Re: canvas item collisions

"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

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