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

src/gpu/gl/GrGLProgramDesc.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLProgramDesc.h"
 #include "GrBackendEffectFactory.h"
 #include "GrDrawEffect.h"
@@ skipping 58 matching lines @@
         desc->fCoverageInput = kTransBlack_ColorInput;
     } else if (covIsSolidWhite) {
         desc->fCoverageInput = kSolidWhite_ColorInput;
     } else if (GR_GL_NO_CONSTANT_ATTRIBUTES && !requiresCoverageAttrib) {
         desc->fCoverageInput = kUniform_ColorInput;
     } else {
         desc->fCoverageInput = kAttribute_ColorInput;
     }
 
     bool readsDst = false;
+    bool readFragPosition = false;
     int lastEnabledStage = -1;
 
     for (int s = 0; s < GrDrawState::kNumStages; ++s) {
 
         bool skip = s < drawState.getFirstCoverageStage() ? skipColor : skipCoverage;
         if (!skip && drawState.isStageEnabled(s)) {
             lastEnabledStage = s;
             const GrEffectRef& effect = *drawState.getStage(s).getEffect();
             const GrBackendEffectFactory& factory = effect->getFactory();
             GrDrawEffect drawEffect(drawState.getStage(s), requiresLocalCoordAttrib);
             desc->fEffectKeys[s] = factory.glEffectKey(drawEffect, gpu->glCaps());
             if (effect->willReadDstColor()) {
                 readsDst = true;
             }
+            if (effect->willReadFragmentPosition()) {
+                readFragPosition = true;
+            }
         } else {
             desc->fEffectKeys[s] = 0;
         }
     }
 
     if (readsDst) {
         GrAssert(NULL != dstCopy || gpu->caps()->dstReadInShaderSupport());
         const GrTexture* dstCopyTexture = NULL;
         if (NULL != dstCopy) {
             dstCopyTexture = dstCopy->texture();
         }
         desc->fDstRead = GrGLShaderBuilder::KeyForDstRead(dstCopyTexture, gpu->glCaps());
         GrAssert(0 != desc->fDstRead);
     } else {
         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
     // other than pass through values from the VS to the FS anyway).
 #if GR_GL_EXPERIMENTAL_GS
 #if 0
     desc->fExperimentalGS = gpu->caps().geometryShaderSupport();
 #else
     desc->fExperimentalGS = false;
 #endif
@@ skipping 71 matching lines @@
 
     if (requiresCoverageAttrib) {
         desc->fCoverageAttributeIndex = drawState.coverageVertexAttributeIndex();
     } else if (GrGLProgramDesc::kAttribute_ColorInput == desc->fCoverageInput) {
         GrAssert(availableAttributeIndex < GrDrawState::kMaxVertexAttribCnt);
         desc->fCoverageAttributeIndex = availableAttributeIndex;
     } else {
         desc->fCoverageAttributeIndex = -1;
     }
 }