rileya@google.com | 2e2aedc | 2012-08-13 20:28:48 +0000 | [diff] [blame] | 1 | |
| 2 | /* |
| 3 | * Copyright 2012 Google Inc. |
| 4 | * |
| 5 | * Use of this source code is governed by a BSD-style license that can be |
| 6 | * found in the LICENSE file. |
| 7 | */ |
| 8 | |
| 9 | #ifndef GrTextureStripAtlas_DEFINED |
| 10 | #define GrTextureStripAtlas_DEFINED |
| 11 | |
| 12 | #include "SkBitmap.h" |
| 13 | #include "GrTHashCache.h" |
| 14 | #include "SkGr.h" |
| 15 | #include "SkTDArray.h" |
| 16 | |
| 17 | /** |
| 18 | * Maintains a single large texture whose rows store many textures of a small fixed height, |
| 19 | * stored in rows across the x-axis such that we can safely wrap/repeat them horizontally. |
| 20 | */ |
| 21 | class GrTextureStripAtlas { |
| 22 | public: |
| 23 | GR_DECLARE_RESOURCE_CACHE_DOMAIN(GetTextureStripAtlasDomain) |
| 24 | |
| 25 | /** |
| 26 | * Descriptor struct which we'll use as a hash table key |
| 27 | **/ |
| 28 | struct Desc { |
| 29 | Desc() { memset(this, 0, sizeof(*this)); } |
| 30 | uint16_t fWidth, fHeight, fRowHeight; |
| 31 | GrPixelConfig fConfig; |
| 32 | GrContext* fContext; |
| 33 | const uint32_t* asKey() const { return reinterpret_cast<const uint32_t*>(this); } |
| 34 | }; |
| 35 | |
| 36 | /** |
| 37 | * Try to find an atlas with the required parameters, creates a new one if necessary |
| 38 | */ |
| 39 | static GrTextureStripAtlas* GetAtlas(const Desc& desc); |
| 40 | |
| 41 | ~GrTextureStripAtlas(); |
| 42 | |
| 43 | /** |
| 44 | * Add a texture to the atlas |
| 45 | * @param data Bitmap data to copy into the row |
| 46 | * @return The row index we inserted into, or -1 if we failed to find an open row. The caller |
| 47 | * is responsible for calling unlockRow() with this row index when it's done with it. |
| 48 | */ |
| 49 | int lockRow(const SkBitmap& data); |
| 50 | void unlockRow(int row); |
| 51 | |
| 52 | /** |
| 53 | * These functions help turn an integer row index in [0, 1, 2, ... numRows] into a scalar y |
| 54 | * texture coordinate in [0, 1] that we can use in a shader. |
| 55 | * |
| 56 | * If a regular texture access without using the atlas looks like: |
| 57 | * |
| 58 | * texture2D(sampler, vec2(x, y)) |
| 59 | * |
| 60 | * Then when using the atlas we'd replace it with: |
| 61 | * |
| 62 | * texture2D(sampler, vec2(x, yOffset + y * scaleFactor)) |
| 63 | * |
| 64 | * Where yOffset, returned by getYOffset(), is the offset to the start of the row within the |
| 65 | * atlas and scaleFactor, returned by getVerticalScaleFactor(), is the y-scale of the row, |
| 66 | * relative to the height of the overall atlas texture. |
| 67 | */ |
| 68 | GrScalar getYOffset(int row) const { return SkIntToScalar(row) / fNumRows; } |
| 69 | GrScalar getVerticalScaleFactor() const { return SkIntToScalar(fDesc.fRowHeight) / fDesc.fHeight; } |
| 70 | |
| 71 | GrContext* getContext() const { return fDesc.fContext; } |
| 72 | GrTexture* getTexture() const { return fEntry.texture(); } |
| 73 | |
| 74 | private: |
| 75 | |
| 76 | // Key to indicate an atlas row without any meaningful data stored in it |
| 77 | const static uint32_t kEmptyAtlasRowKey = 0xffffffff; |
| 78 | |
| 79 | /** |
| 80 | * The state of a single row in our cache, next/prev pointers allow these to be chained |
| 81 | * together to represent LRU status |
| 82 | */ |
| 83 | struct AtlasRow : public GrNoncopyable { |
| 84 | AtlasRow() : fKey(kEmptyAtlasRowKey), fLocks(0), fNext(NULL), fPrev(NULL) { } |
| 85 | // GenerationID of the bitmap that is represented by this row, 0xffffffff means "empty" |
| 86 | uint32_t fKey; |
| 87 | // How many times this has been locked (0 == unlocked) |
| 88 | int32_t fLocks; |
| 89 | // We maintain an LRU linked list between unlocked nodes with these pointers |
| 90 | AtlasRow* fNext; |
| 91 | AtlasRow* fPrev; |
| 92 | }; |
| 93 | |
| 94 | /** |
| 95 | * We'll only allow construction via the static GrTextureStripAtlas::GetAtlas |
| 96 | */ |
| 97 | GrTextureStripAtlas(Desc desc); |
| 98 | |
| 99 | void lockTexture(); |
| 100 | void unlockTexture(); |
| 101 | |
| 102 | /** |
| 103 | * Initialize our LRU list (if one already exists, clear it and start anew) |
| 104 | */ |
| 105 | void initLRU(); |
| 106 | |
| 107 | /** |
| 108 | * Grabs the least recently used free row out of the LRU list, returns NULL if no rows are free. |
| 109 | */ |
| 110 | AtlasRow* getLRU(); |
| 111 | |
| 112 | void appendLRU(AtlasRow* row); |
| 113 | void removeFromLRU(AtlasRow* row); |
| 114 | |
| 115 | /** |
| 116 | * Searches the key table for a key and returns the index if found; if not found, it returns |
| 117 | * the bitwise not of the index at which we could insert the key to maintain a sorted list. |
| 118 | **/ |
| 119 | int searchByKey(uint32_t key); |
| 120 | |
| 121 | /** |
| 122 | * Compare two atlas rows by key, so we can sort/search by key |
| 123 | */ |
| 124 | static int compareKeys(const AtlasRow* lhs, const AtlasRow* rhs) { |
| 125 | return lhs->fKey - rhs->fKey; |
| 126 | } |
| 127 | |
| 128 | #ifdef SK_DEBUG |
| 129 | void validate(); |
| 130 | #endif |
| 131 | |
rileya@google.com | f61c746 | 2012-08-13 21:03:39 +0000 | [diff] [blame^] | 132 | // We increment gCacheCount for each atlas |
rileya@google.com | 2e2aedc | 2012-08-13 20:28:48 +0000 | [diff] [blame] | 133 | static int32_t gCacheCount; |
rileya@google.com | 2e2aedc | 2012-08-13 20:28:48 +0000 | [diff] [blame] | 134 | |
rileya@google.com | f61c746 | 2012-08-13 21:03:39 +0000 | [diff] [blame^] | 135 | // A unique ID for this texture (formed with: gCacheCount++), so we can be sure that if we |
| 136 | // get a texture back from the texture cache, that it's the same one we last used. |
rileya@google.com | 2e2aedc | 2012-08-13 20:28:48 +0000 | [diff] [blame] | 137 | const uint64_t fCacheID; |
| 138 | |
| 139 | // Total locks on all rows (when this reaches zero, we can unlock our texture) |
| 140 | int32_t fLockedRows; |
| 141 | |
| 142 | const Desc fDesc; |
| 143 | const uint16_t fNumRows; |
| 144 | GrContext::TextureCacheEntry fEntry; |
| 145 | |
| 146 | // Array of AtlasRows which store the state of all our rows. Stored in a contiguous array, in |
| 147 | // order that they appear in our texture, this means we can subtract this pointer from a row |
| 148 | // pointer to get its index in the texture, and can save storing a row number in AtlasRow. |
| 149 | AtlasRow* fRows; |
| 150 | |
| 151 | // Head and tail for linked list of least-recently-used rows (front = least recently used). |
| 152 | // Note that when a texture is locked, it gets removed from this list until it is unlocked. |
| 153 | AtlasRow* fLRUFront; |
| 154 | AtlasRow* fLRUBack; |
| 155 | |
| 156 | // A list of pointers to AtlasRows that currently contain cached images, sorted by key |
| 157 | SkTDArray<AtlasRow*> fKeyTable; |
| 158 | }; |
| 159 | |
| 160 | #endif |
| 161 | |