Manuel pointed out, The gimp currently lacks any way for a plugin to get a
coordinate from the image (eg. click on the 'seed' pixel). I've often wanted
to do this, and it is a bit awkward without it. Has implementing this been
avoided, or is it just an oversight?
Some example usages:
* Color mixer: click on any number of pixels then press ENTER to set
FGcolor to a mix of all those colors.
* Zone selector: click on a zone to select it
* Word balloon creation (see a recent post on gimp-user) -- click a series
of 5 points to draw a word balloon (size, point shape and location)
Gimp-developer mailing list