On Wed, Dec 09, 2020 at 03:38:03PM -0700, Ryan Burnside wrote:
Hello cage,
Hi!
Thanks for the reply.
You're welcome! I am always happy to discuss programming with other lispers! :)
Your code did demonstrate the general idea if I was collecting from a field. But as this is a CAD program (think drafting) it's important that the user be able to pick points of interest from a main canvas. As important that the canvas cursor can "snap" to points of interest such as endpoints intersections etc. (I'll handle that myself).
I wrote a (unfortunately never released) software -many years ago- that vaguely remember me what you want to accomplish. I had a canvas and a set of buttons next to the former. Each button allowed the user to draw a shape (nothing too complicated: box, circle a bezier arrow and a few more). If an user would wants to draw a bezier they just have to press the corresponding button (to enter in "bezier mode" so to say) and press four times the mouse button on the canvas; the program collected the points calculated the bezier and drawn a set of segments and an arrow head on the last ends. I am not sure that this workflow fits into your program but all i did was forget about a main loop and just let the user events drive the process. I waited for <1> (i mean, mouse click) event (event bound to the canvas) checked the drawing mode (box, bezier etc.) and acts following the mode (collect two point [one more events] for a box -the diagonal- or for a segment and so on). Once got all the data needed to draw the program updated the canvas with actual drawing. I even draw a little placeholder for each collected point in the canvas for each of this events. There was also interactions that allowed to move control points of a shape (in this case i waited for <Button1-Motion> event). You can even tag canvas items (the shapes) and bind different custom events to each one, see: https://www.autistici.org/interzona/lisp.html#orge51c1f0 If this is -with good approximation- what you want to do i can guarantee is doable with ltk. :)
Here is a diagram if it helps... https://i.imgur.com/5uxY7Tq.png
Looking to the diagram i started to think that if you call the procedure 'draw-foo' inside the function bound to a canvas event you get more or less what i described above, but i could easily be wrong, as usual! :) Inside the event function you can even run another toplevel (modal if needed and hijack completely the input system) as i did in the code i wrote before.
Hopefully this is possible!
I also hope it was! :) Bye!!! C.