1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/layers/ReadbackLayer.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,201 @@
1.4 +/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
1.5 + * This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef GFX_READBACKLAYER_H
1.10 +#define GFX_READBACKLAYER_H
1.11 +
1.12 +#include <stdint.h> // for uint64_t
1.13 +#include "Layers.h" // for Layer, etc
1.14 +#include "gfxColor.h" // for gfxRGBA
1.15 +#include "gfxRect.h" // for gfxRect
1.16 +#include "mozilla/mozalloc.h" // for operator delete
1.17 +#include "nsAutoPtr.h" // for nsAutoPtr
1.18 +#include "nsCOMPtr.h" // for already_AddRefed
1.19 +#include "nsDebug.h" // for NS_ASSERTION
1.20 +#include "nsPoint.h" // for nsIntPoint
1.21 +#include "nsRect.h" // for nsIntRect
1.22 +#include "nsSize.h" // for nsIntSize
1.23 +#include "nscore.h" // for nsACString
1.24 +
1.25 +class gfxContext;
1.26 +
1.27 +namespace mozilla {
1.28 +namespace layers {
1.29 +
1.30 +class ReadbackProcessor;
1.31 +
1.32 +/**
1.33 + * A ReadbackSink receives a stream of updates to a rectangle of pixels.
1.34 + * These update callbacks are always called on the main thread, either during
1.35 + * EndTransaction or from the event loop.
1.36 + */
1.37 +class ReadbackSink {
1.38 +public:
1.39 + ReadbackSink() {}
1.40 + virtual ~ReadbackSink() {}
1.41 +
1.42 + /**
1.43 + * Sends an update to indicate that the background is currently unknown.
1.44 + */
1.45 + virtual void SetUnknown(uint64_t aSequenceNumber) = 0;
1.46 + /**
1.47 + * Called by the layer system to indicate that the contents of part of
1.48 + * the readback area are changing.
1.49 + * @param aRect is the rectangle of content that is being updated,
1.50 + * in the coordinate system of the ReadbackLayer.
1.51 + * @param aSequenceNumber updates issued out of order should be ignored.
1.52 + * Only use updates whose sequence counter is greater than all other updates
1.53 + * seen so far. Return null when a non-fresh sequence value is given.
1.54 + * @return a context into which the update should be drawn. This should be
1.55 + * set up to clip to aRect. Zero should never be passed as a sequence number.
1.56 + * If this returns null, EndUpdate should NOT be called. If it returns
1.57 + * non-null, EndUpdate must be called.
1.58 + *
1.59 + * We don't support partially unknown backgrounds. Therefore, the
1.60 + * first BeginUpdate after a SetUnknown will have the complete background.
1.61 + */
1.62 + virtual already_AddRefed<gfxContext>
1.63 + BeginUpdate(const nsIntRect& aRect, uint64_t aSequenceNumber) = 0;
1.64 + /**
1.65 + * EndUpdate must be called immediately after BeginUpdate, without returning
1.66 + * to the event loop.
1.67 + * @param aContext the context returned by BeginUpdate
1.68 + * Implicitly Restore()s the state of aContext.
1.69 + */
1.70 + virtual void EndUpdate(gfxContext* aContext, const nsIntRect& aRect) = 0;
1.71 +};
1.72 +
1.73 +/**
1.74 + * A ReadbackLayer never renders anything. It enables clients to extract
1.75 + * the rendered contents of the layer tree below the ReadbackLayer.
1.76 + * The rendered contents are delivered asynchronously via calls to a
1.77 + * ReadbackSink object supplied by the client.
1.78 + *
1.79 + * This is a "best effort" API; it is possible for the layer system to tell
1.80 + * the ReadbackSink that the contents of the readback area are unknown.
1.81 + *
1.82 + * This API exists to work around the limitations of transparent windowless
1.83 + * plugin rendering APIs. It should not be used for anything else.
1.84 + */
1.85 +class ReadbackLayer : public Layer {
1.86 +public:
1.87 + MOZ_LAYER_DECL_NAME("ReadbackLayer", TYPE_READBACK)
1.88 +
1.89 + virtual void ComputeEffectiveTransforms(const gfx::Matrix4x4& aTransformToSurface)
1.90 + {
1.91 + // Snap our local transform first, and snap the inherited transform as well.
1.92 + // This makes our snapping equivalent to what would happen if our content
1.93 + // was drawn into a ThebesLayer (gfxContext would snap using the local
1.94 + // transform, then we'd snap again when compositing the ThebesLayer).
1.95 + mEffectiveTransform =
1.96 + SnapTransform(GetLocalTransform(), gfxRect(0, 0, mSize.width, mSize.height),
1.97 + nullptr)*
1.98 + SnapTransformTranslation(aTransformToSurface, nullptr);
1.99 + }
1.100 +
1.101 + /**
1.102 + * CONSTRUCTION PHASE ONLY
1.103 + * Set the callback object to which readback updates will be delivered.
1.104 + * This also resets the "needed rectangle" so that on the next layer tree
1.105 + * transaction we will try to deliver the full contents of the readback
1.106 + * area to the sink.
1.107 + * This layer takes ownership of the sink. It will be deleted when the
1.108 + * layer is destroyed or when a new sink is set.
1.109 + * Initially the contents of the readback area are completely unknown.
1.110 + */
1.111 + void SetSink(ReadbackSink* aSink)
1.112 + {
1.113 + SetUnknown();
1.114 + mSink = aSink;
1.115 + }
1.116 + ReadbackSink* GetSink() { return mSink; }
1.117 +
1.118 + /**
1.119 + * CONSTRUCTION PHASE ONLY
1.120 + * Set the size of content that should be read back. The readback area
1.121 + * has its top-left at 0,0 and has size aSize.
1.122 + * Can only be called while the sink is null!
1.123 + */
1.124 + void SetSize(const nsIntSize& aSize)
1.125 + {
1.126 + NS_ASSERTION(!mSink, "Should have no sink while changing size!");
1.127 + mSize = aSize;
1.128 + }
1.129 + const nsIntSize& GetSize() { return mSize; }
1.130 + nsIntRect GetRect() { return nsIntRect(nsIntPoint(0, 0), mSize); }
1.131 +
1.132 + bool IsBackgroundKnown()
1.133 + {
1.134 + return mBackgroundLayer || mBackgroundColor.a == 1.0;
1.135 + }
1.136 +
1.137 + void NotifyRemoved() {
1.138 + SetUnknown();
1.139 + mSink = nullptr;
1.140 + }
1.141 +
1.142 + void NotifyThebesLayerRemoved(ThebesLayer* aLayer)
1.143 + {
1.144 + if (mBackgroundLayer == aLayer) {
1.145 + mBackgroundLayer = nullptr;
1.146 + }
1.147 + }
1.148 +
1.149 + const nsIntPoint& GetBackgroundLayerOffset() { return mBackgroundLayerOffset; }
1.150 +
1.151 + uint64_t AllocateSequenceNumber() { return ++mSequenceCounter; }
1.152 +
1.153 + void SetUnknown()
1.154 + {
1.155 + if (IsBackgroundKnown()) {
1.156 + if (mSink) {
1.157 + mSink->SetUnknown(AllocateSequenceNumber());
1.158 + }
1.159 + mBackgroundLayer = nullptr;
1.160 + mBackgroundColor = gfxRGBA(0,0,0,0);
1.161 + }
1.162 + }
1.163 +
1.164 +protected:
1.165 + friend class ReadbackProcessor;
1.166 +
1.167 + ReadbackLayer(LayerManager* aManager, void* aImplData) :
1.168 + Layer(aManager, aImplData),
1.169 + mSequenceCounter(0),
1.170 + mSize(0,0),
1.171 + mBackgroundLayer(nullptr),
1.172 + mBackgroundLayerOffset(0, 0),
1.173 + mBackgroundColor(gfxRGBA(0,0,0,0))
1.174 + {}
1.175 +
1.176 + // Print interesting information about this into aTo. Internally
1.177 + // used to implement Dump*() and Log*().
1.178 + virtual nsACString& PrintInfo(nsACString& aTo, const char* aPrefix);
1.179 +
1.180 + uint64_t mSequenceCounter;
1.181 + nsAutoPtr<ReadbackSink> mSink;
1.182 + nsIntSize mSize;
1.183 +
1.184 + // This can refer to any (earlier) sibling ThebesLayer. That ThebesLayer
1.185 + // must have mUsedForReadback set on it. If the ThebesLayer is removed
1.186 + // for the container, this will be set to null by NotifyThebesLayerRemoved.
1.187 + // This ThebesLayer contains the contents which have previously been reported
1.188 + // to mSink. The ThebesLayer had only an integer translation transform,
1.189 + // and it covered the entire readback area. This layer also had only an
1.190 + // integer translation transform.
1.191 + ThebesLayer* mBackgroundLayer;
1.192 + // When mBackgroundLayer is non-null, this is the offset to add to
1.193 + // convert from the coordinates of mBackgroundLayer to the coordinates
1.194 + // of this layer.
1.195 + nsIntPoint mBackgroundLayerOffset;
1.196 + // When mBackgroundColor is opaque, this is the color of the ColorLayer
1.197 + // that contained the contents we reported to mSink, which covered the
1.198 + // entire readback area.
1.199 + gfxRGBA mBackgroundColor;
1.200 +};
1.201 +
1.202 +}
1.203 +}
1.204 +#endif /* GFX_READBACKLAYER_H */
