gemmouse could recoad our mouse event in gemwin, but how can we draw a line in gemwin when we click left or right mouse ?

This is complicated. You can't store 2d information in any of Pd's datatypes. This can be done with recursion and an array each for x and y values.

Hi nestor , met you again
thanks your advise,
I'll try it step by step

If you did really want to store 2-d data you should be able to do it in data structures. Don't know if it would be easier in the long run but it should be possible.

-Jon