Add effect-based clipping for circular "tab" style rrects.

src/gpu/effects/GrRRectEffect.cpp

 /*
  * 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 "GrRRectEffect.h"
 
 #include "gl/GrGLEffect.h"
 #include "gl/GrGLSL.h"
 #include "GrTBackendEffectFactory.h"
 
 #include "SkRRect.h"
 
 class GLRRectEffect;
 
 class RRectEffect : public GrEffect {
 public:
-    // This effect only supports circular corner rrects where all corners have the same radius
-    // which must be <= kRadiusMin.
+    // This effect only supports circular corner rrects where the radius is >= kRadiusMin.
     static const SkScalar kRadiusMin;
 
-    static GrEffectRef* Create(const SkRRect&);
+    /// The types of circular corner rrects supported
+    enum Type {
+        kCircleCorner_Type,     //<! All four corners have the same circular radius.
+        kLeftCircleTab_Type,    //<! The left side has circular corners and the right is a rect.
+        kTopCircleTab_Type,     //<! etc
+        kRightCircleTab_Type,
+        kBottomCircleTab_Type,
+    };
+
+    static GrEffectRef* Create(const SkRRect&, Type);
 
     virtual ~RRectEffect() {};
     static const char* Name() { return "RRect"; }
 
     const SkRRect& getRRect() const { return fRRect; }
 
+    Type getType() const { return fType; }
+
     typedef GLRRectEffect GLEffect;
 
     virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
 
     virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
 
 private:
-    RRectEffect(const SkRRect&);
+    RRectEffect(const SkRRect&, Type);
 
     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
 
     SkRRect fRRect;
+    Type    fType;
 
     GR_DECLARE_EFFECT_TEST;
 
     typedef GrEffect INHERITED;
 };
 
 const SkScalar RRectEffect::kRadiusMin = 0.5f;
 
-GrEffectRef* RRectEffect::Create(const SkRRect& rrect) {
-    return CreateEffectRef(AutoEffectUnref(SkNEW_ARGS(RRectEffect, (rrect))));
+GrEffectRef* RRectEffect::Create(const SkRRect& rrect, Type type) {
+    return CreateEffectRef(AutoEffectUnref(SkNEW_ARGS(RRectEffect, (rrect, type))));
 }
 
 void RRectEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {
     *validFlags = 0;
 }
 
 const GrBackendEffectFactory& RRectEffect::getFactory() const {
     return GrTBackendEffectFactory<RRectEffect>::getInstance();
 }
 
-RRectEffect::RRectEffect(const SkRRect& rrect)
-    : fRRect(rrect) {
+RRectEffect::RRectEffect(const SkRRect& rrect, Type type)
+    : fRRect(rrect)
+    , fType(type) {
     this->setWillReadFragmentPosition();
 }
 
 bool RRectEffect::onIsEqual(const GrEffect& other) const {
     const RRectEffect& rre = CastEffect<RRectEffect>(other);
+    // type is derived from fRRect, so no need to check it.
     return fRRect == rre.fRRect;
 }
 
 //////////////////////////////////////////////////////////////////////////////
 
 GR_DEFINE_EFFECT_TEST(RRectEffect);
 
 GrEffectRef* RRectEffect::TestCreate(SkRandom* random,
                                      GrContext*,
                                      const GrDrawTargetCaps& caps,
@@ skipping 14 matching lines @@
     GLRRectEffect(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&) { return 0; }
+    static inline EffectKey GenKey(const GrDrawEffect&, const GrGLCaps&);
 
     virtual void setData(const GrGLUniformManager&, const GrDrawEffect&) SK_OVERRIDE;
 
 private:
     GrGLUniformManager::UniformHandle   fInnerRectUniform;
     GrGLUniformManager::UniformHandle   fRadiusPlusHalfUniform;
     SkRRect                             fPrevRRect;
     typedef GrGLEffect INHERITED;
 };
 
 GLRRectEffect::GLRRectEffect(const GrBackendEffectFactory& factory,
                              const GrDrawEffect& drawEffect)
     : INHERITED (factory) {
     fPrevRRect.setEmpty();
 }
 
 void GLRRectEffect::emitCode(GrGLShaderBuilder* builder,
                              const GrDrawEffect& drawEffect,
                              EffectKey key,
                              const char* outputColor,
                              const char* inputColor,
                              const TransformedCoordsArray&,
                              const TextureSamplerArray& samplers) {
+    const RRectEffect& rre = drawEffect.castEffect<RRectEffect>();
     const char *rectName;
     const char *radiusPlusHalfName;
     // The inner rect is the rrect bounds inset by the radius. Its top, left, right, and bottom
-    // edges correspond to components x, y, z, and w, respectively.
+    // edges correspond to components x, y, z, and w, respectively. When one side of the rrect has
+    // rectangular corners, that side's value corresponds to the rect edge's value outset by half a
+    // pixel.
     fInnerRectUniform = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
                                             kVec4f_GrSLType,
                                             "innerRect",
                                             &rectName);
     fRadiusPlusHalfUniform = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
                                                  kFloat_GrSLType,
                                                  "radiusPlusHalf",
                                                  &radiusPlusHalfName);
     const char* fragmentPos = builder->fragmentPosition();
     // At each quarter-circle corner we compute a vector that is the offset of the fragment position
     // from the circle center. The vector is pinned in x and y to be in the quarter-plane relevant
     // to that corner. This means that points near the interior near the rrect top edge will have
     // a vector that points straight up for both the TL left and TR corners. Computing an
     // alpha from this vector at either the TR or TL corner will give the correct result. Similarly,
     // fragments near the other three edges will get the correct AA. Fragments in the interior of
     // the rrect will have a (0,0) vector at all four corners. So long as the radius > 0.5 they will
     // correctly produce an alpha value of 1 at all four corners. We take the min of all the alphas.
     // The code below is a simplified version of the above that performs maxs on the vector
     // components before computing distances and alpha values so that only one distance computation
     // need be computed to determine the min alpha.
-    builder->fsCodeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
-    builder->fsCodeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
-    builder->fsCodeAppend("\t\tvec2 dxy = max(max(dxy0, dxy1), 0.0);\n");
-    builder->fsCodeAppendf("\t\tfloat alpha = clamp(%s - length(dxy), 0.0, 1.0);\n",
-                           radiusPlusHalfName);
+    //
+    // For the cases where one half of the rrect is rectangular we drop one of the x or y
+    // computations, compute a separate rect edge alpha for the rect side, and mul the two computed
+    // alphas together.
+    switch (rre.getType()) {
+        case RRectEffect::kCircleCorner_Type:
+            builder->fsCodeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
+            builder->fsCodeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
+            builder->fsCodeAppend("\t\tvec2 dxy = max(max(dxy0, dxy1), 0.0);\n");
+            builder->fsCodeAppendf("\t\tfloat alpha = clamp(%s - length(dxy), 0.0, 1.0);\n",
+                                   radiusPlusHalfName);
+            break;
+        case RRectEffect::kLeftCircleTab_Type:
+            builder->fsCodeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
+            builder->fsCodeAppendf("\t\tfloat dy1 = %s.y - %s.w;\n", fragmentPos, rectName);
+            builder->fsCodeAppend("\t\tvec2 dxy = max(vec2(dxy0.x, max(dxy0.y, dy1)), 0.0);\n");
+            builder->fsCodeAppendf("\t\tfloat rightAlpha = clamp(%s.z - %s.x, 0.0, 1.0);\n",
+                                    rectName, fragmentPos);
+            builder->fsCodeAppendf("\t\tfloat alpha = rightAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
+                                   radiusPlusHalfName);
+            break;
+        case RRectEffect::kTopCircleTab_Type:
+            builder->fsCodeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
+            builder->fsCodeAppendf("\t\tfloat dx1 = %s.x - %s.z;\n", fragmentPos, rectName);
+            builder->fsCodeAppend("\t\tvec2 dxy = max(vec2(max(dxy0.x, dx1), dxy0.y), 0.0);\n");
+            builder->fsCodeAppendf("\t\tfloat bottomAlpha = clamp(%s.w - %s.y, 0.0, 1.0);\n",
+                                   rectName, fragmentPos);
+            builder->fsCodeAppendf("\t\tfloat alpha = bottomAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
+                                   radiusPlusHalfName);
+            break;
+        case RRectEffect::kRightCircleTab_Type:
+            builder->fsCodeAppendf("\t\tfloat dy0 = %s.y - %s.y;\n", rectName, fragmentPos);
+            builder->fsCodeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
+            builder->fsCodeAppend("\t\tvec2 dxy = max(vec2(dxy1.x, max(dy0, dxy1.y)), 0.0);\n");
+            builder->fsCodeAppendf("\t\tfloat leftAlpha = clamp(%s.x - %s.x, 0.0, 1.0);\n",
+                                   fragmentPos, rectName);
+            builder->fsCodeAppendf("\t\tfloat alpha = leftAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
+                                   radiusPlusHalfName);
+            break;
+        case RRectEffect::kBottomCircleTab_Type:
+            builder->fsCodeAppendf("\t\tfloat dx0 = %s.x - %s.x;\n", rectName, fragmentPos);
+            builder->fsCodeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
+            builder->fsCodeAppend("\t\tvec2 dxy = max(vec2(max(dx0, dxy1.x), dxy1.y), 0.0);\n");
+            builder->fsCodeAppendf("\t\tfloat topAlpha = clamp(%s.y - %s.y, 0.0, 1.0);\n",
+                                   fragmentPos, rectName);
+            builder->fsCodeAppendf("\t\tfloat alpha = topAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
+                                   radiusPlusHalfName);
+            break;
+    }
 
     builder->fsCodeAppendf("\t\t%s = %s;\n", outputColor,
                            (GrGLSLExpr4(inputColor) * GrGLSLExpr1("alpha")).c_str());
 }
 
+GrGLEffect::EffectKey GLRRectEffect::GenKey(const GrDrawEffect& drawEffect, const GrGLCaps&) {
+    const RRectEffect& rre = drawEffect.castEffect<RRectEffect>();
+    return rre.getType();
+}
+
 void GLRRectEffect::setData(const GrGLUniformManager& uman, const GrDrawEffect& drawEffect) {
     const RRectEffect& rre = drawEffect.castEffect<RRectEffect>();
     const SkRRect& rrect = rre.getRRect();
     if (rrect != fPrevRRect) {
-        SkASSERT(rrect.isSimpleCircular());
         SkRect rect = rrect.getBounds();
-        SkScalar radius = rrect.getSimpleRadii().fX;
-        SkASSERT(radius >= RRectEffect::kRadiusMin);
-        rect.inset(radius, radius);
+        SkScalar radius = 0;
+        switch (rre.getType()) {
+            case RRectEffect::kCircleCorner_Type:
+                SkASSERT(rrect.isSimpleCircular());
+                radius = rrect.getSimpleRadii().fX;
+                SkASSERT(radius >= RRectEffect::kRadiusMin);
+                rect.inset(radius, radius);
+                break;
+            case RRectEffect::kLeftCircleTab_Type:
+                radius = rrect.radii(SkRRect::kUpperLeft_Corner).fX;
+                rect.fLeft += radius;
+                rect.fTop += radius;
+                rect.fRight += 0.5f;
+                rect.fBottom -= radius;
+                break;
+            case RRectEffect::kTopCircleTab_Type:
+                radius = rrect.radii(SkRRect::kUpperLeft_Corner).fX;
+                rect.fLeft += radius;
+                rect.fTop += radius;
+                rect.fRight -= radius;
+                rect.fBottom += 0.5f;
+                break;
+            case RRectEffect::kRightCircleTab_Type:
+                radius = rrect.radii(SkRRect::kUpperRight_Corner).fX;
+                rect.fLeft -= 0.5f;
+                rect.fTop += radius;
+                rect.fRight -= radius;
+                rect.fBottom -= radius;
+                break;
+            case RRectEffect::kBottomCircleTab_Type:
+                radius = rrect.radii(SkRRect::kLowerLeft_Corner).fX;
+                rect.fLeft += radius;
+                rect.fTop -= 0.5f;
+                rect.fRight -= radius;
+                rect.fBottom -= radius;
+                break;
+        }
         uman.set4f(fInnerRectUniform, rect.fLeft, rect.fTop, rect.fRight, rect.fBottom);
         uman.set1f(fRadiusPlusHalfUniform, radius + 0.5f);
         fPrevRRect = rrect;
     }
 }
 
 //////////////////////////////////////////////////////////////////////////////
 
 GrEffectRef* GrRRectEffect::Create(const SkRRect& rrect) {
-    if (!rrect.isSimpleCircular()) {
+    RRectEffect::Type type;
+    if (rrect.isSimpleCircular()) {
+        if (rrect.getSimpleRadii().fX < RRectEffect::kRadiusMin) {
+            return NULL;
+        }
+        type = RRectEffect::kCircleCorner_Type;
+    } else if (rrect.isComplex()) {
+        // Check for the "tab" cases - two adjacent circular corners and two square corners.
+        SkScalar radius = 0;
+        int circleCornerBitfield = 0;
+        for (int c = 0; c < 4; ++c) {
+            const SkVector& r = rrect.radii((SkRRect::Corner)c);
+            SkASSERT((0 == r.fX) == (0 == r.fY));
+            if (0 == r.fX) {
+                continue;
+            }
+            if (r.fX != r.fY) {
+                return NULL;
+            }
+            if (!circleCornerBitfield) {
+                radius = r.fX;
+                if (radius < RRectEffect::kRadiusMin) {
+                    return NULL;
+                }
+                circleCornerBitfield = 1 << c;
+            } else {
+                if (r.fX != radius) {
+                    return NULL;
+                }
+                circleCornerBitfield |= 1 << c;
+            }
+        }
+
+        GR_STATIC_ASSERT(SkRRect::kUpperLeft_Corner  == 0);
+        GR_STATIC_ASSERT(SkRRect::kUpperRight_Corner == 1);
+        GR_STATIC_ASSERT(SkRRect::kLowerRight_Corner == 2);
+        GR_STATIC_ASSERT(SkRRect::kLowerLeft_Corner  == 3);
+        switch (circleCornerBitfield) {
+            case 3:
+                type = RRectEffect::kTopCircleTab_Type;
+                break;
+            case 6:
+                type = RRectEffect::kRightCircleTab_Type;
+                break;
+            case 9:
+                type = RRectEffect::kLeftCircleTab_Type;
+                break;
+            case 12:
+                type = RRectEffect::kBottomCircleTab_Type;
+                break;
+            default:
+                return NULL;
+        }
+    } else {
         return NULL;
     }
-
-    if (rrect.getSimpleRadii().fX < RRectEffect::kRadiusMin) {
-        return NULL;
-    }
-
-    return RRectEffect::Create(rrect);
+    return RRectEffect::Create(rrect, type);
 }