Hi Henry,
Can you qualify "will work on Macs"?
Is the editor going to be an internal component (similar to existing components such as HTMLArea) that will work on macs using Firefox (Midas) but not in IE or Safari?
I'm also curious, since there are already editors available out there that are very advanced such as TinyMCE, why are you not using something like that and focusing on the PHP/programming side of things?
These questions are not derogatory at all... I'm honestly curious. Perhaps you don't feel the editors available are advanced enough or don't work quite right for your purposes, and I can understand that.
On another note, have you ever considered trying to program a Java HTML editing component? I've always wished that there was a java solution out there for editing- personally I HATE java applets, but in the right circumstances such as an HTML editor, they would be nice, especially since it would solve the problem of using the editor in any browser that supports java.
I've looked at a few java editors but so far none seem to be that great.
Thanks,
-Kevin