Add "sample locations" feature to GrProcessor

src/gpu/GrGpu.cpp

Index: src/gpu/GrGpu.cpp
diff --git a/src/gpu/GrGpu.cpp b/src/gpu/GrGpu.cpp
index 4e0464a4ce6cb74f0e2c734b5fef8b1f3685e391..566f2be8e18264956a96d4ad32b608e3ee0954c0 100644
--- a/src/gpu/GrGpu.cpp
+++ b/src/gpu/GrGpu.cpp
@@ -47,7 +47,8 @@ GrVertices& GrVertices::operator =(const GrVertices& di) {
 GrGpu::GrGpu(GrContext* context)
     : fResetTimestamp(kExpiredTimestamp+1)
     , fResetBits(kAll_GrBackendState)
-    , fContext(context) {
+    , fContext(context)
+    , fNextSamplePatternID(1) {
 }
 
 GrGpu::~GrGpu() {}
@@ -444,6 +445,57 @@ void GrGpu::resolveRenderTarget(GrRenderTarget* target) {
     this->onResolveRenderTarget(target);
 }
 
+const GrGpu::MultisampleSpecs& GrGpu::getMultisampleSpecs(GrRenderTarget* rt,
+                                                          const GrStencilSettings& stencil) {
+    skstd::unique_ptr<MultisampleSpecs>* specsPtr;
+    bool willUseRasterMultisample = rt->hasMixedSamples() && stencil.isDisabled();
+    if (willUseRasterMultisample) {
+        int rasterSampleCnt = rt->desc().fSampleCnt;
+        SkASSERT(rasterSampleCnt > 0 && rasterSampleCnt <= this->caps()->maxRasterSamples());
+        fRasterMultisampleSpecs.resize_back(SkTMax(fRasterMultisampleSpecs.count(),
+                                                   rasterSampleCnt));
+        specsPtr = &fRasterMultisampleSpecs[rasterSampleCnt - 1];
+    } else {
+        specsPtr = rt->renderTargetPriv().accessMultisampleSpecs();
+    }
+    if (!specsPtr->get()) {
+        MultisampleSpecs* specs = new MultisampleSpecs;
+        SkSTArray<16, SkPoint, true> samplePattern;
+        this->onGetMultisampleSpecs(rt, stencil, &specs->fEffectiveSampleCnt, &samplePattern);
+        if (this->caps()->sampleLocationsSupport()) {
+            SkASSERT(!samplePattern.empty());
+            const auto& result = fKnownSamplePatterns.emplace(samplePattern, fNextSamplePatternID);
+            if (result.second) {
+                // This sample pattern didn't exist already in the map. (We don't expect to see very
+                // many unique sample patterns).
+                SkASSERT(fKnownSamplePatterns.size() < 65535);
+                do {} while (0 == ++fNextSamplePatternID);
+            }
+            specs->fSamplePatternID = result.first->second;
+            specs->fSampleLocations = result.first->first.begin();
+        }
+        specsPtr->reset(specs);
+    }
+    return *specsPtr->get();
+}
+
+bool GrGpu::SamplePatternComparator::operator()(const SamplePattern& a,
+                                                const SamplePattern& b) const {
+    if (a.count() != b.count()) {
+        return a.count() < b.count();
+    }
+    for (int i = 0; i < a.count(); ++i) {
+        // This doesn't have geometric meaning. We just need to define an ordering for std::map.
+        if (a[i].x() != b[i].x()) {
+            return a[i].x() < b[i].x();
+        }
+        if (a[i].y() != b[i].y()) {
+            return a[i].y() < b[i].y();
+        }
+    }
+    return false; // Equal.
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 void GrGpu::draw(const DrawArgs& args, const GrVertices& vertices) {