bug#6637: 24.0.50; kill ring being seriously polluted

[Tim Van Holder <tim.vanholder@gmail.com>]

On 15 July 2010 11:55, David De La Harpe Golden <david@harpegolden.net> wrote:
> On 15/07/10 09:50, Tim Van Holder wrote:
>>
>> With the current BZR head, the kill ring seems to be seriously
>> broken, at least in conjunction with pc-selection-mode.
>> It seems that whenever I mark a region (using shift + arrow keys), the
>> contents of that region go into the kill ring, and when I enter text to
>> replace that region, the first character (and only the first character)
>> goes into the kill ring.
>> This seriously breaks some common activities, i.e. copying a piece of
>> code, then pasting it several times, adjusting those parts that need
>> adjusting.
>> Is there an option to disable this less-than-desirable "functionality"
>> until the behaviour is returned to sanity? If not, I suppose I can
>> handle a few extra M-y presses for a while, but I'd like to see this
>> fixed as soon as possible.
>>
>
> [Well, please  bear in mind you're running unstable development code if
> you're running bzr head rather than a release AFAIU]

Yeah I know - but I've been using emacs' CVS HEAD for years and there
have rarely been cases where there was anything obviously broken (and
with no immediately obvious workaround), so I guess I've been spoilt
:-D.

> If you just want shift-arrow selection, note that that has worked in emacs
> anyway for a while, without pc-selection-mode turned on as such.
> But since your bug was for the delete-selection part, well, I guess that's
> less than satisfactory.

The bug is also for the key-based selection ending up in the kill
ring. I don't think that has ever been the case before.
Like I said, I routinely copy/yank stuff and then adjust parts as
needed (usually relying both on S-arrow selection and delete-selection
behaviour for these adjustments) and this is the first time I've
noticed it affecting the next yank. In fact, there have also been many
cases where I selected things for the express purpose of replacing
them via a yank.

> The problem is likely in delete-selection-mode (which pc-selection-mode uses
> underneath) or some of the code it calls in simple.el:
>
> I was totally expecting this to be related to certain recent changes in
> default selection handling, but breakage happened in my short test even with
> them turned off on X11 emacs on debian.  It may/must still be related to
> recent rearrangements, of course, just perhaps not in the area I thought.

I think the root problem is going to be the issue above (S-arrow
selection ending up in kill ring). That the initial region replacement
done by delete-selection ends up in the kill ring is probably a side
effect.

> I for one won't get to look properly at this until the weekend, though I'm
> not the only person about.

I just looked at the emacs-devel archives and it looks like there were
some recent changes relating to integrating emacs' kill ring with the
X clipboard; my guess is that the issue I'm seeing is related to that.
Customizing x-select-enable-clipboard made no difference though.