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189 lines
6.6 KiB
C++
189 lines
6.6 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef GFX_READBACKLAYER_H
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#define GFX_READBACKLAYER_H
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#include "Layers.h"
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namespace mozilla {
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namespace layers {
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class ReadbackProcessor;
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/**
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* A ReadbackSink receives a stream of updates to a rectangle of pixels.
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* These update callbacks are always called on the main thread, either during
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* EndTransaction or from the event loop.
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*/
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class THEBES_API ReadbackSink {
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public:
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ReadbackSink() {}
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virtual ~ReadbackSink() {}
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/**
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* Sends an update to indicate that the background is currently unknown.
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*/
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virtual void SetUnknown(PRUint64 aSequenceNumber) = 0;
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/**
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* Called by the layer system to indicate that the contents of part of
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* the readback area are changing.
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* @param aRect is the rectangle of content that is being updated,
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* in the coordinate system of the ReadbackLayer.
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* @param aSequenceNumber updates issued out of order should be ignored.
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* Only use updates whose sequence counter is greater than all other updates
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* seen so far. Return null when a non-fresh sequence value is given.
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* @return a context into which the update should be drawn. This should be
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* set up to clip to aRect. Zero should never be passed as a sequence number.
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* If this returns null, EndUpdate should NOT be called. If it returns
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* non-null, EndUpdate must be called.
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*
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* We don't support partially unknown backgrounds. Therefore, the
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* first BeginUpdate after a SetUnknown will have the complete background.
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*/
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virtual already_AddRefed<gfxContext>
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BeginUpdate(const nsIntRect& aRect, PRUint64 aSequenceNumber) = 0;
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/**
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* EndUpdate must be called immediately after BeginUpdate, without returning
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* to the event loop.
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* @param aContext the context returned by BeginUpdate
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* Implicitly Restore()s the state of aContext.
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*/
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virtual void EndUpdate(gfxContext* aContext, const nsIntRect& aRect) = 0;
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};
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/**
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* A ReadbackLayer never renders anything. It enables clients to extract
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* the rendered contents of the layer tree below the ReadbackLayer.
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* The rendered contents are delivered asynchronously via calls to a
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* ReadbackSink object supplied by the client.
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*
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* This is a "best effort" API; it is possible for the layer system to tell
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* the ReadbackSink that the contents of the readback area are unknown.
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*
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* This API exists to work around the limitations of transparent windowless
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* plugin rendering APIs. It should not be used for anything else.
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*/
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class THEBES_API ReadbackLayer : public Layer {
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public:
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MOZ_LAYER_DECL_NAME("ReadbackLayer", TYPE_READBACK)
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virtual void ComputeEffectiveTransforms(const gfx3DMatrix& aTransformToSurface)
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{
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// Snap our local transform first, and snap the inherited transform as well.
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// This makes our snapping equivalent to what would happen if our content
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// was drawn into a ThebesLayer (gfxContext would snap using the local
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// transform, then we'd snap again when compositing the ThebesLayer).
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mEffectiveTransform =
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SnapTransform(GetLocalTransform(), gfxRect(0, 0, mSize.width, mSize.height),
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nullptr)*
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SnapTransform(aTransformToSurface, gfxRect(0, 0, 0, 0), nullptr);
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}
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/**
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* CONSTRUCTION PHASE ONLY
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* Set the callback object to which readback updates will be delivered.
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* This also resets the "needed rectangle" so that on the next layer tree
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* transaction we will try to deliver the full contents of the readback
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* area to the sink.
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* This layer takes ownership of the sink. It will be deleted when the
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* layer is destroyed or when a new sink is set.
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* Initially the contents of the readback area are completely unknown.
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*/
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void SetSink(ReadbackSink* aSink)
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{
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SetUnknown();
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mSink = aSink;
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}
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ReadbackSink* GetSink() { return mSink; }
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/**
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* CONSTRUCTION PHASE ONLY
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* Set the size of content that should be read back. The readback area
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* has its top-left at 0,0 and has size aSize.
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* Can only be called while the sink is null!
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*/
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void SetSize(const nsIntSize& aSize)
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{
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NS_ASSERTION(!mSink, "Should have no sink while changing size!");
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mSize = aSize;
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}
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const nsIntSize& GetSize() { return mSize; }
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nsIntRect GetRect() { return nsIntRect(nsIntPoint(0, 0), mSize); }
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bool IsBackgroundKnown()
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{
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return mBackgroundLayer || mBackgroundColor.a == 1.0;
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}
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void NotifyRemoved() {
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SetUnknown();
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mSink = nullptr;
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}
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void NotifyThebesLayerRemoved(ThebesLayer* aLayer)
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{
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if (mBackgroundLayer == aLayer) {
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mBackgroundLayer = nullptr;
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}
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}
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const nsIntPoint& GetBackgroundLayerOffset() { return mBackgroundLayerOffset; }
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PRUint64 AllocateSequenceNumber() { return ++mSequenceCounter; }
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void SetUnknown()
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{
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if (IsBackgroundKnown()) {
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if (mSink) {
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mSink->SetUnknown(AllocateSequenceNumber());
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}
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mBackgroundLayer = nullptr;
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mBackgroundColor = gfxRGBA(0,0,0,0);
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}
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}
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protected:
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friend class ReadbackProcessor;
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ReadbackLayer(LayerManager* aManager, void* aImplData) :
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Layer(aManager, aImplData),
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mSequenceCounter(0),
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mSize(0,0),
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mBackgroundLayer(nullptr),
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mBackgroundLayerOffset(0, 0),
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mBackgroundColor(gfxRGBA(0,0,0,0))
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{}
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// Print interesting information about this into aTo. Internally
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// used to implement Dump*() and Log*().
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virtual nsACString& PrintInfo(nsACString& aTo, const char* aPrefix);
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PRUint64 mSequenceCounter;
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nsAutoPtr<ReadbackSink> mSink;
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nsIntSize mSize;
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// This can refer to any (earlier) sibling ThebesLayer. That ThebesLayer
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// must have mUsedForReadback set on it. If the ThebesLayer is removed
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// for the container, this will be set to null by NotifyThebesLayerRemoved.
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// This ThebesLayer contains the contents which have previously been reported
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// to mSink. The ThebesLayer had only an integer translation transform,
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// and it covered the entire readback area. This layer also had only an
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// integer translation transform.
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ThebesLayer* mBackgroundLayer;
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// When mBackgroundLayer is non-null, this is the offset to add to
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// convert from the coordinates of mBackgroundLayer to the coordinates
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// of this layer.
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nsIntPoint mBackgroundLayerOffset;
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// When mBackgroundColor is opaque, this is the color of the ColorLayer
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// that contained the contents we reported to mSink, which covered the
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// entire readback area.
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gfxRGBA mBackgroundColor;
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};
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}
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}
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#endif /* GFX_READBACKLAYER_H */
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