bug#23571: 25.1.50; Click-mouse-1 = Drag-mouse-1 in Gnus Article buffer

[Stephen Berman]

On Wed, 18 May 2016 15:27:23 +0200 Stephen Berman <stephen.berman@gmx.net> 
wrote:

> Clicking mouse-1 in a Gnus Article buffer, then releasing it and moving
> the mouse (without holding down a mouse key) highlights a region, just
> as when the mouse is dragged with mouse-1 held down.  To reproduce:
>
> 0. emacs -Q
> 1. M-x gnus, type `y' at the prompt, then type `B RET news.gmane.org RET
>    1 RET' to open the most recent article in gmane.announce on the
>    news.gmane.org server.
> 2. Click anywhere in the Article buffer (except on the texts following
>    the From: and To: headers, which are buttons) with mouse-1, release
>    mouse-1, move the mouse.
> => A region is highlighted.
>
> Subsequently clicking and releasing mouse-1 does not deactivate the
> mark (but clicking with mouse-2 or mouse-3 does).
>
> I have not observed this behavior anywhere besides Gnus Article buffers.
>
> This happens in master but not in emacs-25.  It happens at least since
> commit 62d7acae7405732268713006d839a5c3507b9482, which was my first
> build from master after a long pause, so I don't know when this behavior
> first appeared (I didn't save any earlier builds from master, which were
> from many months before, but I'm sure they didn't show this behavior).

Git bisect says:

72166f2f3dba18f1217c666574032f5a0351ed65 is the first bad commit
commit 72166f2f3dba18f1217c666574032f5a0351ed65
Author: Martin Rudalics <rudalics@gmx.at>
Date:   Tue May 3 08:38:49 2016 +0200

    Bind `widget-button-click' to mouse-1/-2 instead of down-mouse-1/-2
    
    * lisp/wid-edit.el (widget-keymap): Bind `widget-button-click'
    to mouse-1/-2 instead of down-mouse-1/-2.  Suggested by Stefan
    Monnier.  (Bug#19185, Bug#20398)

And indeed, when I execute the above recipe on a build from the commit
immediate prior to the above, namely:

commit 3a21ea15aecf7af8237c53dfafdc07650a09be3f
Author: Lee Bochicchio <lboc.home@gmail.com>
Date:   Tue May 3 00:12:53 2016 +0200

    Add more abbrev tests
    
    * test/lisp/abbrev-tests.el
    (clear-abbrev-table-test): Use `abbrev-expansion'
    (abbrev-table-empty-p-test, list-abbrevs-test)
    (prepare-abbrev-list-buffer-test, insert-abbrevs-test)
    (edit-abbrevs-test, define-abbrevs-test)
    (read-write-abbrev-file-test)
    (abbrev-edit-save-to-file-test): New tests (bug#23139).

I do not observe the problem with mouse-1 in a Gnus Article buffer.

Steve Berman