Subject: bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes

From: Eli Zaretskii <[email-masked]>
Date: Thu, 27 Nov 2014 18:17:37 +0200

> Date: Thu, 27 Nov 2014 10:44:56 +0100
> From: martin rudalics <[email-masked]>
> 
> (defun text-scale-adjust (inc)
>    "Adjust the height of the default face by INC.
> 
> AFAICT this does not change the height of the default face - it affects
> how the display engine calculates the height of text when displaying a
> buffer current at the time `text-scale-adjust' was called.

No, it works via face remapping, see text-scale-mode.  IOW, it does
change the height of the default face by replacing it with another
face.