gecko/gfx/layers/TiledLayerBuffer.h

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/* 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
#define TILEDLAYERBUFFER_TILE_SIZE 256
// Debug defines
#ifdef MOZ_ANDROID_OMTC
// This needs to go away as we enabled tiled
// layers everywhere.
#define FORCE_BASICTILEDTHEBESLAYER
#endif
//#define GFX_TILEDLAYER_DEBUG_OVERLAY
//#define GFX_TILEDLAYER_PREF_WARNINGS
#include "nsRect.h"
#include "nsRegion.h"
#include "nsTArray.h"
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 GetTileLength().
//
// 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.
template<typename Derived, typename Tile>
class TiledLayerBuffer
{
public:
TiledLayerBuffer()
: mRetainedWidth(0)
, mRetainedHeight(0)
{}
~TiledLayerBuffer() {}
// Given a tile origin aligned to a multiple of GetTileLength(),
// return the tile that describes that region.
// NOTE: To get the valid area of that tile you must intersect
// (aTileOrigin.x, aTileOrigin.y, GetTileLength(), GetTileLength())
// 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*GetTileLength(), y*GetTileLength(), GetTileLength(), GetTileLength())
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);
uint16_t GetTileLength() const { return TILEDLAYERBUFFER_TILE_SIZE; }
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) const {
return (i >= 0) ? (i % GetTileLength())
: ((GetTileLength() - (-i % GetTileLength())) % GetTileLength());
}
// Rounds the given coordinate down to the nearest tile boundary.
int RoundDownToTileEdge(int aX) const { return aX - GetTileStart(aX); }
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.
*/
nsTArray<Tile> mRetainedTiles;
int mRetainedWidth; // in tiles
int mRetainedHeight; // in tiles
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 BasicTiledLayerBuffer;
// 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.
* The BasicTiledLayerBuffer is expected to be in the ReadLock state
* prior to this being called. aTiledBuffer is copy constructed and
* is retained until it has been uploaded/copyed and unlocked.
*/
virtual void PaintedTiledLayerBuffer(const BasicTiledLayerBuffer* aTiledBuffer) = 0;
virtual void MemoryPressure() = 0;
};
// 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.
int firstTileX = floor_div(mValidRegion.GetBounds().x, GetTileLength());
int firstTileY = floor_div(mValidRegion.GetBounds().y, GetTileLength());
return GetTile(floor_div(aTileOrigin.x, GetTileLength()) - firstTileX,
floor_div(aTileOrigin.y, GetTileLength()) - 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)
{
int firstTileX = floor_div(mValidRegion.GetBounds().x, GetTileLength());
int firstTileY = floor_div(mValidRegion.GetBounds().y, GetTileLength());
return RemoveTile(floor_div(aTileOrigin.x, GetTileLength()) - firstTileX,
floor_div(aTileOrigin.y, GetTileLength()) - 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)
{
nsTArray<Tile> newRetainedTiles;
nsTArray<Tile>& oldRetainedTiles = mRetainedTiles;
const nsIntRect oldBound = mValidRegion.GetBounds();
const nsIntRect newBound = aNewValidRegion.GetBounds();
const nsIntPoint oldBufferOrigin(RoundDownToTileEdge(oldBound.x),
RoundDownToTileEdge(oldBound.y));
const nsIntPoint newBufferOrigin(RoundDownToTileEdge(newBound.x),
RoundDownToTileEdge(newBound.y));
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;
// 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 = GetTileLength() - GetTileStart(x);
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 = GetTileLength() - GetTileStart(y);
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, GetTileLength());
int tileY = floor_div(y - oldBufferOrigin.y, GetTileLength());
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());
}
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;
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);
int width = GetTileLength() - GetTileStart(x);
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);
int height = GetTileLength() - GetTileStart(y);
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, GetTileLength());
int currTileY = floor_div(y - newBufferOrigin.y, GetTileLength());
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, GetTileLength());
int tileY = floor_div(y - newBufferOrigin.y, GetTileLength());
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];
while (IsPlaceholder(newTile) && oldRetainedTiles.Length() > 0) {
AsDerived().SwapTiles(newTile, oldRetainedTiles[oldRetainedTiles.Length()-1]);
oldRetainedTiles.RemoveElementAt(oldRetainedTiles.Length()-1);
}
// 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;
}
// Throw away any tiles we didn't recycle
// TODO: Add a tile pool
while (oldRetainedTiles.Length() > 0) {
Tile oldTile = oldRetainedTiles[oldRetainedTiles.Length()-1];
oldRetainedTiles.RemoveElementAt(oldRetainedTiles.Length()-1);
AsDerived().ReleaseTile(oldTile);
}
mRetainedTiles = newRetainedTiles;
mValidRegion = aNewValidRegion;
mPaintedRegion.Or(mPaintedRegion, aPaintRegion);
}
} // layers
} // mozilla
#endif // GFX_TILEDLAYERBUFFER_H