bug#23478: 25.0.93; Mouse region selection asymmetry

[Stephen Berman <stephen.berman@gmx.net>]

On Sun, 03 Jul 2016 18:38:39 +0300 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <stephen.berman@gmx.net>
>> Cc: Eli Zaretskii <eliz@gnu.org>,  23478@debbugs.gnu.org
>> Date: Sun, 03 Jul 2016 16:33:55 +0200
>> 
>> > Eli Zaretskii <eliz@gnu.org> writes:
>> >
>> >>> From: Stephen Berman <stephen.berman@gmx.net>
>> >>> Do you really think this should be conditioned by a user option?
>> >>
>> >> I do, but let's hear from others.  Anyone?
>> >
>> > This behaviour seems much preferable to me, since otherwise it's not
>> > clear which text gets selected.  I'm not in favour of adding an option,
>> > but if there must be one, at least let this new behaviour be the
>> > default.
>> 
>> I agree on both points (prefer no option, but if so default to new).
>> 
>> > Regarding the code, I notice that using (sit-for 0) works as well.
>> 
>> Thanks.  Indeed, even a negative number works.  But zero does seem the
>> least arbitrary.
>> 
>> > A comment to explain what the calls are for would be nice.
>> 
>> I'll do that when the final version is settled on.  Eli, John, what's
>> the decision on making this behavior customizable (and if yes, what
>> default)?
>
> I think backward-incompatible behavior should almost always be opt-in,
> unless we have no choice.

Opting in does, however, have the problem of discoverability (a NEWS
entry notwithstanding).  I think opting in is best in cases where it's
likely that some people may prefer (or some code may depend on) the
existing behavior, or where the new behavior may bring a disadvantage in
some case.  But I don't think any of that is likely in this case
(indeed, I really think the existing behavior is a misfeature).  Your
concern about the interaction with scroll-conservatively applied to my
initial patch, but you yourself suggested a better alternative that
allays this concern.  Given that, I ask again, and not rhetorically, do
you see a strong downside to having the new behavior be the default?

Steve Berman