bug#66398: 29.1; Buggy handling of transparency changes / blur/unblur

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Tollef Fog Heen <tfheen@err.no>
>> Date: Sat, 07 Oct 2023 22:07:15 +0200
>> 
>> 
>> Hi folks, this is Debian bug #1053298,
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1053298 :
>> 
>> In my setup, I make non-focused windows semi-transparent (using Xmonad
>> and its compose support).  This used to work perfectly, but with the
>> recent-ish update of emacs from 28.2 to 29.1, this broke.  (Basically,
>> what's described on
>> https://hackage.haskell.org/package/xmonad-contrib-0.16/docs/XMonad-Hooks-FadeInactive.html)
>> 
>> I've bisected this down to:
>> 
>> commit b299f173490f5c51476ad3c8436b19bb091c1b00
>> Author: Po Lu <luangruo@yahoo.com>
>> Date:   Tue May 10 09:32:59 2022 +0800
>> 
>>     Update alpha frame parameter when the window manager changes it
>> 
>>     * src/xfns.c (x_set_alpha): New function.  Set
>>     `alpha_identical_p' flag.
>>     (x_frame_parm_handlers): Use it to handle `alpha' instead.
>> 
>>     * src/xterm.c (x_set_frame_alpha): Make tests against current
>>     alpha safer.
>>     (handle_one_xevent): Set frame alpha when alpha property
>>     changes.
>>     * src/xterm.h (struct x_output): New flag `alpha_identical_p'.
>> 
>>  src/xfns.c  | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>>  src/xterm.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++--
>>  src/xterm.h |  4 ++++
>>  3 files changed, 108 insertions(+), 3 deletions(-)
>> 
>> which seems like a plausible change for causing such a bug.
>> 
>> Note that the transparency of the window corrects itself if I switch
>> buffers, and in some cases if there's just a message in the minibuffer,
>> so it seems like emacs isn't always picking up the change in
>> transparency which happens as it is being focused, but on a buffer focus
>> change, it catches up.
>> 
>> Interestingly enough, this only reproduces for me with the nvidia X11
>> driver, on my laptop (with Intel graphics) with the same emacs setup,
>> I've never seen it.
>> 
>> In GNU Emacs 29.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38,
>>  cairo version 1.16.0) of 2023-08-30, modified by Debian built on
>>  x86-csail-01
>> Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
>> System Description: Debian GNU/Linux trixie/sid
>
> Po Lu, any comments?  If possible, I'd like to fix this in Emacs 29.2.

Tollef, would you please create a frame, ascertain the window ID of its
shell window:

      (frame-parameter nil 'outer-window-id)

then run xprop as so illustrated:

      $ xprop -id <outer window ID> -spy

before deactivating and reactivating that frame, posting the output from
xprop here?

TIA.