It was originally set to not alter the appearance of the field, but we received complaints that it was impossible to tell that a LE was read only - and folks thought the field was "broken" or that their keyboard had stopped working - especially in LEs set read-only by programming.

So we set it to use the "default" appearance change for a read only field - the foreground color "lightens" - so, if black it becomes gray. If you are using light text on a dark background there is little to no change in appearance. If using white text (which cannot "lighten" further) the only change is a slight change in the border around the LE.

Yes - FLTK considers "highlighting" to be an "event" and read-only or inactive widgets receive no events. Alec mentioned this in testing some time ago. I'll see if there is anything that can be done about it.