Add flipped gradient branch to two point conical gradient

BUG=skia:
R=bsalomon@google.com, mtklein@google.com

Author: egdaniel@google.com

Review URL: https://codereview.chromium.org/227623004

git-svn-id: http://skia.googlecode.com/svn/trunk@14235 2bbb7eff-a529-9590-31e7-b0007b416f81

6 files changed, 119 insertions, 23 deletions

diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index 441833db36..cd9ff546bf 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -322,13 +322,14 @@ protected:
     // V21: add pushCull, popCull
     // V22: SK_PICT_FACTORY_TAG's size is now the chunk size in bytes
     // V23: SkPaint::FilterLevel became a real enum
+    // V24: SkTwoPointConicalGradient now has fFlipped flag for gradient flipping
 
     // Note: If the picture version needs to be increased then please follow the
     // steps to generate new SKPs in (only accessible to Googlers): http://goo.gl/qATVcw
 
     // Only SKPs within the min/current picture version range (inclusive) can be read.
     static const uint32_t MIN_PICTURE_VERSION = 19;
-    static const uint32_t CURRENT_PICTURE_VERSION = 23;
+    static const uint32_t CURRENT_PICTURE_VERSION = 24;
 
     mutable uint32_t      fUniqueID;
 
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 3547fbec94..36d690ac09 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -203,6 +203,25 @@ void SkGradientShaderBase::flatten(SkWriteBuffer& buffer) const {
     buffer.writeMatrix(fPtsToUnit);
 }
 
+// V23_COMPATIBILITY_CODE
+void SkGradientShaderBase::flipGradientColors() {
+    SkAutoSTArray<8, SkColor> colorsTemp(fColorCount);
+    for (int i = 0; i < fColorCount; ++i) {
+        int offset = fColorCount - i - 1;
+        colorsTemp[i] = fOrigColors[offset];
+    }
+    if (fColorCount > 2) {
+        SkAutoSTArray<8, Rec> recsTemp(fColorCount);
+        for (int i = 0; i < fColorCount; ++i) {
+            int offset = fColorCount - i - 1;
+            recsTemp[i].fPos = 1 - fRecs[offset].fPos;
+            recsTemp[i].fScale = fRecs[offset].fScale;
+        }
+        memcpy(fRecs, recsTemp.get(), fColorCount * sizeof(Rec));
+    }
+    memcpy(fOrigColors, colorsTemp.get(), fColorCount * sizeof(SkColor));
+}
+
 bool SkGradientShaderBase::isOpaque() const {
     return fColorsAreOpaque;
 }
@@ -793,12 +812,36 @@ SkShader* SkGradientShader::CreateTwoPointConical(const SkPoint& start,
     if (start == end && startRadius == endRadius) {
         return SkNEW(SkEmptyShader);
     }
+
     EXPAND_1_COLOR(colorCount);
 
+    bool flipGradient = startRadius > endRadius;
+
     SkGradientShaderBase::Descriptor desc;
-    desc_init(&desc, colors, pos, colorCount, mode, mapper, flags);
-    return SkNEW_ARGS(SkTwoPointConicalGradient,
-                      (start, startRadius, end, endRadius, desc));
+
+    if (!flipGradient) {
+        desc_init(&desc, colors, pos, colorCount, mode, mapper, flags);
+        return SkNEW_ARGS(SkTwoPointConicalGradient,
+                          (start, startRadius, end, endRadius, flipGradient, desc));
+    } else {
+        SkAutoSTArray<8, SkColor> colorsNew(colorCount);
+        SkAutoSTArray<8, SkScalar> posNew(colorCount);
+        for (int i = 0; i < colorCount; ++i) {
+            colorsNew[i] = colors[colorCount - i - 1];
+        }
+
+        if (pos) {
+            for (int i = 0; i < colorCount; ++i) {
+                posNew[i] = 1 - pos[colorCount - i - 1];
+            }
+            desc_init(&desc, colorsNew.get(), posNew.get(), colorCount, mode, mapper, flags);
+        } else {
+            desc_init(&desc, colorsNew.get(), NULL, colorCount, mode, mapper, flags);
+        }
+
+        return SkNEW_ARGS(SkTwoPointConicalGradient,
+                          (end, endRadius, start, startRadius, flipGradient, desc));
+    }
 }
 
 SkShader* SkGradientShader::CreateSweep(SkScalar cx, SkScalar cy,
diff --git a/src/effects/gradients/SkGradientShaderPriv.h b/src/effects/gradients/SkGradientShaderPriv.h
index 1d0f008917..f4f53dee25 100644
--- a/src/effects/gradients/SkGradientShaderPriv.h
+++ b/src/effects/gradients/SkGradientShaderPriv.h
@@ -205,6 +205,11 @@ protected:
 
     void commonAsAGradient(GradientInfo*) const;
 
+    // V23_COMPATIBILITY_CODE
+    // Used for 2-pt conical gradients since we sort start/end cirlces by radius
+    // Assumes space has already been allocated for fOrigColors
+    void flipGradientColors();
+
 private:
     enum {
         kColorStorageCount = 4, // more than this many colors, and we'll use sk_malloc for the space
diff --git a/src/effects/gradients/SkTwoPointConicalGradient.cpp b/src/effects/gradients/SkTwoPointConicalGradient.cpp
index b0955a2583..59a135a642 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient.cpp
+++ b/src/effects/gradients/SkTwoPointConicalGradient.cpp
@@ -32,7 +32,7 @@ static int valid_divide(float numer, float denom, float* ratio) {
 
 // Return the number of distinct real roots, and write them into roots[] in
 // ascending order
-static int find_quad_roots(float A, float B, float C, float roots[2]) {
+static int find_quad_roots(float A, float B, float C, float roots[2], bool descendingOrder = false) {
     SkASSERT(roots);
 
     if (A == 0) {
@@ -66,6 +66,9 @@ static int find_quad_roots(float A, float B, float C, float roots[2]) {
     float r1 = C / Q;
     roots[0] = r0 < r1 ? r0 : r1;
     roots[1] = r0 > r1 ? r0 : r1;
+    if (descendingOrder) {
+        SkTSwap(roots[0], roots[1]);
+    }
     return 2;
 }
 
@@ -76,7 +79,8 @@ static float lerp(float x, float dx, float t) {
 static float sqr(float x) { return x * x; }
 
 void TwoPtRadial::init(const SkPoint& center0, SkScalar rad0,
-                       const SkPoint& center1, SkScalar rad1) {
+                       const SkPoint& center1, SkScalar rad1,
+                       bool flipped) {
     fCenterX = SkScalarToFloat(center0.fX);
     fCenterY = SkScalarToFloat(center0.fY);
     fDCenterX = SkScalarToFloat(center1.fX) - fCenterX;
@@ -87,6 +91,8 @@ void TwoPtRadial::init(const SkPoint& center0, SkScalar rad0,
     fA = sqr(fDCenterX) + sqr(fDCenterY) - sqr(fDRadius);
     fRadius2 = sqr(fRadius);
     fRDR = fRadius * fDRadius;
+
+    fFlipped = flipped;
 }
 
 TwoPtRadialContext::TwoPtRadialContext(const TwoPtRadial& rec, SkScalar fx, SkScalar fy,
@@ -103,7 +109,7 @@ SkFixed TwoPtRadialContext::nextT() {
     float roots[2];
 
     float C = sqr(fRelX) + sqr(fRelY) - fRec.fRadius2;
-    int countRoots = find_quad_roots(fRec.fA, fB, C, roots);
+    int countRoots = find_quad_roots(fRec.fA, fB, C, roots, fRec.fFlipped);
 
     fRelX += fIncX;
     fRelY += fIncY;
@@ -182,7 +188,7 @@ static void twopoint_mirror(TwoPtRadialContext* rec, SkPMColor* SK_RESTRICT dstC
 }
 
 void SkTwoPointConicalGradient::init() {
-    fRec.init(fCenter1, fRadius1, fCenter2, fRadius2);
+    fRec.init(fCenter1, fRadius1, fCenter2, fRadius2, fFlippedGrad);
     fPtsToUnit.reset();
 }
 
@@ -191,12 +197,13 @@ void SkTwoPointConicalGradient::init() {
 SkTwoPointConicalGradient::SkTwoPointConicalGradient(
         const SkPoint& start, SkScalar startRadius,
         const SkPoint& end, SkScalar endRadius,
-        const Descriptor& desc)
+        bool flippedGrad, const Descriptor& desc)
     : SkGradientShaderBase(desc),
     fCenter1(start),
     fCenter2(end),
     fRadius1(startRadius),
-    fRadius2(endRadius) {
+    fRadius2(endRadius),
+    fFlippedGrad(flippedGrad) {
     // this is degenerate, and should be caught by our caller
     SkASSERT(fCenter1 != fCenter2 || fRadius1 != fRadius2);
     this->init();
@@ -345,6 +352,20 @@ SkTwoPointConicalGradient::SkTwoPointConicalGradient(
     fCenter2(buffer.readPoint()),
     fRadius1(buffer.readScalar()),
     fRadius2(buffer.readScalar()) {
+    if (buffer.pictureVersion() >= 24 || 0 == buffer.pictureVersion()) {
+        fFlippedGrad = buffer.readBool();
+    } else {
+        // V23_COMPATIBILITY_CODE
+        // Sort gradient by radius size for old pictures
+        if (fRadius2 < fRadius1) {
+            SkTSwap(fCenter1, fCenter2);
+            SkTSwap(fRadius1, fRadius2);
+            this->flipGradientColors();
+            fFlippedGrad = true;
+        } else {
+            fFlippedGrad = false;
+        }
+    }
     this->init();
 };
 
@@ -355,6 +376,7 @@ void SkTwoPointConicalGradient::flatten(
     buffer.writePoint(fCenter2);
     buffer.writeScalar(fRadius1);
     buffer.writeScalar(fRadius2);
+    buffer.writeBool(fFlippedGrad);
 }
 
 #if SK_SUPPORT_GPU
diff --git a/src/effects/gradients/SkTwoPointConicalGradient.h b/src/effects/gradients/SkTwoPointConicalGradient.h
index 4c049172d3..80aa6fa693 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient.h
+++ b/src/effects/gradients/SkTwoPointConicalGradient.h
@@ -25,9 +25,11 @@ struct TwoPtRadial {
     float   fA;
     float   fRadius2;
     float   fRDR;
+    bool    fFlipped;
 
     void init(const SkPoint& center0, SkScalar rad0,
-              const SkPoint& center1, SkScalar rad1);
+              const SkPoint& center1, SkScalar rad1,
+              bool flipped);
 
     static bool DontDrawT(SkFixed t) {
         return kDontDrawT == (uint32_t)t;
@@ -42,7 +44,7 @@ class SkTwoPointConicalGradient : public SkGradientShaderBase {
 public:
     SkTwoPointConicalGradient(const SkPoint& start, SkScalar startRadius,
                               const SkPoint& end, SkScalar endRadius,
-                              const Descriptor&);
+                              bool flippedGrad, const Descriptor&);
 
 
     virtual SkShader::Context* createContext(const SkBitmap&, const SkPaint&, const SkMatrix&,
@@ -76,6 +78,7 @@ public:
     const SkPoint& getStartCenter() const { return fCenter1; }
     const SkPoint& getEndCenter() const { return fCenter2; }
     SkScalar getEndRadius() const { return fRadius2; }
+    bool isFlippedGrad() const { return fFlippedGrad; }
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkTwoPointConicalGradient)
@@ -85,10 +88,11 @@ protected:
     virtual void flatten(SkWriteBuffer& buffer) const SK_OVERRIDE;
 
 private:
-    const SkPoint fCenter1;
-    const SkPoint fCenter2;
-    const SkScalar fRadius1;
-    const SkScalar fRadius2;
+    SkPoint fCenter1;
+    SkPoint fCenter2;
+    SkScalar fRadius1;
+    SkScalar fRadius2;
+    bool fFlippedGrad;
 
     typedef SkGradientShaderBase INHERITED;
 };
diff --git a/src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp b/src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp
index d7b0384017..7cdb62dc44 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp
+++ b/src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp
@@ -56,6 +56,7 @@ public:
 
     // The radial gradient parameters can collapse to a linear (instead of quadratic) equation.
     bool isDegenerate() const { return SkScalarAbs(fDiffRadius) == SkScalarAbs(fCenterX1); }
+    bool isFlipped() const { return fIsFlipped; }
     SkScalar center() const { return fCenterX1; }
     SkScalar diffRadius() const { return fDiffRadius; }
     SkScalar radius() const { return fRadius0; }
@@ -68,7 +69,8 @@ private:
         return (INHERITED::onIsEqual(sBase) &&
                 this->fCenterX1 == s.fCenterX1 &&
                 this->fRadius0 == s.fRadius0 &&
-                this->fDiffRadius == s.fDiffRadius);
+                this->fDiffRadius == s.fDiffRadius &&
+                this->fIsFlipped == s.fIsFlipped);
     }
 
     Default2PtConicalEffect(GrContext* ctx,
@@ -78,7 +80,8 @@ private:
         : INHERITED(ctx, shader, matrix, tm),
         fCenterX1(shader.getCenterX1()),
         fRadius0(shader.getStartRadius()),
-        fDiffRadius(shader.getDiffRadius()) {
+        fDiffRadius(shader.getDiffRadius()),
+        fIsFlipped(shader.isFlippedGrad()) {
         // We pass the linear part of the quadratic as a varying.
         //    float b = -2.0 * (fCenterX1 * x + fRadius0 * fDiffRadius * z)
         fBTransform = this->getCoordTransform();
@@ -103,6 +106,7 @@ private:
     SkScalar         fCenterX1;
     SkScalar         fRadius0;
     SkScalar         fDiffRadius;
+    bool             fIsFlipped;
 
     // @}
 
@@ -132,6 +136,7 @@ protected:
     const char* fFSVaryingName;
 
     bool fIsDegenerate;
+    bool fIsFlipped;
 
     // @{
     /// Values last uploaded as uniforms
@@ -194,6 +199,7 @@ GLDefault2PtConicalEffect::GLDefault2PtConicalEffect(const GrBackendEffectFactor
 
     const Default2PtConicalEffect& data = drawEffect.castEffect<Default2PtConicalEffect>();
     fIsDegenerate = data.isDegenerate();
+    fIsFlipped = data.isFlipped();
 }
 
 void GLDefault2PtConicalEffect::emitCode(GrGLShaderBuilder* builder,
@@ -281,9 +287,14 @@ void GLDefault2PtConicalEffect::emitCode(GrGLShaderBuilder* builder,
         // Note: If there are two roots that both generate radius(t) > 0, the
         // Canvas spec says to choose the larger t.
 
-        // so we'll look at the larger one first:
-        builder->fsCodeAppendf("\t\tfloat %s = max(%s, %s);\n", tName.c_str(),
-                               r0Name.c_str(), r1Name.c_str());
+        // so we'll look at the larger one first (or smaller if flipped):
+        if (!fIsFlipped) {
+            builder->fsCodeAppendf("\t\tfloat %s = max(%s, %s);\n", tName.c_str(),
+                                   r0Name.c_str(), r1Name.c_str());
+        } else {
+            builder->fsCodeAppendf("\t\tfloat %s = min(%s, %s);\n", tName.c_str(),
+                                   r0Name.c_str(), r1Name.c_str());
+        }
 
         // if r(t) > 0, then we're done; t will be our x coordinate
         builder->fsCodeAppendf("\t\tif (%s * %s + %s > 0.0) {\n", tName.c_str(),
@@ -294,8 +305,13 @@ void GLDefault2PtConicalEffect::emitCode(GrGLShaderBuilder* builder,
 
         // otherwise, if r(t) for the larger root was <= 0, try the other root
         builder->fsCodeAppend("\t\t} else {\n");
-        builder->fsCodeAppendf("\t\t\t%s = min(%s, %s);\n", tName.c_str(),
-                               r0Name.c_str(), r1Name.c_str());
+        if (!fIsFlipped) {
+            builder->fsCodeAppendf("\t\t\t%s = min(%s, %s);\n", tName.c_str(),
+                                   r0Name.c_str(), r1Name.c_str());
+        } else {
+            builder->fsCodeAppendf("\t\t\t%s = max(%s, %s);\n", tName.c_str(),
+                                   r0Name.c_str(), r1Name.c_str());
+        }
 
         // if r(t) > 0 for the smaller root, then t will be our x coordinate
         builder->fsCodeAppendf("\t\t\tif (%s * %s + %s > 0.0) {\n",
@@ -330,6 +346,7 @@ void GLDefault2PtConicalEffect::setData(const GrGLUniformManager& uman,
     INHERITED::setData(uman, drawEffect);
     const Default2PtConicalEffect& data = drawEffect.castEffect<Default2PtConicalEffect>();
     SkASSERT(data.isDegenerate() == fIsDegenerate);
+    SkASSERT(data.isFlipped() == fIsFlipped);
     SkScalar centerX1 = data.center();
     SkScalar radius0 = data.radius();
     SkScalar diffRadius = data.diffRadius();
@@ -365,12 +382,16 @@ GrGLEffect::EffectKey GLDefault2PtConicalEffect::GenKey(const GrDrawEffect& draw
                                                    const GrGLCaps&) {
     enum {
         kIsDegenerate = 1 << kBaseKeyBitCnt,
+        kIsFlipped = 1 << (kBaseKeyBitCnt + 1),
     };
 
     EffectKey key = GenBaseGradientKey(drawEffect);
     if (drawEffect.castEffect<Default2PtConicalEffect>().isDegenerate()) {
         key |= kIsDegenerate;
     }
+    if (drawEffect.castEffect<Default2PtConicalEffect>().isFlipped()) {
+        key |= kIsFlipped;
+    }
     return key;
 }