RE: Rectangular regions

[Drew Adams]

> A possible alternative would be to use a binding that's only active
> when the region is highlighted.
>
> Not sure which key would be appropriate, but restricting this use to
> the "active region case" opens up the possibility of choosing a key
> that's in common use, tho not when the region is active.
> 
> A mnemonic key would be C-r, except that C-r already has a useful
> meaning when the region is active.

It's a good idea.

It would be ideal if it could somehow be limited even more: not
whenever the region is active, but whenever it is active and being
used as a rectangle.  Alas, that is presumably impossible (since it
is this command that is deciding to treat the region as a rectangle).

That's OK.  But it means that whatever key is chosen should not be a
key that one might want to use to act otherwise on the active region.

In particular, it (again) should not be a simple repeatable key, as
those are likely to be useful for acting incrementally on the region.
And this applies even to future operations on the region when it is
interpreted as a rectangle - some of those might need to be easily
repeatable too.

So `C-SPC' is (again) not a good choice for the key, even when the
context is limited to the active region.  Likewise, `C-r' (even
aside from not being available because taken for Isearch).

+1 for the general idea.  But let's not waste an easily repeatable
key for this.

Future commands that operate on the region-as-rectangle would
presumably know that the region is being interpreted as a rectangle.
The keys for those commands, at least, could presumably be bound
for just that context, i.e., not bound whenever the region is
active, but only when the active region is being used as a rectangle.