1 /*
2 * Copyright 2017 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 #include "GrCCCoverageProcessor.h"
9
10 #include "GrMesh.h"
11 #include "glsl/GrGLSLVertexGeoBuilder.h"
12
13 using InputType = GrGLSLGeometryBuilder::InputType;
14 using OutputType = GrGLSLGeometryBuilder::OutputType;
15
16 /**
17 * This class and its subclasses implement the coverage processor with geometry shaders.
18 */
19 class GrCCCoverageProcessor::GSImpl : public GrGLSLGeometryProcessor {
20 protected:
GSImpl(std::unique_ptr<Shader> shader)21 GSImpl(std::unique_ptr<Shader> shader) : fShader(std::move(shader)) {}
22
hasCoverage() const23 virtual bool hasCoverage() const { return false; }
24
setData(const GrGLSLProgramDataManager & pdman,const GrPrimitiveProcessor &,FPCoordTransformIter && transformIter)25 void setData(const GrGLSLProgramDataManager& pdman, const GrPrimitiveProcessor&,
26 FPCoordTransformIter&& transformIter) final {
27 this->setTransformDataHelper(SkMatrix::I(), pdman, &transformIter);
28 }
29
onEmitCode(EmitArgs & args,GrGPArgs * gpArgs)30 void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) final {
31 const GrCCCoverageProcessor& proc = args.fGP.cast<GrCCCoverageProcessor>();
32
33 // The vertex shader simply forwards transposed x or y values to the geometry shader.
34 SkASSERT(1 == proc.numVertexAttributes());
35 gpArgs->fPositionVar = proc.fVertexAttribute.asShaderVar();
36
37 // Geometry shader.
38 GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
39 this->emitGeometryShader(proc, varyingHandler, args.fGeomBuilder, args.fRTAdjustName);
40 varyingHandler->emitAttributes(proc);
41 varyingHandler->setNoPerspective();
42 SkASSERT(!args.fFPCoordTransformHandler->nextCoordTransform());
43
44 // Fragment shader.
45 fShader->emitFragmentCode(proc, args.fFragBuilder, args.fOutputColor, args.fOutputCoverage);
46 }
47
emitGeometryShader(const GrCCCoverageProcessor & proc,GrGLSLVaryingHandler * varyingHandler,GrGLSLGeometryBuilder * g,const char * rtAdjust) const48 void emitGeometryShader(const GrCCCoverageProcessor& proc,
49 GrGLSLVaryingHandler* varyingHandler, GrGLSLGeometryBuilder* g,
50 const char* rtAdjust) const {
51 int numInputPoints = proc.numInputPoints();
52 SkASSERT(3 == numInputPoints || 4 == numInputPoints);
53
54 int inputWidth = (4 == numInputPoints || proc.hasInputWeight()) ? 4 : 3;
55 const char* posValues = (4 == inputWidth) ? "sk_Position" : "sk_Position.xyz";
56 g->codeAppendf("float%ix2 pts = transpose(float2x%i(sk_in[0].%s, sk_in[1].%s));",
57 inputWidth, inputWidth, posValues, posValues);
58
59 GrShaderVar wind("wind", kHalf_GrSLType);
60 g->declareGlobal(wind);
61 Shader::CalcWind(proc, g, "pts", wind.c_str());
62 if (PrimitiveType::kWeightedTriangles == proc.fPrimitiveType) {
63 SkASSERT(3 == numInputPoints);
64 SkASSERT(kFloat4_GrVertexAttribType == proc.fVertexAttribute.cpuType());
65 g->codeAppendf("%s *= half(sk_in[0].sk_Position.w);", wind.c_str());
66 }
67
68 SkString emitVertexFn;
69 SkSTArray<2, GrShaderVar> emitArgs;
70 const char* corner = emitArgs.emplace_back("corner", kFloat2_GrSLType).c_str();
71 const char* bloatdir = emitArgs.emplace_back("bloatdir", kFloat2_GrSLType).c_str();
72 const char* coverage = nullptr;
73 if (this->hasCoverage()) {
74 coverage = emitArgs.emplace_back("coverage", kHalf_GrSLType).c_str();
75 }
76 const char* cornerCoverage = nullptr;
77 if (GSSubpass::kCorners == proc.fGSSubpass) {
78 cornerCoverage = emitArgs.emplace_back("corner_coverage", kHalf2_GrSLType).c_str();
79 }
80 g->emitFunction(kVoid_GrSLType, "emitVertex", emitArgs.count(), emitArgs.begin(), [&]() {
81 SkString fnBody;
82 if (coverage) {
83 fnBody.appendf("%s *= %s;", coverage, wind.c_str());
84 }
85 if (cornerCoverage) {
86 fnBody.appendf("%s.x *= %s;", cornerCoverage, wind.c_str());
87 }
88 fnBody.appendf("float2 vertexpos = fma(%s, float2(bloat), %s);", bloatdir, corner);
89 fShader->emitVaryings(varyingHandler, GrGLSLVarying::Scope::kGeoToFrag, &fnBody,
90 "vertexpos", coverage ? coverage : wind.c_str(), cornerCoverage);
91 g->emitVertex(&fnBody, "vertexpos", rtAdjust);
92 return fnBody;
93 }().c_str(), &emitVertexFn);
94
95 float bloat = kAABloatRadius;
96 #ifdef SK_DEBUG
97 if (proc.debugBloatEnabled()) {
98 bloat *= proc.debugBloat();
99 }
100 #endif
101 g->defineConstant("bloat", bloat);
102
103 this->onEmitGeometryShader(proc, g, wind, emitVertexFn.c_str());
104 }
105
106 virtual void onEmitGeometryShader(const GrCCCoverageProcessor&, GrGLSLGeometryBuilder*,
107 const GrShaderVar& wind, const char* emitVertexFn) const = 0;
108
~GSImpl()109 virtual ~GSImpl() {}
110
111 const std::unique_ptr<Shader> fShader;
112
113 typedef GrGLSLGeometryProcessor INHERITED;
114 };
115
116 /**
117 * Generates conservative rasters around a triangle and its edges, and calculates coverage ramps.
118 *
119 * Triangle rough outlines are drawn in two steps: (1) draw a conservative raster of the entire
120 * triangle, with a coverage of +1, and (2) draw conservative rasters around each edge, with a
121 * coverage ramp from -1 to 0. These edge coverage values convert jagged conservative raster edges
122 * into smooth, antialiased ones.
123 *
124 * The final corners get touched up in a later step by GSTriangleCornerImpl.
125 */
126 class GrCCCoverageProcessor::GSTriangleHullImpl : public GrCCCoverageProcessor::GSImpl {
127 public:
GSTriangleHullImpl(std::unique_ptr<Shader> shader)128 GSTriangleHullImpl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
129
hasCoverage() const130 bool hasCoverage() const override { return true; }
131
onEmitGeometryShader(const GrCCCoverageProcessor &,GrGLSLGeometryBuilder * g,const GrShaderVar & wind,const char * emitVertexFn) const132 void onEmitGeometryShader(const GrCCCoverageProcessor&, GrGLSLGeometryBuilder* g,
133 const GrShaderVar& wind, const char* emitVertexFn) const override {
134 fShader->emitSetupCode(g, "pts", wind.c_str());
135
136 // Visualize the input triangle as upright and equilateral, with a flat base. Paying special
137 // attention to wind, we can identify the points as top, bottom-left, and bottom-right.
138 //
139 // NOTE: We generate the rasters in 5 independent invocations, so each invocation designates
140 // the corner it will begin with as the top.
141 g->codeAppendf("int i = (%s > 0 ? sk_InvocationID : 4 - sk_InvocationID) %% 3;",
142 wind.c_str());
143 g->codeAppend ("float2 top = pts[i];");
144 g->codeAppendf("float2 right = pts[(i + (%s > 0 ? 1 : 2)) %% 3];", wind.c_str());
145 g->codeAppendf("float2 left = pts[(i + (%s > 0 ? 2 : 1)) %% 3];", wind.c_str());
146
147 // Determine which direction to outset the conservative raster from each of the three edges.
148 g->codeAppend ("float2 leftbloat = sign(top - left);");
149 g->codeAppend ("leftbloat = float2(0 != leftbloat.y ? leftbloat.y : leftbloat.x, "
150 "0 != leftbloat.x ? -leftbloat.x : -leftbloat.y);");
151
152 g->codeAppend ("float2 rightbloat = sign(right - top);");
153 g->codeAppend ("rightbloat = float2(0 != rightbloat.y ? rightbloat.y : rightbloat.x, "
154 "0 != rightbloat.x ? -rightbloat.x : -rightbloat.y);");
155
156 g->codeAppend ("float2 downbloat = sign(left - right);");
157 g->codeAppend ("downbloat = float2(0 != downbloat.y ? downbloat.y : downbloat.x, "
158 "0 != downbloat.x ? -downbloat.x : -downbloat.y);");
159
160 // The triangle's conservative raster has a coverage of +1 all around.
161 g->codeAppend ("half4 coverages = half4(+1);");
162
163 // Edges have coverage ramps.
164 g->codeAppend ("if (sk_InvocationID >= 2) {"); // Are we an edge?
165 Shader::CalcEdgeCoverageAtBloatVertex(g, "top", "right",
166 "float2(+rightbloat.y, -rightbloat.x)",
167 "coverages[0]");
168 g->codeAppend ( "coverages.yzw = half3(-1, 0, -1 - coverages[0]);");
169 // Reassign bloats to characterize a conservative raster around a single edge, rather than
170 // the entire triangle.
171 g->codeAppend ( "leftbloat = downbloat = -rightbloat;");
172 g->codeAppend ("}");
173
174 // Here we generate the conservative raster geometry. The triangle's conservative raster is
175 // the convex hull of 3 pixel-size boxes centered on the input points. This translates to a
176 // convex polygon with either one, two, or three vertices at each input point (depending on
177 // how sharp the corner is) that we split between two invocations. Edge conservative rasters
178 // are convex hulls of 2 pixel-size boxes, one at each endpoint. For more details on
179 // conservative raster, see:
180 // https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter42.html
181 g->codeAppendf("bool2 left_right_notequal = notEqual(leftbloat, rightbloat);");
182 g->codeAppend ("if (all(left_right_notequal)) {");
183 // The top corner will have three conservative raster vertices. Emit the
184 // middle one first to the triangle strip.
185 g->codeAppendf( "%s(top, float2(-leftbloat.y, +leftbloat.x), coverages[0]);",
186 emitVertexFn);
187 g->codeAppend ("}");
188 g->codeAppend ("if (any(left_right_notequal)) {");
189 // Second conservative raster vertex for the top corner.
190 g->codeAppendf( "%s(top, rightbloat, coverages[1]);", emitVertexFn);
191 g->codeAppend ("}");
192
193 // Main interior body.
194 g->codeAppendf("%s(top, leftbloat, coverages[2]);", emitVertexFn);
195 g->codeAppendf("%s(right, rightbloat, coverages[1]);", emitVertexFn);
196
197 // Here the invocations diverge slightly. We can't symmetrically divide three triangle
198 // points between two invocations, so each does the following:
199 //
200 // sk_InvocationID=0: Finishes the main interior body of the triangle hull.
201 // sk_InvocationID=1: Remaining two conservative raster vertices for the third hull corner.
202 // sk_InvocationID=2..4: Finish the opposite endpoint of their corresponding edge.
203 g->codeAppendf("bool2 right_down_notequal = notEqual(rightbloat, downbloat);");
204 g->codeAppend ("if (any(right_down_notequal) || 0 == sk_InvocationID) {");
205 g->codeAppendf( "%s((0 == sk_InvocationID) ? left : right, "
206 "(0 == sk_InvocationID) ? leftbloat : downbloat, "
207 "coverages[2]);", emitVertexFn);
208 g->codeAppend ("}");
209 g->codeAppend ("if (all(right_down_notequal) && 0 != sk_InvocationID) {");
210 g->codeAppendf( "%s(right, float2(-rightbloat.y, +rightbloat.x), coverages[3]);",
211 emitVertexFn);
212 g->codeAppend ("}");
213
214 // 5 invocations: 2 triangle hull invocations and 3 edges.
215 g->configure(InputType::kLines, OutputType::kTriangleStrip, 6, 5);
216 }
217 };
218
219 /**
220 * Generates a conservative raster around a convex quadrilateral that encloses a cubic or quadratic.
221 */
222 class GrCCCoverageProcessor::GSCurveHullImpl : public GrCCCoverageProcessor::GSImpl {
223 public:
GSCurveHullImpl(std::unique_ptr<Shader> shader)224 GSCurveHullImpl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
225
onEmitGeometryShader(const GrCCCoverageProcessor &,GrGLSLGeometryBuilder * g,const GrShaderVar & wind,const char * emitVertexFn) const226 void onEmitGeometryShader(const GrCCCoverageProcessor&, GrGLSLGeometryBuilder* g,
227 const GrShaderVar& wind, const char* emitVertexFn) const override {
228 const char* hullPts = "pts";
229 fShader->emitSetupCode(g, "pts", wind.c_str(), &hullPts);
230
231 // Visualize the input (convex) quadrilateral as a square. Paying special attention to wind,
232 // we can identify the points by their corresponding corner.
233 //
234 // NOTE: We split the square down the diagonal from top-right to bottom-left, and generate
235 // the hull in two independent invocations. Each invocation designates the corner it will
236 // begin with as top-left.
237 g->codeAppend ("int i = sk_InvocationID * 2;");
238 g->codeAppendf("float2 topleft = %s[i];", hullPts);
239 g->codeAppendf("float2 topright = %s[%s > 0 ? i + 1 : 3 - i];", hullPts, wind.c_str());
240 g->codeAppendf("float2 bottomleft = %s[%s > 0 ? 3 - i : i + 1];", hullPts, wind.c_str());
241 g->codeAppendf("float2 bottomright = %s[2 - i];", hullPts);
242
243 // Determine how much to outset the conservative raster hull from the relevant edges.
244 g->codeAppend ("float2 leftbloat = float2(topleft.y > bottomleft.y ? +1 : -1, "
245 "topleft.x > bottomleft.x ? -1 : +1);");
246 g->codeAppend ("float2 upbloat = float2(topright.y > topleft.y ? +1 : -1, "
247 "topright.x > topleft.x ? -1 : +1);");
248 g->codeAppend ("float2 rightbloat = float2(bottomright.y > topright.y ? +1 : -1, "
249 "bottomright.x > topright.x ? -1 : +1);");
250
251 // Here we generate the conservative raster geometry. It is the convex hull of 4 pixel-size
252 // boxes centered on the input points, split evenly between two invocations. This translates
253 // to a polygon with either one, two, or three vertices at each input point, depending on
254 // how sharp the corner is. For more details on conservative raster, see:
255 // https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter42.html
256 g->codeAppendf("bool2 left_up_notequal = notEqual(leftbloat, upbloat);");
257 g->codeAppend ("if (all(left_up_notequal)) {");
258 // The top-left corner will have three conservative raster vertices.
259 // Emit the middle one first to the triangle strip.
260 g->codeAppendf( "%s(topleft, float2(-leftbloat.y, leftbloat.x));", emitVertexFn);
261 g->codeAppend ("}");
262 g->codeAppend ("if (any(left_up_notequal)) {");
263 // Second conservative raster vertex for the top-left corner.
264 g->codeAppendf( "%s(topleft, leftbloat);", emitVertexFn);
265 g->codeAppend ("}");
266
267 // Main interior body of this invocation's half of the hull.
268 g->codeAppendf("%s(topleft, upbloat);", emitVertexFn);
269 g->codeAppendf("%s(bottomleft, leftbloat);", emitVertexFn);
270 g->codeAppendf("%s(topright, upbloat);", emitVertexFn);
271
272 // Remaining two conservative raster vertices for the top-right corner.
273 g->codeAppendf("bool2 up_right_notequal = notEqual(upbloat, rightbloat);");
274 g->codeAppend ("if (any(up_right_notequal)) {");
275 g->codeAppendf( "%s(topright, rightbloat);", emitVertexFn);
276 g->codeAppend ("}");
277 g->codeAppend ("if (all(up_right_notequal)) {");
278 g->codeAppendf( "%s(topright, float2(-upbloat.y, upbloat.x));", emitVertexFn);
279 g->codeAppend ("}");
280
281 g->configure(InputType::kLines, OutputType::kTriangleStrip, 7, 2);
282 }
283 };
284
285 /**
286 * Generates conservative rasters around corners (aka pixel-size boxes) and calculates
287 * coverage and attenuation ramps to fix up the coverage values written by the hulls.
288 */
289 class GrCCCoverageProcessor::GSCornerImpl : public GrCCCoverageProcessor::GSImpl {
290 public:
GSCornerImpl(std::unique_ptr<Shader> shader)291 GSCornerImpl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
292
hasCoverage() const293 bool hasCoverage() const override { return true; }
294
onEmitGeometryShader(const GrCCCoverageProcessor & proc,GrGLSLGeometryBuilder * g,const GrShaderVar & wind,const char * emitVertexFn) const295 void onEmitGeometryShader(const GrCCCoverageProcessor& proc, GrGLSLGeometryBuilder* g,
296 const GrShaderVar& wind, const char* emitVertexFn) const override {
297 fShader->emitSetupCode(g, "pts", wind.c_str());
298
299 g->codeAppendf("int corneridx = sk_InvocationID;");
300 if (!proc.isTriangles()) {
301 g->codeAppendf("corneridx *= %i;", proc.numInputPoints() - 1);
302 }
303
304 g->codeAppendf("float2 corner = pts[corneridx];");
305 g->codeAppendf("float2 left = pts[(corneridx + (%s > 0 ? %i : 1)) %% %i];",
306 wind.c_str(), proc.numInputPoints() - 1, proc.numInputPoints());
307 g->codeAppendf("float2 right = pts[(corneridx + (%s > 0 ? 1 : %i)) %% %i];",
308 wind.c_str(), proc.numInputPoints() - 1, proc.numInputPoints());
309
310 g->codeAppend ("float2 leftdir = corner - left;");
311 g->codeAppend ("leftdir = (float2(0) != leftdir) ? normalize(leftdir) : float2(1, 0);");
312
313 g->codeAppend ("float2 rightdir = right - corner;");
314 g->codeAppend ("rightdir = (float2(0) != rightdir) ? normalize(rightdir) : float2(1, 0);");
315
316 // Find "outbloat" and "crossbloat" at our corner. The outbloat points diagonally out of the
317 // triangle, in the direction that should ramp to zero coverage with attenuation. The
318 // crossbloat runs perpindicular to outbloat.
319 g->codeAppend ("float2 outbloat = float2(leftdir.x > rightdir.x ? +1 : -1, "
320 "leftdir.y > rightdir.y ? +1 : -1);");
321 g->codeAppend ("float2 crossbloat = float2(-outbloat.y, +outbloat.x);");
322
323 g->codeAppend ("half attenuation; {");
324 Shader::CalcCornerAttenuation(g, "leftdir", "rightdir", "attenuation");
325 g->codeAppend ("}");
326
327 if (proc.isTriangles()) {
328 g->codeAppend ("half2 left_coverages; {");
329 Shader::CalcEdgeCoveragesAtBloatVertices(g, "left", "corner", "-outbloat",
330 "-crossbloat", "left_coverages");
331 g->codeAppend ("}");
332
333 g->codeAppend ("half2 right_coverages; {");
334 Shader::CalcEdgeCoveragesAtBloatVertices(g, "corner", "right", "-outbloat",
335 "crossbloat", "right_coverages");
336 g->codeAppend ("}");
337
338 // Emit a corner box. The first coverage argument erases the values that were written
339 // previously by the hull and edge geometry. The second pair are multiplied together by
340 // the fragment shader. They ramp to 0 with attenuation in the direction of outbloat,
341 // and linearly from left-edge coverage to right-edge coverage in the direction of
342 // crossbloat.
343 //
344 // NOTE: Since this is not a linear mapping, it is important that the box's diagonal
345 // shared edge points in the direction of outbloat.
346 g->codeAppendf("%s(corner, -crossbloat, right_coverages[1] - left_coverages[1],"
347 "half2(1 + left_coverages[1], 1));",
348 emitVertexFn);
349
350 g->codeAppendf("%s(corner, outbloat, 1 + left_coverages[0] + right_coverages[0], "
351 "half2(0, attenuation));",
352 emitVertexFn);
353
354 g->codeAppendf("%s(corner, -outbloat, -1 - left_coverages[0] - right_coverages[0], "
355 "half2(1 + left_coverages[0] + right_coverages[0], 1));",
356 emitVertexFn);
357
358 g->codeAppendf("%s(corner, crossbloat, left_coverages[1] - right_coverages[1],"
359 "half2(1 + right_coverages[1], 1));",
360 emitVertexFn);
361 } else {
362 // Curves are simpler. The first coverage value of -1 means "wind = -wind", and causes
363 // the Shader to erase what it had written previously for the hull. Then, at each vertex
364 // of the corner box, the Shader will calculate the curve's local coverage value,
365 // interpolate it alongside our attenuation parameter, and multiply the two together for
366 // a final coverage value.
367 g->codeAppendf("%s(corner, -crossbloat, -1, half2(1));", emitVertexFn);
368 g->codeAppendf("%s(corner, outbloat, -1, half2(0, attenuation));",
369 emitVertexFn);
370 g->codeAppendf("%s(corner, -outbloat, -1, half2(1));", emitVertexFn);
371 g->codeAppendf("%s(corner, crossbloat, -1, half2(1));", emitVertexFn);
372 }
373
374 g->configure(InputType::kLines, OutputType::kTriangleStrip, 4, proc.isTriangles() ? 3 : 2);
375 }
376 };
377
initGS()378 void GrCCCoverageProcessor::initGS() {
379 SkASSERT(Impl::kGeometryShader == fImpl);
380 if (4 == this->numInputPoints() || this->hasInputWeight()) {
381 fVertexAttribute =
382 {"x_or_y_values", kFloat4_GrVertexAttribType, kFloat4_GrSLType};
383 GR_STATIC_ASSERT(sizeof(QuadPointInstance) ==
384 2 * GrVertexAttribTypeSize(kFloat4_GrVertexAttribType));
385 GR_STATIC_ASSERT(offsetof(QuadPointInstance, fY) ==
386 GrVertexAttribTypeSize(kFloat4_GrVertexAttribType));
387 } else {
388 fVertexAttribute =
389 {"x_or_y_values", kFloat3_GrVertexAttribType, kFloat3_GrSLType};
390 GR_STATIC_ASSERT(sizeof(TriPointInstance) ==
391 2 * GrVertexAttribTypeSize(kFloat3_GrVertexAttribType));
392 GR_STATIC_ASSERT(offsetof(TriPointInstance, fY) ==
393 GrVertexAttribTypeSize(kFloat3_GrVertexAttribType));
394 }
395 this->setVertexAttributes(&fVertexAttribute, 1);
396 this->setWillUseGeoShader();
397 }
398
appendGSMesh(sk_sp<const GrGpuBuffer> instanceBuffer,int instanceCount,int baseInstance,SkTArray<GrMesh> * out) const399 void GrCCCoverageProcessor::appendGSMesh(sk_sp<const GrGpuBuffer> instanceBuffer, int instanceCount,
400 int baseInstance, SkTArray<GrMesh>* out) const {
401 // GSImpl doesn't actually make instanced draw calls. Instead, we feed transposed x,y point
402 // values to the GPU in a regular vertex array and draw kLines (see initGS). Then, each vertex
403 // invocation receives either the shape's x or y values as inputs, which it forwards to the
404 // geometry shader.
405 SkASSERT(Impl::kGeometryShader == fImpl);
406 GrMesh& mesh = out->emplace_back(GrPrimitiveType::kLines);
407 mesh.setNonIndexedNonInstanced(instanceCount * 2);
408 mesh.setVertexData(std::move(instanceBuffer), baseInstance * 2);
409 }
410
createGSImpl(std::unique_ptr<Shader> shadr) const411 GrGLSLPrimitiveProcessor* GrCCCoverageProcessor::createGSImpl(std::unique_ptr<Shader> shadr) const {
412 if (GSSubpass::kHulls == fGSSubpass) {
413 return this->isTriangles()
414 ? (GSImpl*) new GSTriangleHullImpl(std::move(shadr))
415 : (GSImpl*) new GSCurveHullImpl(std::move(shadr));
416 }
417 SkASSERT(GSSubpass::kCorners == fGSSubpass);
418 return new GSCornerImpl(std::move(shadr));
419 }
420