Re: canvas item collisions

[Colin Fox <cfox telus net>]

"J.W. Bizzaro" wrote:
> 
> Federico Mena Quintero wrote:
> >
> > Oh, so you are doing some sort of DnD across items?
> 
> Yes.  My project (Loci) is akin to Gnogurt, where icons are connected via
> lines.  Each icon has a number of lines, and you connect icons by dragging the
> end of one line on top of the end of another.
> 
> > Hiding the item you are dragging and doing hit testing on the items
> > below somehow sounds horribly hackish, but as it doesn't flicker, I
> > guess it is OK :-)
> 
> Actually, I only do the check on one point (the very tip of the line) when the
> line is dropped (mouse button 1 release).  So there is no problem with
> flickering.  However, I do have large dots (ellipse items) at the end of
> lines, and it would be nice if I could tell what was under every pixel of the
> dot, without doing get_item_at's for the whole area of a circle.  But checking
> _one_ point is acceptable for now.
> 
> > I think we need a better API for hit testing, maybe passing an "ignore
> > list" of items to gnome_canvas_get_item_at().
> 
> Something that could probe the entire area under the item anyway.

Just as a suggestion - why not have a look at Dia? It works extremely
well, and it sounds like your program does the same kinds of things.
Maybe you can use some of the Dia code or techniques.

-- 
Colin Fox
cfox@telus.net