bug#52795: 29.0.50; pgtk: issues with key bindings

[Kévin Le Gouguec]

Hello folks,

tl;dr: right now, --with-pgtk, I must choose between:

- by default, Emacs not recognizing S-SPC: C-h k seems to think I only
  hit SPC; or

- calling (pgtk-use-im-context nil), which gets me S-SPC back, but makes
  dead keys ineffectual: I can no longer input combining diacritics and
  type in "â", "ë", "ñ" and such.

I observe this on all my setups:

- GNOME on Ubuntu 20.04,
- XFCE on Debian 11,
- Plasma on openSUSE Tumbleweed.

On all of these, Emacs's "classical" X11+GTK configuration works fine;
other applications work fine too; the problems I describe only show up
in Emacs compiled --with-pgtk.

Is there a knob to tweak that I've missed?  I've seen other reports of
input problems with the pgtk configuration, but I don't think I found
any insight into my specific issue.

Let me know if there are additional details I should provide about my
setups.  Since all other applications behave fine (including Emacs
configured with X11+GTK), I'm assuming this is a problem with this new
feature, rather than an issue with my DE/window manager/ibus settings?

Thank you for your time.


In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo 
version 1.16.0)
 of 2021-12-22 built on hirondell
Repository revision: 5b0121b708986c836fa970b800387363806a035a
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)

Configured using:
 'configure --with-xwidgets --with-cairo --with-gconf --with-xinput2'

Configured features:
ACL CAIRO DBUS FREETYPE GCONF GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS X11 XDBE XIM XINPUT2 XPM XWIDGETS GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix