Bug#894098: gdm3: HDMI still buggy, DisplayPort not tested

[Bud Heal]

Package: gdm3
Version: 43.0-3
Followup-For: Bug #894098
X-Debbugs-Cc: budheal508 at gmail.com

Dear Maintainer,

   * What led up to the situation?
Fresh install of bookworm weekly build (2023-03-20)
   * What exactly did you do (or not do) that was effective (or
     ineffective)?
HDMI showed extended desktop in both the login screen and now after logged in. I will submit a separate bug report for the "Displays" accessory but its failures could show that gdm3 can lose the frame buffer addresses. If one changes the external display location, either or both displays may go dark, or the laptop's display can show enlarged pixels at a translated place with wrong colors (aha, I remember those fights with the frame buffers, long ago now) and the external monitor may be dark with only the cursor (mouse pointer) showing but not the windows being dragged around). We can't have gdm3 thinking it can scribble at the wrong location.
I did not check DisplayPort and will rummage around for a cable.
   * What was the outcome of this action?
When an HDMI-enabled display was plugged, it was shown as directly to the right of the internal laptop's display. Trying to move the display's location had unexpected results. The displays may go dark or the internal display may show artifccts and dragging fails in those cases.
   * What outcome did you expect instead?
Allow multiple displays extend the desktop display.

-- System Information:
Debian Release: bookworm/sid
Architecture: amd64 (x86_64)

Kernel: Linux 6.1.0-6-amd64 (SMP w/20 CPU threads; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages gdm3 depends on:
ii  accountsservice                              22.08.8-6
ii  adduser                                      3.131
ii  dbus [default-dbus-system-bus]               1.14.6-1
ii  dbus-bin                                     1.14.6-1
ii  dbus-daemon                                  1.14.6-1
ii  dconf-cli                                    0.40.0-4
ii  dconf-gsettings-backend                      0.40.0-4
ii  debconf [debconf-2.0]                        1.5.82
ii  gir1.2-gdm-1.0                               43.0-3
ii  gnome-session [x-session-manager]            43.0-1
ii  gnome-session-bin                            43.0-1
ii  gnome-session-common                         43.0-1
ii  gnome-session-flashback [x-session-manager]  3.46.0-1
ii  gnome-settings-daemon                        43.0-4
ii  gnome-shell                                  43.3-3
ii  gnome-terminal [x-terminal-emulator]         3.46.8-1
ii  gsettings-desktop-schemas                    43.0-1
ii  libaccountsservice0                          22.08.8-6
ii  libaudit1                                    1:3.0.9-1
ii  libc6                                        2.36-8
ii  libcanberra-gtk3-0                           0.30-10
ii  libcanberra0                                 0.30-10
ii  libgdk-pixbuf-2.0-0                          2.42.10+dfsg-1+b1
ii  libgdm1                                      43.0-3
ii  libglib2.0-0                                 2.74.6-1
ii  libglib2.0-bin                               2.74.6-1
ii  libgtk-3-0                                   3.24.37-2
ii  libgudev-1.0-0                               237-2
ii  libkeyutils1                                 1.6.3-2
ii  libpam-modules                               1.5.2-6
ii  libpam-runtime                               1.5.2-6
ii  libpam-systemd [logind]                      252.6-1
ii  libpam0g                                     1.5.2-6
ii  librsvg2-common                              2.54.5+dfsg-1
ii  libselinux1                                  3.4-1+b5
ii  libsystemd0                                  252.6-1
ii  libx11-6                                     2:1.8.4-2
ii  libxau6                                      1:1.0.9-1
ii  libxcb1                                      1.15-1
ii  libxdmcp6                                    1:1.1.2-3
ii  marco [x-window-manager]                     1.26.1-1
ii  mate-session-manager [x-session-manager]     1.26.0-1
ii  mate-terminal [x-terminal-emulator]          1.26.0-1
ii  metacity [x-window-manager]                  1:3.46.1-1
ii  polkitd                                      122-3
ii  procps                                       2:4.0.2-3
ii  systemd-sysv                                 252.6-1
ii  ucf                                          3.0043+nmu1
ii  x11-common                                   1:7.7+23
ii  x11-xserver-utils                            7.7+9+b1

Versions of packages gdm3 recommends:
ii  at-spi2-core                                 2.46.0-5
ii  desktop-base                                 12.0.5
ii  gnome-session [x-session-manager]            43.0-1
ii  gnome-session-flashback [x-session-manager]  3.46.0-1
ii  mate-session-manager [x-session-manager]     1.26.0-1
ii  x11-xkb-utils                                7.7+7
ii  xserver-xephyr                               2:21.1.7-1
ii  xserver-xorg                                 1:7.7+23
ii  zenity                                       3.44.0-1

Versions of packages gdm3 suggests:
pn  libpam-fprintd        <none>
ii  libpam-gnome-keyring  42.1-1+b1
pn  libpam-pkcs11         <none>
pn  libpam-sss            <none>
ii  orca                  43.1-1

-- debconf information:
* shared/default-x-display-manager: gdm3
  gdm3/daemon_name: /usr/sbin/gdm3