bug#38013: [PATCH] Rectangular region selection with mouse

[Eli Zaretskii <eliz@gnu.org>]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Thu, 31 Oct 2019 22:55:26 +0100
> 
> This is a proposal to add mouse-selection of rectangular regions. It turns out to be useful; Emacs should come with the facility built-in.

Could you please tell how to try and test this feature?  The patch
comes without any documentation, so it's hard to understand quickly
what to do to see this in action.

> The main problem is what to bind it to. The common modifiers (shift, control, meta) are already taken. Platforms have different "standard" modifiers: Option on macOS, Alt on Windows, Control in Gnome (?).
> 
> Assuming that the secondary selection is somewhat of an anachronism which is likely to be less used today than the rectangular one would be, the patch uses Meta as default modifier. Both secondary and rectangular mouse selection have defcustoms permitting easy change.

I'd prefer not to step on another feature, if possible.  How about
defining a minor mode, and then using the usual mouse selection
gestures instead?  That would be more natural, IMO, and will not
require users to give up another feature.

Thanks.