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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#include "Units.h" // for ScreenPoint
#include "mozilla/Assertions.h" // for MOZ_ASSERT, etc
#include "mozilla/RefPtr.h" // for already_AddRefed, RefCounted
#include "mozilla/gfx/2D.h" // for DrawTarget
#include "mozilla/gfx/MatrixFwd.h" // for Matrix, Matrix4x4
#include "mozilla/gfx/Point.h" // for IntSize, Point
#include "mozilla/gfx/Polygon.h" // for Polygon
#include "mozilla/gfx/Rect.h" // for Rect, IntRect
#include "mozilla/gfx/Types.h" // for Float
#include "mozilla/gfx/Triangle.h" // for Triangle, TexturedTriangle
#include "mozilla/layers/CompositorTypes.h" // for DiagnosticTypes, etc
#include "mozilla/layers/LayersTypes.h" // for LayersBackend
#include "mozilla/layers/SurfacePool.h" // for SurfacePoolHandle
#include "mozilla/layers/TextureSourceProvider.h"
#include "mozilla/widget/CompositorWidget.h"
#include "nsISupportsImpl.h" // for MOZ_COUNT_CTOR, etc
#include "nsRegion.h"
#include <vector>
#include "mozilla/WidgetUtils.h"
* Different elements of a web pages are rendered into separate "layers" before
* they are flattened into the final image that is brought to the screen.
* See Layers.h for more informations about layers and why we use retained
* structures.
* Most of the documentation for layers is directly in the source code in the
* form of doc comments. An overview can also be found in the the wiki:
* # Main interfaces and abstractions
* - CompositableClient and CompositableHost
* (client/CompositableClient.h composite/CompositableHost.h)
* - TextureClient and TextureHost
* (client/TextureClient.h composite/TextureHost.h)
* - TextureSource
* (composite/TextureHost.h)
* - Forwarders
* (ipc/CompositableForwarder.h ipc/ShadowLayers.h)
* - Compositor
* (this file)
* - IPDL protocols
* (.ipdl files under the gfx/layers/ipc directory)
* The *Client and Shadowable* classes are always used on the content thread.
* Forwarders are always used on the content thread.
* The *Host and Shadow* classes are always used on the compositor thread.
* Compositors, TextureSource, and Effects are always used on the compositor
* thread.
* Most enums and constants are declared in LayersTypes.h and CompositorTypes.h.
* # Texture transfer
* Most layer classes own a Compositable plus some extra information like
* transforms and clip rects. They are platform independent.
* Compositable classes manipulate Texture objects and are reponsible for
* things like tiling, buffer rotation or double buffering. Compositables
* are also platform-independent. Examples of compositable classes are:
* - ImageClient
* - CanvasClient
* - etc.
* Texture classes (TextureClient and TextureHost) are thin abstractions over
* platform-dependent texture memory. They are maniplulated by compositables
* and don't know about buffer rotations and such. The purposes of TextureClient
* and TextureHost are to synchronize, serialize and deserialize texture data.
* TextureHosts provide access to TextureSources that are views on the
* Texture data providing the necessary api for Compositor backend to composite
* them.
* Compositable and Texture clients and hosts are created using factory methods.
* They should only be created by using their constructor in exceptional
* circumstances. The factory methods are located:
* TextureClient - CompositableClient::CreateTextureClient
* TextureHost - TextureHost::CreateTextureHost, which calls a
* platform-specific function, e.g.,
* CreateTextureHostOGL CompositableClient - in the appropriate subclass, e.g.,
* CanvasClient::CreateCanvasClient
* CompositableHost - CompositableHost::Create
* # IPDL
* If off-main-thread compositing (OMTC) is enabled, compositing is performed
* in a dedicated thread. In some setups compositing happens in a dedicated
* process. Documentation may refer to either the compositor thread or the
* compositor process.
* See explanations in ShadowLayers.h.
* # Backend implementations
* Compositor backends like OpenGL or flavours of D3D live in their own
* directory under gfx/layers/. To add a new backend, implement at least the
* following interfaces:
* - Compositor (ex. CompositorOGL)
* - TextureHost (ex. SurfaceTextureHost)
* Depending on the type of data that needs to be serialized, you may need to
* add specific TextureClient implementations.
class nsIWidget;
namespace mozilla {
namespace gfx {
class DrawTarget;
class DataSourceSurface;
} // namespace gfx
namespace layers {
struct Effect;
struct EffectChain;
class Image;
class Layer;
class TextureSource;
class DataTextureSource;
class CompositingRenderTarget;
class CompositorBridgeParent;
class NativeLayer;
class CompositorOGL;
class CompositorD3D11;
class TextureReadLock;
struct GPUStats;
class AsyncReadbackBuffer;
class RecordedFrame;
enum SurfaceInitMode { INIT_MODE_NONE, INIT_MODE_CLEAR };
* Common interface for compositor backends.
* Compositor provides a cross-platform interface to a set of operations for
* compositing quads. Compositor knows nothing about the layer tree. It must be
* told everything about each composited quad - contents, location, transform,
* opacity, etc.
* In theory it should be possible for different widgets to use the same
* compositor. In practice, we use one compositor per window.
* # Usage
* For an example of a user of Compositor, see LayerManagerComposite.
* Initialization: create a Compositor object, call Initialize().
* Destruction: destroy any resources associated with the compositor, call
* Destroy(), delete the Compositor object.
* Composition:
* call BeginFrame,
* for each quad to be composited:
* call MakeCurrent if necessary (not necessary if no other context has been
* made current),
* take care of any texture upload required to composite the quad, this step
* is backend-dependent,
* construct an EffectChain for the quad,
* call DrawQuad,
* call EndFrame.
* By default, the compositor will render to the screen if BeginFrameForWindow
* is called. To render to a target, call BeginFrameForTarget or
* or SetRenderTarget, the latter with a target created
* by CreateRenderTarget or CreateRenderTargetFromSource.
* The target and viewport methods can be called before any DrawQuad call and
* affect any subsequent DrawQuad calls.
class Compositor : public TextureSourceProvider {
virtual ~Compositor();
explicit Compositor(widget::CompositorWidget* aWidget);
bool IsValid() const override { return true; }
virtual bool Initialize(nsCString* const out_failureReason) = 0;
void Destroy() override;
bool IsDestroyed() const { return mIsDestroyed; }
* Creates a Surface that can be used as a rendering target by this
* compositor.
virtual already_AddRefed<CompositingRenderTarget> CreateRenderTarget(
const gfx::IntRect& aRect, SurfaceInitMode aInit) = 0;
* Grab a snapshot of aSource and store it in aDest, so that the pixels can
* be read on the CPU by mapping aDest at some point in the future.
* aSource and aDest must have the same size.
* If this is a GPU compositor, this call must not block on the GPU.
* Returns whether the operation was successful.
virtual bool ReadbackRenderTarget(CompositingRenderTarget* aSource,
AsyncReadbackBuffer* aDest) = 0;
* Create an AsyncReadbackBuffer of the specified size. Can return null.
virtual already_AddRefed<AsyncReadbackBuffer> CreateAsyncReadbackBuffer(
const gfx::IntSize& aSize) = 0;
* Draw a part of aSource into the current render target.
* Scaling is done with linear filtering.
* Returns whether the operation was successful.
virtual bool BlitRenderTarget(CompositingRenderTarget* aSource,
const gfx::IntSize& aSourceSize,
const gfx::IntSize& aDestSize) = 0;
* Sets the given surface as the target for subsequent calls to DrawQuad.
* Passing null as aSurface sets the screen as the target.
virtual void SetRenderTarget(CompositingRenderTarget* aSurface) = 0;
* Returns the current target for rendering. Will return null if we are
* rendering to the screen.
virtual already_AddRefed<CompositingRenderTarget> GetCurrentRenderTarget()
const = 0;
* Returns a render target which contains the entire window's drawing.
* On platforms where no such render target is used during compositing (e.g.
* with buffered BasicCompositor, where only the invalid area is drawn to a
* render target), this will return null.
virtual already_AddRefed<CompositingRenderTarget> GetWindowRenderTarget()
const = 0;
* Mostly the compositor will pull the size from a widget and this method will
* be ignored, but compositor implementations are free to use it if they like.
virtual void SetDestinationSurfaceSize(const gfx::IntSize& aSize) = 0;
* Tell the compositor to draw a quad. What to do draw and how it is
* drawn is specified by aEffectChain. aRect is the quad to draw, in user
* space. aTransform transforms from user space to screen space. If texture
* coords are required, these will be in the primary effect in the effect
* chain. aVisibleRect is used to determine which edges should be antialiased,
* without applying the effect to the inner edges of a tiled layer.
virtual void DrawQuad(const gfx::Rect& aRect, const gfx::IntRect& aClipRect,
const EffectChain& aEffectChain, gfx::Float aOpacity,
const gfx::Matrix4x4& aTransform,
const gfx::Rect& aVisibleRect) = 0;
void SetClearColor(const gfx::DeviceColor& aColor) { mClearColor = aColor; }
* Start a new frame for rendering to the window.
* Needs to be paired with a call to EndFrame() if the return value is not
* Nothing().
* aInvalidRegion is the invalid region of the window.
* aClipRect is the clip rect for all drawing (optional).
* aRenderBounds is the bounding rect for rendering.
* aOpaqueRegion is the area that contains opaque content.
* All coordinates are in window space.
* Returns the non-empty render bounds actually used by the compositor in
* window space, or Nothing() if composition should be aborted.
virtual Maybe<gfx::IntRect> BeginFrameForWindow(
const nsIntRegion& aInvalidRegion, const Maybe<gfx::IntRect>& aClipRect,
const gfx::IntRect& aRenderBounds, const nsIntRegion& aOpaqueRegion) = 0;
* Flush the current frame to the screen and tidy up.
* Derived class overriding this should call Compositor::EndFrame.
virtual void EndFrame();
virtual void CancelFrame(bool aNeedFlush = true) {}
virtual const char* Name() const = 0;
virtual CompositorD3D11* AsCompositorD3D11() { return nullptr; }
Compositor* AsCompositor() override { return this; }
TimeStamp GetLastCompositionEndTime() const override {
return mLastCompositionEndTime;
* Notify the compositor that composition is being paused. This allows the
* compositor to temporarily release any resources.
* Between calling Pause and Resume, compositing may fail.
virtual void Pause() {}
* Notify the compositor that composition is being resumed. The compositor
* regain any resources it requires for compositing.
* Returns true if succeeded.
virtual bool Resume() { return true; }
widget::CompositorWidget* GetWidget() const { return mWidget; }
* Request the compositor to allow recording its frames.
* This is a noop on |CompositorOGL|.
virtual void RequestAllowFrameRecording(bool aWillRecord) {
mRecordFrames = aWillRecord;
* Record the current frame for readback by the |CompositionRecorder|.
* If this compositor does not support this feature, a null pointer is
* returned instead.
already_AddRefed<RecordedFrame> RecordFrame(const TimeStamp& aTimeStamp);
* Whether or not the compositor should be prepared to record frames. While
* this returns true, compositors are expected to maintain a full window
* render target that they return from GetWindowRenderTarget() between
* NormalDrawingDone() and EndFrame().
* This will be true when either we are recording a profile with screenshots
* enabled or the |LayerManagerComposite| has requested us to record frames
* for the |CompositionRecorder|.
bool ShouldRecordFrames() const;
* Last Composition end time.
TimeStamp mLastCompositionEndTime;
widget::CompositorWidget* mWidget;
bool mIsDestroyed;
gfx::DeviceColor mClearColor;
bool mRecordFrames = false;
static LayersBackend sBackend;
// Returns the number of rects. (Up to 4)
typedef gfx::Rect decomposedRectArrayT[4];
size_t DecomposeIntoNoRepeatRects(const gfx::Rect& aRect,
const gfx::Rect& aTexCoordRect,
decomposedRectArrayT* aLayerRects,
decomposedRectArrayT* aTextureRects);
static inline bool BlendOpIsMixBlendMode(gfx::CompositionOp aOp) {
switch (aOp) {
case gfx::CompositionOp::OP_MULTIPLY:
case gfx::CompositionOp::OP_SCREEN:
case gfx::CompositionOp::OP_OVERLAY:
case gfx::CompositionOp::OP_DARKEN:
case gfx::CompositionOp::OP_LIGHTEN:
case gfx::CompositionOp::OP_COLOR_DODGE:
case gfx::CompositionOp::OP_COLOR_BURN:
case gfx::CompositionOp::OP_HARD_LIGHT:
case gfx::CompositionOp::OP_SOFT_LIGHT:
case gfx::CompositionOp::OP_DIFFERENCE:
case gfx::CompositionOp::OP_EXCLUSION:
case gfx::CompositionOp::OP_HUE:
case gfx::CompositionOp::OP_SATURATION:
case gfx::CompositionOp::OP_COLOR:
case gfx::CompositionOp::OP_LUMINOSITY:
return true;
return false;
class AsyncReadbackBuffer {
gfx::IntSize GetSize() const { return mSize; }
virtual bool MapAndCopyInto(gfx::DataSourceSurface* aSurface,
const gfx::IntSize& aReadSize) const = 0;
explicit AsyncReadbackBuffer(const gfx::IntSize& aSize) : mSize(aSize) {}
virtual ~AsyncReadbackBuffer() = default;
gfx::IntSize mSize;
struct TexturedVertex {
float position[2];
float texCoords[2];
nsTArray<TexturedVertex> TexturedTrianglesToVertexArray(
const nsTArray<gfx::TexturedTriangle>& aTriangles);
} // namespace layers
} // namespace mozilla