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1 /*
2  * Copyright 2015 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 "src/gpu/GrCaps.h"
9 
10 #include "include/gpu/GrBackendSurface.h"
11 #include "include/gpu/GrContextOptions.h"
12 #include "include/private/GrTypesPriv.h"
13 #include "src/gpu/GrBackendUtils.h"
14 #include "src/gpu/GrRenderTargetProxy.h"
15 #include "src/gpu/GrSurface.h"
16 #include "src/gpu/GrSurfaceProxy.h"
17 #include "src/gpu/GrWindowRectangles.h"
18 
GrCaps(const GrContextOptions & options)19 GrCaps::GrCaps(const GrContextOptions& options) {
20     fMipmapSupport = false;
21     fNPOTTextureTileSupport = false;
22     fReuseScratchTextures = true;
23     fReuseScratchBuffers = true;
24     fGpuTracingSupport = false;
25     fOversizedStencilSupport = false;
26     fTextureBarrierSupport = false;
27     fSampleLocationsSupport = false;
28     fDrawInstancedSupport = false;
29     fNativeDrawIndirectSupport = false;
30     fUseClientSideIndirectBuffers = false;
31     fConservativeRasterSupport = false;
32     fWireframeSupport = false;
33     fMSAAResolvesAutomatically = false;
34     fUsePrimitiveRestart = false;
35     fPreferClientSideDynamicBuffers = false;
36     fPreferFullscreenClears = false;
37     fTwoSidedStencilRefsAndMasksMustMatch = false;
38     fMustClearUploadedBufferData = false;
39     fShouldInitializeTextures = false;
40     fSupportsAHardwareBufferImages = false;
41     fFenceSyncSupport = false;
42     fSemaphoreSupport = false;
43     fCrossContextTextureSupport = false;
44     fHalfFloatVertexAttributeSupport = false;
45     fDynamicStateArrayGeometryProcessorTextureSupport = false;
46     fPerformPartialClearsAsDraws = false;
47     fPerformColorClearsAsDraws = false;
48     fAvoidLargeIndexBufferDraws = false;
49     fPerformStencilClearsAsDraws = false;
50     fTransferFromBufferToTextureSupport = false;
51     fTransferFromSurfaceToBufferSupport = false;
52     fWritePixelsRowBytesSupport = false;
53     fTransferPixelsToRowBytesSupport = false;
54     fReadPixelsRowBytesSupport = false;
55     fShouldCollapseSrcOverToSrcWhenAble = false;
56     fMustSyncGpuDuringAbandon = true;
57     fDriverDisableMSAAClipAtlas = false;
58     fDisableTessellationPathRenderer = false;
59 
60     fBlendEquationSupport = kBasic_BlendEquationSupport;
61     fAdvBlendEqDisableFlags = 0;
62 
63     fMapBufferFlags = kNone_MapFlags;
64 
65     fMaxVertexAttributes = 0;
66     fMaxRenderTargetSize = 1;
67     fMaxPreferredRenderTargetSize = 1;
68     fMaxTextureSize = 1;
69     fMaxWindowRectangles = 0;
70     fInternalMultisampleCount = 0;
71 
72     fSuppressPrints = options.fSuppressPrints;
73 #if GR_TEST_UTILS
74     fWireframeMode = options.fWireframeMode;
75 #else
76     fWireframeMode = false;
77 #endif
78     fBufferMapThreshold = options.fBufferMapThreshold;
79     fAvoidStencilBuffers = false;
80     fAvoidWritePixelsFastPath = false;
81     fRequiresManualFBBarrierAfterTessellatedStencilDraw = false;
82     fNativeDrawIndexedIndirectIsBroken = false;
83     fAvoidReorderingRenderTasks = false;
84     fAvoidDithering = false;
85 
86     fPreferVRAMUseOverFlushes = true;
87 
88     // Default to true, allow older versions of OpenGL to disable explicitly
89     fClampToBorderSupport = true;
90 
91     fDriverBugWorkarounds = options.fDriverBugWorkarounds;
92 }
93 
finishInitialization(const GrContextOptions & options)94 void GrCaps::finishInitialization(const GrContextOptions& options) {
95     if (!fNativeDrawIndirectSupport) {
96         // We will implement indirect draws with a polyfill, so the commands need to reside in CPU
97         // memory.
98         fUseClientSideIndirectBuffers = true;
99     }
100 
101     this->applyOptionsOverrides(options);
102 
103     // Our render targets are always created with textures as the color attachment, hence this min:
104     fMaxRenderTargetSize = std::min(fMaxRenderTargetSize, fMaxTextureSize);
105     fMaxPreferredRenderTargetSize = std::min(fMaxPreferredRenderTargetSize, fMaxRenderTargetSize);
106 }
107 
applyOptionsOverrides(const GrContextOptions & options)108 void GrCaps::applyOptionsOverrides(const GrContextOptions& options) {
109     fShaderCaps->applyOptionsOverrides(options);
110     this->onApplyOptionsOverrides(options);
111     if (options.fDisableDriverCorrectnessWorkarounds) {
112         SkASSERT(!fDriverDisableMSAAClipAtlas);
113         SkASSERT(!fDisableTessellationPathRenderer);
114         SkASSERT(!fAvoidStencilBuffers);
115         SkASSERT(!fAvoidWritePixelsFastPath);
116         SkASSERT(!fRequiresManualFBBarrierAfterTessellatedStencilDraw);
117         SkASSERT(!fNativeDrawIndexedIndirectIsBroken);
118         SkASSERT(!fAdvBlendEqDisableFlags);
119         SkASSERT(!fPerformColorClearsAsDraws);
120         SkASSERT(!fPerformStencilClearsAsDraws);
121         // Don't check the partial-clear workaround, since that is a backend limitation, not a
122         // driver workaround (it just so happens the fallbacks are the same).
123     }
124     if (GrContextOptions::Enable::kNo == options.fUseDrawInsteadOfClear) {
125         fPerformColorClearsAsDraws = false;
126         fPerformStencilClearsAsDraws = false;
127     } else if (GrContextOptions::Enable::kYes == options.fUseDrawInsteadOfClear) {
128         fPerformColorClearsAsDraws = true;
129         fPerformStencilClearsAsDraws = true;
130     }
131 
132     fMaxTextureSize = std::min(fMaxTextureSize, options.fMaxTextureSizeOverride);
133 #if GR_TEST_UTILS
134     if (options.fSuppressAdvancedBlendEquations) {
135         fBlendEquationSupport = kBasic_BlendEquationSupport;
136     }
137     if (options.fClearAllTextures) {
138         fShouldInitializeTextures = true;
139     }
140     if (options.fDisallowWriteAndTransferPixelRowBytes) {
141         fWritePixelsRowBytesSupport = false;
142         fTransferPixelsToRowBytesSupport = false;
143     }
144     if (options.fAlwaysPreferHardwareTessellation) {
145         fMinPathVerbsForHwTessellation = fMinStrokeVerbsForHwTessellation = 0;
146     }
147 #endif
148     if (options.fSuppressMipmapSupport) {
149         fMipmapSupport = false;
150     }
151 
152     if (fMaxWindowRectangles > GrWindowRectangles::kMaxWindows) {
153         SkDebugf("WARNING: capping window rectangles at %i. HW advertises support for %i.\n",
154                  GrWindowRectangles::kMaxWindows, fMaxWindowRectangles);
155         fMaxWindowRectangles = GrWindowRectangles::kMaxWindows;
156     }
157 
158     fInternalMultisampleCount = options.fInternalMultisampleCount;
159 
160     fAvoidStencilBuffers = options.fAvoidStencilBuffers;
161 
162     fDriverBugWorkarounds.applyOverrides(options.fDriverBugWorkarounds);
163 }
164 
165 
166 #ifdef SK_ENABLE_DUMP_GPU
167 #include "src/gpu/GrTestUtils.h"
168 #include "src/utils/SkJSONWriter.h"
169 
map_flags_to_string(uint32_t flags)170 static SkString map_flags_to_string(uint32_t flags) {
171     SkString str;
172     if (GrCaps::kNone_MapFlags == flags) {
173         str = "none";
174     } else {
175         SkASSERT(GrCaps::kCanMap_MapFlag & flags);
176         SkDEBUGCODE(flags &= ~GrCaps::kCanMap_MapFlag);
177         str = "can_map";
178 
179         if (GrCaps::kSubset_MapFlag & flags) {
180             str.append(" partial");
181         } else {
182             str.append(" full");
183         }
184         SkDEBUGCODE(flags &= ~GrCaps::kSubset_MapFlag);
185         if (GrCaps::kAsyncRead_MapFlag & flags) {
186             str.append(" async_read");
187         } else {
188             str.append(" sync_read");
189         }
190         SkDEBUGCODE(flags &= ~GrCaps::kAsyncRead_MapFlag);
191     }
192     SkASSERT(0 == flags); // Make sure we handled all the flags.
193     return str;
194 }
195 
dumpJSON(SkJSONWriter * writer) const196 void GrCaps::dumpJSON(SkJSONWriter* writer) const {
197     writer->beginObject();
198 
199     writer->appendBool("MIP Map Support", fMipmapSupport);
200     writer->appendBool("NPOT Texture Tile Support", fNPOTTextureTileSupport);
201     writer->appendBool("Reuse Scratch Textures", fReuseScratchTextures);
202     writer->appendBool("Reuse Scratch Buffers", fReuseScratchBuffers);
203     writer->appendBool("Gpu Tracing Support", fGpuTracingSupport);
204     writer->appendBool("Oversized Stencil Support", fOversizedStencilSupport);
205     writer->appendBool("Texture Barrier Support", fTextureBarrierSupport);
206     writer->appendBool("Sample Locations Support", fSampleLocationsSupport);
207     writer->appendBool("Draw Instanced Support", fDrawInstancedSupport);
208     writer->appendBool("Native Draw Indirect Support", fNativeDrawIndirectSupport);
209     writer->appendBool("Use client side indirect buffers", fUseClientSideIndirectBuffers);
210     writer->appendBool("Conservative Raster Support", fConservativeRasterSupport);
211     writer->appendBool("Wireframe Support", fWireframeSupport);
212     writer->appendBool("MSAA Resolves Automatically", fMSAAResolvesAutomatically);
213     writer->appendBool("Use primitive restart", fUsePrimitiveRestart);
214     writer->appendBool("Prefer client-side dynamic buffers", fPreferClientSideDynamicBuffers);
215     writer->appendBool("Prefer fullscreen clears (and stencil discard)", fPreferFullscreenClears);
216     writer->appendBool("Two-sided Stencil Refs And Masks Must Match",
217                        fTwoSidedStencilRefsAndMasksMustMatch);
218     writer->appendBool("Must clear buffer memory", fMustClearUploadedBufferData);
219     writer->appendBool("Should initialize textures", fShouldInitializeTextures);
220     writer->appendBool("Supports importing AHardwareBuffers", fSupportsAHardwareBufferImages);
221     writer->appendBool("Fence sync support", fFenceSyncSupport);
222     writer->appendBool("Semaphore support", fSemaphoreSupport);
223     writer->appendBool("Cross context texture support", fCrossContextTextureSupport);
224     writer->appendBool("Half float vertex attribute support", fHalfFloatVertexAttributeSupport);
225     writer->appendBool("Specify GeometryProcessor textures as a dynamic state array",
226                        fDynamicStateArrayGeometryProcessorTextureSupport);
227     writer->appendBool("Use draws for partial clears", fPerformPartialClearsAsDraws);
228     writer->appendBool("Use draws for color clears", fPerformColorClearsAsDraws);
229     writer->appendBool("Avoid Large IndexBuffer Draws", fAvoidLargeIndexBufferDraws);
230     writer->appendBool("Use draws for stencil clip clears", fPerformStencilClearsAsDraws);
231     writer->appendBool("Supports transfers from buffers to textures",
232                        fTransferFromBufferToTextureSupport);
233     writer->appendBool("Supports transfers from textures to buffers",
234                        fTransferFromSurfaceToBufferSupport);
235     writer->appendBool("Write pixels row bytes support", fWritePixelsRowBytesSupport);
236     writer->appendBool("Transfer pixels to row bytes support", fTransferPixelsToRowBytesSupport);
237     writer->appendBool("Read pixels row bytes support", fReadPixelsRowBytesSupport);
238     writer->appendBool("Disable msaa clip mask atlas on current driver [workaround]",
239                        fDriverDisableMSAAClipAtlas);
240     writer->appendBool("Disable TessellationPathRenderer current driver [workaround]",
241                        fDisableTessellationPathRenderer);
242     writer->appendBool("Clamp-to-border", fClampToBorderSupport);
243 
244     writer->appendBool("Prefer VRAM Use over flushes [workaround]", fPreferVRAMUseOverFlushes);
245     writer->appendBool("Avoid stencil buffers [workaround]", fAvoidStencilBuffers);
246     writer->appendBool("Avoid writePixels fast path [workaround]", fAvoidWritePixelsFastPath);
247     writer->appendBool("Requires manual FB barrier after tessellated stencilDraw [workaround]",
248                        fRequiresManualFBBarrierAfterTessellatedStencilDraw);
249     writer->appendBool("Native draw indexed indirect is broken [workaround]",
250                        fNativeDrawIndexedIndirectIsBroken);
251     writer->appendBool("Avoid DAG reordering [workaround]", fAvoidReorderingRenderTasks);
252     writer->appendBool("Avoid Dithering [workaround]", fAvoidDithering);
253 
254     if (this->advancedBlendEquationSupport()) {
255         writer->appendHexU32("Advanced Blend Equation Disable Flags", fAdvBlendEqDisableFlags);
256     }
257 
258     writer->appendS32("Max Vertex Attributes", fMaxVertexAttributes);
259     writer->appendS32("Max Texture Size", fMaxTextureSize);
260     writer->appendS32("Max Render Target Size", fMaxRenderTargetSize);
261     writer->appendS32("Max Preferred Render Target Size", fMaxPreferredRenderTargetSize);
262     writer->appendS32("Max Window Rectangles", fMaxWindowRectangles);
263     writer->appendS32("Sample Count for Internal MSAA", fInternalMultisampleCount);
264     writer->appendS32("Min Path Verbs for HW Tessellation", fMinPathVerbsForHwTessellation);
265     writer->appendS32("Min Stroke Verbs for HW Tessellation", fMinStrokeVerbsForHwTessellation);
266 
267     static const char* kBlendEquationSupportNames[] = {
268         "Basic",
269         "Advanced",
270         "Advanced Coherent",
271     };
272     static_assert(0 == kBasic_BlendEquationSupport);
273     static_assert(1 == kAdvanced_BlendEquationSupport);
274     static_assert(2 == kAdvancedCoherent_BlendEquationSupport);
275     static_assert(SK_ARRAY_COUNT(kBlendEquationSupportNames) == kLast_BlendEquationSupport + 1);
276 
277     writer->appendString("Blend Equation Support",
278                          kBlendEquationSupportNames[fBlendEquationSupport]);
279     writer->appendString("Map Buffer Support", map_flags_to_string(fMapBufferFlags).c_str());
280 
281     this->onDumpJSON(writer);
282 
283     writer->appendName("shaderCaps");
284     this->shaderCaps()->dumpJSON(writer);
285 
286     writer->endObject();
287 }
288 #else
dumpJSON(SkJSONWriter * writer) const289 void GrCaps::dumpJSON(SkJSONWriter* writer) const { }
290 #endif
291 
surfaceSupportsWritePixels(const GrSurface * surface) const292 bool GrCaps::surfaceSupportsWritePixels(const GrSurface* surface) const {
293     return surface->readOnly() ? false : this->onSurfaceSupportsWritePixels(surface);
294 }
295 
canCopySurface(const GrSurfaceProxy * dst,const GrSurfaceProxy * src,const SkIRect & srcRect,const SkIPoint & dstPoint) const296 bool GrCaps::canCopySurface(const GrSurfaceProxy* dst, const GrSurfaceProxy* src,
297                             const SkIRect& srcRect, const SkIPoint& dstPoint) const {
298     if (dst->readOnly()) {
299         return false;
300     }
301 
302     if (dst->backendFormat() != src->backendFormat()) {
303         return false;
304     }
305     return this->onCanCopySurface(dst, src, srcRect, dstPoint);
306 }
307 
validateSurfaceParams(const SkISize & dimensions,const GrBackendFormat & format,GrRenderable renderable,int renderTargetSampleCnt,GrMipmapped mipped,GrTextureType textureType) const308 bool GrCaps::validateSurfaceParams(const SkISize& dimensions, const GrBackendFormat& format,
309                                    GrRenderable renderable, int renderTargetSampleCnt,
310                                    GrMipmapped mipped, GrTextureType textureType) const {
311     if (textureType != GrTextureType::kNone) {
312         if (!this->isFormatTexturable(format, textureType)) {
313             return false;
314         }
315     }
316 
317     if (GrMipmapped::kYes == mipped && !this->mipmapSupport()) {
318         return false;
319     }
320 
321     if (dimensions.width() < 1 || dimensions.height() < 1) {
322         return false;
323     }
324 
325     if (renderable == GrRenderable::kYes) {
326         if (!this->isFormatRenderable(format, renderTargetSampleCnt)) {
327             return false;
328         }
329         int maxRTSize = this->maxRenderTargetSize();
330         if (dimensions.width() > maxRTSize || dimensions.height() > maxRTSize) {
331             return false;
332         }
333     } else {
334         // We currently do not support multisampled textures
335         if (renderTargetSampleCnt != 1) {
336             return false;
337         }
338         int maxSize = this->maxTextureSize();
339         if (dimensions.width() > maxSize || dimensions.height() > maxSize) {
340             return false;
341         }
342     }
343 
344     return true;
345 }
346 
supportedReadPixelsColorType(GrColorType srcColorType,const GrBackendFormat & srcFormat,GrColorType dstColorType) const347 GrCaps::SupportedRead GrCaps::supportedReadPixelsColorType(GrColorType srcColorType,
348                                                            const GrBackendFormat& srcFormat,
349                                                            GrColorType dstColorType) const {
350     SupportedRead read = this->onSupportedReadPixelsColorType(srcColorType, srcFormat,
351                                                               dstColorType);
352 
353     // There are known problems with 24 vs 32 bit BPP with this color type. Just fail for now if
354     // using a transfer buffer.
355     if (GrColorType::kRGB_888x == read.fColorType) {
356         read.fOffsetAlignmentForTransferBuffer = 0;
357     }
358     // It's very convenient to access 1 byte-per-channel 32 bit color types as uint32_t on the CPU.
359     // Make those aligned reads out of the buffer even if the underlying API doesn't require it.
360     auto channelFlags = GrColorTypeChannelFlags(read.fColorType);
361     if ((channelFlags == kRGBA_SkColorChannelFlags || channelFlags == kRGB_SkColorChannelFlags ||
362          channelFlags == kAlpha_SkColorChannelFlag || channelFlags == kGray_SkColorChannelFlag) &&
363         GrColorTypeBytesPerPixel(read.fColorType) == 4) {
364         switch (read.fOffsetAlignmentForTransferBuffer & 0b11) {
365             // offset alignment already a multiple of 4
366             case 0:
367                 break;
368             // offset alignment is a multiple of 2 but not 4.
369             case 2:
370                 read.fOffsetAlignmentForTransferBuffer *= 2;
371                 break;
372             // offset alignment is not a multiple of 2.
373             default:
374                 read.fOffsetAlignmentForTransferBuffer *= 4;
375                 break;
376         }
377     }
378     return read;
379 }
380 
getDefaultBackendFormat(GrColorType colorType,GrRenderable renderable) const381 GrBackendFormat GrCaps::getDefaultBackendFormat(GrColorType colorType,
382                                                 GrRenderable renderable) const {
383     // Unknown color types are always an invalid format, so early out before calling virtual.
384     if (colorType == GrColorType::kUnknown) {
385         return {};
386     }
387 
388     auto format = this->onGetDefaultBackendFormat(colorType);
389     if (!this->isFormatTexturable(format, GrTextureType::k2D)) {
390         return {};
391     }
392     if (!this->areColorTypeAndFormatCompatible(colorType, format)) {
393         return {};
394     }
395     // Currently we require that it be possible to write pixels into the "default" format. Perhaps,
396     // that could be a separate requirement from the caller. It seems less necessary if
397     // renderability was requested.
398     if (this->supportedWritePixelsColorType(colorType, format, colorType).fColorType ==
399         GrColorType::kUnknown) {
400         return {};
401     }
402     if (renderable == GrRenderable::kYes &&
403         !this->isFormatAsColorTypeRenderable(colorType, format)) {
404         return {};
405     }
406     return format;
407 }
408 
areColorTypeAndFormatCompatible(GrColorType grCT,const GrBackendFormat & format) const409 bool GrCaps::areColorTypeAndFormatCompatible(GrColorType grCT,
410                                              const GrBackendFormat& format) const {
411     if (GrColorType::kUnknown == grCT) {
412         return false;
413     }
414 
415     SkImage::CompressionType compression = GrBackendFormatToCompressionType(format);
416     if (compression != SkImage::CompressionType::kNone) {
417         return grCT == (SkCompressionTypeIsOpaque(compression) ? GrColorType::kRGB_888x
418                                                                : GrColorType::kRGBA_8888);
419     }
420 
421     return this->onAreColorTypeAndFormatCompatible(grCT, format);
422 }
423 
getReadSwizzle(const GrBackendFormat & format,GrColorType colorType) const424 GrSwizzle GrCaps::getReadSwizzle(const GrBackendFormat& format, GrColorType colorType) const {
425     SkImage::CompressionType compression = GrBackendFormatToCompressionType(format);
426     if (compression != SkImage::CompressionType::kNone) {
427         if (colorType == GrColorType::kRGB_888x || colorType == GrColorType::kRGBA_8888) {
428             return GrSwizzle::RGBA();
429         }
430         SkDEBUGFAILF("Illegal color type (%d) and compressed format (%d) combination.",
431                      (int)colorType, (int)compression);
432         return {};
433     }
434 
435     return this->onGetReadSwizzle(format, colorType);
436 }
437 
isFormatCompressed(const GrBackendFormat & format) const438 bool GrCaps::isFormatCompressed(const GrBackendFormat& format) const {
439     return GrBackendFormatToCompressionType(format) != SkImage::CompressionType::kNone;
440 }
441 
getDstSampleFlagsForProxy(const GrRenderTargetProxy * rt,bool drawUsesMSAA) const442 GrDstSampleFlags GrCaps::getDstSampleFlagsForProxy(const GrRenderTargetProxy* rt,
443                                                    bool drawUsesMSAA) const {
444     SkASSERT(rt);
445     if (this->textureBarrierSupport() && (!drawUsesMSAA || this->msaaResolvesAutomatically())) {
446         return this->onGetDstSampleFlagsForProxy(rt);
447     }
448     return GrDstSampleFlags::kNone;
449 }
450 
supportsDynamicMSAA(const GrRenderTargetProxy * rtProxy) const451 bool GrCaps::supportsDynamicMSAA(const GrRenderTargetProxy* rtProxy) const {
452     return rtProxy->numSamples() == 1 &&
453            this->internalMultisampleCount(rtProxy->backendFormat()) > 1 &&
454            this->onSupportsDynamicMSAA(rtProxy);
455 }
456 
color_type_fallback(GrColorType ct)457 static inline GrColorType color_type_fallback(GrColorType ct) {
458     switch (ct) {
459         // kRGBA_8888 is our default fallback for many color types that may not have renderable
460         // backend formats.
461         case GrColorType::kAlpha_8:
462         case GrColorType::kBGR_565:
463         case GrColorType::kABGR_4444:
464         case GrColorType::kBGRA_8888:
465         case GrColorType::kRGBA_1010102:
466         case GrColorType::kBGRA_1010102:
467         case GrColorType::kRGBA_F16:
468         case GrColorType::kRGBA_F16_Clamped:
469             return GrColorType::kRGBA_8888;
470         case GrColorType::kAlpha_F16:
471             return GrColorType::kRGBA_F16;
472         case GrColorType::kGray_8:
473             return GrColorType::kRGB_888x;
474         default:
475             return GrColorType::kUnknown;
476     }
477 }
478 
getFallbackColorTypeAndFormat(GrColorType ct,int sampleCnt) const479 std::tuple<GrColorType, GrBackendFormat> GrCaps::getFallbackColorTypeAndFormat(
480                                                                             GrColorType ct,
481                                                                             int sampleCnt) const {
482     do {
483         auto format = this->getDefaultBackendFormat(ct, GrRenderable::kYes);
484         // We continue to the fallback color type if there no default renderable format or we
485         // requested msaa and the format doesn't support msaa.
486         if (format.isValid() && this->isFormatRenderable(format, sampleCnt)) {
487             return {ct, format};
488         }
489         ct = color_type_fallback(ct);
490     } while (ct != GrColorType::kUnknown);
491     return {GrColorType::kUnknown, {}};
492 }
493