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

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

gfx/layers/TiledLayerBuffer.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.

 /* 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_TILEDLAYERBUFFER_H
 #define GFX_TILEDLAYERBUFFER_H
 // Debug defines
 //#define GFX_TILEDLAYER_DEBUG_OVERLAY
 //#define GFX_TILEDLAYER_PREF_WARNINGS
 #include <stdint.h>                     // for uint16_t, uint32_t
 #include <sys/types.h>                  // for int32_t
 #include "gfxPrefs.h"                   // for gfxPrefs::LayersTileWidth/Height
 #include "nsDebug.h"                    // for NS_ABORT_IF_FALSE
 #include "nsPoint.h"                    // for nsIntPoint
 #include "nsRect.h"                     // for nsIntRect
 #include "nsRegion.h"                   // for nsIntRegion
 #include "nsTArray.h"                   // for nsTArray
 #if defined(MOZ_WIDGET_GONK) && ANDROID_VERSION >= 17
 #include <ui/Fence.h>
 #endif
 namespace mozilla {
 namespace layers {
 // An abstract implementation of a tile buffer. This code covers the logic of
 // moving and reusing tiles and leaves the validation up to the implementor. To
 // avoid the overhead of virtual dispatch, we employ the curiously recurring
 // template pattern.
 //
 // Tiles are aligned to a grid with one of the grid points at (0,0) and other
 // grid points spaced evenly in the x- and y-directions by GetTileSize()
 // multiplied by mResolution. GetScaledTileSize() provides convenience for
 // accessing these values.
 //
 // This tile buffer stores a valid region, which defines the areas that have
 // up-to-date content. The contents of tiles within this region will be reused
 // from paint to paint. It also stores the region that was modified in the last
 // paint operation; this is useful when one tiled layer buffer shadows another
 // (as in an off-main-thread-compositing scenario), so that the shadow tiled
 // layer buffer can correctly reflect the updates of the master layer buffer.
 //
 // The associated Tile may be of any type as long as the derived class can
 // validate and return tiles of that type. Tiles will be frequently copied, so
 // the tile type should be a reference or some other type with an efficient
 // copy constructor.
 //
 // It is required that the derived class specify the base class as a friend. It
 // must also implement the following public method:
 //
 //   Tile GetPlaceholderTile() const;
 //
 //   Returns a temporary placeholder tile used as a marker. This placeholder tile
 //   must never be returned by validateTile and must be == to every instance
 //   of a placeholder tile.
 //
 // Additionally, it must implement the following protected methods:
 //
 //   Tile ValidateTile(Tile aTile, const nsIntPoint& aTileOrigin,
 //                     const nsIntRegion& aDirtyRect);
 //
 //   Validates the dirtyRect. The returned Tile will replace the tile.
 //
 //   void ReleaseTile(Tile aTile);
 //
 //   Destroys the given tile.
 //
 //   void SwapTiles(Tile& aTileA, Tile& aTileB);
 //
 //   Swaps two tiles.
 //
 // The contents of the tile buffer will be rendered at the resolution specified
 // in mResolution, which can be altered with SetResolution. The resolution
 // should always be a factor of the tile length, to avoid tiles covering
 // non-integer amounts of pixels.
 template<typename Derived, typename Tile>
 class TiledLayerBuffer
 {
 public:
   TiledLayerBuffer()
     : mRetainedWidth(0)
     , mRetainedHeight(0)
     , mResolution(1)
     , mTileSize(gfxPrefs::LayersTileWidth(), gfxPrefs::LayersTileHeight())
   {}
   ~TiledLayerBuffer() {}
   // Given a tile origin aligned to a multiple of GetScaledTileSize,
   // return the tile that describes that region.
   // NOTE: To get the valid area of that tile you must intersect
   //       (aTileOrigin.x, aTileOrigin.y,
   //        GetScaledTileSize().width, GetScaledTileSize().height)
   //       and GetValidRegion() to get the area of the tile that is valid.
   Tile GetTile(const nsIntPoint& aTileOrigin) const;
   // Given a tile x, y relative to the top left of the layer, this function
   // will return the tile for
   // (x*GetScaledTileSize().width, y*GetScaledTileSize().height,
   //  GetScaledTileSize().width, GetScaledTileSize().height)
   Tile GetTile(int x, int y) const;
   // This operates the same as GetTile(aTileOrigin), but will also replace the
   // specified tile with the placeholder tile. This does not call ReleaseTile
   // on the removed tile.
   bool RemoveTile(const nsIntPoint& aTileOrigin, Tile& aRemovedTile);
   // This operates the same as GetTile(x, y), but will also replace the
   // specified tile with the placeholder tile. This does not call ReleaseTile
   // on the removed tile.
   bool RemoveTile(int x, int y, Tile& aRemovedTile);
   const gfx::IntSize& GetTileSize() const { return mTileSize; }
   gfx::IntSize GetScaledTileSize() const { return RoundedToInt(gfx::Size(mTileSize) / mResolution); }
   unsigned int GetTileCount() const { return mRetainedTiles.Length(); }
   const nsIntRegion& GetValidRegion() const { return mValidRegion; }
   const nsIntRegion& GetPaintedRegion() const { return mPaintedRegion; }
   void ClearPaintedRegion() { mPaintedRegion.SetEmpty(); }
   // Given a position i, this function returns the position inside the current tile.
   int GetTileStart(int i, int aTileLength) const {
     return (i >= 0) ? (i % aTileLength)
                     : ((aTileLength - (-i % aTileLength)) %
                        aTileLength);
   }
   // Rounds the given coordinate down to the nearest tile boundary.
   int RoundDownToTileEdge(int aX, int aTileLength) const { return aX - GetTileStart(aX, aTileLength); }
   // Get and set draw scaling. mResolution affects the resolution at which the
   // contents of the buffer are drawn. mResolution has no effect on the
   // coordinate space of the valid region, but does affect the size of an
   // individual tile's rect in relation to the valid region.
   // Setting the resolution will invalidate the buffer.
   float GetResolution() const { return mResolution; }
   void SetResolution(float aResolution) {
     if (mResolution == aResolution) {
       return;
     }
     Update(nsIntRegion(), nsIntRegion());
     mResolution = aResolution;
   }
   bool IsLowPrecision() const { return mResolution < 1; }
   typedef Tile* Iterator;
   Iterator TilesBegin() { return mRetainedTiles.Elements(); }
   Iterator TilesEnd() { return mRetainedTiles.Elements() + mRetainedTiles.Length(); }
 protected:
   // The implementor should call Update() to change
   // the new valid region. This implementation will call
   // validateTile on each tile that is dirty, which is left
   // to the implementor.
   void Update(const nsIntRegion& aNewValidRegion, const nsIntRegion& aPaintRegion);
   nsIntRegion     mValidRegion;
   nsIntRegion     mPaintedRegion;
   /**
    * mRetainedTiles is a rectangular buffer of mRetainedWidth x mRetainedHeight
    * stored as column major with the same origin as mValidRegion.GetBounds().
    * Any tile that does not intersect mValidRegion is a PlaceholderTile.
    * Only the region intersecting with mValidRegion should be read from a tile,
    * another other region is assumed to be uninitialized. The contents of the
    * tiles is scaled by mResolution.
    */
   nsTArray<Tile>  mRetainedTiles;
   int             mRetainedWidth;  // in tiles
   int             mRetainedHeight; // in tiles
   float           mResolution;
   gfx::IntSize    mTileSize;
 private:
   const Derived& AsDerived() const { return *static_cast<const Derived*>(this); }
   Derived& AsDerived() { return *static_cast<Derived*>(this); }
   bool IsPlaceholder(Tile aTile) const { return aTile == AsDerived().GetPlaceholderTile(); }
 };
 class ClientTiledLayerBuffer;
 class SurfaceDescriptorTiles;
 class ISurfaceAllocator;
 // Shadow layers may implement this interface in order to be notified when a
 // tiled layer buffer is updated.
 class TiledLayerComposer
 {
 public:
   /**
    * Update the current retained layer with the updated layer data.
    * It is expected that the tiles described by aTiledDescriptor are all in the
    * ReadLock state, so that the locks can be adopted when recreating a
    * ClientTiledLayerBuffer locally. This lock will be retained until the buffer
    * has completed uploading.
    */
   virtual void UseTiledLayerBuffer(ISurfaceAllocator* aAllocator,
                                    const SurfaceDescriptorTiles& aTiledDescriptor) = 0;
   /**
    * If some part of the buffer is being rendered at a lower precision, this
    * returns that region. If it is not, an empty region will be returned.
    */
   virtual const nsIntRegion& GetValidLowPrecisionRegion() const = 0;
 #if defined(MOZ_WIDGET_GONK) && ANDROID_VERSION >= 17
   /**
    * Store a fence that will signal when the current buffer is no longer being read.
    * Similar to android's GLConsumer::setReleaseFence()
    */
   virtual void SetReleaseFence(const android::sp<android::Fence>& aReleaseFence) = 0;
 #endif
 };
 // Normal integer division truncates towards zero,
 // we instead want to floor to hangle negative numbers.
 static inline int floor_div(int a, int b)
 {
   int rem = a % b;
   int div = a/b;
   if (rem == 0) {
     return div;
   } else {
     // If the signs are different substract 1.
     int sub;
     sub = a ^ b;
     // The results of this shift is either 0 or -1.
     sub >>= 8*sizeof(int)-1;
     return div+sub;
   }
 }
 template<typename Derived, typename Tile> Tile
 TiledLayerBuffer<Derived, Tile>::GetTile(const nsIntPoint& aTileOrigin) const
 {
   // TODO Cache firstTileOriginX/firstTileOriginY
   // Find the tile x/y of the first tile and the target tile relative to the (0, 0)
   // origin, the difference is the tile x/y relative to the start of the tile buffer.
   gfx::IntSize scaledTileSize = GetScaledTileSize();
   int firstTileX = floor_div(mValidRegion.GetBounds().x, scaledTileSize.width);
   int firstTileY = floor_div(mValidRegion.GetBounds().y, scaledTileSize.height);
   return GetTile(floor_div(aTileOrigin.x, scaledTileSize.width) - firstTileX,
                  floor_div(aTileOrigin.y, scaledTileSize.height) - firstTileY);
 }
 template<typename Derived, typename Tile> Tile
 TiledLayerBuffer<Derived, Tile>::GetTile(int x, int y) const
 {
   int index = x * mRetainedHeight + y;
   return mRetainedTiles.SafeElementAt(index, AsDerived().GetPlaceholderTile());
 }
 template<typename Derived, typename Tile> bool
 TiledLayerBuffer<Derived, Tile>::RemoveTile(const nsIntPoint& aTileOrigin,
                                             Tile& aRemovedTile)
 {
   gfx::IntSize scaledTileSize = GetScaledTileSize();
   int firstTileX = floor_div(mValidRegion.GetBounds().x, scaledTileSize.width);
   int firstTileY = floor_div(mValidRegion.GetBounds().y, scaledTileSize.height);
   return RemoveTile(floor_div(aTileOrigin.x, scaledTileSize.width) - firstTileX,
                     floor_div(aTileOrigin.y, scaledTileSize.height) - firstTileY,
                     aRemovedTile);
 }
 template<typename Derived, typename Tile> bool
 TiledLayerBuffer<Derived, Tile>::RemoveTile(int x, int y, Tile& aRemovedTile)
 {
   int index = x * mRetainedHeight + y;
   const Tile& tileToRemove = mRetainedTiles.SafeElementAt(index, AsDerived().GetPlaceholderTile());
   if (!IsPlaceholder(tileToRemove)) {
     aRemovedTile = tileToRemove;
     mRetainedTiles[index] = AsDerived().GetPlaceholderTile();
     return true;
   }
   return false;
 }
 template<typename Derived, typename Tile> void
 TiledLayerBuffer<Derived, Tile>::Update(const nsIntRegion& aNewValidRegion,
                                         const nsIntRegion& aPaintRegion)
 {
   gfx::IntSize scaledTileSize = GetScaledTileSize();
   nsTArray<Tile>  newRetainedTiles;
   nsTArray<Tile>& oldRetainedTiles = mRetainedTiles;
   const nsIntRect oldBound = mValidRegion.GetBounds();
   const nsIntRect newBound = aNewValidRegion.GetBounds();
   const nsIntPoint oldBufferOrigin(RoundDownToTileEdge(oldBound.x, scaledTileSize.width),
                                    RoundDownToTileEdge(oldBound.y, scaledTileSize.height));
   const nsIntPoint newBufferOrigin(RoundDownToTileEdge(newBound.x, scaledTileSize.width),
                                    RoundDownToTileEdge(newBound.y, scaledTileSize.height));
   const nsIntRegion& oldValidRegion = mValidRegion;
   const nsIntRegion& newValidRegion = aNewValidRegion;
   const int oldRetainedHeight = mRetainedHeight;
   // Pass 1: Recycle valid content from the old buffer
   // Recycle tiles from the old buffer that contain valid regions.
   // Insert placeholders tiles if we have no valid area for that tile
   // which we will allocate in pass 2.
   // TODO: Add a tile pool to reduce new allocation
   int tileX = 0;
   int tileY = 0;
   int tilesMissing = 0;
   // Iterate over the new drawing bounds in steps of tiles.
   for (int32_t x = newBound.x; x < newBound.XMost(); tileX++) {
     // Compute tileRect(x,y,width,height) in layer space coordinate
     // giving us the rect of the tile that hits the newBounds.
     int width = scaledTileSize.width - GetTileStart(x, scaledTileSize.width);
     if (x + width > newBound.XMost()) {
       width = newBound.x + newBound.width - x;
     }
     tileY = 0;
     for (int32_t y = newBound.y; y < newBound.YMost(); tileY++) {
       int height = scaledTileSize.height - GetTileStart(y, scaledTileSize.height);
       if (y + height > newBound.y + newBound.height) {
         height = newBound.y + newBound.height - y;
       }
       const nsIntRect tileRect(x,y,width,height);
       if (oldValidRegion.Intersects(tileRect) && newValidRegion.Intersects(tileRect)) {
         // This old tiles contains some valid area so move it to the new tile
         // buffer. Replace the tile in the old buffer with a placeholder
         // to leave the old buffer index unaffected.
         int tileX = floor_div(x - oldBufferOrigin.x, scaledTileSize.width);
         int tileY = floor_div(y - oldBufferOrigin.y, scaledTileSize.height);
         int index = tileX * oldRetainedHeight + tileY;
         // The tile may have been removed, skip over it in this case.
         if (IsPlaceholder(oldRetainedTiles.
                           SafeElementAt(index, AsDerived().GetPlaceholderTile()))) {
           newRetainedTiles.AppendElement(AsDerived().GetPlaceholderTile());
         } else {
           Tile tileWithPartialValidContent = oldRetainedTiles[index];
           newRetainedTiles.AppendElement(tileWithPartialValidContent);
           oldRetainedTiles[index] = AsDerived().GetPlaceholderTile();
         }
       } else {
         // This tile is either:
         // 1) Outside the new valid region and will simply be an empty
         // placeholder forever.
         // 2) The old buffer didn't have any data for this tile. We postpone
         // the allocation of this tile after we've reused any tile with
         // valid content because then we know we can safely recycle
         // with taking from a tile that has recyclable content.
         newRetainedTiles.AppendElement(AsDerived().GetPlaceholderTile());
         if (aPaintRegion.Intersects(tileRect)) {
           tilesMissing++;
         }
       }
       y += height;
     }
     x += width;
   }
   // Keep track of the number of horizontal/vertical tiles
   // in the buffer so that we can easily look up a tile.
   mRetainedWidth = tileX;
   mRetainedHeight = tileY;
   // Pass 1.5: Release excess tiles in oldRetainedTiles
   // Tiles in oldRetainedTiles that aren't in newRetainedTiles will be recycled
   // before creating new ones, but there could still be excess unnecessary
   // tiles. As tiles may not have a fixed memory cost (for example, due to
   // double-buffering), we should release these excess tiles first.
   int oldTileCount = 0;
   for (size_t i = 0; i < oldRetainedTiles.Length(); i++) {
     Tile oldTile = oldRetainedTiles[i];
     if (IsPlaceholder(oldTile)) {
       continue;
     }
     if (oldTileCount >= tilesMissing) {
       oldRetainedTiles[i] = AsDerived().GetPlaceholderTile();
       AsDerived().ReleaseTile(oldTile);
     } else {
       oldTileCount ++;
     }
   }
   NS_ABORT_IF_FALSE(aNewValidRegion.Contains(aPaintRegion), "Painting a region outside the visible region");
 #ifdef DEBUG
   nsIntRegion oldAndPainted(oldValidRegion);
   oldAndPainted.Or(oldAndPainted, aPaintRegion);
 #endif
   NS_ABORT_IF_FALSE(oldAndPainted.Contains(newValidRegion), "newValidRegion has not been fully painted");
   nsIntRegion regionToPaint(aPaintRegion);
   // Pass 2: Validate
   // We know at this point that any tile in the new buffer that had valid content
   // from the previous buffer is placed correctly in the new buffer.
   // We know that any tile in the old buffer that isn't a place holder is
   // of no use and can be recycled.
   // We also know that any place holder tile in the new buffer must be
   // allocated.
   tileX = 0;
 #ifdef GFX_TILEDLAYER_PREF_WARNINGS
   printf_stderr("Update %i, %i, %i, %i\n", newBound.x, newBound.y, newBound.width, newBound.height);
 #endif
   for (int x = newBound.x; x < newBound.x + newBound.width; tileX++) {
     // Compute tileRect(x,y,width,height) in layer space coordinate
     // giving us the rect of the tile that hits the newBounds.
     int tileStartX = RoundDownToTileEdge(x, scaledTileSize.width);
     int width = scaledTileSize.width - GetTileStart(x, scaledTileSize.width);
     if (x + width > newBound.XMost())
       width = newBound.XMost() - x;
     tileY = 0;
     for (int y = newBound.y; y < newBound.y + newBound.height; tileY++) {
       int tileStartY = RoundDownToTileEdge(y, scaledTileSize.height);
       int height = scaledTileSize.height - GetTileStart(y, scaledTileSize.height);
       if (y + height > newBound.YMost()) {
         height = newBound.YMost() - y;
       }
       const nsIntRect tileRect(x, y, width, height);
       nsIntRegion tileDrawRegion;
       tileDrawRegion.And(tileRect, regionToPaint);
       if (tileDrawRegion.IsEmpty()) {
         // We have a tile but it doesn't hit the draw region
         // because we can reuse all of the content from the
         // previous buffer.
 #ifdef DEBUG
         int currTileX = floor_div(x - newBufferOrigin.x, scaledTileSize.width);
         int currTileY = floor_div(y - newBufferOrigin.y, scaledTileSize.height);
         int index = currTileX * mRetainedHeight + currTileY;
         NS_ABORT_IF_FALSE(!newValidRegion.Intersects(tileRect) ||
                           !IsPlaceholder(newRetainedTiles.
                                          SafeElementAt(index, AsDerived().GetPlaceholderTile())),
                           "If we don't draw a tile we shouldn't have a placeholder there.");
 #endif
         y += height;
         continue;
       }
       int tileX = floor_div(x - newBufferOrigin.x, scaledTileSize.width);
       int tileY = floor_div(y - newBufferOrigin.y, scaledTileSize.height);
       int index = tileX * mRetainedHeight + tileY;
       NS_ABORT_IF_FALSE(index >= 0 &&
                         static_cast<unsigned>(index) < newRetainedTiles.Length(),
                         "index out of range");
       Tile newTile = newRetainedTiles[index];
       // Try to reuse a tile from the old retained tiles that had no partially
       // valid content.
       while (IsPlaceholder(newTile) && oldRetainedTiles.Length() > 0) {
         AsDerived().SwapTiles(newTile, oldRetainedTiles[oldRetainedTiles.Length()-1]);
         oldRetainedTiles.RemoveElementAt(oldRetainedTiles.Length()-1);
         if (!IsPlaceholder(newTile)) {
           oldTileCount--;
         }
       }
       // We've done our best effort to recycle a tile but it can be null
       // in which case it's up to the derived class's ValidateTile()
       // implementation to allocate a new tile before drawing
       nsIntPoint tileOrigin(tileStartX, tileStartY);
       newTile = AsDerived().ValidateTile(newTile, nsIntPoint(tileStartX, tileStartY),
                                          tileDrawRegion);
       NS_ABORT_IF_FALSE(!IsPlaceholder(newTile), "index out of range");
 #ifdef GFX_TILEDLAYER_PREF_WARNINGS
       printf_stderr("Store Validate tile %i, %i -> %i\n", tileStartX, tileStartY, index);
 #endif
       newRetainedTiles[index] = newTile;
       y += height;
     }
     x += width;
   }
   // At this point, oldTileCount should be zero
   NS_ABORT_IF_FALSE(oldTileCount == 0, "Failed to release old tiles");
   mRetainedTiles = newRetainedTiles;
   mValidRegion = aNewValidRegion;
   mPaintedRegion.Or(mPaintedRegion, aPaintRegion);
 }
 } // layers
 } // mozilla
 #endif // GFX_TILEDLAYERBUFFER_H

The Tor Browser / annotate

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

gfx/layers/TiledLayerBuffer.h