graph drawing tool

start implementing the mouse handler

Until now the hover actions were happening in surface coordinates sx/sy but the mouse press action (done so far) was happening in viewport coordinates vx/vy. Now it's consistent. Surface coordinates make more sense since most data in memory uses them.

Created by  Kartik K. Agaram  on April 18, 2023
FHLFZZ3SG5VGJX25JID6A6C5XLT6Q76RAJDQSYQSZTXQMSIUTCCAC
Change contents