Key shader on whether frag pos read is relative to top-left or bottom-left

src/gpu/gl/GrGLProgramDesc.cpp

Index: src/gpu/gl/GrGLProgramDesc.cpp
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index a1cd85e9f4afb6d5ad2770fd9ac03a50292ccdca..61f6dd9e1095bfcad00e07143a62d9f83c1953b3 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -76,6 +76,7 @@ void GrGLProgramDesc::Build(const GrDrawState& drawState,
     }
 
     bool readsDst = false;
+    bool readFragPosition = false;
     int lastEnabledStage = -1;
 
     for (int s = 0; s < GrDrawState::kNumStages; ++s) {
@@ -90,6 +91,9 @@ void GrGLProgramDesc::Build(const GrDrawState& drawState,
             if (effect->willReadDstColor()) {
                 readsDst = true;
             }
+            if (effect->willReadFragmentPosition()) {
+                readFragPosition = true;
+            }
         } else {
             desc->fEffectKeys[s] = 0;
         }
@@ -107,6 +111,13 @@ void GrGLProgramDesc::Build(const GrDrawState& drawState,
         desc->fDstRead = 0;
     }
 
+    if (readFragPosition) {
+        desc->fFragPos = GrGLShaderBuilder::KeyForFragmentPosition(drawState.getRenderTarget(),
+                                                                   gpu->glCaps());
+    } else {

[robertphillips, 2013/05/10 13:53:58]

Use 'kNoFragPosRead_FragPosKey' here?

[bsalomon, 2013/05/13 15:16:49]

It's private. I think in the long run the desc should be a nested class of the
builder and this enum could be visible to both.

+        desc->fFragPos = 0;
+    }
+
     desc->fCoverageOutput = kModulate_CoverageOutput;
 
     // Currently the experimental GS will only work with triangle prims (and it doesn't do anything