bug#18195: 24.3.92; window-screen-lines is not accurate

[Eli Zaretskii]

> Date: Wed, 06 Aug 2014 19:07:32 +0400
> From: Dmitry Gutov <dgutov@yandex.ru>
> CC: rudalics@gmx.at, 18195@debbugs.gnu.org
> 
> >> Well, there are also text decorations, and users should be able to add
> >> (most of) them without running into problems.
> >
> > Which decorations are those?
> 
> Underline, bold, italic..?

They all use fonts that are different from the default one, and thus
change the height of the screen lines, if only by a few pixels.