bug#2459: 22.2.1: global-font-lock-mode does not turn off colors:ido.el, minibuffer prompt

[Drew Adams]

> > These features, and several other places that use colour, are not
> > implemented using font-lock, so toggling global-font-lock-mode
> > has no effect. In this specific case, you can set ido-use-faces 
> > and customize the minibuffer-prompt face.
> 
> Several places now use the `font-lock-face' property so that toggling
> font-lock indeed also toggles the corresponding highlighting. 
> Maybe we should use that a bit more.
> 
> This said, font-lock has traditionally been used for the highlighting
> of buffer's contents, as opposed to modelines, menu-bars, and 
> minibuffers.
> 
> What Jari seems to be suggesting is to let the minibuffer highlighting
> obey font-lock as well.  Maybe it's a good idea.  I do not know.

My 2c: It's not a good idea. That would dilute the meaning of the concept
font-lock and its behavior. It would mean that you could not turn on/off
font-lock highlighting independently of the highlighting of such features.

The use case seems to be only to turn off *all* highlighting. We should find a
good way to handle that particular use case. Equating all highlighting to
font-lock highlighting, just to respond to this use case, would be using a
sledge hammer to kill a fly - a step backward.

This is not the first time someone has complained about not being able to turn
off the highlighting added by such things as the minibuffer prompt. This is a
reaction to our adding that highlighting, and enabling it by default. It has
nothing per se to do with font-lock and syntax highlighting.

TRT is to look for an easy way for a user to turn off *all* highlighting (but
without affecting other face properties, presumably) - without messing with
font-lock behavior.