Add convex polygon rendering effect and GM to test it.

src/gpu/effects/GrConvexPolyEffect.cpp

Index: src/gpu/effects/GrConvexPolyEffect.cpp
diff --git a/src/gpu/effects/GrConvexPolyEffect.cpp b/src/gpu/effects/GrConvexPolyEffect.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..d780e283310c999fa014ed61a7510c40d4560379
--- /dev/null
+++ b/src/gpu/effects/GrConvexPolyEffect.cpp
@@ -0,0 +1,185 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrConvexPolyEffect.h"
+
+#include "gl/GrGLEffect.h"
+#include "gl/GrGLSL.h"
+#include "gl/GrGLVertexEffect.h"
+#include "GrTBackendEffectFactory.h"
+
+#include "SkPath.h"
+
+class GrGLConvexPolyEffect : public GrGLEffect {
+public:
+    GrGLConvexPolyEffect(const GrBackendEffectFactory&, const GrDrawEffect&);
+
+    virtual void emitCode(GrGLShaderBuilder* builder,
+                          const GrDrawEffect& drawEffect,
+                          EffectKey key,
+                          const char* outputColor,
+                          const char* inputColor,
+                          const TransformedCoordsArray&,
+                          const TextureSamplerArray&) SK_OVERRIDE;
+
+    static inline EffectKey GenKey(const GrDrawEffect&, const GrGLCaps&);
+
+    virtual void setData(const GrGLUniformManager&, const GrDrawEffect&) SK_OVERRIDE;
+
+private:
+    GrGLUniformManager::UniformHandle   fEdgeUniform;
+    SkScalar                            fPrevEdges[3 * GrConvexPolyEffect::kMaxEdges];
+    typedef GrGLEffect INHERITED;
+};
+
+GrGLConvexPolyEffect::GrGLConvexPolyEffect(const GrBackendEffectFactory& factory,
+                                           const GrDrawEffect& drawEffect)
+    : INHERITED (factory) {
+    fPrevEdges[0] = SK_ScalarNaN;
+}
+
+void GrGLConvexPolyEffect::emitCode(GrGLShaderBuilder* builder,
+                                    const GrDrawEffect& drawEffect,
+                                    EffectKey key,
+                                    const char* outputColor,
+                                    const char* inputColor,
+                                    const TransformedCoordsArray&,
+                                    const TextureSamplerArray& samplers) {
+    const GrConvexPolyEffect& cpe = drawEffect.castEffect<GrConvexPolyEffect>();
+
+    const char *edgeArrayName;
+    fEdgeUniform = builder->addUniformArray(GrGLShaderBuilder::kFragment_Visibility,
+                                            kVec3f_GrSLType,
+                                            "edges",
+                                            cpe.getEdgeCount(),
+                                            &edgeArrayName);
+    builder->fsCodeAppend("\t\tfloat alpha = 1.0;\n");
+    builder->fsCodeAppend("\t\tfloat edge;\n");
+    const char* fragmentPos = builder->fragmentPosition();
+    for (int i = 0; i < cpe.getEdgeCount(); ++i) {
+        builder->fsCodeAppendf("\t\tedge = dot(%s[%d], vec3(%s.x, %s.y, 1));\n",
+                               edgeArrayName, i, fragmentPos, fragmentPos);
+        switch (cpe.getEdgeType()) {
+            case GrConvexPolyEffect::kFillAA_EdgeType:
+                builder->fsCodeAppend("\t\tedge = clamp(edge, 0.0, 1.0);\n");
+                builder->fsCodeAppend("\t\talpha *= edge;\n");
+                break;
+            case GrConvexPolyEffect::kFillNoAA_EdgeType:
+                builder->fsCodeAppend("\t\tedge = edge >= 0.5 ? 1.0 : 0.0;\n");
+                builder->fsCodeAppend("\t\talpha *= edge;\n");
+                break;
+        }
+    }
+
+    builder->fsCodeAppendf("\t%s = %s;\n", outputColor,
+                           (GrGLSLExpr4(inputColor) * GrGLSLExpr1("alpha")).c_str());
+}
+
+void GrGLConvexPolyEffect::setData(const GrGLUniformManager& uman, const GrDrawEffect& drawEffect) {
+    const GrConvexPolyEffect& cpe = drawEffect.castEffect<GrConvexPolyEffect>();
+    size_t byteSize = 3 * cpe.getEdgeCount() * sizeof(SkScalar);
+    if (0 != memcmp(fPrevEdges, cpe.getEdges(), byteSize)) {
+        uman.set3fv(fEdgeUniform, cpe.getEdgeCount(), cpe.getEdges());
+        memcpy(fPrevEdges, cpe.getEdges(), byteSize);
+    }
+}
+
+GrGLEffect::EffectKey GrGLConvexPolyEffect::GenKey(const GrDrawEffect& drawEffect,
+                                                   const GrGLCaps&) {
+    const GrConvexPolyEffect& cpe = drawEffect.castEffect<GrConvexPolyEffect>();
+    GR_STATIC_ASSERT(GrConvexPolyEffect::kEdgeTypeCnt <= 4);
+    return (cpe.getEdgeCount() << 2) | cpe.getEdgeType();
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+GrEffectRef* GrConvexPolyEffect::Create(EdgeType type, const SkPath& path) {
+    if (path.getSegmentMasks() != SkPath::kLine_SegmentMask ||
+        !path.isConvex() ||
+        path.isInverseFillType()) {
+        return NULL;
+    }
+
+    if (path.countPoints() > kMaxEdges) {
+        return NULL;
+    }
+
+    SkPoint pts[kMaxEdges];
+    SkScalar edges[3 * kMaxEdges];
+
+    SkPath::Direction dir;
+    SkAssertResult(path.cheapComputeDirection(&dir));
+
+    int count = path.getPoints(pts, kMaxEdges);
+    int n = 0;
+    for (int lastPt = count - 1, i = 0; i < count; lastPt = i++) {
+        if (pts[lastPt] != pts[i]) {
+            SkVector v = pts[i] - pts[lastPt];
+            v.normalize();
+            if (SkPath::kCCW_Direction == dir) {
+                edges[3 * n] = v.fY;
+                edges[3 * n + 1] = -v.fX;
+            } else {
+                edges[3 * n] = -v.fY;
+                edges[3 * n + 1] = v.fX;
+            }
+            edges[3 * n + 2] = -(edges[3 * n] * pts[i].fX + edges[3 * n + 1] * pts[i].fY);
+            ++n;
+        }
+    }
+    return Create(type, n, edges);
+}
+
+GrConvexPolyEffect::~GrConvexPolyEffect() {}
+
+void GrConvexPolyEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {
+    *validFlags = 0;
+}
+
+const GrBackendEffectFactory& GrConvexPolyEffect::getFactory() const {
+    return GrTBackendEffectFactory<GrConvexPolyEffect>::getInstance();
+}
+
+GrConvexPolyEffect::GrConvexPolyEffect(EdgeType edgeType, int n, const SkScalar edges[])
+    : fEdgeType(edgeType)
+    , fEdgeCount(n) {
+    // Factory function should have already ensured this.
+    SkASSERT(n <= kMaxEdges);
+    memcpy(fEdges, edges, 3 * n * sizeof(SkScalar));
+    // Outset the edges by 0.5 so that a pixel with center on an edge is 50% covered in the AA case
+    // and 100% covered in the non-AA case.
+    for (int i = 0; i < n; ++i) {
+        fEdges[3 * i + 2] += SK_ScalarHalf;
+    }
+    this->setWillReadFragmentPosition();
+}
+
+bool GrConvexPolyEffect::onIsEqual(const GrEffect& other) const {
+    const GrConvexPolyEffect& cpe = CastEffect<GrConvexPolyEffect>(other);
+    // ignore the fact that 0 == -0 and just use memcmp.
+    return (cpe.fEdgeType == fEdgeType && cpe.fEdgeCount == fEdgeCount &&
+            0 == memcmp(cpe.fEdges, fEdges, 3 * fEdgeCount * sizeof(SkScalar)));
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+GR_DEFINE_EFFECT_TEST(GrConvexPolyEffect);
+
+GrEffectRef* GrConvexPolyEffect::TestCreate(SkRandom* random,
+                                            GrContext*,
+                                            const GrDrawTargetCaps& caps,
+                                            GrTexture*[]) {
+    EdgeType edgeType = static_cast<EdgeType>(random->nextULessThan(kEdgeTypeCnt));
+    int count = random->nextULessThan(kMaxEdges + 1);
+    SkScalar edges[kMaxEdges * 3];
+    for (int i = 0; i < 3 * count; ++i) {
+        edges[i] = random->nextSScalar1();
+    }
+
+    return GrConvexPolyEffect::Create(edgeType, count, edges);
+}
+