Re: display-mm-width return value off on Windows

[Ralf Angeli <angeli@caeruleus.net>]

* Stefan Monnier (2006-07-14) writes:

>>>> Would that not be a case for a terminal-local variable?
>>> 
>>> It sounds attractive (the idea of adding a frame-local parameter for it
>>> doesn't seem too appealing since it implies the possibility of returning
>>> different results for different frames of the same display).
>>> 
>>> Tho I'm not sure what would happen with multi-head configs.
>
>> Doesn't multi-head imply multi-display for Emacs?
>
> It probably depends on the setup (I guess most recent multihead configs use
> Xinerama so Emacs should be completely oblivious, but in other cases it may
> be separate displays but with a single keyboard, now whether that means
> a single (Emacs) terminal or not, I don't know).

The info node pointed out by David says it does:

,----[ (info "(elisp)Multiple Displays") ]
|    A single X server can handle more than one screen.  A display name
| `HOST:SERVER.SCREEN' has three parts; the last part specifies the
| screen number for a given server.  When you use two screens belonging
| to one server, Emacs knows by the similarity in their names that they
| share a single keyboard, and it treats them as a single terminal.
`----

So one rather needs screen-dependent or display-dependent values for
screen width and height.  (Obviously.)  A pragmatic way for specifying
this would be an alist with (DISPLAY . LENGTH) elements as suggested
by Kim (assuming display is equivalent to screen).

-- 
Ralf