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

[martin rudalics]

>> 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.

On a per-buffer basis.  The height of the default face is unaffected
here.  I suppose the display engine applies the scaling lazily, whenever
it has to retrieve the height of the default face.

martin