Re: region-active-p

[Andreas Röhler]

Am Freitag, 26. Oktober 2007 11:21 schrieb Stephen J. Turnbull:
> Andreas Röhler writes:
>  > If there is no extension, just the mark set,
>  > `zmacs-region-extent' is nil and `region-active-p'
>  > returns nil therefor.
>
> Right.  However, if zmacs-region-extent is non-nil, it is possible
> that (region-beginning) equals (region-end), 

If this is possible--my little check rather
contradicts--than I consider it as not congruent with
its name "extent" or a bug.

At stake are AFAIU tree different and hierarchical
conditions:

1 region exists but has no extent
2 region has extent but is not visible
3 region is visible

For appropriate names I held something like

1 region-exist-p
2 region-extent-p
3 region-visible-p

In GNU Emacs these conditions are expressed by

1 mark-active
2 (and mark-active (not (eq (region-beginning) (region-end))))
3 (and transient-mark-mode mark-active
     (not (eq (region-beginning) (region-end))))

XEmacs has AFAIS

1 region-exist-p

3 region-active-p

Andreas Röhler

> in which case there is 
> (usually) no point in operating on the region.  It is that check that
> Richard is asking about AFAICS.
>
>