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Give the kiosk a window manager, and a debug mode to go with it

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The role ran no window manager on the theory that Firefox is the only X client and
--kiosk makes it full-screen by itself. It doesn't: --kiosk *asks* to be full-screen
over EWMH, and with no WM running nobody answers. Firefox kept its default window
size in the top-left corner - on musicdolphin's 1920x1080 monitor, a 1280x972 window
with black bands down the right edge and along the bottom, which looks exactly like
an overscan problem and isn't one. Openbox answers the request and does nothing else.

pi_kiosk_mode=debug then turns the attached screen into something workable: Firefox
as an ordinary window that is not relaunched when you close it, a visible pointer,
Openbox as the session leader with a root menu offering a terminal, and xterm,
x11-utils and mesa-utils installed. musicdolphin is set to debug for now.

The templates notify the getty handler, so a mode switch restarts the session on its
own - Xorg lives in that unit's cgroup.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Martin Bauer
2026-09-20 13:03:14 +02:00
parent b3f1ff69b1
commit a2ed74093a
7 changed files with 156 additions and 12 deletions
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roles/pi_kiosk/README.md
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# pi_kiosk
Turns a Pi with a monitor attached into a full-screen Firefox kiosk display, with no
window manager: an autologin console user runs `startx`, whose `.xinitrc` launches
Firefox in `--kiosk` mode pointed at `pi_kiosk_url` and relaunches it if it ever exits.
If X itself crashes, `.bash_profile` restarts it.
Turns a Pi with a monitor attached into a full-screen Firefox display: an autologin
console user runs `startx`, whose `.xinitrc` starts Openbox and then Firefox pointed at
`pi_kiosk_url`, relaunching it if it ever exits. If X itself crashes, `.bash_profile`
restarts it.
Vars:
- `pi_kiosk_user` (default `kiosk`) - the account that autologs into tty1.
- `pi_kiosk_url` (default `http://localhost:8080`) - what Firefox shows.
- `pi_kiosk_mode` (default `kiosk`) - `kiosk` or `debug`, see below.
Meant to run alongside `pi_musicmouse` on the same host when it's serving the page
locally (the default `pi_kiosk_url`), gated in `mediapis.yml` by `mediapi_has_monitor`.
niri was considered instead of plain X/no-WM, but isn't packaged for Debian Bookworm
yet (no official apt package, only third-party `.deb`s or a from-source Rust build) -
revisit once it is.
## Why there is a window manager
This role used to run no WM at all, on the theory that Firefox is the only X client and
`--kiosk` makes it full-screen by itself. It doesn't. `--kiosk` *asks* to be
full-screen, over EWMH, and with no window manager running there is nobody to answer:
Firefox falls back to its default window size in the top-left corner. On the 1920x1080
monitor on musicdolphin that came out as a 1280x972 window with black bands down the
right edge and along the bottom - looking for all the world like an overscan problem,
which it is not. Openbox answers the request and otherwise stays out of the way.
## Debug mode
`pi_kiosk_mode: debug` turns the device's own screen into something you can work on:
- Firefox runs as an ordinary window with its chrome, so the URL bar and devtools are
reachable, and it is **not** relaunched when you close it.
- The pointer is visible (no `-nocursor`, no `unclutter`).
- Openbox is the session leader. Right-click the desktop for a menu with a terminal,
both ways of opening the page again, and "End this X session", which drops back to
the autologin loop and starts a fresh one.
- `xterm`, `x11-utils` and `mesa-utils` get installed, so `xwininfo`, `xprop`,
`glxinfo` and `glxgears` are on the device. (The menu's Terminal entry runs
`x-terminal-emulator`, which on the Pi OS image is `zutty`, not the xterm we
install - both work; xterm is the fallback if the alternatives link ever points
somewhere that doesn't.)
Switch a host over in `host_vars`, or for one run:
```sh
just run mediapis.yml musicdolphin -e pi_kiosk_mode=debug
just run mediapis.yml musicdolphin -e pi_kiosk_mode=kiosk
```
Either way the session restarts itself: the templates notify the getty handler, and
restarting `getty@tty1` takes X down with it because Xorg lives in that unit's cgroup.
Going back to `kiosk` does not uninstall the debug packages; they are small and inert.
niri was considered instead of Openbox, but isn't packaged for Debian Bookworm yet (no
official apt package, only third-party `.deb`s or a from-source Rust build) - revisit
once it is.