bug#19395: 25.0.50; Setting left fringe to 0 messes up window-width

[martin rudalics <rudalics@gmx.at>]

 > The thing is that the value is not fully determined by the buffer, so I
 > think the name buffer-font-width is a little
 > misleading.  `frame-buffer-font-width' is more precise but also a little
 > unwieldy.

I've been confused enough already.  It would be nice to get this right
once and for all.

 > The other problem is that `default-font-height' is already a
 > standard Emacs function and renaming it will cause problems.

We would add an alias, obviously.

 >>   > I also added the bonus feature which lets you specify a specific face
 >>   > that should be used for the calculations.
 >>
 >> So are you now sure that we don't need a specific character ("M") any
 >> more?
 >
 > If I understand correctly, the returned value is based on the width of a
 > space.  In proportional fonts that will of course differ from the width
 > of other characters.  But I think this is not a big problem because the
 > notion of characters per line doesn't make sense for proportional fonts
 > and using proportional fonts in Emacs is a terrible idea
 > anyway.  But perhaps this issue should be mentioned in the doc string.

I forgot that it was Joe Corneli who asked for this in another thread.
But once we have a function like `window-max-characters-per-line' it
would make sense to have it consider the maximum width of a proportional
font character as well and we'd fix his problem as well

BTW, do we have some character or letter spacing which we should
consider as well?  IIRC somone asked here for an orthogonal function
that would consider line spacing.

martin