bug#17768: 24.3; problem with two ruler-mode windows

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 15 Jun 2014 17:09:26 +0200
> From: martin rudalics <rudalics@gmx.at>
> CC: andrea.rossetti@gmail.com, 17768@debbugs.gnu.org
> 
>  > How else can column and row be measured, except from the window edge?
> 
>  From the left upper edge of the frame, just as the x-y-coordinates.

A column is fundamentally window-related.  It's not a coordinate, it's
a place in the text, and frames don't display text.

> At least that's apparently what the author of ruler mode thought.

I'd prefer not to second-guess someone's misconceptions.

>  > I don't understand the confusion, but I went out and made it more
>  > clear anyway (r117242 on the emacs-24 branch).
> 
> Thank you.  But IIUC the reference to "window edge" is still missing
> from the manual entry.

The manual text explicitly talks about a column and row of text in a
window, so I think it's clear enough.

>  > In general, one should stay away of columns when dealing with
>  > coordinates, since columns are measured in logical order, i.e. in a
>  > R2L line they are measured from the right edge of the window.  But
>  > since in this case columns are just x coordinates measured in other
>  > units (and therefore calling them "columns" is a misnomer), I think
>  > it's OK in this case.
> 
> This means that we shouldn't provide `posn-col-row' in the first place
> which I'd consider the best solution.

I see no reason to delete well established APIs, just because Emacs
overgrew the time when they were named.