Expose vertex position to GrGLEffect via GrGLShaderBuilder.

R=robertphillips@google.com
Review URL: https://codereview.appspot.com/6814054

git-svn-id: http://skia.googlecode.com/svn/branches/gpu_dev@6195 2bbb7eff-a529-9590-31e7-b0007b416f81

4 files changed, 24 insertions, 13 deletions

diff --git a/src/gpu/gl/GrGLProgram.cpp b/src/gpu/gl/GrGLProgram.cpp
index f9912aafb6..44502095d1 100644
--- a/src/gpu/gl/GrGLProgram.cpp
+++ b/src/gpu/gl/GrGLProgram.cpp
@@ -25,7 +25,6 @@ SK_DEFINE_INST_COUNT(GrGLProgram)
 
 typedef GrGLProgram::Desc::StageDesc StageDesc;
 
-#define POS_ATTR_NAME "aPosition"
 #define COL_ATTR_NAME "aColor"
 #define COV_ATTR_NAME "aCoverage"
 #define EDGE_ATTR_NAME "aEdge"
@@ -567,13 +566,10 @@ bool GrGLProgram::genProgram(const GrEffectStage* stages[]) {
     fUniforms.fViewMatrixUni = builder.addUniform(GrGLShaderBuilder::kVertex_ShaderType,
                                                   kMat33f_GrSLType, "ViewM", &viewMName);
 
-    builder.fVSAttrs.push_back().set(kVec2f_GrSLType,
-                                     GrGLShaderVar::kAttribute_TypeModifier,
-                                     POS_ATTR_NAME);
-
-    builder.fVSCode.appendf("\tvec3 pos3 = %s * vec3("POS_ATTR_NAME", 1);\n"
+    
+    builder.fVSCode.appendf("\tvec3 pos3 = %s * vec3(%s, 1);\n"
                             "\tgl_Position = vec4(pos3.xy, 0, pos3.z);\n",
-                            viewMName);
+                            viewMName, builder.positionAttribute().getName().c_str());
 
     // incoming color to current stage being processed.
     SkString inColor;
@@ -616,7 +612,7 @@ bool GrGLProgram::genProgram(const GrEffectStage* stages[]) {
                 // figure out what our input coords are
                 int tcIdx = GrDrawTarget::VertexTexCoordsForStage(s, layout);
                 if (tcIdx < 0) {
-                    inCoords = POS_ATTR_NAME;
+                    inCoords = builder.positionAttribute().c_str();
                 } else {
                     // must have input tex coordinates if stage is enabled.
                     GrAssert(texCoordAttrs[tcIdx].size());
@@ -713,7 +709,7 @@ bool GrGLProgram::genProgram(const GrEffectStage* stages[]) {
                     int tcIdx =
                         GrDrawTarget::VertexTexCoordsForStage(s, layout);
                     if (tcIdx < 0) {
-                        inCoords = POS_ATTR_NAME;
+                        inCoords = builder.positionAttribute().c_str();
                     } else {
                         // must have input tex coordinates if stage is
                         // enabled.
@@ -801,7 +797,8 @@ bool GrGLProgram::genProgram(const GrEffectStage* stages[]) {
         return false;
     }
 
-    if (!this->bindOutputsAttribsAndLinkProgram(texCoordAttrs,
+    if (!this->bindOutputsAttribsAndLinkProgram(builder,
+                                                texCoordAttrs,
                                                 isColorDeclared,
                                                 dualSourceOutputWritten)) {
         return false;
@@ -814,7 +811,8 @@ bool GrGLProgram::genProgram(const GrEffectStage* stages[]) {
     return true;
 }
 
-bool GrGLProgram::bindOutputsAttribsAndLinkProgram(SkString texCoordAttrNames[],
+bool GrGLProgram::bindOutputsAttribsAndLinkProgram(const GrGLShaderBuilder& builder,
+                                                   SkString texCoordAttrNames[],
                                                    bool bindColorOut,
                                                    bool bindDualSrcOut) {
     GL_CALL_RET(fProgramID, CreateProgram());
@@ -836,7 +834,9 @@ bool GrGLProgram::bindOutputsAttribsAndLinkProgram(SkString texCoordAttrNames[],
     }
 
     // Bind the attrib locations to same values for all shaders
-    GL_CALL(BindAttribLocation(fProgramID, PositionAttributeIdx(), POS_ATTR_NAME));
+    GL_CALL(BindAttribLocation(fProgramID,
+                               PositionAttributeIdx(),
+                               builder.positionAttribute().c_str()));
     for (int t = 0; t < GrDrawState::kMaxTexCoords; ++t) {
         if (texCoordAttrNames[t].size()) {
             GL_CALL(BindAttribLocation(fProgramID,
diff --git a/src/gpu/gl/GrGLProgram.h b/src/gpu/gl/GrGLProgram.h
index 000ebe8f19..a023de79d1 100644
--- a/src/gpu/gl/GrGLProgram.h
+++ b/src/gpu/gl/GrGLProgram.h
@@ -194,7 +194,8 @@ private:
     bool genEdgeCoverage(SkString* coverageVar, GrGLShaderBuilder* builder) const;
 
     // Creates a GL program ID, binds shader attributes to GL vertex attrs, and links the program
-    bool bindOutputsAttribsAndLinkProgram(SkString texCoordAttrNames[GrDrawState::kMaxTexCoords],
+    bool bindOutputsAttribsAndLinkProgram(const GrGLShaderBuilder& builder,
+                                          SkString texCoordAttrNames[GrDrawState::kMaxTexCoords],
                                           bool bindColorOut,
                                           bool bindDualSrcOut);
 
diff --git a/src/gpu/gl/GrGLShaderBuilder.cpp b/src/gpu/gl/GrGLShaderBuilder.cpp
index ec7199b782..463c0363eb 100644
--- a/src/gpu/gl/GrGLShaderBuilder.cpp
+++ b/src/gpu/gl/GrGLShaderBuilder.cpp
@@ -96,6 +96,9 @@ GrGLShaderBuilder::GrGLShaderBuilder(const GrGLContextInfo& ctx, GrGLUniformMana
     , fSetupFragPosition(false)
     , fRTHeightUniform(GrGLUniformManager::kInvalidUniformHandle)
     , fTexCoordVaryingType(kVoid_GrSLType) {
+    
+    fPositionVar = &fVSAttrs.push_back();
+    fPositionVar->set(kVec2f_GrSLType, GrGLShaderVar::kAttribute_TypeModifier, "aPosition");
 }
 
 void GrGLShaderBuilder::setupTextureAccess(const char* varyingFSName, GrSLType varyingType) {
diff --git a/src/gpu/gl/GrGLShaderBuilder.h b/src/gpu/gl/GrGLShaderBuilder.h
index 8f5d6956ac..6fdec63e36 100644
--- a/src/gpu/gl/GrGLShaderBuilder.h
+++ b/src/gpu/gl/GrGLShaderBuilder.h
@@ -170,6 +170,11 @@ public:
         is in device space (e.g. 0,0 is the top left and pixel centers are at half-integers). */
     const char* fragmentPosition();
 
+    /** Returns a vertex attribute that represents the vertex position in the VS. This is the
+        pre-matrix position and is commonly used by effects to compute texture coords via a matrix.
+      */
+    const GrGLShaderVar& positionAttribute() const { return *fPositionVar; }
+
     /** Called after building is complete to get the final shader string. */
     void getShader(ShaderType, SkString*) const;
 
@@ -227,6 +232,8 @@ private:
     bool                                fSetupFragPosition;
     GrGLUniformManager::UniformHandle   fRTHeightUniform;
 
+    GrGLShaderVar*                      fPositionVar;
+
     /// Per-stage settings - only valid while we're inside GrGLProgram::genStageCode().
     //@{
     GrSLType         fTexCoordVaryingType;  // the type, either Vec2f or Vec3f, of the coords passed