Run the kiosk on Chromium, and take the stray media server off musicdolphin

Chromium: same page, same machine, idle, Firefox 24.2% of a core against Chromium's
11.4%. The build comes from archive.raspberrypi.com (a "+rpt" version) and is patched
for this board's V3D GPU; Debian ships a much older chromium, so the archive matters.
The whole userland here is 32-bit armhf on a 64-bit kernel, which Firefox handles worse
than Chromium does. --use-gl=egl, --enable-gpu-rasterization, --ignore-gpu-blocklist
and --enable-zero-copy are what keep rasterization on the GPU: Chromium's blocklist
does not recognise this driver and silently falls back to software without them.
pi_kiosk_browser: firefox still works, as the fallback if an update ever regresses.

Debug mode also gains xdotool, scrot and --remote-debugging-port=9222 (on 127.0.0.1),
because firing XTEST key events at a window lands about half the time and a benchmark
you cannot verify the state of is worse than none.

pi_squeezeserver gains an absent path, and mediapis.yml derives its state from
mediapi_has_squeezeserver, which defaults to false for the whole group. false means
"actively remove", not "skip": musicdolphin has been running a Logitech Media Server
that no playbook installs and nothing talks to - every squeezelite in the fleet points
at pi_squeezelite_squeezeserver (192.168.178.80, the server) - while costing ~30 MB
resident and ~47 MB of swap on a 2 GB Pi that also drives the kiosk. The absent path
stops it, purges the package, unregisters it from sysdweb, drops the port 80 -> 9000
redirect and deletes its database and logs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

roles/pi_kiosk/README.md

@@ -1,19 +1,41 @@
 # pi_kiosk
 
-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`
+Turns a Pi with a monitor attached into a full-screen browser display: an autologin
+console user runs `startx`, whose `.xinitrc` starts Openbox and then the browser 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_url` (default `http://localhost:8080`) - what the browser shows.
+- `pi_kiosk_browser` (default `chromium`) - `chromium` or `firefox`, see below.
 - `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`.
 
+## Why Chromium
+
+Firefox was the original choice and lost on measurement. Same page, same machine, idle:
+**Firefox 24.2% of a core, Chromium 11.4%**. Two reasons, and they compound:
+
+- Chromium here comes from `archive.raspberrypi.com` (versions carry a `+rpt` suffix)
+  and is patched by Raspberry Pi for this board's V3D GPU. Debian also ships a much
+  older `chromium`; pinning the wrong archive would quietly undo the point of choosing
+  it.
+- The whole userland on these images is 32-bit `armhf` on a 64-bit kernel
+  (`dpkg --print-architecture` says `armhf`, `uname -m` says `aarch64`), and Firefox
+  fares worse than Chromium on that target.
+
+The flags in `.xinitrc` are not decoration: `--use-gl=egl`,
+`--enable-gpu-rasterization`, `--ignore-gpu-blocklist` and `--enable-zero-copy` are
+what keep rasterization on the GPU. Chromium's blocklist does not recognise this driver,
+so without `--ignore-gpu-blocklist` it quietly falls back to software.
+
+`pi_kiosk_browser: firefox` still works and is the fallback if a Chromium update ever
+regresses.
+
 ## 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
@@ -34,8 +56,13 @@ which it is not. Openbox answers the request and otherwise stays out of the way.
 - 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
+- `xterm`, `x11-utils`, `mesa-utils`, `xdotool` and `scrot` get installed, so
+  `xwininfo`, `xprop`, `glxinfo`, `glxgears`, synthetic input and screenshots are all
+  available over ssh.
+- Chromium gets `--remote-debugging-port=9222`, bound to 127.0.0.1. `curl
+  localhost:9222/json` lists the tabs, and the DevTools protocol will drive and measure
+  the page properly - which beats firing XTEST key events at a window and hoping they
+  land, as they only do about half the time. (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.)

roles/pi_kiosk/defaults/main.yml

@@ -2,8 +2,15 @@
 pi_kiosk_user: "kiosk"
 pi_kiosk_url: "http://localhost:8080"
 
+# "chromium" - the build from archive.raspberrypi.com (versions carry a "+rpt" suffix),
+#              which Raspberry Pi patch for this board's V3D GPU. Faster than Firefox
+#              here by a wide margin; see the README.
+# "firefox"   - firefox-esr from Debian. Kept switchable because it was the original
+#              kiosk browser and is the fallback if a Chromium update ever regresses.
+pi_kiosk_browser: "chromium"
+
 # "kiosk" - the page full-screen with no browser chrome and no pointer. The normal mode.
-# "debug" - the same page in an ordinary Firefox window, pointer visible, with an
+# "debug" - the same page in an ordinary browser window, pointer visible, with an
 #           Openbox root menu (right-click the desktop) offering a terminal, so the
 #           device can be poked at on its own screen. Switch back with
 #           `just run mediapis.yml musicdolphin -e pi_kiosk_mode=kiosk`, or by editing

roles/pi_kiosk/files/chromium-policies.json

@@ -0,0 +1,15 @@
+{
+  "DefaultBrowserSettingEnabled": false,
+  "PasswordManagerEnabled": false,
+  "MetricsReportingEnabled": false,
+  "SearchSuggestEnabled": false,
+  "TranslateEnabled": false,
+  "SyncDisabled": true,
+  "BrowserSignin": 0,
+  "BackgroundModeEnabled": false,
+  "AutofillAddressEnabled": false,
+  "AutofillCreditCardEnabled": false,
+  "PromptForDownloadLocation": false,
+  "ShowHomeButton": false,
+  "BookmarkBarEnabled": false
+}

roles/pi_kiosk/tasks/main.yml

@@ -5,14 +5,23 @@
       - xserver-xorg
       - xinit
       - x11-xserver-utils
-      # Without a window manager, Firefox's request to go full-screen (which is all
+      # Without a window manager, a browser's request to go full-screen (which is all
       # --kiosk does) has nobody to answer it, and it settles for its default window
       # size in the corner of the screen. Openbox answers it, and nothing else.
       - openbox
-      - firefox-esr
       - unclutter
     cache_valid_time: 7200
 
+- name: Browser
+  # Chromium comes from archive.raspberrypi.com, not Debian: that build carries the
+  # "+rpt" suffix and Raspberry Pi's own patches for the V3D GPU on this board. Debian
+  # also ships a much older `chromium`, so pinning the wrong archive here would quietly
+  # undo the reason for choosing it.
+  ansible.builtin.apt:
+    name: "{{ 'chromium' if pi_kiosk_browser == 'chromium' else 'firefox-esr' }}"
+    cache_valid_time: 7200
+  notify: Reload systemd and restart getty
+
 - name: Debugging tools for the attached screen
   # Only pulled in for pi_kiosk_mode=debug; apt does not take them away again when the
   # host goes back to kiosk mode, which is fine - they are inert and small.
@@ -21,6 +30,9 @@
       - xterm       # a terminal that is ours, whatever x-terminal-emulator points at
       - x11-utils   # xwininfo, xprop: is the window actually the size of the screen?
       - mesa-utils  # glxinfo, glxgears: is anything accelerated, or is this llvmpipe?
+      - xdotool     # drive the UI from ssh, so a measurement can be taken on a real
+                    # screen rather than an idle one
+      - scrot       # and see what that screen actually shows, over ssh
     cache_valid_time: 7200
   when: pi_kiosk_mode == 'debug'
 
@@ -81,7 +93,7 @@
     mode: "0644"
   notify: Reload systemd and restart getty
 
-- name: Install .xinitrc (starts Openbox, then Firefox)
+- name: Install .xinitrc (starts Openbox, then the browser)
   ansible.builtin.template:
     src: xinitrc.j2
     dest: "/home/{{ pi_kiosk_user }}/.xinitrc"
@@ -90,18 +102,24 @@
     mode: "0755"
   notify: Reload systemd and restart getty
 
-- name: Ensure firefox-esr policy directory exists
+- name: Ensure the browser policy directory exists
   ansible.builtin.file:
-    path: /etc/firefox-esr
+    path: "{{ '/etc/chromium/policies/managed' if pi_kiosk_browser == 'chromium' else '/etc/firefox-esr' }}"
     state: directory
     mode: "0755"
-  # apt normally creates this; a backstop in case the package layout doesn't
+  # The packages normally create these; a backstop in case a layout changes
 
-- name: Install Firefox enterprise policy (suppress session-restore/update prompts)
+- name: Install the browser's enterprise policy
+  # Everything that is a setting rather than a startup flag: no sign-in, no sync, no
+  # metrics, no password manager, no translate bar. The flags themselves are in
+  # .xinitrc, where they have to be.
   ansible.builtin.copy:
-    src: policies.json
-    dest: /etc/firefox-esr/policies.json
+    src: "{{ 'chromium-policies.json' if pi_kiosk_browser == 'chromium' else 'policies.json' }}"
+    dest: >-
+      {{ '/etc/chromium/policies/managed/kiosk.json'
+         if pi_kiosk_browser == 'chromium' else '/etc/firefox-esr/policies.json' }}
     mode: "0644"
+  notify: Reload systemd and restart getty
 
 - name: Ensure the Openbox config directories exist
   # Both levels explicitly, and owned by the user: a file: task creates missing parents

roles/pi_kiosk/templates/openbox-menu.xml.j2

@@ -13,12 +13,12 @@
     <separator/>
     <item label="Open the MusicMouse page">
       <action name="Execute">
-        <command>firefox {{ pi_kiosk_url }}</command>
+        <command>{{ pi_kiosk_browser_command }} {{ pi_kiosk_url }}</command>
       </action>
     </item>
     <item label="Open it full-screen (kiosk)">
       <action name="Execute">
-        <command>firefox --kiosk {{ pi_kiosk_url }}</command>
+        <command>{{ pi_kiosk_browser_command }} --kiosk {{ pi_kiosk_url }}</command>
       </action>
     </item>
     <separator/>

roles/pi_kiosk/templates/xinitrc.j2

@@ -3,21 +3,52 @@
 #
 # Openbox is here for one concrete reason: a browser asks to be full-screen over EWMH,
 # and only a window manager answers that request. With no WM running, --kiosk was
-# silently ignored and Firefox fell back to its default 1280x972 window on a 1920x1080
-# screen - the page in the top-left corner with black bands down the right edge and
-# along the bottom. Openbox costs a couple of MB and does nothing else here.
+# silently ignored and the browser fell back to its default window size in the
+# top-left corner of a 1920x1080 screen - black bands down the right edge and along
+# the bottom, looking exactly like an overscan problem and not being one.
 
 xset s off
 xset -dpms
 xset s noblank
 
+{% if pi_kiosk_browser == 'chromium' %}
+BROWSER=chromium
+
+# The first four flags are the difference between compositing on the GPU and
+# rasterizing every frame on the CPU:
+#   --use-gl=egl                 reach V3D through EGL rather than desktop GLX
+#   --enable-gpu-rasterization   rasterize layer content on the GPU
+#   --ignore-gpu-blocklist       Chromium's blocklist does not know this driver, and
+#                                without this it quietly falls back to software
+#   --enable-zero-copy           hand tiles to the compositor without a CPU copy
+# The rest are about a machine nobody sits in front of: no update checks, no crash
+# bubbles, no keyring prompt, no first-run wizard, no "restore pages?" after a power
+# cut. Anything policy-shaped rather than flag-shaped is in
+# /etc/chromium/policies/managed/.
+BROWSER_ARGS="--use-gl=egl --enable-gpu-rasterization --ignore-gpu-blocklist --enable-zero-copy"
+BROWSER_ARGS="$BROWSER_ARGS --noerrdialogs --disable-infobars --no-first-run"
+BROWSER_ARGS="$BROWSER_ARGS --no-default-browser-check --disable-session-crashed-bubble"
+BROWSER_ARGS="$BROWSER_ARGS --password-store=basic --check-for-update-interval=31536000"
 {% if pi_kiosk_mode == 'debug' %}
-# Debug session. Firefox is an ordinary window with its chrome (so devtools and the URL
-# bar are reachable) and is *not* relaunched when it exits - quitting it should leave a
-# usable desktop, not fight you for the screen. Openbox is the session leader instead:
-# when it exits (root menu -> Exit) the X session ends and .bash_profile starts a fresh
-# one. Right-click the desktop for a terminal.
-firefox "{{ pi_kiosk_url }}" &
+# Debug mode only. Binds to 127.0.0.1, so it is reachable over an ssh tunnel and from
+# nowhere else. Lets the page be driven and measured from a shell - `curl
+# localhost:9222/json` lists the tabs - instead of by poking XTEST key events at a
+# window and hoping they land.
+BROWSER_ARGS="$BROWSER_ARGS --remote-debugging-port=9222"
+{% endif %}
+{% else %}
+BROWSER=firefox
+BROWSER_ARGS=""
+{% endif %}
+
+{% if pi_kiosk_mode == 'debug' %}
+# Debug session. The browser is an ordinary window with its chrome (so devtools and the
+# URL bar are reachable) and is *not* relaunched when it exits - quitting it should
+# leave a usable desktop, not fight you for the screen. Openbox is the session leader
+# instead: when it exits (root menu -> Exit) the X session ends and .bash_profile
+# starts a fresh one. Right-click the desktop for a terminal.
+# shellcheck disable=SC2086  # BROWSER_ARGS is a word list on purpose
+$BROWSER $BROWSER_ARGS "{{ pi_kiosk_url }}" &
 
 exec openbox
 {% else %}
@@ -26,9 +57,10 @@ openbox &
 unclutter -idle 0.5 -root &
 
 # The loop is what takes the place of a WM's "keep something on screen" job: Openbox
-# manages the window, but nothing else would bring Firefox back if it died.
+# manages the window, but nothing else would bring the browser back if it died.
 while true; do
-  firefox --kiosk "{{ pi_kiosk_url }}"
+  # shellcheck disable=SC2086
+  $BROWSER --kiosk $BROWSER_ARGS "{{ pi_kiosk_url }}"
   sleep 2
 done
 {% endif %}

roles/pi_kiosk/vars/main.yml

@@ -0,0 +1,4 @@
+---
+# The executable name for each supported browser. In vars/ rather than defaults/
+# because it is derived from pi_kiosk_browser, not something to override.
+pi_kiosk_browser_command: "{{ 'chromium' if pi_kiosk_browser == 'chromium' else 'firefox' }}"