SkPoint conic(SkPoint p0, SkPoint p1, SkPoint p2, float w, float t) {

    float s = 1 - t;

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

                    ((s * s) + (w * 2 * s * t) + (t * t)),

            ((s * s * p0.y()) + (2 * s * t * w * p1.y()) + (t * t * p2.y())) /

                    ((s * s) + (w * 2 * s * t) + (t * t))};

}

​

void draw(SkCanvas* canvas) {

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

​

    SkPaint paint;

    paint.setAntiAlias(true);

    paint.setStyle(SkPaint::kStroke_Style);

    paint.setStrokeWidth(2.5);

​

    SkPoint center = {256, 256};

    float r = 192;

    SkRect oval = {center.x() - r, center.y() - r, center.x() + r, center.y() + r};

    canvas->drawOval(oval, paint);

    float startAngle = 0;

    float sweepAngle = 179;

​

    SkPath arc;

    arc.arcTo(oval, startAngle, sweepAngle, false);

​

    paint.setStrokeWidth(5);

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

    canvas->drawPath(arc, paint);

​

    SkPaint pointPaint;

    pointPaint.setAntiAlias(true);

    pointPaint.setStrokeWidth(8);

    pointPaint.setStrokeCap(SkPaint::kRound_Cap);

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

​

    float finalAngle = startAngle + sweepAngle;

    float middleAngle = startAngle + 0.5f * sweepAngle;

    float weight = cos(SkDegreesToRadians(sweepAngle) / 2);

    SkPoint p0 = {r * SkScalarCos(SkDegreesToRadians(startAngle)),

                  r * SkScalarSin(SkDegreesToRadians(startAngle))};

    float d = r / weight;

    SkPoint p1 = {d * SkScalarCos(SkDegreesToRadians(middleAngle)),

                  d * SkScalarSin(SkDegreesToRadians(middleAngle))};

    SkPoint p2 = {r * SkScalarCos(SkDegreesToRadians(finalAngle)),

                  r * SkScalarSin(SkDegreesToRadians(finalAngle))};

    p0 += center;

    p1 += center;

    p2 += center;

​

    const int N = 8;

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

        SkPoint p = conic(p0, p1, p2, weight, (float)i / N);

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

    }

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

    canvas->drawPoint(p0.x(), p0.y(), pointPaint);

    canvas->drawPoint(p1.x(), p1.y(), pointPaint);

    canvas->drawPoint(p2.x(), p2.y(), pointPaint);

​

    SkPath weightedQuadratic;

    weightedQuadratic.moveTo(p0);

    weightedQuadratic.conicTo(p1, p2, weight);

    paint.setColor(SK_ColorCYAN);

    paint.setStrokeWidth(1);

    canvas->drawPath(weightedQuadratic, paint);

}