commit d31b5e748943ed30412cc3d02ea12952a99c9e07
author Chris Dalton <csmartdalton@google.com> Tue Feb 26 18:02:16 2019 -0700
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Thu Feb 28 21:19:22 2019 +0000
tree b45135ee33d5a5bb06d93c6a92092f79e9ed365a
parent 3d76d1bf4689d1b95fbcadd8da3fc42d9430d13d

Revert "Drop unused shader support for sample variables"

This restores support for sample variables and improves on the
original API.

A test will come once we restore support for sample locations.

Bug: skia:
Change-Id: I350cc08477c532a13ff7acdd8055c0aa65c51d26
Reviewed-on: https://skia-review.googlesource.com/c/195720
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp

diff --git a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
index 511df10..361221a 100644
--- a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
@@ -72,6 +72,7 @@
     , fHasCustomColorOutput(false)
     , fCustomColorOutputIndex(-1)
     , fHasSecondaryOutput(false)
+    , fHasInitializedSampleMask(false)
     , fForceHighPrecision(false) {
     fSubstageIndices.push_back(0);
 #ifdef SK_DEBUG
@@ -92,6 +93,28 @@
     return coords2D;
 }
 
+void GrGLSLFragmentShaderBuilder::maskOffMultisampleCoverage(const char* mask, Scope scope) {
+    const GrShaderCaps& shaderCaps = *fProgramBuilder->shaderCaps();
+    if (!shaderCaps.sampleVariablesSupport()) {
+        SkDEBUGFAIL("Attempted to mask sample coverage without support.");
+        return;
+    }
+    if (const char* extension = shaderCaps.sampleVariablesExtensionString()) {
+        this->addFeature(1 << kSampleVariables_GLSLPrivateFeature, extension);
+    }
+
+    if (!fHasInitializedSampleMask && Scope::kTopLevel == scope) {
+        this->codeAppendf("gl_SampleMask[0] = (%s);", mask);
+        fHasInitializedSampleMask = true;
+        return;
+    }
+    if (!fHasInitializedSampleMask) {
+        this->codePrependf("gl_SampleMask[0] = ~0;");
+        fHasInitializedSampleMask = true;
+    }
+    this->codeAppendf("gl_SampleMask[0] &= (%s);", mask);
+}
+
 const char* GrGLSLFragmentShaderBuilder::dstColor() {
     SkDEBUGCODE(fHasReadDstColor = true;)