Re: Making Emacs Lisp easier to debug

[Eli Zaretskii]

> Date: Fri, 10 Nov 2023 20:56:54 +0000
> From: Alan Mackenzie <acm@muc.de>
> 
> (ii) Edebugging font locking code.  It would be nice to be able to debug
> font locking code which is being called from redisplay, as well as other
> hooks which are also called from redisplay.  At the moment this isn't
> possible.  To make it possible would require redisplay to become
> reentrant, so that a frame or window in the inner redisplay call 
> could be where debugging of the outer redisplay call happens.  I don't
> know how practicable it would be to enhance redisplay for this (it is
> certainly possible).  Has anybody ever looked into this before?

Yes, see jit-lock-debug-mode.  (It's described in the ELisp manual.)