ccpr: Add an attenuation parameter to triangle corners

Adds an attenuation parameter to corners that corrects the over-coverage
from linear interpolation.

Adds a GM for shared corners that ensures we're doing this right.

Bug: skia:
Change-Id: Iff8bd40554f9fda2e7e03faa3c9fbefe65f27568
Reviewed-on: https://skia-review.googlesource.com/114272
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/gpu/ccpr/GrCCCubicShader.cpp b/src/gpu/ccpr/GrCCCubicShader.cpp
index 5ae51c7d9b..066f086a58 100644
--- a/src/gpu/ccpr/GrCCCubicShader.cpp
+++ b/src/gpu/ccpr/GrCCCubicShader.cpp
@@ -79,9 +79,10 @@ void GrCCCubicShader::emitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
 
 void GrCCCubicShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
                                      GrGLSLVarying::Scope scope, SkString* code,
-                                     const char* position, const char* inputCoverage,
-                                     const char* /*wind*/) {
-    SkASSERT(!inputCoverage);
+                                     const char* position, const char* coverage,
+                                     const char* attenuatedCoverage, const char* /*wind*/) {
+    SkASSERT(!coverage);
+    SkASSERT(!attenuatedCoverage);
 
     fKLMD.reset(kFloat4_GrSLType, scope);
     varyingHandler->addVarying("klmd", &fKLMD);