Add "sample locations" feature to GrProcessor

src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp

Index: src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
diff --git a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
index 44db57e68d840067e7cd6da474b026bb60e84366..a7d383532e3bf090aa44f425043bfa742156fc6e 100644
--- a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
@@ -170,6 +170,11 @@ const char* GrGLSLFragmentShaderBuilder::fragmentPosition() {
     }
 }
 
+void GrGLSLFragmentShaderBuilder::appendSampleOffset(const char* sampleIdx) {
+    SkASSERT(fProgramBuilder->pipeline().hasSampleLocations());

[Chris Dalton, 2016/02/23 01:51:01]

I guess maskSampleCoverage() does a test/SkDEBUGFAIL/return instead of just an
assert.

Is there a preference on how to handle this? I don't see much precedent in this
file for asserts.

+    this->codeAppendf("sampleOffsets[%s]", sampleIdx);
+}
+
 void GrGLSLFragmentShaderBuilder::maskSampleCoverage(const char* mask, bool invert) {
     const GrGLSLCaps& glslCaps = *fProgramBuilder->glslCaps();
     if (!glslCaps.sampleVariablesSupport()) {
@@ -306,6 +311,23 @@ void GrGLSLFragmentShaderBuilder::onFinalize() {
     GrGLSLAppendDefaultFloatPrecisionDeclaration(kDefault_GrSLPrecision,
                                                  *fProgramBuilder->glslCaps(),
                                                  &this->precisionQualifier());
+    if (fProgramBuilder->pipeline().hasSampleLocations()) {
+        const GrPipeline& pipeline = fProgramBuilder->pipeline();
+        int effectiveSampleCnt = pipeline.effectiveSampleCount();
+        const SkPoint* sampleLocations = pipeline.getSampleLocations();
+        this->definitions().append("const ");
+        if (fProgramBuilder->glslCaps()->usesPrecisionModifiers()) {
+            this->definitions().append("highp ");
+        }
+        this->definitions().appendf("vec2 sampleOffsets[] = vec2[](");
+        for (int i = 0; i < effectiveSampleCnt; ++i) {
+            this->definitions().appendf("vec2(%f, %f)%s",
+                                        sampleLocations[i].x() - 0.5f,
+                                        sampleLocations[i].y() - 0.5f,
+                                        i + 1 != effectiveSampleCnt ? ", " : ");\n");
+        }
+        SkASSERT(fProgramBuilder->header().fSamplePatternKey == pipeline.getSamplePatternID());
+    }
 }
 
 void GrGLSLFragmentShaderBuilder::onBeforeChildProcEmitCode() {