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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 http://mozilla.org/MPL/2.0/. */
#ifndef GFX_READBACKLAYER_H
#define GFX_READBACKLAYER_H
#include <stdint.h> // for uint64_t
#include "Layers.h" // for Layer, etc
#include "mozilla/gfx/Rect.h" // for gfxRect
#include "mozilla/gfx/Point.h" // for IntPoint
#include "mozilla/mozalloc.h" // for operator delete
#include "nsCOMPtr.h" // for already_AddRefed
#include "nsDebug.h" // for NS_ASSERTION
#include "nsPoint.h" // for nsIntPoint
#include "nscore.h" // for nsACString
class gfxContext;
namespace mozilla {
namespace layers {
class ReadbackProcessor;
namespace layerscope {
class LayersPacket;
} // namespace layerscope
/**
* A ReadbackSink receives a stream of updates to a rectangle of pixels.
* These update callbacks are always called on the main thread, either during
* EndTransaction or from the event loop.
*/
class ReadbackSink {
public:
ReadbackSink() = default;
virtual ~ReadbackSink() = default;
/**
* Sends an update to indicate that the background is currently unknown.
*/
virtual void SetUnknown(uint64_t aSequenceNumber) = 0;
/**
* Called by the layer system to indicate that the contents of part of
* the readback area are changing.
* @param aRect is the rectangle of content that is being updated,
* in the coordinate system of the ReadbackLayer.
* @param aSequenceNumber updates issued out of order should be ignored.
* Only use updates whose sequence counter is greater than all other updates
* seen so far. Return null when a non-fresh sequence value is given.
* @return a context into which the update should be drawn. This should be
* set up to clip to aRect. Zero should never be passed as a sequence number.
* If this returns null, EndUpdate should NOT be called. If it returns
* non-null, EndUpdate must be called.
*
* We don't support partially unknown backgrounds. Therefore, the
* first BeginUpdate after a SetUnknown will have the complete background.
*/
virtual already_AddRefed<gfx::DrawTarget> BeginUpdate(
const gfx::IntRect& aRect, uint64_t aSequenceNumber) = 0;
/**
* EndUpdate must be called immediately after BeginUpdate, without returning
* to the event loop.
* @param aContext the context returned by BeginUpdate
* Implicitly Restore()s the state of aContext.
*/
virtual void EndUpdate(const gfx::IntRect& aRect) = 0;
};
/**
* A ReadbackLayer never renders anything. It enables clients to extract
* the rendered contents of the layer tree below the ReadbackLayer.
* The rendered contents are delivered asynchronously via calls to a
* ReadbackSink object supplied by the client.
*
* This is a "best effort" API; it is possible for the layer system to tell
* the ReadbackSink that the contents of the readback area are unknown.
*
* This API exists to work around the limitations of transparent windowless
* plugin rendering APIs. It should not be used for anything else.
*/
class ReadbackLayer : public Layer {
public:
MOZ_LAYER_DECL_NAME("ReadbackLayer", TYPE_READBACK)
virtual void ComputeEffectiveTransforms(
const gfx::Matrix4x4& aTransformToSurface) override {
// Snap our local transform first, and snap the inherited transform as well.
// This makes our snapping equivalent to what would happen if our content
// was drawn into a PaintedLayer (gfxContext would snap using the local
// transform, then we'd snap again when compositing the PaintedLayer).
mEffectiveTransform =
SnapTransform(GetLocalTransform(),
gfxRect(0, 0, mSize.width, mSize.height), nullptr) *
SnapTransformTranslation(aTransformToSurface, nullptr);
}
/**
* CONSTRUCTION PHASE ONLY
* Set the callback object to which readback updates will be delivered.
* This also resets the "needed rectangle" so that on the next layer tree
* transaction we will try to deliver the full contents of the readback
* area to the sink.
* This layer takes ownership of the sink. It will be deleted when the
* layer is destroyed or when a new sink is set.
* Initially the contents of the readback area are completely unknown.
*/
void SetSink(ReadbackSink* aSink) {
SetUnknown();
mSink = mozilla::WrapUnique(aSink);
}
ReadbackSink* GetSink() { return mSink.get(); }
/**
* CONSTRUCTION PHASE ONLY
* Set the size of content that should be read back. The readback area
* has its top-left at 0,0 and has size aSize.
* Can only be called while the sink is null!
*/
void SetSize(const gfx::IntSize& aSize) {
NS_ASSERTION(!mSink, "Should have no sink while changing size!");
mSize = aSize;
}
const gfx::IntSize& GetSize() { return mSize; }
gfx::IntRect GetRect() { return gfx::IntRect(gfx::IntPoint(0, 0), mSize); }
bool IsBackgroundKnown() {
return mBackgroundLayer || mBackgroundColor.a == 1.f;
}
void NotifyRemoved() {
SetUnknown();
mSink = nullptr;
}
void NotifyPaintedLayerRemoved(PaintedLayer* aLayer) {
if (mBackgroundLayer == aLayer) {
mBackgroundLayer = nullptr;
}
}
const nsIntPoint& GetBackgroundLayerOffset() {
return mBackgroundLayerOffset;
}
uint64_t AllocateSequenceNumber() { return ++mSequenceCounter; }
void SetUnknown() {
if (IsBackgroundKnown()) {
if (mSink) {
mSink->SetUnknown(AllocateSequenceNumber());
}
mBackgroundLayer = nullptr;
mBackgroundColor = gfx::DeviceColor();
}
}
protected:
friend class ReadbackProcessor;
ReadbackLayer(LayerManager* aManager, void* aImplData)
: Layer(aManager, aImplData),
mSequenceCounter(0),
mSize(0, 0),
mBackgroundLayer(nullptr),
mBackgroundLayerOffset(0, 0),
mBackgroundColor(gfx::DeviceColor()) {}
virtual void PrintInfo(std::stringstream& aStream,
const char* aPrefix) override;
virtual void DumpPacket(layerscope::LayersPacket* aPacket,
const void* aParent) override;
uint64_t mSequenceCounter;
UniquePtr<ReadbackSink> mSink;
gfx::IntSize mSize;
// This can refer to any (earlier) sibling PaintedLayer. That PaintedLayer
// must have mUsedForReadback set on it. If the PaintedLayer is removed
// for the container, this will be set to null by NotifyPaintedLayerRemoved.
// This PaintedLayer contains the contents which have previously been reported
// to mSink. The PaintedLayer had only an integer translation transform,
// and it covered the entire readback area. This layer also had only an
// integer translation transform.
PaintedLayer* mBackgroundLayer;
// When mBackgroundLayer is non-null, this is the offset to add to
// convert from the coordinates of mBackgroundLayer to the coordinates
// of this layer.
nsIntPoint mBackgroundLayerOffset;
// When mBackgroundColor is opaque, this is the color of the ColorLayer
// that contained the contents we reported to mSink, which covered the
// entire readback area.
gfx::DeviceColor mBackgroundColor;
};
} // namespace layers
} // namespace mozilla
#endif /* GFX_READBACKLAYER_H */
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