Add clip effect for circles

src/gpu/effects/GrOvalEffect.cpp

Index: src/gpu/effects/GrOvalEffect.cpp
diff --git a/src/gpu/effects/GrOvalEffect.cpp b/src/gpu/effects/GrOvalEffect.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..0a07cfe2dd854b1fe4af5a8cfdc88f4a686e98f3
--- /dev/null
+++ b/src/gpu/effects/GrOvalEffect.cpp
@@ -0,0 +1,193 @@
+/*
+ * 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 "GrOvalEffect.h"
+
+#include "gl/GrGLEffect.h"
+#include "gl/GrGLSL.h"
+#include "GrTBackendEffectFactory.h"
+
+#include "SkRect.h"
+
+//////////////////////////////////////////////////////////////////////////////
+
+class GLCircleEffect;
+
+class CircleEffect : public GrEffect {
+public:
+    static GrEffectRef* Create(GrEffectEdgeType, const SkPoint& center, SkScalar radius);
+
+    virtual ~CircleEffect() {};
+    static const char* Name() { return "Circle"; }
+
+    const SkPoint& getCenter() const { return fCenter; }
+    SkScalar getRadius() const { return fRadius; }
+
+    GrEffectEdgeType getEdgeType() const { return fEdgeType; }
+
+    typedef GLCircleEffect GLEffect;
+
+    virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
+
+    virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
+
+private:
+    CircleEffect(GrEffectEdgeType, const SkPoint& center, SkScalar radius);
+
+    virtual bool onIsEqual(const GrEffect&) const SK_OVERRIDE;
+
+    SkPoint             fCenter;
+    SkScalar            fRadius;
+    GrEffectEdgeType    fEdgeType;
+
+    GR_DECLARE_EFFECT_TEST;
+
+    typedef GrEffect INHERITED;
+};
+
+GrEffectRef* CircleEffect::Create(GrEffectEdgeType edgeType,
+                                  const SkPoint& center,
+                                  SkScalar radius) {
+    SkASSERT(radius >= 0);
+    return CreateEffectRef(AutoEffectUnref(SkNEW_ARGS(CircleEffect,
+                                                      (edgeType, center, radius))));
+}
+
+void CircleEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {
+    *validFlags = 0;
+}
+
+const GrBackendEffectFactory& CircleEffect::getFactory() const {
+    return GrTBackendEffectFactory<CircleEffect>::getInstance();
+}
+
+CircleEffect::CircleEffect(GrEffectEdgeType edgeType, const SkPoint& c, SkScalar r)
+    : fCenter(c)
+    , fRadius(r)
+    , fEdgeType(edgeType) {
+    this->setWillReadFragmentPosition();
+}
+
+bool CircleEffect::onIsEqual(const GrEffect& other) const {
+    const CircleEffect& crre = CastEffect<CircleEffect>(other);
+    return fEdgeType == crre.fEdgeType && fCenter == crre.fCenter && fRadius == crre.fRadius;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+GR_DEFINE_EFFECT_TEST(CircleEffect);
+
+GrEffectRef* CircleEffect::TestCreate(SkRandom* random,
+                                      GrContext*,
+                                      const GrDrawTargetCaps& caps,
+                                      GrTexture*[]) {
+    SkPoint center;
+    center.fX = random->nextRangeScalar(0.f, 1000.f);
+    center.fY = random->nextRangeScalar(0.f, 1000.f);
+    SkScalar radius = random->nextRangeF(0.f, 1000.f);
+    GrEffectEdgeType et;
+    do {
+        et = (GrEffectEdgeType)random->nextULessThan(kGrEffectEdgeTypeCnt);
+    } while (kHairlineAA_GrEffectEdgeType == et);
+    return CircleEffect::Create(et, center, radius);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+class GLCircleEffect : public GrGLEffect {
+public:
+    GLCircleEffect(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   fCircleUniform;
+    SkPoint                             fPrevCenter;
+    SkScalar                            fPrevRadius;
+
+    typedef GrGLEffect INHERITED;
+};
+
+GLCircleEffect::GLCircleEffect(const GrBackendEffectFactory& factory,
+                               const GrDrawEffect& drawEffect)
+    : INHERITED (factory) {
+    fPrevRadius = -1.f;
+}
+
+void GLCircleEffect::emitCode(GrGLShaderBuilder* builder,
+                              const GrDrawEffect& drawEffect,
+                              EffectKey key,
+                              const char* outputColor,
+                              const char* inputColor,
+                              const TransformedCoordsArray&,
+                              const TextureSamplerArray& samplers) {
+    const CircleEffect& ce = drawEffect.castEffect<CircleEffect>();
+    const char *circleName;
+    // The circle uniform is (center.x, center.y, radius + 0.5)
+    fCircleUniform = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
+                                         kVec3f_GrSLType,
+                                         "circle",
+                                         &circleName);
+    const char* fragmentPos = builder->fragmentPosition();
+
+    SkASSERT(kHairlineAA_GrEffectEdgeType != ce.getEdgeType());
+    if (GrEffectEdgeTypeIsInverseFill(ce.getEdgeType())) {
+        builder->fsCodeAppendf("\t\tfloat d = length(%s.xy - %s.xy) - %s.z;\n", 
+                                circleName, fragmentPos, circleName);
+    } else {
+        builder->fsCodeAppendf("\t\tfloat d = %s.z - length(%s.xy - %s.xy);\n",
+                               circleName, fragmentPos, circleName);
+    }
+    if (GrEffectEdgeTypeIsAA(ce.getEdgeType())) {
+        builder->fsCodeAppend("\t\td = clamp(d, 0.0, 1.0);\n");
+    } else {
+        builder->fsCodeAppend("\t\td = d > 0.5 ? 1.0 : 0.0;\n");
+    }
+
+    builder->fsCodeAppendf("\t\t%s = %s;\n", outputColor,
+                           (GrGLSLExpr4(inputColor) * GrGLSLExpr1("d")).c_str());
+}
+
+GrGLEffect::EffectKey GLCircleEffect::GenKey(const GrDrawEffect& drawEffect,
+                                             const GrGLCaps&) {
+    const CircleEffect& ce = drawEffect.castEffect<CircleEffect>();
+    return ce.getEdgeType();
+}
+
+void GLCircleEffect::setData(const GrGLUniformManager& uman, const GrDrawEffect& drawEffect) {
+    const CircleEffect& ce = drawEffect.castEffect<CircleEffect>();
+    if (ce.getRadius() != fPrevRadius || ce.getCenter() != fPrevCenter) {
+        uman.set3f(fCircleUniform, ce.getCenter().fX, ce.getCenter().fY, ce.getRadius() + 0.5f);
+        fPrevCenter = ce.getCenter();
+        fPrevRadius = ce.getRadius();
+    }
+}
+//////////////////////////////////////////////////////////////////////////////
+
+GrEffectRef* GrOvalEffect::Create(GrEffectEdgeType edgeType, const SkRect& oval) {
+    if (kHairlineAA_GrEffectEdgeType == edgeType) {
+        return NULL;
+    }
+    SkScalar w = oval.width();
+    SkScalar h = oval.height();
+    if (SkScalarNearlyEqual(w, h)) {
+        w /= 2;
+        return CircleEffect::Create(edgeType, SkPoint::Make(oval.fLeft + w, oval.fTop + w), w);
+    }
+
+    return NULL;
+}