Implement support for KHR_blend_equation_advanced

src/gpu/gl/GrGLCaps.cpp

Index: src/gpu/gl/GrGLCaps.cpp
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index c9009b905362eb02ce9534af794610ebfe979294..9d14081494bb57c666adf99b1c9aba99b1e140ca 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -296,6 +296,14 @@ bool GrGLCaps::init(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {
         fStencilWrapOpsSupport = true;
     }
 
+    if (ctxInfo.hasExtension("GL_KHR_blend_equation_advanced_coherent")) {

[Mark Kilgard, 2015/04/03 18:30:04]

can you also look for NV_blend_equation_advanced_coherent here?

there was a lengthy time interval (10 months, maybe more?) before KHR
standardization where NVIDIA shipped NV_blend_equation_advanced (all Fermi and
all Kepler GPUs, except K1) & NV_blend_equation_advanced_coherent (K1 and all
Maxwell GPUs)

The KHR extension is a proper subset of the NV extension with identical enum
values for tokens in both the NV and KHR version.  So you should be able to look
for either string.

Stating this in a comment would be good historical context.

[Chris Dalton, 2015/04/17 08:37:19]

Done.

+        fBlendEquationSupport = kAdvancedCoherent_BlendEquationSupport;
+    } else if (ctxInfo.hasExtension("GL_KHR_blend_equation_advanced")) {
+        fBlendEquationSupport = kAdvanced_BlendEquationSupport;
+    } else {
+        fBlendEquationSupport = kBasic_BlendEquationSupport;
+    }
+
     if (kGL_GrGLStandard == standard) {
         fMapBufferFlags = kCanMap_MapFlag; // we require VBO support and the desktop VBO
                                             // extension includes glMapBuffer.