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1 /* | |
2 * Copyright 2012 Google Inc. | |
3 * | |
4 * Use of this source code is governed by a BSD-style license that can be | |
5 * found in the LICENSE file. | |
6 */ | |
7 | |
8 #ifndef GrTextureStripAtlas_DEFINED | |
9 #define GrTextureStripAtlas_DEFINED | |
10 | |
11 #include "SkBitmap.h" | |
12 #include "SkOpts.h" | |
13 #include "SkGr.h" | |
14 #include "SkTDArray.h" | |
15 #include "SkTDynamicHash.h" | |
16 #include "SkTypes.h" | |
17 | |
18 /** | |
19 * Maintains a single large texture whose rows store many textures of a small fi
xed height, | |
20 * stored in rows across the x-axis such that we can safely wrap/repeat them hor
izontally. | |
21 */ | |
22 class GrTextureStripAtlas { | |
23 public: | |
24 /** | |
25 * Descriptor struct which we'll use as a hash table key | |
26 **/ | |
27 struct Desc { | |
28 Desc() { sk_bzero(this, sizeof(*this)); } | |
29 GrContext* fContext; | |
30 GrPixelConfig fConfig; | |
31 uint16_t fWidth, fHeight, fRowHeight; | |
32 uint16_t fUnusedPadding; | |
33 bool operator==(const Desc& other) const { | |
34 return 0 == memcmp(this, &other, sizeof(Desc)); | |
35 } | |
36 }; | |
37 | |
38 /** | |
39 * Try to find an atlas with the required parameters, creates a new one if n
ecessary | |
40 */ | |
41 static GrTextureStripAtlas* GetAtlas(const Desc& desc); | |
42 | |
43 ~GrTextureStripAtlas(); | |
44 | |
45 /** | |
46 * Add a texture to the atlas | |
47 * @param data Bitmap data to copy into the row | |
48 * @return The row index we inserted into, or -1 if we failed to find an op
en row. The caller | |
49 * is responsible for calling unlockRow() with this row index when it's
done with it. | |
50 */ | |
51 int lockRow(const SkBitmap& data); | |
52 void unlockRow(int row); | |
53 | |
54 /** | |
55 * These functions help turn an integer row index in [0, 1, 2, ... numRows]
into a scalar y | |
56 * texture coordinate in [0, 1] that we can use in a shader. | |
57 * | |
58 * If a regular texture access without using the atlas looks like: | |
59 * | |
60 * texture2D(sampler, vec2(x, y)) | |
61 * | |
62 * Then when using the atlas we'd replace it with: | |
63 * | |
64 * texture2D(sampler, vec2(x, yOffset + y * scaleFactor)) | |
65 * | |
66 * Where yOffset, returned by getYOffset(), is the offset to the start of th
e row within the | |
67 * atlas and scaleFactor, returned by getNormalizedTexelHeight, is the norma
lized height of | |
68 * one texel row. | |
69 */ | |
70 SkScalar getYOffset(int row) const { return SkIntToScalar(row) / fNumRows; } | |
71 SkScalar getNormalizedTexelHeight() const { return fNormalizedYHeight; } | |
72 | |
73 GrContext* getContext() const { return fDesc.fContext; } | |
74 GrTexture* getTexture() const { return fTexture; } | |
75 | |
76 private: | |
77 | |
78 // Key to indicate an atlas row without any meaningful data stored in it | |
79 const static uint32_t kEmptyAtlasRowKey = 0xffffffff; | |
80 | |
81 /** | |
82 * The state of a single row in our cache, next/prev pointers allow these to
be chained | |
83 * together to represent LRU status | |
84 */ | |
85 struct AtlasRow : SkNoncopyable { | |
86 AtlasRow() : fKey(kEmptyAtlasRowKey), fLocks(0), fNext(nullptr), fPrev(n
ullptr) { } | |
87 // GenerationID of the bitmap that is represented by this row, 0xfffffff
f means "empty" | |
88 uint32_t fKey; | |
89 // How many times this has been locked (0 == unlocked) | |
90 int32_t fLocks; | |
91 // We maintain an LRU linked list between unlocked nodes with these poin
ters | |
92 AtlasRow* fNext; | |
93 AtlasRow* fPrev; | |
94 }; | |
95 | |
96 /** | |
97 * We'll only allow construction via the static GrTextureStripAtlas::GetAtla
s | |
98 */ | |
99 GrTextureStripAtlas(Desc desc); | |
100 | |
101 void lockTexture(); | |
102 void unlockTexture(); | |
103 | |
104 /** | |
105 * Initialize our LRU list (if one already exists, clear it and start anew) | |
106 */ | |
107 void initLRU(); | |
108 | |
109 /** | |
110 * Grabs the least recently used free row out of the LRU list, returns nullp
tr if no rows are free. | |
111 */ | |
112 AtlasRow* getLRU(); | |
113 | |
114 void appendLRU(AtlasRow* row); | |
115 void removeFromLRU(AtlasRow* row); | |
116 | |
117 /** | |
118 * Searches the key table for a key and returns the index if found; if not f
ound, it returns | |
119 * the bitwise not of the index at which we could insert the key to maintain
a sorted list. | |
120 **/ | |
121 int searchByKey(uint32_t key); | |
122 | |
123 /** | |
124 * Compare two atlas rows by key, so we can sort/search by key | |
125 */ | |
126 static bool KeyLess(const AtlasRow& lhs, const AtlasRow& rhs) { | |
127 return lhs.fKey < rhs.fKey; | |
128 } | |
129 | |
130 #ifdef SK_DEBUG | |
131 void validate(); | |
132 #endif | |
133 | |
134 /** | |
135 * Clean up callback registered with GrContext. Allows this class to | |
136 * free up any allocated AtlasEntry and GrTextureStripAtlas objects | |
137 */ | |
138 static void CleanUp(const GrContext* context, void* info); | |
139 | |
140 // Hash table entry for atlases | |
141 class AtlasEntry : public ::SkNoncopyable { | |
142 public: | |
143 // for SkTDynamicHash | |
144 static const Desc& GetKey(const AtlasEntry& entry) { return entry.fDesc;
} | |
145 static uint32_t Hash(const Desc& desc) { return SkOpts::hash(&desc, size
of(Desc)); } | |
146 | |
147 // AtlasEntry proper | |
148 AtlasEntry() : fAtlas(nullptr) {} | |
149 ~AtlasEntry() { delete fAtlas; } | |
150 Desc fDesc; | |
151 GrTextureStripAtlas* fAtlas; | |
152 }; | |
153 | |
154 class Hash; | |
155 static Hash* gAtlasCache; | |
156 | |
157 static Hash* GetCache(); | |
158 | |
159 // We increment gCacheCount for each atlas | |
160 static int32_t gCacheCount; | |
161 | |
162 // A unique ID for this texture (formed with: gCacheCount++), so we can be s
ure that if we | |
163 // get a texture back from the texture cache, that it's the same one we last
used. | |
164 const int32_t fCacheKey; | |
165 | |
166 // Total locks on all rows (when this reaches zero, we can unlock our textur
e) | |
167 int32_t fLockedRows; | |
168 | |
169 const Desc fDesc; | |
170 const uint16_t fNumRows; | |
171 GrTexture* fTexture; | |
172 | |
173 SkScalar fNormalizedYHeight; | |
174 | |
175 // Array of AtlasRows which store the state of all our rows. Stored in a con
tiguous array, in | |
176 // order that they appear in our texture, this means we can subtract this po
inter from a row | |
177 // pointer to get its index in the texture, and can save storing a row numbe
r in AtlasRow. | |
178 AtlasRow* fRows; | |
179 | |
180 // Head and tail for linked list of least-recently-used rows (front = least
recently used). | |
181 // Note that when a texture is locked, it gets removed from this list until
it is unlocked. | |
182 AtlasRow* fLRUFront; | |
183 AtlasRow* fLRUBack; | |
184 | |
185 // A list of pointers to AtlasRows that currently contain cached images, sor
ted by key | |
186 SkTDArray<AtlasRow*> fKeyTable; | |
187 }; | |
188 | |
189 #endif | |
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