rotateOffset method

Offset rotateOffset(
  1. num angle, {
  2. Offset center = Offset.zero,
})

返回绕center点旋转angle角度后的位置坐标 逆时针 angle 为负数 顺时针 angle 为正数

Implementation

Offset rotateOffset(num angle, {Offset center = Offset.zero}) {
  angle = angle % 360;
  num t = angle * Constants.angleUnit;
  double x = (dx - center.dx) * cos(t) - (dy - center.dy) * sin(t) + center.dx;
  double y = (dx - center.dx) * sin(t) + (dy - center.dy) * cos(t) + center.dy;
  return Offset(x, y);
}