The Tor Browser: gfx/layers/ReadbackLayer.h@97036ab72558 (annotated)

gfx/layers/ReadbackLayer.h@97036ab72558 (annotated)

gfx/layers/ReadbackLayer.h

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- 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 */

The Tor Browser / annotate

gfx/layers/ReadbackLayer.h@97036ab72558 (annotated)

gfx/layers/ReadbackLayer.h