flutter) How do I check if the touched point (offset) is on the line on the canvas?

I'm working on drawing shapes and editing them using CustomPainr() and GestureDetector(). I've successfully drawn the shapes and now I'm going to select and drag the drawn shapes to move them.

I didn't understand much about implementing it yet, but dragging and moving the rectangle succeeded in the following way.

 List<Rectangle>? _rects;
 List<Line>? _lines;

 GestureDetector(
      onScaleStart: (details) {
      RenderBox box = context.findRenderObject() as RenderBox;
      Offset point = box.globalToLocal(details.focalPoint);

       // check point on shape
      final selectedRectIndex =
          _rects!.lastIndexWhere((rect) => rect.rect!.contains(point));     
      }

// canvas
canvas.drawOval(shape.rect!, shape.paint);
canvas.drawLine(shape.p1!, shape.p2!, shape.paint);

The contents() could be used to determine if the offset was in a Rect() of rectangle. And the move was successful by updating points in onScaleUpdate().

Then, how do I check if the point I touched is in the Line shape? Is there a method for this, like "rect!.contains(point)"?

• And then I'm going to add this function, when the shape is selected like in the image below, there's a point at the vertex, and drag it to change the rotation or scale.

Can I get some advice to do this?