Refactor position computation to enable device space "nudge"

src/gpu/GrGeometryProcessor.cpp

Index: src/gpu/GrGeometryProcessor.cpp
diff --git a/src/gpu/GrGeometryProcessor.cpp b/src/gpu/GrGeometryProcessor.cpp
index 344dccc731861f7e71b32562eb8b18ced4884049..662f28f38694eaee2556a0eff6b15016b8569469 100644
--- a/src/gpu/GrGeometryProcessor.cpp
+++ b/src/gpu/GrGeometryProcessor.cpp
@@ -163,13 +163,13 @@ void GrGLPrimitiveProcessor::setUniformViewMatrix(const GrGLProgramDataManager&
 
 void GrGLGeometryProcessor::emitCode(EmitArgs& args) {
     GrGLVertexBuilder* vsBuilder = args.fPB->getVertexShaderBuilder();
-    vsBuilder->codeAppendf("vec3 %s;", this->position());
-    this->onEmitCode(args);
-    vsBuilder->transformToNormalizedDeviceSpace(this->position());
+    GrGPArgs gpArgs;
+    this->onEmitCode(args, &gpArgs);
+    vsBuilder->transformToNormalizedDeviceSpace(gpArgs.fPositionVar);
 }
 
 void GrGLGeometryProcessor::emitTransforms(GrGLGPBuilder* pb,
-                                           const char* position,
+                                           const GrShaderVar& posVar,
                                            const char* localCoords,
                                            const SkMatrix& localMatrix,
                                            const TransformsIn& tin,
@@ -214,9 +214,19 @@ void GrGLGeometryProcessor::emitTransforms(GrGLGPBuilder* pb,
             // varying = matrix * coords (logically)
             if (kDevice_GrCoordSet == coordType) {
                 if (kVec2f_GrSLType == varyingType) {
-                    vb->codeAppendf("%s = (%s * %s).xy;", v.vsOut(), uniName, position);
+                    if (kVec2f_GrSLType == posVar.getType()) {
+                        vb->codeAppendf("%s = (%s * vec3(%s, 1)).xy;",
+                                        v.vsOut(), uniName, posVar.c_str());
+                    } else {
+                        vb->codeAppendf("%s = (%s * %s).xy;", v.vsOut(), uniName, posVar.c_str());

[bsalomon, 2015/01/20 15:19:51]

Is this right? It seems like we know that the vm is likely persp since the GP
emitted a vec3 pos but that the coordxform is non-persp. Don't we have to
homogenize either before or after the xform matrix multiply? Or would we never
get here because varyingType would already be vec3 because we earlier checked
the vm for persp?

+                    }
                 } else {
-                    vb->codeAppendf("%s = %s * %s;", v.vsOut(), uniName, position);
+                    if (kVec2f_GrSLType == posVar.getType()) {
+                        vb->codeAppendf("%s = %s * vec3(%s, 1);",
+                                        v.vsOut(), uniName, posVar.c_str());
+                    } else {
+                        vb->codeAppendf("%s = %s * %s;", v.vsOut(), uniName, posVar.c_str());
+                    }
                 }
             } else {
                 if (kVec2f_GrSLType == varyingType) {
@@ -247,6 +257,28 @@ GrGLGeometryProcessor::setTransformData(const GrPrimitiveProcessor* primProc,
     }
 }
 
+void GrGLGeometryProcessor::SetupPosition(GrGLVertexBuilder* vsBuilder,
+                                          GrGPArgs* gpArgs,
+                                          const char* posName,
+                                          const SkMatrix& mat,
+                                          const char* matName) {
+    if (mat.isIdentity()) {
+        gpArgs->fPositionVar.set(kVec2f_GrSLType, "pos2");
+
+        vsBuilder->codeAppendf("vec2 %s = %s;", gpArgs->fPositionVar.c_str(), posName);
+    } else if (!mat.hasPerspective()) {
+        gpArgs->fPositionVar.set(kVec2f_GrSLType, "pos2");
+
+        vsBuilder->codeAppendf("vec2 %s = vec2(%s * vec3(%s, 1));",
+                               gpArgs->fPositionVar.c_str(), matName, posName);
+    } else {
+        gpArgs->fPositionVar.set(kVec3f_GrSLType, "pos3");
+
+        vsBuilder->codeAppendf("vec3 %s = %s * vec3(%s, 1);",
+                               gpArgs->fPositionVar.c_str(), matName, posName);
+    }
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 #include "gl/GrGLGpu.h"