Flutter CustomPainter 平移和缩放

Question

I have created a family tree widget via CustomPainter. How do I implement pan and zoom because parts of it overflowed.

I have tried GestureDetector and Translating the points via onPanUpdate but it is resetting to the current offset.

onPanUpdate: (d) {
          RenderBox box = context.findRenderObject();
          Offset point = box.globalToLocal(d.globalPosition);
          point = point.translate(0.0, AppBar().preferredSize.height);


           setState(() {
             _offset = point;
           });

          // print(point);
        },

// this is from CustomPainter

canvas.translate(offset.dx, offset.dy);

Answer 1

https://gist.github.com/klaszlo8207/0df97fb3ba7484e20b0061076f3be842

Here is my gist for this, this is a custom GestureDetector that can Scale and Pan