hello! I am trying to write a patch that can draw discontinuous lines: when the mouse button is not pressed the position of the first x and y coordinates is modified in order to drew new lines. However, when i try to move the position there is always an annoying line appearing before i can start drawing the new set of lines, any ideas?, what am i missing?

second question: how can i know dynamically the size of my window so i can rescale the position of the lines when i go full screen?

here the patch:

thank you!! -emmanuel