bug#19972: 24.4; Font size change doesn't update (window-total-width)

[martin rudalics]

> For the purposes of this discussion, I think the only thing that
> matters is that it applies the change in the default face's font.

If `set-frame-font' were involved, then it has a `keep-size' argument
which, when set, should keep the frame's pixel size constant.  But I
nowhere see `set-frame-font' getting called with that argument non-nil.

>> Anyway.  Why do you think that `window-total-width' should return 192 in
>> the first call?  In principle, face/font changes are supposed to keep
>> the number of columns/lines unchanged so returning 240 seems reasonable
>> to me.
>
> Indeed.  It does for me.  Could this be something specific to GTK or
> the window manager?

I tried with Gtk and the numbers of lines/columns remain unaltered.  On
Windows I lose one line because the tool bar gets larger by one pixel.

> Also, I don't understand why the initial value is 240 in the first
> place.  By default, "emacs -Q" creates a 80-column window, so I'd
> expect window-total-width to return a value slightly larger than 80 (I
> get 84 here).
>
> So it sounds like some additional factors are at work here.

Indeed.  This issue needs clarification too.

martin