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

[martin rudalics]

>> (4) I don't know whether and how the frame's `font' parameter can/should
>>       affect the height of the "default face".  Likely this is not a
>>       problem - Eli will tell.
>
> Sorry, I don't understand the question.  In particular, a frame
> doesn't have a font; a face does.

I meant that from section 28.3.3.8 "Font and Color Parameters" of the
Elisp manual:

`font'
     The name of the font for displaying text in the frame.  This is a
     string, either a valid font name for your system or the name of an
     Emacs fontset (*note Fontsets::).  It is equivalent to the `font'
     attribute of the `default' face.

> Perhaps you are talking about the
> font of the frame's 'default' face -- this is what the frame's 'font'
> parameter determines, AFAIR.

Maybe.  The nomenclature is incomprehensible for me.  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?

> You mean, like what default-font-height returns?

Does this take text scaling into account?  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?  And how does
`default-font-height' differ from `default-line-height'?

In any case, somehing like `default-font-width' seems all we need.

>> Next we should try to incorporate this in `window-body-height'
>
> You mean, like what window-screen-lines returns?

This sounds like a good idea as well, but then ...

> Btw, the OP wanted the width of the window, not its height, AFAIR.

... we would need `window-screen-columns' too.

martin