void draw(SkCanvas* canvas) {

    SkXfermode::Mode modes[] = {

        SkXfermode::kClear_Mode,

        SkXfermode::kSrc_Mode,

        SkXfermode::kDst_Mode,

        SkXfermode::kSrcOver_Mode,

        SkXfermode::kDstOver_Mode,

        SkXfermode::kSrcIn_Mode,

        SkXfermode::kDstIn_Mode,

        SkXfermode::kSrcOut_Mode,

        SkXfermode::kDstOut_Mode,

        SkXfermode::kSrcATop_Mode,

        SkXfermode::kDstATop_Mode,

        SkXfermode::kXor_Mode,

        SkXfermode::kPlus_Mode,

        SkXfermode::kModulate_Mode,

        SkXfermode::kScreen_Mode,

        SkXfermode::kOverlay_Mode,

        SkXfermode::kDarken_Mode,

        SkXfermode::kLighten_Mode,

        SkXfermode::kColorDodge_Mode,

        SkXfermode::kColorBurn_Mode,

        SkXfermode::kHardLight_Mode,

        SkXfermode::kSoftLight_Mode,

        SkXfermode::kDifference_Mode,

        SkXfermode::kExclusion_Mode,

        SkXfermode::kMultiply_Mode,

        SkXfermode::kHue_Mode,

        SkXfermode::kSaturation_Mode,

        SkXfermode::kColor_Mode,

        SkXfermode::kLuminosity_Mode,

    };

    SkRect rect = SkRect::MakeWH(64.0f, 64.0f);

    SkPaint text, stroke, src, dst;

    stroke.setStyle(SkPaint::kStroke_Style);

    text.setTextSize(20.0f);

    text.setAntiAlias(true);

    SkPoint srcPoints[2] = {

        SkPoint::Make(0.0f, 0.0f),

        SkPoint::Make(64.0f, 0.0f)

    };

    SkColor srcColors[2] = {

        SK_ColorMAGENTA & 0x00FFFFFF,

        SK_ColorMAGENTA};

    sk_sp<SkShader> srcShader(

        SkGradientShader::MakeLinear(

                srcPoints, srcColors, NULL, 2,

                SkShader::kClamp_TileMode, 0, NULL));

    src.setShader(srcShader);

​

    SkPoint dstPoints[2] = {

        SkPoint::Make(0.0f, 0.0f),

        SkPoint::Make(0.0f, 64.0f)

    };

    SkColor dstColors[2] = {

        SK_ColorCYAN & 0x00FFFFFF,

        SK_ColorCYAN};

    sk_sp<SkShader> dstShader(

        SkGradientShader::MakeLinear(

                dstPoints, dstColors, NULL, 2,

                SkShader::kClamp_TileMode, 0, NULL));

    dst.setShader(dstShader);

    canvas->clear(SK_ColorWHITE);

    size_t N = sizeof(modes) / sizeof(modes[0]);

    size_t K = (N - 1) / 3 + 1;

    SkASSERT(K * 64 == 640);  // tall enough

    for (size_t i = 0; i < N; ++i) {

        SkAutoCanvasRestore autoCanvasRestore(canvas, true);

        canvas->translate(192.0f * (i / K), 64.0f * (i % K));

        char* desc = strdup(SkXfermode::ModeName(modes[i]));

        desc[0] = desc[0] + 0x20;

        canvas->drawText(desc, strlen(desc), 68.0f, 30.0f, text);

        free(desc);

        canvas->clipRect(SkRect::MakeWH(64.0f, 64.0f));

        canvas->drawColor(SK_ColorLTGRAY);

        (void)canvas->saveLayer(NULL, NULL);

        canvas->clear(SK_ColorTRANSPARENT);

        canvas->drawPaint(dst);

        src.setXfermodeMode(modes[i]);

        canvas->drawPaint(src);

        canvas->drawRect(rect, stroke);

    }

}