bug#67457: 29.1; Error when dragging mode line in terminal

[Jared Finder via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Leaving this as one email so both changes are easy to follow.  I believe 
both patches are valuable to apply.

On 2023-12-06 15:55, Jared Finder wrote:
> On 2023-11-27 08:34, Eli Zaretskii wrote:
>>> Date: Mon, 27 Nov 2023 07:16:34 -0800
>>> From: Jared Finder <jared@finder.org>
>>> Cc: stephen.berman@gmx.net, visuweshm@gmail.com, 
>>> 67457@debbugs.gnu.org
>>> 
>>> >> 1. My original patch is likely inaccurate.  A better fix would be to
>>> >> align the mouse-movement event with how it is emitted under GPM and
>>> >> DOS.
>>> >>   I will investigate.

And I have a better patch here.  The real issue is that xt-mouse 
generated mouse-movement events were getting prefixed with mode-line or 
tab-line symbols but other mouse-movement events were not.  The 
following simple change fixes that:

--- a/lisp/xt-mouse.el
+++ b/lisp/xt-mouse.el
@@ -63,9 +63,14 @@ xterm-mouse-translate-1
            (is-move (eq 'mouse-movement ev-command))
            (is-down (string-match "down-" (symbol-name ev-command))))

-      ;; Mouse events symbols must have an 'event-kind property with
-      ;; the value 'mouse-click.
-      (when ev-command (put ev-command 'event-kind 'mouse-click))
+      ;; Mouse events symbols must have an 'event-kind property set.
+      ;; Most of them use the value 'mouse-click, but 'mouse-movement
+      ;; has a different value.  See head_table in
+      ;; keyboard.c. (bug#67457)
+      (when ev-command (put ev-command 'event-kind
+                            (if (eq ev-command 'mouse-movement)
+                                'mouse-movement
+                              'mouse-click)))

>>> >>
>>> >> 2. Something broke with how GPM mouse mode is enabled between Emacs
>>> >> 28.2
>>> >> and HEAD.  I can help with a bisect here.
>>> >
>>> > Thanks, please do, on both counts.
>>> 
>>> Bisect identified the following commit as the bad commit, confirmed
>>> locally:
>>> 
>>> jared@debian:^/emacs-devel$ git bisect bad
>>> a28ede3a61a70cf83dfcba6c9d314fbb051a3a94 is the first bad commit
>>> commit a28ede3a61a70cf83dfcba6c9d314fbb051a3a94
>>> Author: Stefan Monnier <monnier@iro.umontreal.ca>
>>> Date:
>>> t-mouse.el: Make sure we apply the setting to new terminals
>>> * lisp/t-mouse.el (gpm-mouse-tty-setup): New function.
>>> (gpm-mouse-mode): Use it as well as 'tty-setup-hook".
>>> * lisp/term/linux.el (terminal-init-linux): Remove gpm-specific code,
>>> not neded any more.
>>> lisp/t-mouse.el
>>> lisp/term/linux.el | 2 --
>> 
>> Thanks, adding Stefan to the discussion.
> 
> Following up on #2:  The issue here is that after a28ede, 
> gpm-mouse-tty-setup is never added to tty-setup-hook since it is only 
> added within gpm-mouse-mode. This is clearly visible by checking the 
> value of tty-setup-hook at startup, and after toggling gpm-mouse-mode 
> off and on again.
> 
> The following simple patch fixes that, while leaving the details of how 
> gpm-mouse-mode works an internal detail:
> 
> --- a/lisp/term/linux.el
> +++ b/lisp/term/linux.el
> @@ -13,6 +13,9 @@ terminal-init-linux
>   ;; Compositions confuse cursor movement.
>   (setq-default auto-composition-mode "linux")
> 
> + ;; Ensure additional terminal setup is done when `gpm-mouse-mode' is 
> enabled.
> + (ignore-errors (when gpm-mouse-mode (gpm-mouse-mode 1)))
> +
>   ;; Don't translate ESC TAB to backtab as directed by ncurses-6.3.
>   (define-key input-decode-map "\e\t" nil)
> 
> One could also just revert just the linux.el changes in a28ede, though 
> that assumes that gpm-mouse-enable exists.
> 
>   -- MJF