SkPoint quad(SkPoint p0, SkPoint p1, SkPoint p2, float t) {

    float s = 1 - t;

    return {(s * s * p0.x()) + (2 * s * t * p1.x()) + (t * t * p2.x()),

            (s * s * p0.y()) + (2 * s * t * p1.y()) + (t * t * p2.y())};

}

​

/*

​

        If the starting point is (x0, y0), then this curve is defined as the

        paramentric curve as `t` goes from 0 to 1:

​

          s := 1 - t

          x := (s * s * x0) + (2 * s * t * x1) + (t * t * x2)

          y := (s * s * y0) + (2 * s * t * y1) + (t * t * y2)

​

*/

​

void draw(SkCanvas* canvas) {

    canvas->clear(SkColorSetARGB(255, 255, 255, 255));

​

    SkPaint paint;

    paint.setAntiAlias(true);

    paint.setStyle(SkPaint::kStroke_Style);

    paint.setStrokeWidth(5);

​

    SkPoint a{100, 100};

    SkPoint b{200, 400};

    SkPoint c{300, 100};

​

    SkPath twoSegments;

    twoSegments.moveTo(a);

    twoSegments.lineTo(b);

    twoSegments.lineTo(c);

​

    canvas->drawPath(twoSegments, paint);

​

    paint.setColor(SkColorSetARGB(255, 0, 0, 255));

    SkPath quadraticCurve;

    quadraticCurve.moveTo(a);

    quadraticCurve.quadTo(b, c);

    canvas->drawPath(quadraticCurve, paint);

​

    SkFont font(fontMgr->matchFamilyStyle(nullptr, {}), 32);

    SkPaint textPaint;

    textPaint.setAntiAlias(true);

    canvas->drawString("a", a.x(), a.y(), font, textPaint);

    canvas->drawString("b", b.x() + 20, b.y() + 20, font, textPaint);

    canvas->drawString("c", c.x(), c.y(), font, textPaint);

​

    SkPaint pointPaint;

    pointPaint.setAntiAlias(true);

    pointPaint.setStrokeWidth(8);

    pointPaint.setStrokeCap(SkPaint::kRound_Cap);

    pointPaint.setColor(SkColorSetARGB(255, 0, 255, 0));

    int N = 15;

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

        SkPoint p = quad(a, b, c, (float)i / N);

        canvas->drawPoint(p.x(), p.y(), pointPaint);

    }

}