[Apologies to the postmaster if this was originally sent via rburnside@fumico.net, please delete that thread. This account is the registered one] Hello All, I'm currently caught in a catch22. I wish to make a CAD like program for diagram drawing. This means I need to draw lines and boxes and such - stuff Ltk's canvas is quite capable of. Here is the kicker, I want to let the user define their own complex drawing functions which would get sucked up into my Ltk program when it starts. The problem is, the minute a user's function gets executed, Ltk would stop updating. So, if they had a dynamic user defined function that needed points (as clicked by the canvas) Ltk would freeze and their user defined function could not get the points from the interface. Suppose a user loaded a command like so: (defun draw-foo (&key (pt1 nil) (pt2 nil)) (unless (or pt1 pt2) (setf pt1 (prompt-canvas "Define point 1 of FOO.")) (setf pt2 (prompt-canvas "Define point 2 of FOO."))) (user-defined-drawing-nonsense pt1 pt2)) We can't hit PROMPT-CANVAS because at that point the program flow is entered the DRAW-FOO body. Ltk is great for forms but keeping both Lisp waiting for a value and Ltk catching events seems very tricky. Sincerely, Ryan Burnside (Pixel_Outlaw)