData(int&,
                                        int&,
                                        SourceDrawingBuffer,
                                        WTF::ArrayBufferContents&);

  int SampleCount() const { return sample_count_; }
  bool ExplicitResolveOfMultisampleData() const {
    return anti_aliasing_mode_ == kMSAAExplicitResolve;
  }

  // Rebind the read and draw framebuffers that WebGL is expecting.
  void RestoreFramebufferBindings();

  // Restore all state that may have been dirtied by any call.
  void RestoreAllState();

  // This class helps implement correct semantics for BlitFramebuffer
  // when the DrawingBuffer is using a CHROMIUM image for its backing
  // store and RGB emulation is in use (basically, macOS only).
  class PLATFORM_EXPORT ScopedRGBEmulationForBlitFramebuffer {
   public:
    ScopedRGBEmulationForBlitFramebuffer(DrawingBuffer*);
    ~ScopedRGBEmulationForBlitFramebuffer();

   private:
    RefPtr<DrawingBuffer> drawing_buffer_;
    bool doing_work_ = false;
  };

 protected:  // For unittests
  DrawingBuffer(std::unique_ptr<WebGraphicsContext3DProvider>,
                std::unique_ptr<Extensions3DUtil>,
                Client*,
                bool discard_framebuffer_supported,
                bool want_alpha_channel,
                bool premultiplied_alpha,
                PreserveDrawingBuffer,
                WebGLVersion,
                bool wants_depth,
                bool wants_stencil,
                ChromiumImageUsage,
                const CanvasColorParams&);

  bool Initialize(const IntSize&, bool use_multisampling);

  // Shared memory bitmaps that were released by the compositor and can be used
  // again by this DrawingBuffer.
  struct RecycledBitmap {
    std::unique_ptr<viz::SharedBitmap> bitmap;
    IntSize size;
  };
  Vector<RecycledBitmap> recycled_bitmaps_;

 private:
  friend class ScopedRGBEmulationForBlitFramebuffer;
  friend class ScopedStateRestorer;
  friend class ColorBuffer;

  // This structure should wrap all public entrypoints that may modify GL state.
  // It will restore all state when it drops out of scope.
  class ScopedStateRestorer {
   public:
    ScopedStateRestorer(DrawingBuffer*);
    ~ScopedStateRestorer();

    // Mark parts of the state that are dirty and need to be restored.
    void SetClearStateDirty() { clear_state_dirty_ = true; }
    void SetPixelPackParametersDirty() { pixel_pack_parameters_dirty_ = true; }
    void SetTextureBindingDirty() { texture_binding_dirty_ = true; }
    void SetRenderbufferBindingDirty() { renderbuffer_binding_dirty_ = true; }
    void SetFramebufferBindingDirty() { framebuffer_binding_dirty_ = true; }
    void SetPixelUnpackBufferBindingDirty() {
      pixel_unpack_buffer_binding_dirty_ = true;
    }
    void SetPixelPackBufferBindingDirty() {
      pixel_pack_buffer_binding_dirty_ = true;
    }

   private:
    RefPtr<DrawingBuffer> drawing_buffer_;
    // The previous state restorer, in case restorers are nested.
    ScopedStateRestorer* previous_state_restorer_ = nullptr;
    bool clear_state_dirty_ = false;
    bool pixel_pack_parameters_dirty_ = false;
    bool texture_binding_dirty_ = false;
    bool renderbuffer_binding_dirty_ = false;
    bool framebuffer_binding_dirty_ = false;
    bool pixel_unpack_buffer_binding_dirty_ = false;
    bool pixel_pack_buffer_binding_dirty_ = false;
  };

  // All parameters necessary to generate the texture for the ColorBuffer.
  struct ColorBufferParameters {
    DISALLOW_NEW();
    GLenum target = 0;
    bool allocate_alpha_channel = false;
  };

  struct ColorBuffer : public RefCounted<ColorBuffer> {
    ColorBuffer(DrawingBuffer*,
                const ColorBufferParameters&,
                const IntSize&,
                GLuint texture_id,
                GLuint image_id,
                std::unique_ptr<gfx::GpuMemoryBuffer>);
    ~ColorBuffer();

    // The owning DrawingBuffer. Note that DrawingBuffer is explicitly destroyed
    // by the beginDestruction method, which will eventually drain all of its
    // ColorBuffers.
    RefPtr<DrawingBuffer> drawing_buffer;

    const ColorBufferParameters parameters;
    const IntSize size;

    const GLuint texture_id = 0;
    const GLuint image_id = 0;
    std::unique_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer;

    // If we're emulating an RGB back buffer using an RGBA Chromium
    // image (essentially macOS only), then when performing
    // BlitFramebuffer calls, we have to swap in an RGB texture in
    // place of the RGBA texture bound to the image. The reason is
    // that BlitFramebuffer requires the internal formats of the
    // source and destination to match (e.g. RGB8 on both sides).
    // There are bugs in the semantics of RGB8 textures in this
    // situation (the alpha channel is zeroed), requiring more fixups.
    GLuint rgb_workaround_texture_id = 0;

    // The mailbox used to send this buffer to the compositor.
    gpu::Mailbox mailbox;

    // The sync token for when this buffer was sent to the compositor.
    gpu::SyncToken produce_sync_token;

    // The sync token for when this buffer was received back from the
    // compositor.
    gpu::SyncToken receive_sync_token;

   private:
    WTF_MAKE_NONCOPYABLE(ColorBuffer);
  };

  // The same as clearFramebuffers(), but leaves GL state dirty.
  void ClearFramebuffersInternal(GLbitfield clear_mask);

  // The same as reset(), but leaves GL state dirty.
  bool ResizeFramebufferInternal(const IntSize&);

  // The same as resolveAndBindForReadAndDraw(), but leaves GL state dirty.
  void ResolveMultisampleFramebufferInternal();

  // Resolves m_multisampleFBO into m_fbo, if multisampling.
  void ResolveIfNeeded();

  bool PrepareTextureMailboxInternal(
      viz::TextureMailbox* out_mailbox,
      std::unique_ptr<cc::SingleReleaseCallback>* out_release_callback,
      bool force_gpu_result);

  // Helper functions to be called only by prepareTextureMailboxInternal.
  bool FinishPrepareTextureMailboxGpu(
      viz::TextureMailbox* out_mailbox,
      std::unique_ptr<cc::SingleReleaseCallback>* out_release_callback);
  bool FinishPrepareTextureMailboxSoftware(
      viz::TextureMailbox* out_mailbox,
      std::unique_ptr<cc::SingleReleaseCallback>* out_release_callback);

  // Callbacks for mailboxes given to the compositor from
  // finishPrepareTextureMailboxGpu and finishPrepareTextureMailboxSoftware.
  void MailboxReleasedGpu(RefPtr<ColorBuffer>,
                          const gpu::SyncToken&,
                          bool lost_resource);
  void MailboxReleasedSoftware(std::unique_ptr<viz::SharedBitmap>,
                               const IntSize&,
                               const gpu::SyncToken&,
                               bool lost_resource);

  // The texture parameters to use for a texture that will be backed by a
  // CHROMIUM_image, backed by a GpuMemoryBuffer.
  ColorBufferParameters GpuMemoryBufferColorBufferParameters();

  // The texture parameters to use for an ordinary GL texture.
  ColorBufferParameters TextureColorBufferParameters();

  // Attempts to allocator storage for, or resize all buffers. Returns whether
  // the operation was successful.
  bool ResizeDefaultFramebuffer(const IntSize&);

  void ClearPlatformLayer();

  std::unique_ptr<viz::SharedBitmap> CreateOrRecycleBitmap();

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

  // This is the order of bytes to use when doing a readback.
  enum ReadbackOrder { kReadbackRGBA, kReadbackSkia };

  // Helper function which does a readback from the currently-bound
  // framebuffer into a buffer of a certain size with 4-byte pixels.
  void ReadBackFramebuffer(unsigned char* pixels,
                           int width,
                           int height,
                           ReadbackOrder,
                           WebGLImageConversion::AlphaOp);

  // Helper function to flip a bitmap vertically.
  void FlipVertically(uint8_t* data, int width, int height);

  // If RGB emulation is required, then the CHROMIUM image's alpha channel
  // must be immediately cleared after it is bound to a texture. Nothing
  // should be allowed to change the alpha channel after this.
  void ClearChromiumImageAlpha(const ColorBuffer&);

  // Tries to create a CHROMIUM_image backed texture if
  // RuntimeEnabledFeatures::WebGLImageChromiumEnabled() is true. On failure,
  // or if the flag is false, creates a default texture. Always returns a valid
  // ColorBuffer.
  RefPtr<ColorBuffer> CreateColorBuffer(const IntSize&);

  // Creates or recycles a ColorBuffer of size |m_size|.
  PassRefPtr<ColorBuffer> CreateOrRecycleColorBuffer();

  // Attaches |m_backColorBuffer| to |m_fbo|, which is always the source for
  // read operations.
  void AttachColorBufferToReadFramebuffer();

  // Whether the WebGL client desires an explicit resolve. This is
  // implemented by forwarding all draw operations to a multisample
  // renderbuffer, which is resolved before any read operations or swaps.
  bool WantExplicitResolve();

  // Whether the WebGL client wants a depth or stencil buffer.
  bool WantDepthOrStencil();

  // The format to use when creating a multisampled renderbuffer.
  GLenum GetMultisampledRenderbufferFormat();

  // Helpers to ensure correct behavior of BlitFramebuffer when using
  // an emulated RGB CHROMIUM_image back buffer.
  bool SetupRGBEmulationForBlitFramebuffer();
  void CleanupRGBEmulationForBlitFramebuffer();

  // Weak, reset by beginDestruction.
  Client* client_ = nullptr;

  const PreserveDrawingBuffer preserve_drawing_buffer_;
  const WebGLVersion webgl_version_;

  std::unique_ptr<WebGraphicsContext3DProviderWrapper> context_provider_;
  // Lifetime is tied to the m_contextProvider.
  gpu::gles2::GLES2Interface* gl_;
  std::unique_ptr<Extensions3DUtil> extensions_util_;
  IntSize size_ = {-1, -1};
  const bool discard_framebuffer_supported_;
  const bool want_alpha_channel_;
  const bool premultiplied_alpha_;
  const bool software_rendering_;
  bool has_implicit_stencil_buffer_ = false;
  bool storage_texture_supported_ = false;

  // The current state restorer, which is used to track state dirtying. It is an
  // error to dirty state shared with WebGL while there is no existing state
  // restorer.
  ScopedStateRestorer* state_restorer_ = nullptr;

  // This is used when the user requests either a depth or stencil buffer.
  GLuint depth_stencil_buffer_ = 0;

  // When wantExplicitResolve() returns true, the target of all draw
  // operations.
  GLuint multisample_fbo_ = 0;

  // The id of the renderbuffer storage for |m_multisampleFBO|.
  GLuint multisample_renderbuffer_ = 0;

  // When wantExplicitResolve() returns false, the target of all draw and
  // read operations. When wantExplicitResolve() returns true, the target of
  // all read operations.
  GLuint fbo_ = 0;

  // The ColorBuffer that backs |m_fbo|.
  RefPtr<ColorBuffer> back_color_buffer_;

  // The ColorBuffer that was most recently presented to the compositor by
  // prepareTextureMailboxInternal.
  RefPtr<ColorBuffer> front_color_buffer_;

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

  // True if resolveIfNeeded() has been called since the last time
  // markContentsChanged() had been called.
  bool contents_change_resolved_ = false;
  bool buffer_clear_needed_ = false;

  // Whether the client wants a depth or stencil buffer.
  const bool want_depth_;
  const bool want_stencil_;

  // The color space of this buffer. All buffers are assumed to be sRGB until
  // a mechanism for creating otherwise is exposed to the web.
  const gfx::ColorSpace color_space_;

  enum AntialiasingMode {
    kNone,
    kMSAAImplicitResolve,
    kMSAAExplicitResolve,
    kScreenSpaceAntialiasing,
  };

  AntialiasingMode anti_aliasing_mode_ = kNone;

  int max_texture_size_ = 0;
  int sample_count_ = 0;
  bool destruction_in_progress_ = false;
  bool is_hidden_ = false;
  SkFilterQuality filter_quality_ = kLow_SkFilterQuality;

  std::unique_ptr<WebExternalTextureLayer> layer_;

  // Mailboxes that were released by the compositor can be used again by this
  // DrawingBuffer.
  Deque<RefPtr<ColorBuffer>> recycled_color_buffer_queue_;

  // If the width and height of the Canvas's backing store don't
  // match those that we were given in the most recent call to
  // reshape(), then we need an intermediate bitmap to read back the
  // frame buffer into. This seems to happen when CSS styles are
  // used to resize the Canvas.
  SkBitmap resizing_bitmap_;

  // In the case of OffscreenCanvas, we do not want to enable the
  // WebGLImageChromium flag, so we replace all the
  // RuntimeEnabledFeatures::WebGLImageChromiumEnabled() call with
  // shouldUseChromiumImage() calls, and set m_chromiumImageUsage to
  // DisallowChromiumImage in the case of OffscreenCanvas.
  ChromiumImageUsage chromium_image_usage_;
  bool ShouldUseChromiumImage();
};

}  // namespace blink

#endif  // DrawingBuffer_h