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

[Eli Zaretskii]

> Date: Thu, 27 Nov 2014 20:58:45 +0100
> From: martin rudalics <rudalics@gmx.at>
> CC: holtzermann17@gmail.com, 19194@debbugs.gnu.org
> 
> Could you try to explain how the height of a character assigned the
> default face (the one whose attributes are all specified) can change
> in dependence of the frame where the character is displayed?

Faces are frame-specific.  The same face can have different attributes
on each frame, and that includes the size.

>  > You mean, like what default-font-height returns?
> 
> Does this take text scaling into account?

Yes.  You can try it yourself: call it before and after "C-x C-+", and
see for yourself.

> Is this the final value as it would be displayed or could the height
> of "the font of the frame's 'default' face" get mixed in afterwards?

The former, I think.

> And how does `default-font-height' differ from
> `default-line-height'?

default-line-height includes the line-spacing.

>  > Btw, the OP wanted the width of the window, not its height, AFAIR.
> 
> ... we would need `window-screen-columns' too.

That will be harder, unless we change some APIs.  We currently don't
have the font width in what font-info returns.