Subject: Re: bug#20628: 25.0.50; Incorrect line height for some fonts

From: Eli Zaretskii <[email-masked]>
Date: Fri, 29 May 2015 21:18:20 +0300

> From: Oleh Krehel <[email-masked]>
> Cc: [email-masked],  [email-masked],  [email-masked]
> Date: Fri, 29 May 2015 15:16:44 +0200
> 
> Actually now, I notice that they are fine in this buffer. This
> issue happens if I use them for `prettify-symbols-mode' stuff, like:
> 
> (font-lock-add-keywords
>  'emacs-lisp-mode
>  '(("\\\\\\\\|"
>     (0 font-lock-keyword-face t)
>     (0
>      (prog1
>          (compose-region
>           (match-beginning 0)
>           (match-end 0)
>           "∨")
>        nil)))))

That explains the difference in what we see: compose-region causes the
display engine to take a different path through the code.