static void draw_centered(

        const char* s, const SkFont& font, SkColor color, SkPoint xy, SkCanvas* c) {

    sk_sp<SkTextBlob> b = SkTextBlob::MakeFromString(s, font);

    xy -= SkPoint{b->bounds().centerX(), b->bounds().centerY()};

    SkPaint p;

    p.setColor(color);

    c->drawTextBlob(b.get(), xy.x(), xy.y(), p);

}

​

SkPoint from_polar_deg(float r, float d) {

    float a = d * 0.017453292519943295;

    return {r * cosf(a), r * sinf(a)};

}

​

void draw_wheel(SkCanvas* c) {

    const SkScalar scale = 512;

    SkAutoCanvasRestore autoCanvasRestore(c, true);

    c->translate(0.5f * scale, 0.5f * scale);

    SkPaint p;

    p.setAntiAlias(true);

    p.setColor(SK_ColorWHITE);

    c->drawCircle(0.0f, 0.0f, scale * 0.475f, p);

​

    const SkColor sweep_colors[] = {SK_ColorRED,  SK_ColorYELLOW,  SK_ColorGREEN, SK_ColorCYAN,

                                    SK_ColorBLUE, SK_ColorMAGENTA, SK_ColorRED};

    SkMatrix rot;

    rot.setRotate(90.0f);

    p.setShader(SkGradientShader::MakeSweep(0, 0, sweep_colors, nullptr,

                                            std::size(sweep_colors), 0, &rot));

    p.setStrokeWidth(0.05f * scale);

    p.setStyle(SkPaint::kStroke_Style);

    c->drawCircle(0.0f, 0.0f, 0.475f * scale, p);

​

    SkFont f(nullptr, 0.28125f * scale);

    draw_centered("K", f, SK_ColorBLACK, {0.0f, 0.0f}, c);

    draw_centered("R", f, SK_ColorRED, from_polar_deg(0.3f * scale, 90), c);

    draw_centered("G", f, SK_ColorGREEN, from_polar_deg(0.3f * scale, 210), c);

    draw_centered("B", f, SK_ColorBLUE, from_polar_deg(0.3f * scale, 330), c);

    draw_centered("C", f, SK_ColorCYAN, from_polar_deg(0.3f * scale, 270), c);

    draw_centered("M", f, SK_ColorMAGENTA, from_polar_deg(0.3f * scale, 30), c);

    draw_centered("Y", f, SK_ColorYELLOW, from_polar_deg(0.3f * scale, 150), c);

}

​

void draw(SkCanvas* canvas) {

    canvas->clear(SK_ColorWHITE);

    SkMatrix matrix;

    matrix.setScale(0.25f, 0.25f);

    matrix.preRotate(30.0f);

    SkPaint paint;

    SkPictureRecorder rec;

    draw_wheel(rec.beginRecording(512, 512));

    paint.setShader(rec.finishRecordingAsPicture()->makeShader(

            SkTileMode::kRepeat, SkTileMode::kRepeat, SkFilterMode::kNearest, &matrix, nullptr));

    canvas->drawPaint(paint);

}