Revert "ccpr: Draw curves in a single pass"

This reverts commit df04ce29490a24f9d5b4f5caafd8f6a3368a19e0.

Reason for revert: Going to revisit AAA quality

Original change's description:
> ccpr: Draw curves in a single pass
> 
> Throws out the complicated MSAA curve corner shaders, and instead just
> ramps coverage to zero at bloat vertices that fall outside the curve.
> 
> Updates SampleCCPRGeometry to better visualize this new geometry by
> clearing to black and drawing with SkBlendMode::kPlus.
> 
> Bug: skia:
> Change-Id: Ibe86cbc741d8b015127b10dd43e3b52e7cb35732
> Reviewed-on: https://skia-review.googlesource.com/112626
> Commit-Queue: Chris Dalton <csmartdalton@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>

TBR=bsalomon@google.com,csmartdalton@google.com

Change-Id: I014baa60b248d870717f5ee8794e0bed66da86e6
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/113181
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/src/gpu/ccpr/GrCCQuadraticShader.cpp b/src/gpu/ccpr/GrCCQuadraticShader.cpp
index baa10fd..090e29f 100644
--- a/src/gpu/ccpr/GrCCQuadraticShader.cpp
+++ b/src/gpu/ccpr/GrCCQuadraticShader.cpp
@@ -14,7 +14,7 @@
 using Shader = GrCCCoverageProcessor::Shader;
 
 void GrCCQuadraticShader::emitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
-                                        const char* /*repetitionID*/, const char* /*wind*/,
+                                        const char* repetitionID, const char* wind,
                                         GeometryVars* vars) const {
     s->declareGlobal(fCanonicalMatrix);
     s->codeAppendf("%s = float3x3(0.0, 0, 1, "
@@ -25,6 +25,41 @@
                                          "%s[2], 1));",
                    fCanonicalMatrix.c_str(), pts, pts, pts);
 
+    s->declareGlobal(fEdgeDistanceEquation);
+    s->codeAppendf("float2 edgept0 = %s[%s > 0 ? 2 : 0];", pts, wind);
+    s->codeAppendf("float2 edgept1 = %s[%s > 0 ? 0 : 2];", pts, wind);
+    Shader::EmitEdgeDistanceEquation(s, "edgept0", "edgept1", fEdgeDistanceEquation.c_str());
+
+    this->onEmitSetupCode(s, pts, repetitionID, vars);
+}
+
+void GrCCQuadraticShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
+                                         GrGLSLVarying::Scope scope, SkString* code,
+                                         const char* position, const char* inputCoverage,
+                                         const char* wind) {
+    SkASSERT(!inputCoverage);
+
+    fXYDW.reset(kFloat4_GrSLType, scope);
+    varyingHandler->addVarying("xydw", &fXYDW);
+    code->appendf("%s.xy = (%s * float3(%s, 1)).xy;",
+                  OutName(fXYDW), fCanonicalMatrix.c_str(), position);
+    code->appendf("%s.z = dot(%s.xy, %s) + %s.z;",
+                  OutName(fXYDW), fEdgeDistanceEquation.c_str(), position,
+                  fEdgeDistanceEquation.c_str());
+    code->appendf("%s.w = %s;", OutName(fXYDW), wind);
+
+    this->onEmitVaryings(varyingHandler, scope, code);
+}
+
+void GrCCQuadraticShader::onEmitFragmentCode(GrGLSLFPFragmentBuilder* f,
+                                             const char* outputCoverage) const {
+    this->emitCoverage(f, outputCoverage);
+    f->codeAppendf("%s *= %s.w;", outputCoverage, fXYDW.fsIn()); // Sign by wind.
+}
+
+void GrCCQuadraticHullShader::onEmitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
+                                              const char* /*repetitionID*/,
+                                              GeometryVars* vars) const {
     // Find the T value whose tangent is halfway between the tangents at the endpionts.
     s->codeAppendf("float2 tan0 = %s[1] - %s[0];", pts, pts);
     s->codeAppendf("float2 tan1 = %s[2] - %s[1];", pts, pts);
@@ -41,31 +76,66 @@
     vars->fHullVars.fAlternatePoints = "quadratic_hull";
 }
 
-void GrCCQuadraticShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
-                                         GrGLSLVarying::Scope scope, SkString* code,
-                                         const char* position, const char* inputCoverage,
-                                         const char* wind) {
-    fCoords.reset(kFloat4_GrSLType, scope);
-    varyingHandler->addVarying("coords", &fCoords);
-    code->appendf("%s.xy = (%s * float3(%s, 1)).xy;",
-                  OutName(fCoords), fCanonicalMatrix.c_str(), position);
-    code->appendf("%s.zw = float2(2 * %s.x, -1) * float2x2(%s);",
-                  OutName(fCoords), OutName(fCoords), fCanonicalMatrix.c_str());
-
-    fCoverageTimesWind.reset(kHalf_GrSLType, scope);
-    varyingHandler->addVarying("coverage_times_wind", &fCoverageTimesWind);
-    code->appendf("%s = %s * %s;", OutName(fCoverageTimesWind), inputCoverage, wind);
+void GrCCQuadraticHullShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
+                                             GrGLSLVarying::Scope scope, SkString* code) {
+    fGrad.reset(kFloat2_GrSLType, scope);
+    varyingHandler->addVarying("grad", &fGrad);
+    code->appendf("%s = float2(2 * %s.x, -1) * float2x2(%s);",
+                  OutName(fGrad), OutName(fXYDW), fCanonicalMatrix.c_str());
 }
 
-void GrCCQuadraticShader::onEmitFragmentCode(const GrCCCoverageProcessor& proc,
-                                             GrGLSLFPFragmentBuilder* f,
+void GrCCQuadraticHullShader::emitCoverage(GrGLSLFPFragmentBuilder* f,
+                                           const char* outputCoverage) const {
+    f->codeAppendf("float d = (%s.x * %s.x - %s.y) * inversesqrt(dot(%s, %s));",
+                   fXYDW.fsIn(), fXYDW.fsIn(), fXYDW.fsIn(), fGrad.fsIn(), fGrad.fsIn());
+    f->codeAppendf("%s = clamp(0.5 - d, 0, 1);", outputCoverage);
+    f->codeAppendf("%s += min(%s.z, 0);", outputCoverage, fXYDW.fsIn()); // Flat closing edge.
+}
+
+void GrCCQuadraticCornerShader::onEmitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
+                                                const char* repetitionID,
+                                                GeometryVars* vars) const {
+    s->codeAppendf("float2 corner = %s[%s * 2];", pts, repetitionID);
+    vars->fCornerVars.fPoint = "corner";
+}
+
+void GrCCQuadraticCornerShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
+                                               GrGLSLVarying::Scope scope, SkString* code) {
+    using Interpolation = GrGLSLVaryingHandler::Interpolation;
+
+    fdXYDdx.reset(kFloat3_GrSLType, scope);
+    varyingHandler->addVarying("dXYDdx", &fdXYDdx, Interpolation::kCanBeFlat);
+    code->appendf("%s = float3(%s[0].x, %s[0].y, %s.x);",
+                  OutName(fdXYDdx), fCanonicalMatrix.c_str(), fCanonicalMatrix.c_str(),
+                  fEdgeDistanceEquation.c_str());
+
+    fdXYDdy.reset(kFloat3_GrSLType, scope);
+    varyingHandler->addVarying("dXYDdy", &fdXYDdy, Interpolation::kCanBeFlat);
+    code->appendf("%s = float3(%s[1].x, %s[1].y, %s.y);",
+                  OutName(fdXYDdy), fCanonicalMatrix.c_str(), fCanonicalMatrix.c_str(),
+                  fEdgeDistanceEquation.c_str());
+}
+
+void GrCCQuadraticCornerShader::emitCoverage(GrGLSLFPFragmentBuilder* f,
                                              const char* outputCoverage) const {
-    f->codeAppendf("float d = (%s.x * %s.x - %s.y) * inversesqrt(dot(%s.zw, %s.zw));",
-                   fCoords.fsIn(), fCoords.fsIn(), fCoords.fsIn(), fCoords.fsIn(), fCoords.fsIn());
-#ifdef SK_DEBUG
-    if (proc.debugVisualizationsEnabled()) {
-        f->codeAppendf("d /= %f;", proc.debugBloat());
-    }
-#endif
-    f->codeAppendf("%s = clamp(0.5 - d, 0, 1) * %s;", outputCoverage, fCoverageTimesWind.fsIn());
+    f->codeAppendf("float x = %s.x, y = %s.y, d = %s.z;",
+                   fXYDW.fsIn(), fXYDW.fsIn(), fXYDW.fsIn());
+    f->codeAppendf("float2x3 grad_xyd = float2x3(%s, %s);", fdXYDdx.fsIn(), fdXYDdy.fsIn());
+
+    // Erase what the previous hull shader wrote. We don't worry about the two corners falling on
+    // the same pixel because those cases should have been weeded out by this point.
+    f->codeAppend ("float f = x*x - y;");
+    f->codeAppend ("float2 grad_f = float2(2*x, -1) * float2x2(grad_xyd);");
+    f->codeAppendf("%s = -(0.5 - f * inversesqrt(dot(grad_f, grad_f)));", outputCoverage);
+    f->codeAppendf("%s -= d;", outputCoverage);
+
+    // Use software msaa to approximate coverage at the corner pixels.
+    int sampleCount = Shader::DefineSoftSampleLocations(f, "samples");
+    f->codeAppendf("float3 xyd_center = float3(%s.xy, %s.z + 0.5);", fXYDW.fsIn(), fXYDW.fsIn());
+    f->codeAppendf("for (int i = 0; i < %i; ++i) {", sampleCount);
+    f->codeAppend (    "float3 xyd = grad_xyd * samples[i] + xyd_center;");
+    f->codeAppend (    "half f = xyd.y - xyd.x * xyd.x;"); // f > 0 -> inside curve.
+    f->codeAppendf(    "%s += all(greaterThan(float2(f,xyd.z), float2(0))) ? %f : 0;",
+                       outputCoverage, 1.0 / sampleCount);
+    f->codeAppendf("}");
 }