gm/gradients.cpp

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "gm.h"
#include "SkGradientShader.h"

namespace skiagm {

struct GradData {
    int             fCount;
    const SkColor*  fColors;
    const SkScalar* fPos;
};

static const SkColor gColors[] = {
    SK_ColorRED, SK_ColorGREEN, SK_ColorBLUE, SK_ColorWHITE, SK_ColorBLACK
};
static const SkScalar gPos0[] = { 0, SK_Scalar1 };
static const SkScalar gPos1[] = { SK_Scalar1/4, SK_Scalar1*3/4 };
static const SkScalar gPos2[] = {
    0, SK_Scalar1/8, SK_Scalar1/2, SK_Scalar1*7/8, SK_Scalar1
};

static const SkScalar gPosClamp[]   = {0.0f, 0.0f, 1.0f, 1.0f};
static const SkColor  gColorClamp[] = {
    SK_ColorRED, SK_ColorGREEN, SK_ColorGREEN, SK_ColorBLUE
};

static const GradData gGradData[] = {
    { 2, gColors, nullptr },
    { 2, gColors, gPos0 },
    { 2, gColors, gPos1 },
    { 5, gColors, nullptr },
    { 5, gColors, gPos2 },
    { 4, gColorClamp, gPosClamp }
};

static SkShader* MakeLinear(const SkPoint pts[2], const GradData& data,
                            SkShader::TileMode tm, const SkMatrix& localMatrix) {
    return SkGradientShader::CreateLinear(pts, data.fColors, data.fPos,
                                          data.fCount, tm, 0, &localMatrix);
}

static SkShader* MakeRadial(const SkPoint pts[2], const GradData& data,
                            SkShader::TileMode tm, const SkMatrix& localMatrix) {
    SkPoint center;
    center.set(SkScalarAve(pts[0].fX, pts[1].fX),
               SkScalarAve(pts[0].fY, pts[1].fY));
    return SkGradientShader::CreateRadial(center, center.fX, data.fColors,
                                          data.fPos, data.fCount, tm, 0, &localMatrix);
}

static SkShader* MakeSweep(const SkPoint pts[2], const GradData& data,
                           SkShader::TileMode, const SkMatrix& localMatrix) {
    SkPoint center;
    center.set(SkScalarAve(pts[0].fX, pts[1].fX),
               SkScalarAve(pts[0].fY, pts[1].fY));
    return SkGradientShader::CreateSweep(center.fX, center.fY, data.fColors,
                                         data.fPos, data.fCount, 0, &localMatrix);
}

static SkShader* Make2Radial(const SkPoint pts[2], const GradData& data,
                             SkShader::TileMode tm, const SkMatrix& localMatrix) {
    SkPoint center0, center1;
    center0.set(SkScalarAve(pts[0].fX, pts[1].fX),
                SkScalarAve(pts[0].fY, pts[1].fY));
    center1.set(SkScalarInterp(pts[0].fX, pts[1].fX, SkIntToScalar(3)/5),
                SkScalarInterp(pts[0].fY, pts[1].fY, SkIntToScalar(1)/4));
    return SkGradientShader::CreateTwoPointConical(
                                                   center1, (pts[1].fX - pts[0].fX) / 7,
                                                   center0, (pts[1].fX - pts[0].fX) / 2,
                                                   data.fColors, data.fPos, data.fCount, tm,
                                                   0, &localMatrix);
}

static SkShader* Make2Conical(const SkPoint pts[2], const GradData& data,
                             SkShader::TileMode tm, const SkMatrix& localMatrix) {
    SkPoint center0, center1;
    SkScalar radius0 = (pts[1].fX - pts[0].fX) / 10;
    SkScalar radius1 = (pts[1].fX - pts[0].fX) / 3;
    center0.set(pts[0].fX + radius0, pts[0].fY + radius0);
    center1.set(pts[1].fX - radius1, pts[1].fY - radius1);
    return SkGradientShader::CreateTwoPointConical(center1, radius1,
                                                   center0, radius0,
                                                   data.fColors, data.fPos,
                                                   data.fCount, tm, 0, &localMatrix);
}

typedef SkShader* (*GradMaker)(const SkPoint pts[2], const GradData& data,
                               SkShader::TileMode tm, const SkMatrix& localMatrix);
static const GradMaker gGradMakers[] = {
    MakeLinear, MakeRadial, MakeSweep, Make2Radial, Make2Conical
};

///////////////////////////////////////////////////////////////////////////////

class GradientsGM : public GM {
public:
    GradientsGM(bool dither) : fDither(dither) {
        this->setBGColor(sk_tool_utils::color_to_565(0xFFDDDDDD));
    }

protected:

    SkString onShortName() {
        return SkString(fDither ? "gradients" : "gradients_nodither");
    }

    virtual SkISize onISize() { return SkISize::Make(840, 815); }

    virtual void onDraw(SkCanvas* canvas) {

        SkPoint pts[2] = {
            { 0, 0 },
            { SkIntToScalar(100), SkIntToScalar(100) }
        };
        SkShader::TileMode tm = SkShader::kClamp_TileMode;
        SkRect r = { 0, 0, SkIntToScalar(100), SkIntToScalar(100) };
        SkPaint paint;
        paint.setAntiAlias(true);
        paint.setDither(fDither);

        canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
        for (size_t i = 0; i < SK_ARRAY_COUNT(gGradData); i++) {
            canvas->save();
            for (size_t j = 0; j < SK_ARRAY_COUNT(gGradMakers); j++) {
                SkMatrix scale = SkMatrix::I();

                if (i == 5) { // if the clamp case
                    scale.setScale(0.5f, 0.5f);
                    scale.postTranslate(25.f, 25.f);
                }

                SkShader* shader = gGradMakers[j](pts, gGradData[i], tm, scale);

                paint.setShader(shader);
                canvas->drawRect(r, paint);
                shader->unref();
                canvas->translate(0, SkIntToScalar(120));
            }
            canvas->restore();
            canvas->translate(SkIntToScalar(120), 0);
        }
    }

protected:
    bool fDither;

private:
    typedef GM INHERITED;
};
DEF_GM( return new GradientsGM(true); )
DEF_GM( return new GradientsGM(false); )

// Based on the original gradient slide, but with perspective applied to the
// gradient shaders' local matrices
class GradientsLocalPerspectiveGM : public GM {
public:
    GradientsLocalPerspectiveGM(bool dither) : fDither(dither) {
        this->setBGColor(sk_tool_utils::color_to_565(0xFFDDDDDD));
    }

protected:

    SkString onShortName() {
        return SkString(fDither ? "gradients_local_perspective" :
                                  "gradients_local_perspective_nodither");
    }

    virtual SkISize onISize() { return SkISize::Make(840, 815); }

    virtual void onDraw(SkCanvas* canvas) {

        SkPoint pts[2] = {
            { 0, 0 },
            { SkIntToScalar(100), SkIntToScalar(100) }
        };
        SkShader::TileMode tm = SkShader::kClamp_TileMode;
        SkRect r = { 0, 0, SkIntToScalar(100), SkIntToScalar(100) };
        SkPaint paint;
        paint.setAntiAlias(true);
        paint.setDither(fDither);

        canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
        for (size_t i = 0; i < SK_ARRAY_COUNT(gGradData); i++) {
            canvas->save();
            for (size_t j = 0; j < SK_ARRAY_COUNT(gGradMakers); j++) {
                // apply an increasing y perspective as we move to the right
                SkMatrix perspective;
                perspective.setIdentity();
                perspective.setPerspY(SkIntToScalar(i+1) / 500);
                perspective.setSkewX(SkIntToScalar(i+1) / 10);

                SkShader* shader = gGradMakers[j](pts, gGradData[i], tm, perspective);

                paint.setShader(shader);
                canvas->drawRect(r, paint);
                shader->unref();
                canvas->translate(0, SkIntToScalar(120));
            }
            canvas->restore();
            canvas->translate(SkIntToScalar(120), 0);
        }
    }

private:
    bool fDither;

    typedef GM INHERITED;
};
DEF_GM( return new GradientsLocalPerspectiveGM(true); )
DEF_GM( return new GradientsLocalPerspectiveGM(false); )

// Based on the original gradient slide, but with perspective applied to
// the view matrix
class GradientsViewPerspectiveGM : public GradientsGM {
public:
    GradientsViewPerspectiveGM(bool dither) : INHERITED(dither) { }

protected:
    SkString onShortName() {
        return SkString(fDither ? "gradients_view_perspective" :
                                  "gradients_view_perspective_nodither");
    }

    virtual SkISize onISize() { return SkISize::Make(840, 500); }

    virtual void onDraw(SkCanvas* canvas) {
        SkMatrix perspective;
        perspective.setIdentity();
        perspective.setPerspY(0.001f);
        perspective.setSkewX(SkIntToScalar(8) / 25);
        canvas->concat(perspective);
        INHERITED::onDraw(canvas);
    }

private:
    typedef GradientsGM INHERITED;
};
DEF_GM( return new GradientsViewPerspectiveGM(true); )
DEF_GM( return new GradientsViewPerspectiveGM(false); )

/*
 Inspired by this <canvas> javascript, where we need to detect that we are not
 solving a quadratic equation, but must instead solve a linear (since our X^2
 coefficient is 0)

 ctx.fillStyle = '#f00';
 ctx.fillRect(0, 0, 100, 50);

 var g = ctx.createRadialGradient(-80, 25, 70, 0, 25, 150);
 g.addColorStop(0, '#f00');
 g.addColorStop(0.01, '#0f0');
 g.addColorStop(0.99, '#0f0');
 g.addColorStop(1, '#f00');
 ctx.fillStyle = g;
 ctx.fillRect(0, 0, 100, 50);
 */
class GradientsDegenrate2PointGM : public GM {
public:
    GradientsDegenrate2PointGM(bool dither) : fDither(dither) {}

protected:
    SkString onShortName() {
        return SkString(fDither ? "gradients_degenerate_2pt" : "gradients_degenerate_2pt_nodither");
    }

    virtual SkISize onISize() { return SkISize::Make(320, 320); }

    void drawBG(SkCanvas* canvas) {
        canvas->drawColor(SK_ColorBLUE);
    }

    virtual void onDraw(SkCanvas* canvas) {
        this->drawBG(canvas);

        SkColor colors[] = { SK_ColorRED, SK_ColorGREEN, SK_ColorGREEN, SK_ColorRED };
        SkScalar pos[] = { 0, 0.01f, 0.99f, SK_Scalar1 };
        SkPoint c0;
        c0.iset(-80, 25);
        SkScalar r0 = SkIntToScalar(70);
        SkPoint c1;
        c1.iset(0, 25);
        SkScalar r1 = SkIntToScalar(150);
        SkShader* s = SkGradientShader::CreateTwoPointConical(c0, r0, c1, r1, colors,
                                                              pos, SK_ARRAY_COUNT(pos),
                                                              SkShader::kClamp_TileMode);
        SkPaint paint;
        paint.setDither(fDither);
        paint.setShader(s)->unref();
        canvas->drawPaint(paint);
    }

private:
    bool fDither;

    typedef GM INHERITED;
};
DEF_GM( return new GradientsDegenrate2PointGM(true); )
DEF_GM( return new GradientsDegenrate2PointGM(false); )

/// Tests correctness of *optimized* codepaths in gradients.

class ClampedGradientsGM : public GM {
public:
    ClampedGradientsGM(bool dither) : fDither(dither) {}

protected:
    SkString onShortName() {
        return SkString(fDither ? "clamped_gradients" : "clamped_gradients_nodither");
    }

    virtual SkISize onISize() { return SkISize::Make(640, 510); }

    void drawBG(SkCanvas* canvas) {
        canvas->drawColor(sk_tool_utils::color_to_565(0xFFDDDDDD));
    }

    virtual void onDraw(SkCanvas* canvas) {
        this->drawBG(canvas);

        SkRect r = { 0, 0, SkIntToScalar(100), SkIntToScalar(300) };
        SkPaint paint;
        paint.setDither(fDither);
        paint.setAntiAlias(true);

        SkPoint center;
        center.iset(0, 300);
        canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
        SkShader* shader = SkGradientShader::CreateRadial(
            SkPoint(center),
            SkIntToScalar(200), gColors, nullptr, 5,
            SkShader::kClamp_TileMode);
        paint.setShader(shader);
        canvas->drawRect(r, paint);
        shader->unref();
    }

private:
    bool fDither;

    typedef GM INHERITED;
};
DEF_GM( return new ClampedGradientsGM(true); )
DEF_GM( return new ClampedGradientsGM(false); )

/// Checks quality of large radial gradients, which may display
/// some banding.

class RadialGradientGM : public GM {
public:
    RadialGradientGM() {}

protected:

    SkString onShortName() override { return SkString("radial_gradient"); }
    SkISize onISize() override { return SkISize::Make(1280, 1280); }
    void drawBG(SkCanvas* canvas) {
        canvas->drawColor(0xFF000000);
    }
    void onDraw(SkCanvas* canvas) override {
        const SkISize dim = this->getISize();

        this->drawBG(canvas);

        SkPaint paint;
        paint.setDither(true);
        SkPoint center;
        center.set(SkIntToScalar(dim.width())/2, SkIntToScalar(dim.height())/2);
        SkScalar radius = SkIntToScalar(dim.width())/2;
        const SkColor colors[] = { 0x7f7f7f7f, 0x7f7f7f7f, 0xb2000000 };
        const SkScalar pos[] = { 0.0f,
                             0.35f,
                             1.0f };
        SkShader* shader =
            SkGradientShader::CreateRadial(center, radius, colors,
                                           pos, SK_ARRAY_COUNT(pos),
                                           SkShader::kClamp_TileMode);
        paint.setShader(shader)->unref();
        SkRect r = {
            0, 0, SkIntToScalar(dim.width()), SkIntToScalar(dim.height())
        };
        canvas->drawRect(r, paint);
    }
private:
    typedef GM INHERITED;
};
DEF_GM( return new RadialGradientGM; )

class RadialGradient2GM : public GM {
public:
    RadialGradient2GM(bool dither) : fDither(dither) {}

protected:

    SkString onShortName() override {
        return SkString(fDither ? "radial_gradient2" : "radial_gradient2_nodither");
    }

    SkISize onISize() override { return SkISize::Make(800, 400); }
    void drawBG(SkCanvas* canvas) {
        canvas->drawColor(0xFF000000);
    }

    // Reproduces the example given in bug 7671058.
    void onDraw(SkCanvas* canvas) override {
        SkPaint paint1, paint2, paint3;
        paint1.setStyle(SkPaint::kFill_Style);
        paint2.setStyle(SkPaint::kFill_Style);
        paint3.setStyle(SkPaint::kFill_Style);

        const SkColor sweep_colors[] =
            { 0xFFFF0000, 0xFFFFFF00, 0xFF00FF00, 0xFF00FFFF, 0xFF0000FF, 0xFFFF00FF, 0xFFFF0000 };
        const SkColor colors1[] = { 0xFFFFFFFF, 0x00000000 };
        const SkColor colors2[] = { 0xFF000000, 0x00000000 };

        const SkScalar cx = 200, cy = 200, radius = 150;
        SkPoint center;
        center.set(cx, cy);

        // We can either interpolate endpoints and premultiply each point (default, more precision),
        // or premultiply the endpoints first, avoiding the need to premultiply each point (cheap).
        const uint32_t flags[] = { 0, SkGradientShader::kInterpolateColorsInPremul_Flag };

        for (size_t i = 0; i < SK_ARRAY_COUNT(flags); i++) {
            SkAutoTUnref<SkShader> sweep(
                    SkGradientShader::CreateSweep(cx, cy, sweep_colors,
                                                  nullptr, SK_ARRAY_COUNT(sweep_colors),
                                                  flags[i], nullptr));
            SkAutoTUnref<SkShader> radial1(
                    SkGradientShader::CreateRadial(center, radius, colors1,
                                                   nullptr, SK_ARRAY_COUNT(colors1),
                                                   SkShader::kClamp_TileMode,
                                                   flags[i], nullptr));
            SkAutoTUnref<SkShader> radial2(
                    SkGradientShader::CreateRadial(center, radius, colors2,
                                                   nullptr, SK_ARRAY_COUNT(colors2),
                                                   SkShader::kClamp_TileMode,
                                                   flags[i], nullptr));
            paint1.setShader(sweep);
            paint1.setDither(fDither);
            paint2.setShader(radial1);
            paint2.setDither(fDither);
            paint3.setShader(radial2);
            paint3.setDither(fDither);

            canvas->drawCircle(cx, cy, radius, paint1);
            canvas->drawCircle(cx, cy, radius, paint3);
            canvas->drawCircle(cx, cy, radius, paint2);

            canvas->translate(400, 0);
        }
    }

private:
    bool fDither;

    typedef GM INHERITED;
};
DEF_GM( return new RadialGradient2GM(true); )
DEF_GM( return new RadialGradient2GM(false); )

// Shallow radial (shows banding on raster)
class RadialGradient3GM : public GM {
public:
    RadialGradient3GM(bool dither) : fDither(dither) { }

protected:
    SkString onShortName() override {
        return SkString(fDither ? "radial_gradient3" : "radial_gradient3_nodither");
    }

    SkISize onISize() override { return SkISize::Make(500, 500); }

    bool runAsBench() const override { return true; }

    void onOnceBeforeDraw() override {
        const SkPoint center = { 0, 0 };
        const SkScalar kRadius = 3000;
        const SkColor gColors[] = { 0xFFFFFFFF, 0xFF000000 };
        fShader.reset(SkGradientShader::CreateRadial(center, kRadius, gColors, nullptr, 2,
                                                     SkShader::kClamp_TileMode));
    }

    void onDraw(SkCanvas* canvas) override {
        SkPaint paint;
        paint.setShader(fShader);
        paint.setDither(fDither);
        canvas->drawRect(SkRect::MakeWH(500, 500), paint);
    }
    
private:
    SkAutoTUnref<SkShader> fShader;
    bool fDither;

    typedef GM INHERITED;
};
DEF_GM( return new RadialGradient3GM(true); )
DEF_GM( return new RadialGradient3GM(false); )

class RadialGradient4GM : public GM {
public:
    RadialGradient4GM(bool dither) : fDither(dither) { }

protected:
    SkString onShortName() override {
        return SkString(fDither ? "radial_gradient4" : "radial_gradient4_nodither");
    }

    SkISize onISize() override { return SkISize::Make(500, 500); }

    void onOnceBeforeDraw() override {
        const SkPoint center = { 250, 250 };
        const SkScalar kRadius = 250;
        const SkColor colors[] = { SK_ColorRED, SK_ColorRED, SK_ColorWHITE, SK_ColorWHITE,
                SK_ColorRED };
        const SkScalar pos[] = { 0, .4f, .4f, .8f, .8f, 1 };
        fShader.reset(SkGradientShader::CreateRadial(center, kRadius, colors, pos, 
                SK_ARRAY_COUNT(gColors), SkShader::kClamp_TileMode));
    }

    void onDraw(SkCanvas* canvas) override {
        SkPaint paint;
        paint.setAntiAlias(true);
        paint.setDither(fDither);
        paint.setShader(fShader);
        canvas->drawRect(SkRect::MakeWH(500, 500), paint);
    }
    
private:
    SkAutoTUnref<SkShader> fShader;
    bool fDither;

    typedef GM INHERITED;
};
DEF_GM( return new RadialGradient4GM(true); )
DEF_GM( return new RadialGradient4GM(false); )

class LinearGradientGM : public GM {
public:
    LinearGradientGM(bool dither) : fDither(dither) { }

protected:
    SkString onShortName() override {
        return SkString(fDither ? "linear_gradient" : "linear_gradient_nodither");
    }

    const SkScalar kWidthBump = 30.f;
    const SkScalar kHeight = 5.f;
    const SkScalar kMinWidth = 540.f;

    SkISize onISize() override { return SkISize::Make(500, 500); }

    void onOnceBeforeDraw() override {
        SkPoint pts[2] = { {0, 0}, {0, 0} };
        const SkColor colors[] = { SK_ColorWHITE, SK_ColorWHITE, 0xFF008200, 0xFF008200,
                SK_ColorWHITE, SK_ColorWHITE };
        const SkScalar unitPos[] = { 0, 50, 70, 500, 540 };
        SkScalar pos[6];
        pos[5] = 1;
        for (int index = 0; index < (int) SK_ARRAY_COUNT(fShader); ++index) {
            pts[1].fX = 500.f + index * kWidthBump;
            for (int inner = 0; inner < (int) SK_ARRAY_COUNT(unitPos); ++inner) {
                pos[inner] = unitPos[inner] / (kMinWidth + index * kWidthBump);
            }
            fShader[index].reset(SkGradientShader::CreateLinear(pts, colors, pos, 
                    SK_ARRAY_COUNT(gColors), SkShader::kClamp_TileMode));
        }
    }

    void onDraw(SkCanvas* canvas) override {
        SkPaint paint;
        paint.setAntiAlias(true);
        paint.setDither(fDither);
        for (int index = 0; index < (int) SK_ARRAY_COUNT(fShader); ++index) {
            paint.setShader(fShader[index]);
            canvas->drawRect(SkRect::MakeLTRB(0, index * kHeight, kMinWidth + index * kWidthBump,
                    (index + 1) * kHeight), paint);
        }
    }
    
private:
    SkAutoTUnref<SkShader> fShader[100];
    bool fDither;

    typedef GM INHERITED;
};
DEF_GM( return new LinearGradientGM(true); )
DEF_GM( return new LinearGradientGM(false); )

class LinearGradientTinyGM : public GM {
protected:
    SkString onShortName() override {
        return SkString("linear_gradient_tiny");
    }

    SkISize onISize() override {
        return SkISize::Make(600, 500);
    }

    void onDraw(SkCanvas* canvas) override {
        const SkScalar kRectSize = 100;
        const unsigned kStopCount = 3;
        const SkColor colors[kStopCount] = { SK_ColorGREEN, SK_ColorRED, SK_ColorGREEN };
        const struct {
            SkPoint pts[2];
            SkScalar pos[kStopCount];
        } configs[] = {
            { { SkPoint::Make(0, 0),        SkPoint::Make(10, 0) },       { 0, 0.999999f,    1 }},
            { { SkPoint::Make(0, 0),        SkPoint::Make(10, 0) },       { 0, 0.000001f,    1 }},
            { { SkPoint::Make(0, 0),        SkPoint::Make(10, 0) },       { 0, 0.999999999f, 1 }},
            { { SkPoint::Make(0, 0),        SkPoint::Make(10, 0) },       { 0, 0.000000001f, 1 }},

            { { SkPoint::Make(0, 0),        SkPoint::Make(0, 10) },       { 0, 0.999999f,    1 }},
            { { SkPoint::Make(0, 0),        SkPoint::Make(0, 10) },       { 0, 0.000001f,    1 }},
            { { SkPoint::Make(0, 0),        SkPoint::Make(0, 10) },       { 0, 0.999999999f, 1 }},
            { { SkPoint::Make(0, 0),        SkPoint::Make(0, 10) },       { 0, 0.000000001f, 1 }},

            { { SkPoint::Make(0, 0),        SkPoint::Make(0.00001f, 0) }, { 0, 0.5f, 1 }},
            { { SkPoint::Make(9.99999f, 0), SkPoint::Make(10, 0) },       { 0, 0.5f, 1 }},
            { { SkPoint::Make(0, 0),        SkPoint::Make(0, 0.00001f) }, { 0, 0.5f, 1 }},
            { { SkPoint::Make(0, 9.99999f), SkPoint::Make(0, 10) },       { 0, 0.5f, 1 }},
        };

        SkPaint paint;
        for (unsigned i = 0; i < SK_ARRAY_COUNT(configs); ++i) {
            SkAutoCanvasRestore acr(canvas, true);
            SkAutoTUnref<SkShader> gradient(
                SkGradientShader::CreateLinear(configs[i].pts, colors, configs[i].pos, kStopCount,
                                               SkShader::kClamp_TileMode));
            canvas->translate(kRectSize * ((i % 4) * 1.5f + 0.25f),
                              kRectSize * ((i / 4) * 1.5f + 0.25f));

            paint.setShader(gradient);
            canvas->drawRect(SkRect::MakeWH(kRectSize, kRectSize), paint);
        }
    }

private:
    typedef GM INHERITED;
};
DEF_GM( return new LinearGradientTinyGM(); )

}

///////////////////////////////////////////////////////////////////////////////////////////////////

struct GradRun {
    SkColor  fColors[4];
    SkScalar fPos[4];
    int      fCount;
};

#define SIZE 121

static SkShader* make_linear(const GradRun& run, SkShader::TileMode mode) {
    const SkPoint pts[] { { 30, 30 }, { SIZE - 30, SIZE - 30 } };
    return SkGradientShader::CreateLinear(pts, run.fColors, run.fPos, run.fCount, mode);
}

static SkShader* make_radial(const GradRun& run, SkShader::TileMode mode) {
    const SkScalar half = SIZE * 0.5f;
    return SkGradientShader::CreateRadial({half,half}, half - 10,
                                          run.fColors, run.fPos, run.fCount, mode);
}

static SkShader* make_conical(const GradRun& run, SkShader::TileMode mode) {
    const SkScalar half = SIZE * 0.5f;
    const SkPoint center { half, half };
    return SkGradientShader::CreateTwoPointConical(center, 20, center, half - 10,
                                          run.fColors, run.fPos, run.fCount, mode);
}

static SkShader* make_sweep(const GradRun& run, SkShader::TileMode) {
    const SkScalar half = SIZE * 0.5f;
    return SkGradientShader::CreateSweep(half, half, run.fColors, run.fPos, run.fCount);
}

/*
 *  Exercise duplicate color-stops, at the ends, and in the middle
 *
 *  At the time of this writing, only Linear correctly deals with duplicates at the ends,
 *  and then only correctly on CPU backend.
 */
DEF_SIMPLE_GM(gradients_dup_color_stops, canvas, 704, 564) {
    const SkColor preColor  = 0xFFFF0000;   // clamp color before start
    const SkColor postColor = 0xFF0000FF;   // clamp color after end
    const SkColor color0    = 0xFF000000;
    const SkColor color1    = 0xFF00FF00;
    const SkColor badColor  = 0xFF3388BB;   // should never be seen, fills out fixed-size array

    const GradRun runs[] = {
        {   { color0, color1, badColor, badColor },
            { 0, 1, -1, -1 },
            2,
        },
        {   { preColor, color0, color1, badColor },
            { 0, 0, 1, -1 },
            3,
        },
        {   { color0, color1, postColor, badColor },
            { 0, 1, 1, -1 },
            3,
        },
        {   { preColor, color0, color1, postColor },
            { 0, 0, 1, 1 },
            4,
        },
        {   { color0, color0, color1, color1 },
            { 0, 0.5f, 0.5f, 1 },
            4,
        },
    };
    SkShader* (*factories[])(const GradRun&, SkShader::TileMode) {
        make_linear, make_radial, make_conical, make_sweep
    };

    const SkRect rect = SkRect::MakeWH(SIZE, SIZE);
    const SkScalar dx = SIZE + 20;
    const SkScalar dy = SIZE + 20;
    const SkShader::TileMode mode = SkShader::kClamp_TileMode;

    SkPaint paint;
    canvas->translate(10, 10 - dy);
    for (auto factory : factories) {
        canvas->translate(0, dy);
        SkAutoCanvasRestore acr(canvas, true);
        for (const auto& run : runs) {
            paint.setShader(factory(run, mode))->unref();
            canvas->drawRect(rect, paint);
            canvas->translate(dx, 0);
        }
    }
}