how should selections work

[Adrian Page]

Boudewijn Rempt wrote:
> That would be interesting. When I was working on selections I found I
> wasn't even able to come up with an idea that would work. Unless scanning
> all scanlines of an image and doing something clever when the difference between
> the previous and the current pixel passes a threshold is what would work,
> after all... The gimp does something frightfully clever with segments -- I
> never grasped that at all.

It does scan the image/selection, yes. It builds up a list of line 
segments for the boundary. The main question is whether that list can be 
updated in sync with the selection changes, rather than scanning the 
whole thing every time, which would be very slow.

I haven't looked at the gimp selection code recently. I'll have a look 
at that sometime too to see how they do it.

Adrian