void drawOval(Rect rect, Paint paint)

Draws an axis-aligned oval that fills the given axis-aligned rectangle with the given Paint. Whether the oval is filled or stroked (or both) is controlled by Paint.style.

Source

void drawOval(Rect rect, Paint paint) {
  _drawOval(rect.left, rect.top, rect.right, rect.bottom,
            paint._objects, paint._data);
}