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comparison: gfx/skia/trunk/src/gpu/GrStencil.h

gfx/skia/trunk/src/gpu/GrStencil.h

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1
2 /*
3 * Copyright 2011 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
10 #ifndef GrStencil_DEFINED
11 #define GrStencil_DEFINED
12
13 #include "GrTypes.h"
14 #include "SkRegion.h"
15
16 /**
17 * Gr uses the stencil buffer to implement complex clipping inside the
18 * GrDrawTarget class. The GrDrawTarget makes a subset of the stencil buffer
19 * bits available for other uses by external code (clients). Client code can
20 * modify these bits. GrDrawTarget will ignore ref, mask, and writemask bits
21 * provided by clients that overlap the bits used to implement clipping.
22 *
23 * When code outside the GrDrawTarget class uses the stencil buffer the contract
24 * is as follows:
25 *
26 * > Normal stencil funcs allow the client to pass / fail regardless of the
27 * reserved clip bits.
28 * > Additional functions allow a test against the clip along with a limited
29 * set of tests against the client bits.
30 * > Client can assume all client bits are zero initially.
31 * > Client must ensure that after all its passes are finished it has only
32 * written to the color buffer in the region inside the clip. Furthermore, it
33 * must zero all client bits that were modifed (both inside and outside the
34 * clip).
35 */
36
37 /**
38 * Determines which pixels pass / fail the stencil test.
39 * Stencil test passes if (ref & mask) FUNC (stencil & mask) is true
40 */
41 enum GrStencilFunc {
42 kAlways_StencilFunc = 0,
43 kNever_StencilFunc,
44 kGreater_StencilFunc,
45 kGEqual_StencilFunc,
46 kLess_StencilFunc,
47 kLEqual_StencilFunc,
48 kEqual_StencilFunc,
49 kNotEqual_StencilFunc,
50
51 // Gr stores the current clip in the
52 // stencil buffer in the high bits that
53 // are not directly accessible modifiable
54 // via the GrDrawTarget interface. The below
55 // stencil funcs test against the current
56 // clip in addition to the GrDrawTarget
57 // client's stencil bits.
58
59 // pass if inside the clip
60 kAlwaysIfInClip_StencilFunc,
61 kEqualIfInClip_StencilFunc,
62 kLessIfInClip_StencilFunc,
63 kLEqualIfInClip_StencilFunc,
64 kNonZeroIfInClip_StencilFunc, // this one forces the ref to be 0
65
66 // counts
67 kStencilFuncCount,
68 kClipStencilFuncCount = kNonZeroIfInClip_StencilFunc -
69 kAlwaysIfInClip_StencilFunc + 1,
70 kBasicStencilFuncCount = kStencilFuncCount - kClipStencilFuncCount
71 };
72
73 /**
74 * Operations to perform based on whether stencil test passed failed.
75 */
76 enum GrStencilOp {
77 kKeep_StencilOp = 0, // preserve existing stencil value
78 kReplace_StencilOp, // replace with reference value from stencl test
79 kIncWrap_StencilOp, // increment and wrap at max
80 kIncClamp_StencilOp, // increment and clamp at max
81 kDecWrap_StencilOp, // decrement and wrap at 0
82 kDecClamp_StencilOp, // decrement and clamp at 0
83 kZero_StencilOp, // zero stencil bits
84 kInvert_StencilOp, // invert stencil bits
85
86 kStencilOpCount
87 };
88
89 enum GrStencilFlags {
90 kIsDisabled_StencilFlag = 0x1,
91 kNotDisabled_StencilFlag = 0x2,
92 kDoesWrite_StencilFlag = 0x4,
93 kDoesNotWrite_StencilFlag = 0x8,
94 };
95
96 /**
97 * GrStencilState needs to be a class with accessors and setters so that it
98 * can maintain flags related to its current state. However, we also want to
99 * be able to declare pre-made stencil settings at compile time (without
100 * inserting static initializer code). So all the data members are in this
101 * struct. A macro defined after the class can be used to jam an instance of
102 * this struct that is created from an initializer list into a
103 * GrStencilSettings. (We hang our heads in shame.)
104 */
105 struct GrStencilSettingsStruct {
106 uint8_t fPassOps[2]; // op to perform when faces pass (GrStencilOp)
107 uint8_t fFailOps[2]; // op to perform when faces fail (GrStencilOp)
108 uint8_t fFuncs[2]; // test function for faces (GrStencilFunc)
109 uint8_t fPad0;
110 uint8_t fPad1;
111 uint16_t fFuncMasks[2]; // mask for face tests
112 uint16_t fFuncRefs[2]; // reference values for face tests
113 uint16_t fWriteMasks[2]; // stencil write masks
114 mutable uint32_t fFlags;
115 };
116 // We rely on this being packed and aligned (memcmp'ed and memcpy'ed)
117 GR_STATIC_ASSERT(sizeof(GrStencilSettingsStruct) % 4 == 0);
118 GR_STATIC_ASSERT(sizeof(GrStencilSettingsStruct) ==
119 4*sizeof(uint8_t) + // ops
120 2*sizeof(uint8_t) + // funcs
121 2*sizeof(uint8_t) + // pads
122 2*sizeof(uint16_t) + // func masks
123 2*sizeof(uint16_t) + // ref values
124 2*sizeof(uint16_t) + // write masks
125 sizeof(uint32_t)); // flags
126
127 // This macro is used to compute the GrStencilSettingsStructs flags
128 // associated to disabling. It is used both to define constant structure
129 // initializers and inside GrStencilSettings::isDisabled()
130 //
131 #define GR_STENCIL_SETTINGS_IS_DISABLED( \
132 FRONT_PASS_OP, BACK_PASS_OP, \
133 FRONT_FAIL_OP, BACK_FAIL_OP, \
134 FRONT_FUNC, BACK_FUNC) \
135 ((FRONT_PASS_OP) == kKeep_StencilOp && \
136 (BACK_PASS_OP) == kKeep_StencilOp && \
137 (FRONT_FAIL_OP) == kKeep_StencilOp && \
138 (BACK_FAIL_OP) == kKeep_StencilOp && \
139 (FRONT_FUNC) == kAlways_StencilFunc && \
140 (BACK_FUNC) == kAlways_StencilFunc)
141
142 #define GR_STENCIL_SETTINGS_DOES_WRITE( \
143 FRONT_PASS_OP, BACK_PASS_OP, \
144 FRONT_FAIL_OP, BACK_FAIL_OP, \
145 FRONT_FUNC, BACK_FUNC) \
146 (!(((FRONT_FUNC) == kNever_StencilFunc || \
147 (FRONT_PASS_OP) == kKeep_StencilOp) && \
148 ((BACK_FUNC) == kNever_StencilFunc || \
149 (BACK_PASS_OP) == kKeep_StencilOp) && \
150 ((FRONT_FUNC) == kAlways_StencilFunc || \
151 (FRONT_FAIL_OP) == kKeep_StencilOp) && \
152 ((BACK_FUNC) == kAlways_StencilFunc || \
153 (BACK_FAIL_OP) == kKeep_StencilOp)))
154
155 #define GR_STENCIL_SETTINGS_DEFAULT_FLAGS( \
156 FRONT_PASS_OP, BACK_PASS_OP, \
157 FRONT_FAIL_OP, BACK_FAIL_OP, \
158 FRONT_FUNC, BACK_FUNC) \
159 ((GR_STENCIL_SETTINGS_IS_DISABLED(FRONT_PASS_OP,BACK_PASS_OP, \
160 FRONT_FAIL_OP,BACK_FAIL_OP,FRONT_FUNC,BACK_FUNC) ? \
161 kIsDisabled_StencilFlag : kNotDisabled_StencilFlag) | \
162 (GR_STENCIL_SETTINGS_DOES_WRITE(FRONT_PASS_OP,BACK_PASS_OP, \
163 FRONT_FAIL_OP,BACK_FAIL_OP,FRONT_FUNC,BACK_FUNC) ? \
164 kDoesWrite_StencilFlag : kDoesNotWrite_StencilFlag))
165
166 /**
167 * Class representing stencil state.
168 */
169 class GrStencilSettings : private GrStencilSettingsStruct {
170
171 public:
172 enum Face {
173 kFront_Face = 0,
174 kBack_Face = 1,
175 };
176
177 GrStencilSettings() {
178 fPad0 = fPad1 = 0;
179 this->setDisabled();
180 }
181
182 GrStencilOp passOp(Face f) const { return static_cast<GrStencilOp>(fPassOps[f]); }
183 GrStencilOp failOp(Face f) const { return static_cast<GrStencilOp>(fFailOps[f]); }
184 GrStencilFunc func(Face f) const { return static_cast<GrStencilFunc>(fFuncs[f]); }
185 uint16_t funcMask(Face f) const { return fFuncMasks[f]; }
186 uint16_t funcRef(Face f) const { return fFuncRefs[f]; }
187 uint16_t writeMask(Face f) const { return fWriteMasks[f]; }
188
189 void setPassOp(Face f, GrStencilOp op) { fPassOps[f] = op; fFlags = 0;}
190 void setFailOp(Face f, GrStencilOp op) { fFailOps[f] = op; fFlags = 0;}
191 void setFunc(Face f, GrStencilFunc func) { fFuncs[f] = func; fFlags = 0;}
192 void setFuncMask(Face f, unsigned short mask) { fFuncMasks[f] = mask; }
193 void setFuncRef(Face f, unsigned short ref) { fFuncRefs[f] = ref; }
194 void setWriteMask(Face f, unsigned short writeMask) { fWriteMasks[f] = writeMask; }
195
196 void copyFrontSettingsToBack() {
197 fPassOps[kBack_Face] = fPassOps[kFront_Face];
198 fFailOps[kBack_Face] = fFailOps[kFront_Face];
199 fFuncs[kBack_Face] = fFuncs[kFront_Face];
200 fFuncMasks[kBack_Face] = fFuncMasks[kFront_Face];
201 fFuncRefs[kBack_Face] = fFuncRefs[kFront_Face];
202 fWriteMasks[kBack_Face] = fWriteMasks[kFront_Face];
203 fFlags = 0;
204 }
205
206 void setSame(GrStencilOp passOp,
207 GrStencilOp failOp,
208 GrStencilFunc func,
209 unsigned short funcMask,
210 unsigned short funcRef,
211 unsigned short writeMask) {
212 fPassOps[kFront_Face] = fPassOps[kBack_Face] = passOp;
213 fFailOps[kFront_Face] = fFailOps[kBack_Face] = failOp;
214 fFuncs[kFront_Face] = fFuncs[kBack_Face] = func;
215 fFuncMasks[kFront_Face] = fFuncMasks[kBack_Face] = funcMask;
216 fFuncRefs[kFront_Face] = fFuncRefs[kBack_Face] = funcRef;
217 fWriteMasks[kFront_Face] = fWriteMasks[kBack_Face] = writeMask;
218 fFlags = 0;
219 }
220
221 void setDisabled() {
222 memset(this, 0, sizeof(*this));
223 GR_STATIC_ASSERT(0 == kKeep_StencilOp);
224 GR_STATIC_ASSERT(0 == kAlways_StencilFunc);
225 fFlags = kIsDisabled_StencilFlag | kDoesNotWrite_StencilFlag;
226 }
227
228 bool isTwoSided() const {
229 return fPassOps[kFront_Face] != fPassOps[kBack_Face] ||
230 fFailOps[kFront_Face] != fFailOps[kBack_Face] ||
231 fFuncs[kFront_Face] != fFuncs[kBack_Face] ||
232 fFuncMasks[kFront_Face] != fFuncMasks[kBack_Face] ||
233 fFuncRefs[kFront_Face] != fFuncRefs[kBack_Face] ||
234 fWriteMasks[kFront_Face] != fWriteMasks[kBack_Face];
235 }
236
237 bool usesWrapOp() const {
238 return kIncWrap_StencilOp == fPassOps[kFront_Face] ||
239 kDecWrap_StencilOp == fPassOps[kFront_Face] ||
240 kIncWrap_StencilOp == fPassOps[kBack_Face] ||
241 kDecWrap_StencilOp == fPassOps[kBack_Face] ||
242 kIncWrap_StencilOp == fFailOps[kFront_Face] ||
243 kDecWrap_StencilOp == fFailOps[kFront_Face] ||
244 kIncWrap_StencilOp == fFailOps[kBack_Face] ||
245 kDecWrap_StencilOp == fFailOps[kBack_Face];
246 }
247
248 bool isDisabled() const {
249 if (fFlags & kIsDisabled_StencilFlag) {
250 return true;
251 }
252 if (fFlags & kNotDisabled_StencilFlag) {
253 return false;
254 }
255 bool disabled = GR_STENCIL_SETTINGS_IS_DISABLED(
256 fPassOps[kFront_Face], fPassOps[kBack_Face],
257 fFailOps[kFront_Face], fFailOps[kBack_Face],
258 fFuncs[kFront_Face], fFuncs[kBack_Face]);
259 fFlags |= disabled ? kIsDisabled_StencilFlag : kNotDisabled_StencilFlag;
260 return disabled;
261 }
262
263 bool doesWrite() const {
264 if (fFlags & kDoesWrite_StencilFlag) {
265 return true;
266 }
267 if (fFlags & kDoesNotWrite_StencilFlag) {
268 return false;
269 }
270 bool writes = GR_STENCIL_SETTINGS_DOES_WRITE(
271 fPassOps[kFront_Face], fPassOps[kBack_Face],
272 fFailOps[kFront_Face], fFailOps[kBack_Face],
273 fFuncs[kFront_Face], fFuncs[kBack_Face]);
274 fFlags |= writes ? kDoesWrite_StencilFlag : kDoesNotWrite_StencilFlag;
275 return writes;
276 }
277
278 void invalidate() {
279 // write an illegal value to the first member
280 fPassOps[0] = (GrStencilOp)(uint8_t)-1;
281 fFlags = 0;
282 }
283
284 bool operator == (const GrStencilSettings& s) const {
285 static const size_t gCompareSize = sizeof(GrStencilSettings) -
286 sizeof(fFlags);
287 SkASSERT((const char*)&fFlags + sizeof(fFlags) ==
288 (const char*)this + sizeof(GrStencilSettings));
289 if (this->isDisabled() & s.isDisabled()) { // using & not &&
290 return true;
291 }
292 return 0 == memcmp(this, &s, gCompareSize);
293 }
294
295 bool operator != (const GrStencilSettings& s) const {
296 return !(*this == s);
297 }
298
299 GrStencilSettings& operator =(const GrStencilSettings& s) {
300 memcpy(this, &s, sizeof(GrStencilSettings));
301 return *this;
302 }
303
304 private:
305 friend class GrClipMaskManager;
306
307 enum {
308 kMaxStencilClipPasses = 2 // maximum number of passes to add a clip
309 // element to the stencil buffer.
310 };
311
312 /**
313 * Given a thing to draw into the stencil clip, a fill type, and a set op
314 * this function determines:
315 * 1. Whether the thing can be draw directly to the stencil clip or
316 * needs to be drawn to the client portion of the stencil first.
317 * 2. How many passes are needed.
318 * 3. What those passes are.
319 * 4. The fill rule that should actually be used to render (will
320 * always be non-inverted).
321 *
322 * @param op the set op to combine this element with the
323 * existing clip
324 * @param stencilClipMask mask with just the stencil bit used for clipping
325 * enabled.
326 * @param invertedFill is this path inverted
327 * @param numPasses out: the number of passes needed to add the
328 * element to the clip.
329 * @param settings out: the stencil settings to use for each pass
330 *
331 * @return true if the clip element's geometry can be drawn directly to the
332 * stencil clip bit. Will only be true if canBeDirect is true.
333 * numPasses will be 1 if return value is true.
334 */
335 static bool GetClipPasses(SkRegion::Op op,
336 bool canBeDirect,
337 unsigned int stencilClipMask,
338 bool invertedFill,
339 int* numPasses,
340 GrStencilSettings settings[kMaxStencilClipPasses]);
341 };
342
343 GR_STATIC_ASSERT(sizeof(GrStencilSettingsStruct) == sizeof(GrStencilSettings));
344
345 #define GR_STATIC_CONST_STENCIL_STRUCT(STRUCT_NAME, \
346 FRONT_PASS_OP, BACK_PASS_OP, \
347 FRONT_FAIL_OP, BACK_FAIL_OP, \
348 FRONT_FUNC, BACK_FUNC, \
349 FRONT_MASK, BACK_MASK, \
350 FRONT_REF, BACK_REF, \
351 FRONT_WRITE_MASK, BACK_WRITE_MASK) \
352 static const GrStencilSettingsStruct STRUCT_NAME = { \
353 {(FRONT_PASS_OP), (BACK_PASS_OP) }, \
354 {(FRONT_FAIL_OP), (BACK_FAIL_OP) }, \
355 {(FRONT_FUNC), (BACK_FUNC) }, \
356 (0), (0), \
357 {(FRONT_MASK), (BACK_MASK) }, \
358 {(FRONT_REF), (BACK_REF) }, \
359 {(FRONT_WRITE_MASK), (BACK_WRITE_MASK)}, \
360 GR_STENCIL_SETTINGS_DEFAULT_FLAGS( \
361 FRONT_PASS_OP, BACK_PASS_OP, FRONT_FAIL_OP, BACK_FAIL_OP, \
362 FRONT_FUNC, BACK_FUNC) \
363 };
364
365 #define GR_CONST_STENCIL_SETTINGS_PTR_FROM_STRUCT_PTR(STRUCT_PTR) \
366 reinterpret_cast<const GrStencilSettings*>(STRUCT_PTR)
367
368 #define GR_STATIC_CONST_SAME_STENCIL_STRUCT(STRUCT_NAME, \
369 PASS_OP, FAIL_OP, FUNC, MASK, REF, WRITE_MASK) \
370 GR_STATIC_CONST_STENCIL_STRUCT(STRUCT_NAME, (PASS_OP), (PASS_OP), \
371 (FAIL_OP),(FAIL_OP), (FUNC), (FUNC), (MASK), (MASK), (REF), (REF), \
372 (WRITE_MASK),(WRITE_MASK))
373
374 #define GR_STATIC_CONST_STENCIL(NAME, \
375 FRONT_PASS_OP, BACK_PASS_OP, \
376 FRONT_FAIL_OP, BACK_FAIL_OP, \
377 FRONT_FUNC, BACK_FUNC, \
378 FRONT_MASK, BACK_MASK, \
379 FRONT_REF, BACK_REF, \
380 FRONT_WRITE_MASK, BACK_WRITE_MASK) \
381 GR_STATIC_CONST_STENCIL_STRUCT(NAME ## _STRUCT, \
382 (FRONT_PASS_OP),(BACK_PASS_OP),(FRONT_FAIL_OP),(BACK_FAIL_OP), \
383 (FRONT_FUNC),(BACK_FUNC),(FRONT_MASK),(BACK_MASK), \
384 (FRONT_REF),(BACK_REF),(FRONT_WRITE_MASK),(BACK_WRITE_MASK)) \
385 static const GrStencilSettings& NAME = \
386 *GR_CONST_STENCIL_SETTINGS_PTR_FROM_STRUCT_PTR(&(NAME ## _STRUCT));
387
388
389 #define GR_STATIC_CONST_SAME_STENCIL(NAME, \
390 PASS_OP, FAIL_OP, FUNC, MASK, REF, WRITE_MASK) \
391 GR_STATIC_CONST_STENCIL(NAME, (PASS_OP), (PASS_OP), (FAIL_OP), \
392 (FAIL_OP), (FUNC), (FUNC), (MASK), (MASK), (REF), (REF), (WRITE_MASK), \
393 (WRITE_MASK))
394
395 #endif

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