fix interior issues in convex path renderer

git-svn-id: http://skia.googlecode.com/svn/trunk@3078 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 21 insertions, 10 deletions

diff --git a/src/gpu/GrGLProgram.cpp b/src/gpu/GrGLProgram.cpp
index ce5a284710..610446d615 100644
--- a/src/gpu/GrGLProgram.cpp
+++ b/src/gpu/GrGLProgram.cpp
@@ -528,23 +528,34 @@ void GrGLProgram::genEdgeCoverage(const GrGLInterface* gl,
         if (GrDrawState::kHairLine_EdgeType == fProgramDesc.fVertexEdgeType) {
             segments->fFSCode.appendf("\tfloat edgeAlpha = abs(dot(vec3(gl_FragCoord.xy,1), %s.xyz));\n", fsName);
             segments->fFSCode.append("\tedgeAlpha = max(1.0 - edgeAlpha, 0.0);\n");
+        } else if (GrDrawState::kQuad_EdgeType == fProgramDesc.fVertexEdgeType) {
+            segments->fFSCode.appendf("\tfloat edgeAlpha;\n");
+            // keep the derivative instructions outside the conditional 
+            segments->fFSCode.appendf("\tvec2 duvdx = dFdx(%s.xy);\n", fsName);
+            segments->fFSCode.appendf("\tvec2 duvdy = dFdy(%s.xy);\n", fsName);
+            segments->fFSCode.appendf("\tif (%s.z > 0.0 && %s.w > 0.0) {\n", fsName, fsName);
+            // today we know z and w are in device space. We could use derivatives
+            segments->fFSCode.appendf("\t\tedgeAlpha = min(min(%s.z, %s.w) + 0.5, 1.0);\n", fsName, fsName);
+            segments->fFSCode.append ("\t} else {\n");
+            segments->fFSCode.appendf("\t\tvec2 gF = vec2(2.0*%s.x*duvdx.x - duvdx.y,\n"
+                                      "\t\t               2.0*%s.x*duvdy.x - duvdy.y);\n",
+                                      fsName, fsName);
+            segments->fFSCode.appendf("\t\tedgeAlpha = (%s.x*%s.x - %s.y);\n", fsName, fsName, fsName);
+            segments->fFSCode.appendf("\t\tedgeAlpha = clamp(0.5 - edgeAlpha / length(gF), 0.0, 1.0);\n"
+                                      "\t}\n");
+            if (gl->supportsES2()) {
+                segments->fHeader.printf("#extension GL_OES_standard_derivatives: enable\n");
+            }
         } else {
-            GrAssert(GrDrawState::kHairQuad_EdgeType == fProgramDesc.fVertexEdgeType ||
-                     GrDrawState::kQuad_EdgeType == fProgramDesc.fVertexEdgeType);
-            // for now we know we're not in perspective, so we could compute this
-            // per-quadratic rather than per pixel
+            GrAssert(GrDrawState::kHairQuad_EdgeType == fProgramDesc.fVertexEdgeType);
             segments->fFSCode.appendf("\tvec2 duvdx = dFdx(%s.xy);\n", fsName);
             segments->fFSCode.appendf("\tvec2 duvdy = dFdy(%s.xy);\n", fsName);
             segments->fFSCode.appendf("\tvec2 gF = vec2(2.0*%s.x*duvdx.x - duvdx.y,\n"
                                       "\t               2.0*%s.x*duvdy.x - duvdy.y);\n",
                                       fsName, fsName);
             segments->fFSCode.appendf("\tfloat edgeAlpha = (%s.x*%s.x - %s.y);\n", fsName, fsName, fsName);
-            if (GrDrawState::kQuad_EdgeType == fProgramDesc.fVertexEdgeType) {
-                segments->fFSCode.append("\tedgeAlpha = clamp(0.5 - edgeAlpha / length(gF), 0.0, 1.0);\n");
-            } else {
-                segments->fFSCode.append("\tedgeAlpha = sqrt(edgeAlpha*edgeAlpha / dot(gF, gF));\n");
-                segments->fFSCode.append("\tedgeAlpha = max(1.0 - edgeAlpha, 0.0);\n");
-            }
+            segments->fFSCode.append("\tedgeAlpha = sqrt(edgeAlpha*edgeAlpha / dot(gF, gF));\n");
+            segments->fFSCode.append("\tedgeAlpha = max(1.0 - edgeAlpha, 0.0);\n");
             if (gl->supportsES2()) {
                 segments->fHeader.printf("#extension GL_OES_standard_derivatives: enable\n");
             }