[mutter.wiki] Create Debug tips and utilities

[Jonas Ådahl <jadahl src gnome org>]

commit 8bfc85823bcf136587da4ca2628ba6b7a49a624f
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Jun 9 15:18:25 2021 +0000

    Create Debug tips and utilities

 Debug-tips-and-utilities.md | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
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+## Nested D-Bus session
+
+### Installing
+
+Download and place [dbus-session.sh](uploads/a209c8f1fe6b51df669b58bab1300199/dbus-session.sh) in 
`~/.local/bin/` and make it executable.
+
+### Using
+
+To create a nested D-Bus user session, run
+
+```sh
+dbus-session.sh -n
+```
+
+This will create a D-Bus session, and attach to it.
+
+To attach to the same session from another terminal, run
+
+```sh
+dbus-run-session.sh -x
+```
+
+## Nested mutter or gnome-shell
+
+To run a nested mutter or gnome-shell instance, i.e. when you are presented with a floating window running 
mutter or gnome-shell, first enter a [nested D-Bus session](#nested-d-bus-session), then pass `--nested` to 
either gnome-shell or mutter. E.g.
+
+```sh
+mutter --nested
+```
+
+## Headless GNOME Shell and GNOME Remote Desktop
+
+First create [nested D-Bus session](#nested-d-bus-session). In this, run gnome-shell in headless mode with a 
virtual monitor. E.g.
+
+```sh
+[jonas@localhost gnome-shell]$ dbus-session.sh -n
+[ D-Bus 60ff ][jonas@localhost gnome-shell]$ gnome-shell --headless --virtual-monitor 1280x720
+```
+
+```sh
+[jonas@localhost gnome-remote-desktop]$ dbus-session.sh -x
+[ D-Bus 60ff ][jonas@localhost gnome-remote-desktop]$ ./build/src/gnome-remote-desktop-daemon
+```
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