bug#6316: 24.0.50; unexpected region highlighting

[Stephen Berman]

Ping, in case this has been forgotten.  The problem persists in the
current trunk.  I've also truncated the title of the bug report, since
transient-mark-mode is actually irrelevant, as an unrelated posting to
emacs-devel (http://permalink.gmane.org/gmane.emacs.devel/127927>),
excerpted below, shows.  It would be very nice to have this bug fixed.

Steve Berman

On Mon, 31 May 2010 14:29:16 +0200 Stephen Berman <Stephen.Berman@gmx.net> 
wrote:

> On Mon, 31 May 2010 09:30:34 +0200 Stephen Berman <stephen.berman@gmx.net> 
> wrote:
>
>> 1. emacs -Q
>> 2. Type `M-x transient-mark-mode' to disable transient-mark-mode.
>> 3. Select some text with the mouse.  To give a specific example for the
>> sake of replication, type `C-h v transient-mark-mode RET', then in the
>> *Help* buffer double click on the left parenthesis of "(only . OLDVAL)"
>> to select the whole sexp, which thus gets highlighted.
>> 4. Type `M-w', then put point at the start of the paragraph (in *Help*)
>> beginning "Non-nil also enables highlighting".  Note that the region is
>> not highlighted.
>> 5. Paste "(only . OLDVAL)" into *scratch*, then double click on "OLDVAL",
>> selecting and highlighting it.
>> 6. Type `C-x o' to switch back to the *Help* buffer.
>> => The region in *Help* between point and the left parenthesis of 
>> "(only . OLDVAL)" is now highlighted.
>
> I should have mentioned that selection with the mouse is not crucial;
> the same unexpected highlighting occurs if selection is done via the
> keyboard -- with the important qualification that in step 5, the
> selection must be made by typing `C-SPC' twice to activate the mark,
> then moving point to the end of "OLDVAL", so that it is highlighted.
> (Mark activation is not necessary in step 3, in which case the selected
> text would not be highlighted.)
>
> Steve Berman


On Wed, 28 Jul 2010 00:44:34 +0100 David De La Harpe Golden
<david@harpegolden.net> wrote:

[...]
> Note that I can replicate similar issues in emacs 23.2, really:
>
> emacs -Q
> C-x 3
> shift-select "is for notes" in LHS *scratch*. It is highlighted.
> C-x o to RHS *scratch*
>
> Everything from the start of "is for notes" to the end of the buffer is
> highlighted, because that's where the point was in the other window, and
> select-window is "naive" (it just warps to the point saved in the the window).
>
> A fix for select-active-regions somewhat similar to the zero-length regions
> fix proposed approach should certainly be possible - really we don't want to
> propagate the active region of a newly switched-to-window until it "really"
> changes anew post-restoration.