The Tor Browser: comparison gfx/layers/ReadbackLayer.h

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+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+* 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 "gfxColor.h"                   // for gfxRGBA
+#include "gfxRect.h"                    // for gfxRect
+#include "mozilla/mozalloc.h"           // for operator delete
+#include "nsAutoPtr.h"                  // for nsAutoPtr
+#include "nsCOMPtr.h"                   // for already_AddRefed
+#include "nsDebug.h"                    // for NS_ASSERTION
+#include "nsPoint.h"                    // for nsIntPoint
+#include "nsRect.h"                     // for nsIntRect
+#include "nsSize.h"                     // for nsIntSize
+#include "nscore.h"                     // for nsACString
+class gfxContext;
+namespace mozilla {
+namespace layers {
+class ReadbackProcessor;
+/**
+* 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() {}
+virtual ~ReadbackSink() {}
+/**
+* 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<gfxContext>
+BeginUpdate(const nsIntRect& 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(gfxContext* aContext, const nsIntRect& 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)
+{
+// 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 ThebesLayer (gfxContext would snap using the local
+// transform, then we'd snap again when compositing the ThebesLayer).
+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 = aSink;
+}
+ReadbackSink* GetSink() { return mSink; }
+/**
+* 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 nsIntSize& aSize)
+{
+NS_ASSERTION(!mSink, "Should have no sink while changing size!");
+mSize = aSize;
+}
+const nsIntSize& GetSize() { return mSize; }
+nsIntRect GetRect() { return nsIntRect(nsIntPoint(0, 0), mSize); }
+bool IsBackgroundKnown()
+{
+return mBackgroundLayer || mBackgroundColor.a == 1.0;
+}
+void NotifyRemoved() {
+SetUnknown();
+mSink = nullptr;
+}
+void NotifyThebesLayerRemoved(ThebesLayer* 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 = gfxRGBA(0,0,0,0);
+}
+}
+protected:
+friend class ReadbackProcessor;
+ReadbackLayer(LayerManager* aManager, void* aImplData) :
+Layer(aManager, aImplData),
+mSequenceCounter(0),
+mSize(0,0),
+mBackgroundLayer(nullptr),
+mBackgroundLayerOffset(0, 0),
+mBackgroundColor(gfxRGBA(0,0,0,0))
+{}
+// Print interesting information about this into aTo.  Internally
+// used to implement Dump*() and Log*().
+virtual nsACString& PrintInfo(nsACString& aTo, const char* aPrefix);
+uint64_t mSequenceCounter;
+nsAutoPtr<ReadbackSink> mSink;
+nsIntSize mSize;
+// This can refer to any (earlier) sibling ThebesLayer. That ThebesLayer
+// must have mUsedForReadback set on it. If the ThebesLayer is removed
+// for the container, this will be set to null by NotifyThebesLayerRemoved.
+// This ThebesLayer contains the contents which have previously been reported
+// to mSink. The ThebesLayer had only an integer translation transform,
+// and it covered the entire readback area. This layer also had only an
+// integer translation transform.
+ThebesLayer* 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.
+gfxRGBA      mBackgroundColor;
+};
+}
+}
+#endif /* GFX_READBACKLAYER_H */

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comparison: gfx/layers/ReadbackLayer.h

gfx/layers/ReadbackLayer.h