bug#6310: hi-lock-set-pattern, font-lock-mode, overlays and occur

[Lennart Borgman]

I will never understand font-lock-add-keywords, but here are some
thoughts about it and hi-lock-set-pattern.

hi-lock-set-pattern can operate with and without font lock. In the
latter case it uses overlays.

However it locks to me like it mixes those two ways a bit:

- It calls font-lock-add-keywords even when it is going to use overlays.

- Secondly it checks font-lock-fontified instead of font-lock-mode to
see whether to use overlays or not.

And it does not seem to know about jit-lock:

- It calls font-lock-fontify-buffer instead of jit-lock-refontify.


This mean that it can't work in ocurr buffers.

Beside that font-lock-mode is t in occur buffers. Is font lock used there, or?