bug#19972: Font size change doesn't update (window-total-width)

[Steve Purcell]

> 
> On 2 Mar 2015, at 13:27, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Steve Purcell <steve@sanityinc.com>
>> Date: Mon, 2 Mar 2015 07:57:26 +0000
>> 
>> - Consider the case of full-screen frames, which never change in pixel size.
> 
> They do for me.  See the previous messages.


I’m on OS X, and NS Emacs uses the native full-screen support there, so Emacs 
isn’t managing the pixel size directly.

And indeed it’s only in that native full-screen mode that window-size doesn’t 
get updated for me, so perhaps that’s the only real problem here.

Given that window-width returns a number based on both the current frame/window 
size and the width of the ‘default face, then if the value is going to be 
stored for later re-use, any change to the default face should also cause it to 
be recomputed.

What I’m picking up is that only frame/window size changes currently cause that 
recomputation, hence this issue.