diff -r 000000000000 -r 6474c204b198 gfx/skia/trunk/src/gpu/effects/GrTextureStripAtlas.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/gfx/skia/trunk/src/gpu/effects/GrTextureStripAtlas.h Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,194 @@ +/* + * Copyright 2012 Google Inc. + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + +#ifndef GrTextureStripAtlas_DEFINED +#define GrTextureStripAtlas_DEFINED + +#include "GrBinHashKey.h" +#include "GrTHashTable.h" +#include "SkBitmap.h" +#include "SkGr.h" +#include "SkTDArray.h" +#include "SkTypes.h" + +/** + * Maintains a single large texture whose rows store many textures of a small fixed height, + * stored in rows across the x-axis such that we can safely wrap/repeat them horizontally. + */ +class GrTextureStripAtlas { +public: + /** + * Descriptor struct which we'll use as a hash table key + **/ + struct Desc { + Desc() { memset(this, 0, sizeof(*this)); } + uint16_t fWidth, fHeight, fRowHeight; + GrPixelConfig fConfig; + GrContext* fContext; + const uint32_t* asKey() const { return reinterpret_cast(this); } + }; + + /** + * Try to find an atlas with the required parameters, creates a new one if necessary + */ + static GrTextureStripAtlas* GetAtlas(const Desc& desc); + + ~GrTextureStripAtlas(); + + /** + * Add a texture to the atlas + * @param data Bitmap data to copy into the row + * @return The row index we inserted into, or -1 if we failed to find an open row. The caller + * is responsible for calling unlockRow() with this row index when it's done with it. + */ + int lockRow(const SkBitmap& data); + void unlockRow(int row); + + /** + * These functions help turn an integer row index in [0, 1, 2, ... numRows] into a scalar y + * texture coordinate in [0, 1] that we can use in a shader. + * + * If a regular texture access without using the atlas looks like: + * + * texture2D(sampler, vec2(x, y)) + * + * Then when using the atlas we'd replace it with: + * + * texture2D(sampler, vec2(x, yOffset + y * scaleFactor)) + * + * Where yOffset, returned by getYOffset(), is the offset to the start of the row within the + * atlas and scaleFactor, returned by getVerticalScaleFactor(), is the y-scale of the row, + * relative to the height of the overall atlas texture. + */ + SkScalar getYOffset(int row) const { return SkIntToScalar(row) / fNumRows; } + SkScalar getVerticalScaleFactor() const { return SkIntToScalar(fDesc.fRowHeight) / fDesc.fHeight; } + + GrContext* getContext() const { return fDesc.fContext; } + GrTexture* getTexture() const { return fTexture; } + +private: + + // Key to indicate an atlas row without any meaningful data stored in it + const static uint32_t kEmptyAtlasRowKey = 0xffffffff; + + /** + * The state of a single row in our cache, next/prev pointers allow these to be chained + * together to represent LRU status + */ + struct AtlasRow : public SkNoncopyable { + AtlasRow() : fKey(kEmptyAtlasRowKey), fLocks(0), fNext(NULL), fPrev(NULL) { } + // GenerationID of the bitmap that is represented by this row, 0xffffffff means "empty" + uint32_t fKey; + // How many times this has been locked (0 == unlocked) + int32_t fLocks; + // We maintain an LRU linked list between unlocked nodes with these pointers + AtlasRow* fNext; + AtlasRow* fPrev; + }; + + /** + * We'll only allow construction via the static GrTextureStripAtlas::GetAtlas + */ + GrTextureStripAtlas(Desc desc); + + void lockTexture(); + void unlockTexture(); + + /** + * Initialize our LRU list (if one already exists, clear it and start anew) + */ + void initLRU(); + + /** + * Grabs the least recently used free row out of the LRU list, returns NULL if no rows are free. + */ + AtlasRow* getLRU(); + + void appendLRU(AtlasRow* row); + void removeFromLRU(AtlasRow* row); + + /** + * Searches the key table for a key and returns the index if found; if not found, it returns + * the bitwise not of the index at which we could insert the key to maintain a sorted list. + **/ + int searchByKey(uint32_t key); + + /** + * Compare two atlas rows by key, so we can sort/search by key + */ + static bool KeyLess(const AtlasRow& lhs, const AtlasRow& rhs) { + return lhs.fKey < rhs.fKey; + } + +#ifdef SK_DEBUG + void validate(); +#endif + + /** + * Clean up callback registered with GrContext. Allows this class to + * free up any allocated AtlasEntry and GrTextureStripAtlas objects + */ + static void CleanUp(const GrContext* context, void* info); + + // Hash table entry for atlases + class AtlasEntry; + class AtlasHashKey : public GrBinHashKey { + public: + static bool Equals(const AtlasEntry& entry, const AtlasHashKey& key); + static bool LessThan(const AtlasEntry& entry, const AtlasHashKey& key); + }; + class AtlasEntry : public ::SkNoncopyable { + public: + AtlasEntry() : fAtlas(NULL) {} + ~AtlasEntry() { SkDELETE(fAtlas); } + AtlasHashKey fKey; + GrTextureStripAtlas* fAtlas; + }; + + static GrTHashTable* gAtlasCache; + + static GrTHashTable* GetCache(); + + // We increment gCacheCount for each atlas + static int32_t gCacheCount; + + // A unique ID for this texture (formed with: gCacheCount++), so we can be sure that if we + // get a texture back from the texture cache, that it's the same one we last used. + const int32_t fCacheKey; + + // Total locks on all rows (when this reaches zero, we can unlock our texture) + int32_t fLockedRows; + + const Desc fDesc; + const uint16_t fNumRows; + GrTexture* fTexture; + + // Array of AtlasRows which store the state of all our rows. Stored in a contiguous array, in + // order that they appear in our texture, this means we can subtract this pointer from a row + // pointer to get its index in the texture, and can save storing a row number in AtlasRow. + AtlasRow* fRows; + + // Head and tail for linked list of least-recently-used rows (front = least recently used). + // Note that when a texture is locked, it gets removed from this list until it is unlocked. + AtlasRow* fLRUFront; + AtlasRow* fLRUBack; + + // A list of pointers to AtlasRows that currently contain cached images, sorted by key + SkTDArray fKeyTable; +}; + +inline bool GrTextureStripAtlas::AtlasHashKey::Equals(const AtlasEntry& entry, + const AtlasHashKey& key) { + return entry.fKey == key; +} + +inline bool GrTextureStripAtlas::AtlasHashKey::LessThan(const AtlasEntry& entry, + const AtlasHashKey& key) { + return entry.fKey < key; +} + +#endif