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

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

gfx/layers/RotatedBuffer.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 ROTATEDBUFFER_H_
 #define ROTATEDBUFFER_H_
 #include "gfxTypes.h"
 #include <stdint.h>                     // for uint32_t
 #include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc
 #include "mozilla/RefPtr.h"             // for RefPtr, TemporaryRef
 #include "mozilla/gfx/2D.h"             // for DrawTarget, etc
 #include "mozilla/mozalloc.h"           // for operator delete
 #include "nsAutoPtr.h"                  // for nsRefPtr
 #include "nsCOMPtr.h"                   // for already_AddRefed
 #include "nsDebug.h"                    // for NS_RUNTIMEABORT
 #include "nsISupportsImpl.h"            // for MOZ_COUNT_CTOR, etc
 #include "nsPoint.h"                    // for nsIntPoint
 #include "nsRect.h"                     // for nsIntRect
 #include "nsRegion.h"                   // for nsIntRegion
 #include "LayersTypes.h"
 struct nsIntSize;
 namespace mozilla {
 namespace gfx {
 class Matrix;
 }
 namespace layers {
 class TextureClient;
 class ThebesLayer;
 /**
  * This is a cairo/Thebes surface, but with a literal twist. Scrolling
  * causes the layer's visible region to move. We want to keep
  * reusing the same surface if the region size hasn't changed, but we don't
  * want to keep moving the contents of the surface around in memory. So
  * we use a trick.
  * Consider just the vertical case, and suppose the buffer is H pixels
  * high and we're scrolling down by N pixels. Instead of copying the
  * buffer contents up by N pixels, we leave the buffer contents in place,
  * and paint content rows H to H+N-1 into rows 0 to N-1 of the buffer.
  * Then we can refresh the screen by painting rows N to H-1 of the buffer
  * at row 0 on the screen, and then painting rows 0 to N-1 of the buffer
  * at row H-N on the screen.
  * mBufferRotation.y would be N in this example.
  */
 class RotatedBuffer {
 public:
   typedef gfxContentType ContentType;
   RotatedBuffer(gfx::DrawTarget* aDTBuffer, gfx::DrawTarget* aDTBufferOnWhite,
                 const nsIntRect& aBufferRect,
                 const nsIntPoint& aBufferRotation)
     : mDTBuffer(aDTBuffer)
     , mDTBufferOnWhite(aDTBufferOnWhite)
     , mBufferRect(aBufferRect)
     , mBufferRotation(aBufferRotation)
     , mDidSelfCopy(false)
   { }
   RotatedBuffer()
     : mDidSelfCopy(false)
   { }
   /*
    * Which buffer should be drawn to/read from.
    */
   enum ContextSource {
     BUFFER_BLACK, // The normal buffer, or buffer with black background when using component alpha.
     BUFFER_WHITE, // The buffer with white background, only valid with component alpha.
     BUFFER_BOTH // The combined black/white buffers, only valid for writing operations, not reading.
   };
   // It is the callers repsonsibility to ensure aTarget is flushed after calling
   // this method.
   void DrawBufferWithRotation(gfx::DrawTarget* aTarget, ContextSource aSource,
                               float aOpacity = 1.0,
                               gfx::CompositionOp aOperator = gfx::CompositionOp::OP_OVER,
                               gfx::SourceSurface* aMask = nullptr,
                               const gfx::Matrix* aMaskTransform = nullptr) const;
   /**
    * |BufferRect()| is the rect of device pixels that this
    * RotatedBuffer covers.  That is what DrawBufferWithRotation()
    * will paint when it's called.
    */
   const nsIntRect& BufferRect() const { return mBufferRect; }
   const nsIntPoint& BufferRotation() const { return mBufferRotation; }
   virtual bool HaveBuffer() const { return mDTBuffer; }
   virtual bool HaveBufferOnWhite() const { return mDTBufferOnWhite; }
 protected:
   enum XSide {
     LEFT, RIGHT
   };
   enum YSide {
     TOP, BOTTOM
   };
   nsIntRect GetQuadrantRectangle(XSide aXSide, YSide aYSide) const;
   gfx::Rect GetSourceRectangle(XSide aXSide, YSide aYSide) const;
   /*
    * If aMask is non-null, then it is used as an alpha mask for rendering this
    * buffer. aMaskTransform must be non-null if aMask is non-null, and is used
    * to adjust the coordinate space of the mask.
    */
   void DrawBufferQuadrant(gfx::DrawTarget* aTarget, XSide aXSide, YSide aYSide,
                           ContextSource aSource,
                           float aOpacity,
                           gfx::CompositionOp aOperator,
                           gfx::SourceSurface* aMask,
                           const gfx::Matrix* aMaskTransform) const;
   RefPtr<gfx::DrawTarget> mDTBuffer;
   RefPtr<gfx::DrawTarget> mDTBufferOnWhite;
   /** The area of the ThebesLayer that is covered by the buffer as a whole */
   nsIntRect             mBufferRect;
   /**
    * The x and y rotation of the buffer. Conceptually the buffer
    * has its origin translated to mBufferRect.TopLeft() - mBufferRotation,
    * is tiled to fill the plane, and the result is clipped to mBufferRect.
    * So the pixel at mBufferRotation within the buffer is what gets painted at
    * mBufferRect.TopLeft().
    * This is "rotation" in the sense of rotating items in a linear buffer,
    * where items falling off the end of the buffer are returned to the
    * buffer at the other end, not 2D rotation!
    */
   nsIntPoint            mBufferRotation;
   // When this is true it means that all pixels have moved inside the buffer.
   // It's not possible to sync with another buffer without a full copy.
   bool                  mDidSelfCopy;
 };
 // Mixin class for classes which need logic for loaning out a draw target.
 // See comments on BorrowDrawTargetForQuadrantUpdate.
 class BorrowDrawTarget
 {
 protected:
   void ReturnDrawTarget(gfx::DrawTarget*& aReturned);
   // The draw target loaned by BorrowDrawTargetForQuadrantUpdate. It should not
   // be used, we just keep a reference to ensure it is kept alive and so we can
   // correctly restore state when it is returned.
   RefPtr<gfx::DrawTarget> mLoanedDrawTarget;
   gfx::Matrix mLoanedTransform;
 };
 /**
  * This class encapsulates the buffer used to retain ThebesLayer contents,
  * i.e., the contents of the layer's GetVisibleRegion().
  */
 class RotatedContentBuffer : public RotatedBuffer
                            , public BorrowDrawTarget
 {
 public:
   typedef gfxContentType ContentType;
   /**
    * Controls the size of the backing buffer of this.
    * - SizedToVisibleBounds: the backing buffer is exactly the same
    *   size as the bounds of ThebesLayer's visible region
    * - ContainsVisibleBounds: the backing buffer is large enough to
    *   fit visible bounds.  May be larger.
    */
   enum BufferSizePolicy {
     SizedToVisibleBounds,
     ContainsVisibleBounds
   };
   RotatedContentBuffer(BufferSizePolicy aBufferSizePolicy)
     : mBufferProvider(nullptr)
     , mBufferProviderOnWhite(nullptr)
     , mBufferSizePolicy(aBufferSizePolicy)
   {
     MOZ_COUNT_CTOR(RotatedContentBuffer);
   }
   virtual ~RotatedContentBuffer()
   {
     MOZ_COUNT_DTOR(RotatedContentBuffer);
   }
   /**
    * Wipe out all retained contents. Call this when the entire
    * buffer becomes invalid.
    */
   void Clear()
   {
     mDTBuffer = nullptr;
     mDTBufferOnWhite = nullptr;
     mBufferProvider = nullptr;
     mBufferProviderOnWhite = nullptr;
     mBufferRect.SetEmpty();
   }
   /**
    * This is returned by BeginPaint. The caller should draw into mTarget.
    * mRegionToDraw must be drawn. mRegionToInvalidate has been invalidated
    * by RotatedContentBuffer and must be redrawn on the screen.
    * mRegionToInvalidate is set when the buffer has changed from
    * opaque to transparent or vice versa, since the details of rendering can
    * depend on the buffer type.  mDidSelfCopy is true if we kept our buffer
    * but used MovePixels() to shift its content.
    */
   struct PaintState {
     PaintState()
       : mMode(SurfaceMode::SURFACE_NONE)
       , mContentType(gfxContentType::SENTINEL)
       , mDidSelfCopy(false)
     {}
     nsIntRegion mRegionToDraw;
     nsIntRegion mRegionToInvalidate;
     SurfaceMode mMode;
     DrawRegionClip mClip;
     ContentType mContentType;
     bool mDidSelfCopy;
   };
   enum {
     PAINT_WILL_RESAMPLE = 0x01,
     PAINT_NO_ROTATION = 0x02,
     PAINT_CAN_DRAW_ROTATED = 0x04
   };
   /**
    * Start a drawing operation. This returns a PaintState describing what
    * needs to be drawn to bring the buffer up to date in the visible region.
    * This queries aLayer to get the currently valid and visible regions.
    * The returned mTarget may be null if mRegionToDraw is empty.
    * Otherwise it must not be null.
    * mRegionToInvalidate will contain mRegionToDraw.
    * @param aFlags when PAINT_WILL_RESAMPLE is passed, this indicates that
    * buffer will be resampled when rendering (i.e the effective transform
    * combined with the scale for the resolution is not just an integer
    * translation). This will disable buffer rotation (since we don't want
    * to resample across the rotation boundary) and will ensure that we
    * make the entire buffer contents valid (since we don't want to sample
    * invalid pixels outside the visible region, if the visible region doesn't
    * fill the buffer bounds).
    * PAINT_CAN_DRAW_ROTATED can be passed if the caller supports drawing
    * rotated content that crosses the physical buffer boundary. The caller
    * will need to call BorrowDrawTargetForPainting multiple times to achieve
    * this.
    */
   PaintState BeginPaint(ThebesLayer* aLayer,
                         uint32_t aFlags);
   struct DrawIterator {
     friend class RotatedContentBuffer;
     friend class ContentClientIncremental;
     DrawIterator()
       : mCount(0)
     {}
     nsIntRegion mDrawRegion;
   private:
     uint32_t mCount;
   };
   /**
    * Fetch a DrawTarget for rendering. The DrawTarget remains owned by
    * this. See notes on BorrowDrawTargetForQuadrantUpdate.
    * May return null. If the return value is non-null, it must be
    * 'un-borrowed' using ReturnDrawTarget.
    *
    * If PAINT_CAN_DRAW_ROTATED was specified for BeginPaint, then the caller
    * must call this function repeatedly (with an iterator) until it returns
    * nullptr. The caller should draw the mDrawRegion of the iterator instead
    * of mRegionToDraw in the PaintState.
    *
    * @param aPaintState Paint state data returned by a call to BeginPaint
    * @param aIter Paint state iterator. Only required if PAINT_CAN_DRAW_ROTATED
    * was specified to BeginPaint.
    */
   gfx::DrawTarget* BorrowDrawTargetForPainting(const PaintState& aPaintState,
                                                DrawIterator* aIter = nullptr);
   enum {
     ALLOW_REPEAT = 0x01,
     BUFFER_COMPONENT_ALPHA = 0x02 // Dual buffers should be created for drawing with
                                   // component alpha.
   };
   /**
    * Return a new surface of |aSize| and |aType|.
    * @param aFlags if ALLOW_REPEAT is set, then the buffer should be configured
    * to allow repeat-mode, otherwise it should be in pad (clamp) mode
    * If the created buffer supports azure content, then the result(s) will
    * be returned in aBlackDT/aWhiteDT, otherwise aBlackSurface/aWhiteSurface
    * will be used.
    */
   virtual void
   CreateBuffer(ContentType aType, const nsIntRect& aRect, uint32_t aFlags,
                RefPtr<gfx::DrawTarget>* aBlackDT, RefPtr<gfx::DrawTarget>* aWhiteDT) = 0;
   /**
    * Get the underlying buffer, if any. This is useful because we can pass
    * in the buffer as the default "reference surface" if there is one.
    * Don't use it for anything else!
    */
   gfx::DrawTarget* GetDTBuffer() { return mDTBuffer; }
   gfx::DrawTarget* GetDTBufferOnWhite() { return mDTBufferOnWhite; }
   /**
    * Complete the drawing operation. The region to draw must have been
    * drawn before this is called. The contents of the buffer are drawn
    * to aTarget.
    */
   void DrawTo(ThebesLayer* aLayer,
               gfx::DrawTarget* aTarget,
               float aOpacity,
               gfx::CompositionOp aOp,
               gfx::SourceSurface* aMask,
               const gfx::Matrix* aMaskTransform);
 protected:
   // new texture client versions
   void SetBufferProvider(TextureClient* aClient)
   {
     // Only this buffer provider can give us a buffer.  If we
     // already have one, something has gone wrong.
     MOZ_ASSERT(!aClient || !mDTBuffer);
     mBufferProvider = aClient;
     if (!mBufferProvider) {
       mDTBuffer = nullptr;
     }
   }
   void SetBufferProviderOnWhite(TextureClient* aClient)
   {
     // Only this buffer provider can give us a buffer.  If we
     // already have one, something has gone wrong.
     MOZ_ASSERT(!aClient || !mDTBufferOnWhite);
     mBufferProviderOnWhite = aClient;
     if (!mBufferProviderOnWhite) {
       mDTBufferOnWhite = nullptr;
     }
   }
   /**
    * Get a draw target at the specified resolution for updating |aBounds|,
    * which must be contained within a single quadrant.
    *
    * The result should only be held temporarily by the caller (it will be kept
    * alive by this). Once used it should be returned using ReturnDrawTarget.
    * BorrowDrawTargetForQuadrantUpdate may not be called more than once without
    * first calling ReturnDrawTarget.
    *
    * ReturnDrawTarget will restore the transform on the draw target. But it is
    * the callers responsibility to restore the clip. The caller should flush the
    * draw target, if necessary.
    */
   gfx::DrawTarget*
   BorrowDrawTargetForQuadrantUpdate(const nsIntRect& aBounds,
                                     ContextSource aSource,
                                     DrawIterator* aIter);
   static bool IsClippingCheap(gfx::DrawTarget* aTarget, const nsIntRegion& aRegion);
 protected:
   /**
    * Return the buffer's content type.  Requires a valid buffer or
    * buffer provider.
    */
   gfxContentType BufferContentType();
   bool BufferSizeOkFor(const nsIntSize& aSize);
   /**
    * If the buffer hasn't been mapped, map it.
    */
   bool EnsureBuffer();
   bool EnsureBufferOnWhite();
   // Flush our buffers if they are mapped.
   void FlushBuffers();
   /**
    * True if we have a buffer where we can get it (but not necessarily
    * mapped currently).
    */
   virtual bool HaveBuffer() const;
   virtual bool HaveBufferOnWhite() const;
   /**
    * Any actions that should be performed at the last moment before we begin
    * rendering the next frame. I.e., after we calculate what we will draw,
    * but before we rotate the buffer and possibly create new buffers.
    * aRegionToDraw is the region which is guaranteed to be overwritten when
    * drawing the next frame.
    */
   virtual void FinalizeFrame(const nsIntRegion& aRegionToDraw) {}
   /**
    * These members are only set transiently.  They're used to map mDTBuffer
    * when we're using surfaces that require explicit map/unmap. Only one
    * may be used at a time.
    */
   TextureClient* mBufferProvider;
   TextureClient* mBufferProviderOnWhite;
   BufferSizePolicy      mBufferSizePolicy;
 };
 }
 }
 #endif /* ROTATEDBUFFER_H_ */

The Tor Browser / annotate

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

gfx/layers/RotatedBuffer.h