Classroom_Desktop/docs/classroom-v2-experiment.md

# Classroom v2 architecture experiment

An open re-evaluation of the whole Ekklesia Classroom desktop stack, with
reliability as the first requirement. Nothing here reaches a stable, canary
or hyprland room, and nothing here changes the development host.

## Base

| | |
| --- | --- |
| branch | `experiment/classroom-v2` |
| base commit | `aadb1b881977b0eb25e1ca10e060977bed31a48f` |
| base subject | *fix: keep the system print dialog in front of the window that rendered it* |
| `VERSION` at base | `0.1.44` |

That commit is the published **stable** build, verified rather than assumed:
`repo/stable/manifest.json` names `ekklesia-classroom_0.1.44_amd64.deb` with
sha256 `7de568…81041`, and the copy in `repo/packages/` hashes to exactly
that. The branch is not built on `experiment/hyprland`; `git ls-files` on it
contains no Hyprland file.

## The answer, in one paragraph

Every user-visible failure the church reported is a piece of desktop
infrastructure the classroom wrote itself. The shell that disappeared had no
supervisor. The minimised window with no feedback exists because wlroots has
no minimise and the classroom invented one. The secondary window that fights
the browser needed a 314-line arbiter because sway tiles. The unrecognisable
browser icon was hand-drawn to match a monochrome set. Debian 13 already
ships a desktop that solves all four, so **the recommendation is Plasma 6.3
on the Debian the classroom already runs**, configured rather than written,
and it was built and tested here rather than argued for.

## The development host, as found

Recorded because it bounds what could be tested.

| | |
| --- | --- |
| OS | Debian 13 trixie (13.5), kernel 6.12.90 |
| machine | already a VM — root is `/dev/vda2`, GPU is `bochs-drm`, CPU is `QEMU Virtual CPU` |
| nested virtualisation | **none** — `/dev/kvm` does not exist |
| libvirt / qemu / VirtualBox | not installed |
| containers | Docker 26.1.5, cgroup v2 |
| resources | 6 vCPU, 11 GiB RAM, 160 GiB free |

**This session could not create a virtual machine**, so the candidate desktop
was given a systemd container instead. Nothing outside Docker was changed on
the host: no packages installed, no configuration touched, no service
altered. See *Alternate operating systems* for what still needs a real VM.

## The lab

`tools/lab/` builds a Debian 13 container with a full Plasma 6.3 desktop in
it, runs systemd as PID 1 so the session is supervised the way a real machine
supervises it, and nests the session inside a headless sway so that `grim`
can photograph it and a real pointer can be aimed at it.

To resume: the lab is left running, built from the package, with Parent
Call's test rig **not** started — so the classroom's broker settings are
off and nothing can reach anything. `tools/lab/parent-call-rig up` brings
the coordinator back, and it re-establishes and re-verifies the block on
the church's networks before it will start.

```
tools/lab/lab build          # the image
tools/lab/from-package       # a fresh machine, the .deb, and nothing else
tools/lab/cold-start 3       # three complete cold starts, from nothing
tools/lab/lab session        # compositor + Plasma session
tools/lab/lab shot NAME      # docs/screenshots/NAME.png
tools/lab/lab click X Y      # a real pointer press
tools/lab/kwin-script FILE   # ask KWin what it believes about a window
tools/lab/recovery-check     # every recovery property, measured
tools/lab/parent-call-rig    # the real coordinator, safely walled off
```

Every window measurement in this document came from `kwin-script`, not from
looking at a screenshot. Every click came through libinput.

Three lab-only deviations, recorded because they bound what was proven:

* **Software rendering.** llvmpipe throughout, with KWin nested in sway. This
  proves behaviour and layout, not performance on classroom hardware.
* **No sound card and no optical drive.** The audio policy was therefore
  tested as a pure function against the real room's reported hardware state
  rather than end to end, and DVD playback was not exercised.
* **Video did not decode.** VLC came up fullscreen at exactly 1920×1080 with
  the panel covered, which is the window-management result being tested, but
  the picture was black under software XWayland.

## What was measured

Each of these changed a decision.

### The panel gives up after three crashes

Plasma's own unit restarts a crashed `plasmashell`, but with
`StartLimitBurst=3` inside sixty seconds. Measured:

| | |
| --- | --- |
| kill 1 | back in 0.3 s |
| kill 2 | back in 0.4 s |
| kill 3 | **never came back** |

That is the production failure the church already had, reproduced on stock
Plasma. A four-line systemd drop-in
(`systemd/user/plasma-plasmashell.service.d/ekklesia-classroom.conf`) makes
the restart unconditional. Re-measured: **eight consecutive `SIGKILL`s one
second apart, back every time in about 2.4 s**, with the open application
window untouched.

This is the single most important line in the whole experiment, and it is a
supported override rather than a supervisor of our own.

### KWin already recovers, and takes nothing with it

`kill -9 kwin_wayland` twice: back in **0.1 s** each time, via
`kwin_wayland_wrapper`, with the running application still on screen and its
Wayland connection intact.

### A deleted panel rebuilds itself

`plasma-org.kde.plasma.desktop-appletsrc` was deleted and the shell
restarted. The classroom bar came back exactly as designed, from the layout
script in the look-and-feel package. So the recovery procedure for a damaged
desktop is one file removed and one service restarted — no reflash, and no
technician in the room.

### Plasma cannot show all five application states

The brief asks for closed, running, active, minimised and behind. Measured by
sampling the pixels of the indicator strip rather than by eye:

| state | indicator | icon |
| --- | --- | --- |
| closed | none — panel background `(26, 29, 32)` | full colour |
| running, behind | grey `(42, 45, 48)` | full colour |
| running, active | teal `(65, 127, 121)` | full colour |
| **minimised** | grey `(42, 45, 48)` — **identical to behind** | full colour |

Three marks for four states. Rather than write a task manager that draws a
fourth — which is exactly the kind of custom desktop code this experiment
exists to remove — **the classroom removes the state**: clicking a launcher
always means *show me this*, never *hide it*, and the window decoration has
no minimise button. There is nothing on the idle desktop a teacher could want
to see, so minimising in this room only ever loses the lesson.

A window minimised by some other route is still shown as running and comes
back with one click, so it can never be lost even then.

### A window rule cannot tell a browser from its popup

The first attempt maximised the browser with a KWin rule on `google-chrome`.
Measured: the window a lesson page opened was maximised too, because Chrome
gives both the same class — the very behaviour the current architecture
spends 314 lines preventing.

Chrome can tell them apart, so `--start-maximized` in the launcher does it.
Measured afterwards:

| | |
| --- | --- |
| main browser | `[0,0] 1920×1004` — the whole desktop above the bar |
| window the page opened | `[509,160] 902×683` — centred, the size the page asked for |
| main browser afterwards | unchanged |

The secondary window carries an ordinary title bar with a close button, so
the dock's sticky Close button has nothing left to do.

### Printing

A page's own Print button produced a **native KDE print dialog** through
`xdg-desktop-portal-kde`, `transient=true` on the browser, centred over it,
in the classroom's colours, offering only **Elmer**. Stacking is the window
manager's ordinary behaviour and needed no rule.

### An immutable colour scheme cannot be toggled

Marking `[General]` immutable in `/etc/xdg/kdeglobals` froze the palette so
hard that `classroom-theme light` changed the running session and lost the
change at the next start. Immutability now covers the Kiosk restrictions and
nothing else. Measured both ways afterwards.

### Two packages cannot own one file

`dpkg -i` refused the first package outright: `plasma-workspace` already
owns `/etc/xdg/plasmanotifyrc`, and `kdeglobals`, `kwinrc` and the rest are
the same story. The room's settings live in
`/etc/ekklesia-classroom/xdg/` instead, with
`/etc/environment.d/90-ekklesia-classroom.conf` putting that directory in
front of `/etc/xdg` in `XDG_CONFIG_DIRS`. That is KConfig's own cascade
rather than a fight over a path, and it was checked at runtime:
`systemctl --user show-environment` carries it, and `kreadconfig6` in the
session reads the classroom's values.

The `postinst` then failed on a `chmod` for a command that had been
removed. It walks what the package actually installed now.

### VLC calls itself `Vlc`

KWin's window matching is case sensitive, and a lower-case substring rule
matched nothing while reporting nothing. The rule is a regular expression
now.

## The architecture

| | |
| --- | --- |
| distribution | **Debian 13 trixie** — unchanged, so the `.deb` and OTA work survives |
| desktop | **KDE Plasma 6.3.6** (Debian's own packages) |
| compositor | **KWin 6.3.6**, Wayland |
| panel | **Plasma panel**, one full-width bar, built by a look-and-feel layout script |
| task feedback | **Icons-only Task Manager** |
| notifications | **Plasma's own** |
| browser | **Google Chrome**, unchanged |
| Wonder Ink | Chrome app mode, **its own profile** |
| session start | **SDDM autologin** (recommended; not yet tested — see risks) |
| lockdown | **KDE Kiosk** action restrictions |
| audio | one small classroom service, event driven |

### The bar

One continuous full-width bar, 76 px, the height the room already has.

* **Left** — Parent Call, drawn as a line mark in the accent rather than a
  colour tile, so it reads as a different kind of thing from the applications
  and is visibly not one of them.
* **Centre** — the applications: Wonder Ink, and the browser wearing
  **Chrome's own icon, in colour**. That is the direct answer to the teacher
  who asked whether the old monochrome glyph meant "the Internet".
* **Right** — network, volume, removable media, notifications, clock. Four
  applets placed directly on the bar rather than a system tray: the tray
  discovers whatever is installed and hides most of it behind an arrow, and
  in the lab it collected battery, brightness, clipboard, keyboard layout,
  camera, vaults and screen management on a machine with none of those.

The bar launches applications, shows their state, and shows a little status.
It is not the Live View, not Parent Call, and not a shell framework.

### Wonder Ink as an application

```
Wonder Ink   chrome --app=https://app.wonderink.org/ --user-data-dir=…/wonderink
Browser      chrome                                   the room's own profile
```

Its window class is `chrome-app.wonderink.org__-Default` — measured on a
running session, and the launcher's `StartupWMClass` matches it exactly, so
the panel shows one button rather than a launcher and a window side by side.

The separate profile buys something the current single-profile design cannot:
if a teacher signs into Wonder Ink through Google, that Google session is in
the Wonder Ink profile and closing the window ends it, while the church
YouTube sign-in lives in the browser's profile and is untouched. The
documented conflict in `browser.md` — that clearing `wonderink.org` leaves
the next teacher one click from the previous teacher's account — does not
arise.

The ordinary browser therefore no longer opens Wonder Ink. Its home page is
YouTube, because a second way in through that window would put a teacher's
lesson session in the room's shared profile, which is the leak the split
exists to prevent.

### Windows

KWin's ordinary behaviour, with one rule.

* Main windows fill the desktop above the bar, edge to edge, because Chrome
  is told to start maximized.
* Windows a page opens float over the main one, centred, at the size the page
  asked for, with a title bar and a close button.
* Dialogs are transient on their parent and stack correctly with no help.
* Fullscreen video covers the whole display: `[0,0] 1920×1080`, panel
  included, no rounding, no wallpaper.
* One rule, and it is `noborder` for VLC.

**The outer margin and the 10 px rounding were dropped.** Chrome squares its
own corners when maximised, so margin and rounding are the same decision, and
expressing "the screen minus 16 px" needs a rule generated per resolution at
every boot. That is glue in exchange for appearance, and the brief says
reliability wins. Full-bleed above the bar is also what every other appliance
does.

### Theme

One set of design tokens in `EkklesiaDark.colors`; the light scheme is
**generated** from it by `tools/build-light-scheme`, so a colour can only be
changed in one place. Plasma applies either to the panel, the notifications,
the decorations and every dialog at once. `classroom-theme light|dark|toggle`
is the whole switch. Accent teal `#4FB3A8`, taken from the wallpaper.

### Wallpaper

`config/wallpapers/classroom-calm.png` is a **stand-in**, generated by
`tools/build-wallpaper` in the sage/teal/blue/lavender palette with a river
leading into the picture and a quiet upper middle. The illustrated wallpaper
the church selected is not in this repository; when it arrives it replaces
that file and nothing else changes.

### Lockdown

`/etc/xdg/kdeglobals`, `[KDE Action Restrictions][$i]`. Verified by clicking,
not by reading the file: right-clicking the wallpaper produced no menu,
right-clicking the bar produced no menu, and KRunner was not running and
could not be summoned. `run_command`, `shell_access`, `logout`,
`action/lock_screen`, `action/kwin_rmb` and `plasma/plasmashell/unlockedDesktop`
all read back `false`. There is no lock screen and no session restore.

Nothing was achieved by deleting a binary. Lifting a restriction for
maintenance is one line and a session restart.

### Audio

The one place custom code is still right, because no desktop expresses this
policy. `lib/classroom_audio.py` is a pure function so it can be tested
against the room that failed rather than against a machine:

* a port that reports itself unavailable is not a candidate;
* an analog port existing is not evidence that a cable is in it;
* an explicit `AUDIO_OUTPUT=hdmi|analog` overrides everything.

`scripts/classroom-audio` follows PipeWire's own event stream — no polling —
and on every change sets the card profile, sets the default sink, and
**moves streams that are already playing**. That last step is the fix for the
teacher who had to restart the browser after changing the output.

Twelve test cases in `tests/test-classroom-audio.sh`, the real room among
them. The service is supervised the same way the panel is; measured, it came
back from four consecutive kills.

### DVD

**How much of the DVD player survives this change was measured, not
assumed**, because the room's disc playback works and breaking it for
tidiness would be a bad trade.

* Its loading cover and control bar are `gtk-layer-shell` surfaces. KWin
  implements `zwlr_layer_shell_v1` — the Plasma panel is one — and a probe
  overlay came up full-screen under it. So the DVD surfaces keep working
  and `python3-gi` and `gir1.2-gtklayershell-0.1` stay in the package.
  Removing them broke `classroom-dvd toggle` immediately, which is how this
  was found.
* Its stylesheet was the dock's. The dock is gone; the template survives as
  `config/overlay/style.css.in`, renamed to say what still uses it.
* `classroom-dvd` calls `classroom-window`, which speaks sway's IPC.
  Measured with no sway running: it exits 0 and does nothing, so it
  degrades rather than hanging — but the DVD player's focus handling is not
  yet ported, and that is the largest piece of work this change leaves.
* One behavioural difference: under sway the loading cover hid the dock;
  under KWin the panel draws above it, so the bar stays visible while a
  disc spins up. Fullscreen VLC still covers everything, which is the state
  that matters.

`/usr/share/solid/actions/ekklesia-dvd.desktop` with an
`X-KDE-Solid-Predicate` for a video DVD. Plasma's device notifier offers
"Play the DVD" while a disc is in the drive and withdraws it when the disc
leaves, so a room without a drive shows nothing and no room needs
`DVD_ENABLED` edited. Nothing polls, and `classroom_optical`'s two-second
loop goes away. **Not exercised** — the lab has no optical drive.


## Parent Call

The coordinator already existed and its contract is frozen. It was read
from `/home/media/docker/parent-call/README.md` and its source on the
control computer, not guessed, and nothing here changes it.

### What the teacher does

Click the mark on the left of the bar. A small card appears in the middle
of the screen, above whatever they were reading. It already knows the
room. They type a child's name and press **Call parent**. The card says
what happened, in the coordinator's own words, and closes itself four
seconds after a call is on its way.

Four steps, one of which is typing a name. The room is never asked for:
this machine knows which room it is, and offering a list is a chance to
pick the wrong one.

### The mark

Three were put on a real panel and judged at the size the bar draws them.

| tried | why it lost |
| --- | --- |
| a bell | sat inches from Plasma's own notification bell in the same bar |
| `call-outgoing`, a handset with an arrow | read as a telephone feature, not as fetching somebody |
| **an adult, a child, and one speech bubble** | kept |

Breeze has people and it has telephones and the two never meet, so the
kept mark is drawn rather than picked — on Breeze's 22-unit grid, with its
`ColorScheme-Text` class, so it recolours with the session and needs no
second file for the light theme. `docs/screenshots/pc-icon-vs-notifications.png`
is it beside the notification bell.

It is carried by **Quick Launch**, on the left, apart from the
applications. Two other widgets were tried first and both failed in ways
worth writing down:

* the **Icon** widget copies the desktop entry into the user's home and
  uses the copy, so an update can never change the icon or the command —
  it kept showing a bell out of a package that no longer contained one;
* a **task manager** reads the entry live, which fixes that, but a task
  manager also shows every running window, so the auxiliary corner filled
  up with the lesson's tasks.

### The states a teacher sees

Every word comes back from the coordinator in the `message` field. The
classroom never composes one for a call, because the coordinator is the
only thing that knows what happened.

| coordinator status | on screen | what the card does |
| --- | --- | --- |
| `submitted` | Sending | waits |
| `waiting_approval` | Waiting for approval | waits, amber |
| `sending` | Sending to sanctuary | waits |
| `sent_to_sanctuary` | Sent to sanctuary | green, closes after 4s |
| `rejected` | Not approved | red, offers Try again |
| `expired` | Expired before it was sent | red, offers Try again |
| `unavailable` | Parent Call is unavailable | red, no way to send |
| `error` | Could not reach the sanctuary | red, offers Try again |

**Nothing says "displayed".** A ProPresenter call that succeeded means the
message was accepted, not that anyone saw it, and *Sent to sanctuary* is
the strongest claim the room is entitled to make.

Before a name can be typed at all, the card reads the two retained topics
and refuses in four different ways: no broker (*Cannot reach the church
network*), no coordinator (*The sanctuary system is not running*), mode
`off` (*Parent Call is unavailable*, the coordinator's own wording), and
no retained mode at all (*Parent Call has not been set up yet*). A teacher
is never left believing a call went out.

### How it is built

```
Quick Launch  ->  classroom-parent-call   a separate process
                     |
                     +-- classroom_parent_call   topics, payloads, states
                     +-- paho, one short-lived clean session
```

Not a Plasma applet. A broker library, a network timeout and a text entry
have no business inside the only way a teacher has of getting anywhere.
Measured: killing the card leaves the panel untouched, and clicking the
mark again starts a new one.

Three properties the contract asks for and this keeps:

* the status topic is subscribed **before** the request is published, so
  an answer cannot arrive before anyone is listening;
* the session is **clean** and nothing is retained, so a call from last
  Sunday cannot replay into this one;
* listening stops the moment a status is terminal.

Bounded everywhere: 5s to reach the broker, 1.5s for retained state, 8s
for the coordinator's first answer, and 210s overall — its own
`REQUEST_TTL` is 180. Silence is reported as *No answer from the
sanctuary*, which is not the same as a refusal and is not shown as one.

Sixty tests cover the contract with no broker at all
(`tests/test-classroom-parent-call.sh`).

### Testing it without touching the sanctuary

`tools/lab/parent-call-rig` runs the **real coordinator** — copied from
the control computer — against a broker on loopback and a ProPresenter
that is a mock, and it **rejects the church's own networks from inside
the container before it will start**. That guard is not a convention; the
rig exits if either address is still reachable. It was needed:
`10.40.0.2:1883` is reachable from this development host.

Verified end to end on the packaged install: request accepted, queued,
approved by an operator, delivered as
`Name=Emma, Room=Nursery`, and *Sent to sanctuary* shown. Also `off`,
`rejected`, and the broker stopped.


## DVD

### It is an application now

DVD used to sit in the status row beside the clock, as though a disc were
a machine reading. It is in the row with Wonder Ink and the browser, with
Breeze's optical-disc mark, and Plasma gives it the same closed / running
/ active treatment as the others.

`DVD_ENABLED` is gone. `classroom-desktop-layout` asks the machine for
`/dev/sr*` and removes the launcher from the layout on a room that has no
drive. A computer that moves between rooms takes its drive with it, and
nobody remembers to edit a file when it does.

**Disc presence is not shown on the launcher.** Doing that needs either
polling or rewriting the panel while it runs, and rewriting the panel
while it runs was measured to destroy it. The launcher tracks the drive,
not the disc; a room with a drive and no disc gets a notification saying
so when it is pressed.

### The panel is rebuilt from the package at every login

Plasma keeps whatever panel it first built. An update could therefore
change the bar in the package and never change it in a room — which is
exactly what happened to an icon that outlived the file it came from.

`classroom-desktop-reset` removes the panel configuration before
plasmashell starts, so the bar is built from the layout every time. The
desktop is stateless: there is nothing in a teacher's home an update
cannot reach, and a damaged panel is repaired by the next login. Nothing
is lost, because Kiosk policy means a teacher never had anything in that
file.

Editing the live configuration instead was tried first and destroyed the
panel — the shell owns that file and rewrites it, so an edit races with
it. That is why this runs `Before=plasma-plasmashell.service`.

### The last of sway

The DVD player was the only thing still speaking a compositor the room no
longer runs. It asked sway's tree whether VLC's window had really gone
fullscreen, because VLC reports playing while its window is still the
black startup one the loading cover exists to hide.

**VLC's own status was measured as a replacement and is not one.** It
reports `<fullscreen>true</fullscreen>` in the same 250ms poll as
`<state>playing</state>`, because the flag is the option it was started
with and not a report about its window. So the cover is held for a floor
(`MINIMUM_COVER_SECONDS`) and still capped by the deadline that was
already there, and the compositor is not asked anything at all.

Focus-or-launch went the same way: the session already takes an exclusive
lock so a second one cannot start, and bringing an existing one to the
front is the panel's job.

Gone with it: `classroom-window`, `classroom_sway.py`, and
`classroom_chrome.py`, which turned out to be reachable from nothing.
**One mention of sway remains in the whole tree**, and it is the upgrade
step in `postinst` that removes the sway-era login shell from a room
being upgraded. Nothing executes it, imports it, or asks it anything.

Still unproven, and it is the same gap as before: playback end to end.
The lab has a drive with no readable disc and no libdvdcss, so VLC exits
on `--key-length=`. The loading cover, the control bar and the session's
own lifecycle all run; the picture does not.


## Audio: how to test it on the hardware

Nothing below can be done in the lab: the container has no sound card, so
the policy is tested as a function and applying it is not tested at all.
`classroom-audio show` prints what it can see and what it would choose,
and changes nothing — start there.

1. **Television on before the computer.** Boot with the TV on and an
   input selected. Expected: sound comes out of the TV with nothing
   touched. Check with `classroom-audio show`; the chosen port should be
   an `hdmi-output-*`.
2. **Television off during boot, switched on afterwards.** Boot with the
   TV off, wait for the desktop, then switch the TV on. Expected: within
   a couple of seconds the output moves to HDMI by itself. This is the
   case the room actually failed on, and the one worth watching.
3. **Browser already playing.** Start a YouTube video, then switch the TV
   on or change the output. Expected: the sound follows **without
   restarting Chrome**. That is the whole point of moving existing
   streams; if Chrome still has to be restarted, the policy is not doing
   its job and `journalctl --user -u ekklesia-classroom-audio` will say
   how many streams it moved.
4. **Unplug and replug HDMI** while something is playing. Expected: falls
   back, then returns.
5. **VLC already playing**, same as 3.
6. **Overrides.** `AUDIO_OUTPUT=analog` in
   `/etc/ekklesia-classroom/device.conf`, restart the user service, and
   confirm it obeys even with the TV on. Then `hdmi`, then back to
   `auto`.

What to capture if something is wrong: `classroom-audio show`,
`pactl list cards short`, `pactl list sinks short`, and the service
journal. The decision is a pure function, so a bad choice can be
reproduced as a test case from what those print.

## Custom code this deletes

Deleted on this branch across both milestones, and counted rather than
estimated:

| | lines | replaced by |
| --- | --- | --- |
| `scripts/classroom-dock` | 754 | the Plasma panel |
| `scripts/classroom-chrome-windows` | 314 | `--start-maximized`, and a window manager |
| `tests/test-classroom-chrome-windows.sh` | 280 | — |
| `config/dock/style.css.in` | 102 | the colour scheme |
| `scripts/classroom-notifications` | 74 | Plasma notifications |
| `config/sway/config` | 62 | `kwinrc` |
| `config/mako/config.in` | 48 | `plasmanotifyrc` |
| `config/waybar/*` | 55 | the Plasma panel |
| `config/bash_profile`, getty autologin | 6 | SDDM |
| `config/icons/browser.svg` | — | Chrome's own icon |
| `scripts/classroom-window` | 208 | the panel, and a lock the DVD session already took |
| `lib/classroom_sway.py` | 127 | — |
| `lib/classroom_chrome.py` | 66 | nothing: it was reachable from nowhere |
| `tests/test-classroom-window.sh` | 214 | — |
| `config/icons/*` (dock set) | — | Breeze, and two marks the classroom draws |
| **total** | **≈ 2 310** | |

Rewritten rather than deleted: `classroom-browser` (41 → 30 lines, it no
longer decides launch-or-focus-or-minimise), `classroom-scale` (sway output
scale → `kscreen-doctor`), `classroom-notify` (found the session by looking
for sway and refused to run without mako; now looks for the compositor and
the shell).

**Nothing in the classroom speaks to a compositor any more.**
`classroom_icons.py`,
`classroom_style.py` and `classroom_optical.py` remain, reachable only
from the DVD player and the MQTT notifier: the DVD overlay draws its own
layer-shell surfaces and still needs the icon and stylesheet helpers the
dock shared, and disc detection is still ours.

Added since: the audio policy and its tests, the theme switch, Parent
Call and its contract module, the layout tailor, the panel reset, and
configuration.

Kept because they are the classroom's own subject matter: the DVD session
and CSS setup, printer setup, provisioning, MQTT, the updater, shutdown.
Added: the audio policy and its test, the theme switch, and configuration.

The package was built and its contents checked: every `/usr/local` path any
classroom command names is in it.

## Alternatives, and why they lost

**Stay on sway, add Waybar.** Cheapest migration, and it loses on the thing
that matters. wlroots has no minimise, so the invented hidden workspace
stays; sway tiles, so the 314-line window arbiter stays; there is no
window-manager decoration, so the dock's sticky Close button stays; and
Waybar is one more unsupervised process to lose. It removes none of the four
reported problems.

**Hyprland** (`experiment/hyprland`). Already measured on this repository and
already carrying two findings against it: the legacy config silently matches
nothing, and a Lua config changes the IPC language so the classroom would be
adopting a brand-new format early. For critical production UI in a room
nobody attends on a Sunday morning, that is the wrong end of the maturity
curve.

**GNOME.** Task state, a bottom bar and application pinning all need
extensions, and extensions break on GNOME updates. That is precisely the
"several fragile independently-maintained components" the brief rules out.

**Fedora KDE / Arch.** Both would supply the same Plasma. Neither supplies
anything Debian 13 does not, and both would cost the entire `.deb` and OTA
investment. Arch's rolling updates are the wrong risk for an appliance that
must survive unattended. **Changing distribution buys nothing here**, which
is the most useful negative result in this document.

**Firefox ESR / Chromium instead of Chrome.** No concrete benefit. Firefox
has no app mode, which is what makes Wonder Ink an application; Debian's
Chromium ships no Widevine. Chrome is what Wonder Ink is known to work in.


### Recovery, measured against the package

`tools/lab/recovery-check`, run after `tools/lab/from-package`, against
the lab exactly as the `.deb` built it:

| | |
| --- | --- |
| panel, 8 × SIGKILL one second apart | back every time, 2.2–2.5s |
| compositor, 2 × SIGKILL | back in 0.1s |
| audio policy, 3 × SIGKILL | active every time |
| Parent Call killed | panel untouched |
| browser killed | panel untouched |
| afterwards | panel, compositor, 10 applets, audio all standing |

The drop-in that makes the panel restart unconditional is in the package,
not only in a hand-edited session: `/etc/systemd/user/plasma-plasmashell.service.d/`.

## Reliability results

| test | result |
| --- | --- |
| cold start, 3 identical runs | 16, 16, 17 s — panel, compositor and 11 applets every time |
| `plasmashell` SIGKILL ×8 at 1 s | back every time, ≈2.4 s |
| `plasmashell` on stock settings | **dead on the third kill** — fixed by the drop-in |
| `kwin_wayland` SIGKILL ×2 | back in 0.1 s, windows survived |
| audio service SIGKILL ×4 | active every time |
| panel configuration deleted | rebuilt itself from the layout script |
| right-click desktop / panel | no menu |
| KRunner | not running, not reachable |
| light ⇄ dark | persists both ways |
| memory, 3 samples over 6 minutes | flat: plasmashell 399 MB, KWin 141 MB under llvmpipe |
| package install on a clean machine | clean, and the session came up from it |

## The package

`tools/build-release.sh` builds it, and it was installed on a fresh machine
and booted from rather than described. `ekklesia-classroom_0.1.45` is 65
files: the desktop under `/etc/ekklesia-classroom/xdg`, a look and feel
package, two colour schemes, the launchers, the Solid action, two supervised
user services, and the classroom's own commands. Dependencies swap
`sway, swaybg, waybar, mako-notifier, python3-gi, gir1.2-gtklayershell-0.1`
for `plasma-desktop, plasma-workspace, kwin-wayland, plasma-nm, plasma-pa,
sddm`, and it `Conflicts` with the welcome tour, the software centre and the
phone pairing daemon that `plasma-desktop` would otherwise recommend into a
classroom.

Checked mechanically: every `/usr/local` path any classroom command names is
in the package.

The OTA mechanism is untouched. This is an ordinary version on the ordinary
channel structure, and an experimental build would go out as
`0.1.45~plasma1` on a channel of its own, exactly as the Hyprland milestone
did.

## Screenshots

Twenty-nine, in `docs/screenshots/`, indexed in
[screenshots/README.md](screenshots/README.md) — including the two that
record failures rather than successes.

## Not done, and honest about it

* **DVD end to end.** The overlay surfaces and disc detection were checked;
  playback was not, and the focus helper is not ported. See *the DVD
  player* above.
* **Real audio hardware.** Policy tested as a function; no card to apply it to.
* **Video decode and performance.** Software rendering only.
* **SDDM.** Recommended over the current `bash_profile` `exec`, because when
  the session ends SDDM starts another one instead of leaving a teacher at a
  shell prompt. Not yet configured or tested.
* **Packaging.** `tools/build-release.sh` still installs the sway-era file
  list. The desktop is installed by `tools/lab/install-desktop`, which is the
  shape the package needs but is not the package.
* **Parent Call and Live View.** Placed in the architecture, not built. Live
  View's pin is KWin's Keep Above, which is already a title-bar button.
* **UI scale.** `classroom-scale` now asks `kscreen-doctor` instead of the
  compositor, and 1.25 was applied and read back correctly. The *look* of it
  could not be judged: a nested session shrinks its own canvas to the
  logical size instead of keeping the display's mode, so everything got
  smaller rather than larger. On a real output it does the opposite. Judge
  this one on hardware.
* **Network states.** plasma-nm is in the bar and live — it correctly showed
  a problem state throughout, because Docker configures the container's
  interface before NetworkManager sees it and NM reports limited
  connectivity for it. Online, connecting and offline transitions need a
  machine whose network NetworkManager actually owns.


## Live View, and whether this desktop can carry it

Not implemented. What the KDE architecture already provides for it:

* **A small status widget on the idle desktop.** A Plasma applet, or —
  preferring less custom desktop code — a notification when the sanctuary
  goes live plus a launcher in the bar.
* **A preview that expands.** A separate application window, not
  something embedded in the panel. The panel may launch it and show that
  something is live; it must not be the player.
* **Pin above other applications.** This is KWin's *Keep Above*, which is
  already a window state with a title-bar button, and a window rule can
  force it for the preview's class. Nothing has to be invented, which was
  the open question when this experiment started.
* **Unpin returns it to normal stacking.** The same button.

The likely media path (MediaMTX, WHEP) is a property of the player
application and does not touch the desktop architecture.


## The power button, and the way back in

### A press does nothing

Two layers, and both are needed. While a graphical session is running,
PowerDevil takes logind's `handle-power-key` inhibitor and acts on the
button itself, so a logind drop-in on its own would be overruled.

| layer | file | what it says |
| --- | --- | --- |
| logind | `/etc/systemd/logind.conf.d/ekklesia-classroom.conf` | `HandlePowerKey`, `HandleSuspendKey`, `HandleHibernateKey`, `HandleRebootKey` and every lid switch set to `ignore`, long-press included |
| PowerDevil | `/etc/ekklesia-classroom/xdg/powermanagementprofilesrc` | `powerButtonAction=0` and `lidAction=0` in all three profiles, groups marked `[$i]` so the session cannot put an action back |

logind covers the machine before the session starts, after it ends, and
if PowerDevil is not running at all. PowerDevil covers it while a teacher
is using it.

Measured in the lab: with the drop-in installed and logind reloaded,
logind reports `ignore` for the power, suspend, hibernate and lid keys —
it reported `poweroff` and `suspend` before — and the running graphical
session was not disturbed by the reload. The `postinst` therefore
reloads logind, so the button stops working at install time rather than
at the next boot.

**Holding the button still cuts the power.** That is firmware, below any
operating system, and it is left alone on purpose: it is the only
recovery a person standing at a wedged machine has.

**Needs the hardware.** Nothing in a container has a power button. What
is proven is that both layers are configured, packaged, and read back
the way they should. Pressing the button is a bench test.

### One chord opens a terminal

`Meta+Ctrl+Alt+Shift+K`.

Normal administration is still SSH. This is for the case where somebody
is standing at a machine and SSH is not available.

The chord is declared in the package — `X-KDE-Shortcuts` in
`ekklesia-admin-terminal.desktop` — rather than seeded into a teacher's
configuration, where an update could not reach it. KGlobalAccel read the
entry and registered a component for it; invoking that component's
`_launch` over D-Bus opened a working shell, which is how the whole path
was verified without a keyboard.

It needed a wrapper, for a reason worth recording. The classroom's Kiosk
policy sets `shell_access=false` and **Konsole honours it**: with the
classroom configuration in its cascade, Konsole starts and prints
*Program to run not set.* rather than opening a shell. That restriction
is worth keeping for everything else, so `classroom-admin-terminal`
lifts it for one process by leaving the classroom's configuration
directory out of that process's `XDG_CONFIG_DIRS`. Nothing is patched,
no binary is replaced, and the terminal therefore looks like stock KDE
rather than like the classroom — which is fair, because it is not part
of the classroom.

**It grants no privilege.** The classroom user has no sudo rule, and
anything needing root still needs the administrator's own account and
password. `shell_access` was always a barrier in the interface, never a
privilege boundary.

Konsole is a package dependency, so the route exists on every machine.
Its own entry is shadowed from `/usr/local/share/applications` with
`NoDisplay=true`, leaving Konsole's file exactly where its package put
it.

One thing found while testing, and kept as a second layer rather than
removed: **Konsole ships `X-KDE-Shortcuts=Ctrl+Alt+T`**, a chord a great
many people know. The shadow entry blanks it, but the registration comes
from Konsole's own file and survives that — so it is still registered.
It is also inert: Konsole's entry carries
`X-KDE-AuthorizeAction=shell_access`, and with the classroom's
`shell_access=false` the launch is refused. Measured: invoking that
component over D-Bus opened nothing.

Nothing is pinned to the panel. A task button appears only while a
terminal is open, and closing it returns the bar to three launchers.

**Needs the hardware.** The chord itself has never been pressed — key
injection cannot reach the nested session in this lab. What is verified
is that the shortcut is registered from the packaged entry and that its
action opens a shell.


## Long-Escape to turn the television off: it should change

The gesture asked for was: hold Escape, silence for three seconds, then a
five-second visible countdown, cancel on release. Deliberate, hard to
trigger by accident, and a clear intent.

### What was measured

* **KGlobalAccel accepts a bare `Escape`.** A probe entry declaring
  `X-KDE-Shortcuts=Escape` was registered and given its own component. So
  the binding is possible.
* **Press *and release* are both observable.** The component's D-Bus
  interface carries `globalShortcutPressed` **and**
  `globalShortcutReleased`. Hold duration and cancel-on-release are
  therefore expressible without any input daemon of our own.
* **KWin's scripting API has no key events at all** — `registerShortcut`
  and screen edges, and nothing that reports a key going up.

### What was not measured, and why it decides the answer

Whether a registered global shortcut **takes the key away from
applications**. Key injection cannot reach the nested session in this
lab, so this could not be pressed.

The mechanism says it does: on Wayland, KWin matches global shortcuts in
an input filter that runs before the event reaches the focused surface,
and a match stops propagation. That is how `Meta+Q` never arrives at an
application. A bare `Escape` bound globally should therefore stop
reaching anything — no leaving a fullscreen video, no dismissing a Chrome
dialog, no closing the Parent Call card.

**This is inference, not a measurement, and it is a thirty-second bench
test**: bind the probe entry above, press Escape in a fullscreen video,
and see whether it leaves fullscreen.

### The recommendation

**Change the gesture.** Even if Escape were forwarded as well as
observed, the whole ceremony would rest on a global grab of the key an
appliance uses most, and a countdown driven from the process holding
that grab is an input daemon in all but name. That is the fragile thing
the classroom keeps removing.

Two clean alternatives, both using mechanisms already proven here:

1. **Hold-to-confirm on screen.** A television control where the volume
   applet is now: press and hold it, a countdown runs, releasing
   cancels. Press, hold and release inside an application's own surface
   are ordinary Qt and need no global input at all. This keeps every
   property the gesture was for — deliberate, visible countdown,
   cancel-on-release — and costs nothing in reliability.
2. **A modifier chord**, the same mechanism as the maintenance terminal
   and proven to work in this session. Instant rather than ceremonial,
   but impossible to press by accident. Worth adding as a second route
   for somebody who cannot find the mouse.

If a keyboard hold is still wanted after the bench test, it should be on
a key the classroom does not otherwise use — never Escape.

## The television control service

Unchanged in shape from the previous checkpoint, and now with the
gesture question answered:

```
panel control  /  chord                 presentation only
        |
        v
ekklesia-classroom-tv.service           small, supervised, ours
        |
        +-- backend: CEC over the adapter
        +-- interface: on, off, volume up, volume down, mute, input
```

* The keyboard and the panel request **"TV off"**. They never speak CEC.
* The service decides how. CEC hardware can change without the desktop
  noticing.
* The same service will own automatic TV-on at session start, volume,
  mute and input, and it is why the computer's own volume applet is
  expected to leave the bar.
* Supervised and self-recovering, the same way the audio policy is.

**No CEC code has been written and no protocol has been guessed.** The
adapters arrive today; the commands get measured before anything is
built on them.

## The upgrade that failed

The clean-install result was real and the migration was not. A classroom
machine that had been through the sway build and then the Hyprland
experiment took the 0.1.45 package and came up as **stock Debian Plasma**:
kickoff, a pager, a full system tray, the Debian wallpaper, the old Waybar
still across the top, mako still catching notifications — and then a lock
screen, on an account that has no password. Somebody had to give the
appliance account a password over SSH to get back in.

None of that was visible here, because the lab had been answering an
easier question than the one a room asks.

### Reproducing it

One line of the harness:

```
tools/lab/lab plasma-up:  -e XDG_CONFIG_DIRS=/etc/ekklesia-classroom/xdg:/etc/xdg
```

The lab had been handing the session under test the very setting whose
delivery was the thing in doubt. Removing it and starting the session the
way a machine does reproduced the failure exactly: 23 applets, kickoff,
pager, system tray, Debian wallpaper — `docs/screenshots/migration-before.png`
is that screen, and it is the teacher's screen.

### Root causes

**1. The classroom's settings never reached the session.** Everything the
room is — the panel layout, the lock screen that must never appear, the
idle behaviour, every Kiosk restriction — lives in
`/etc/ekklesia-classroom/xdg`, and reaches Plasma only if that directory
is in `XDG_CONFIG_DIRS`. It was set in `/etc/environment.d`, which
systemd's **user manager** reads. SDDM starts the session through PAM, and
PAM does not read `/etc/environment.d`. Debian's own
`/etc/xdg/plasma-workspace/env/env.sh` then set the variable from scratch,
because it was empty, and `startplasma` pushed its own environment back
into the user manager — so the value was not merely bypassed, it was
overwritten for every user service too. Measured in the session that came
up:

```
XDG_CONFIG_DIRS=/home/classroom/.config/kdedefaults:/etc/xdg:/usr/share/desktop-base/kf5-settings
LookAndFeelPackage = org.debian.desktop
Autolock           = (unset, so on)
shell_access       = (unset, so allowed)
```

The stock panel, the lock screen and the absence of every Kiosk
restriction are all that one line.

**2. Deleting the panel configuration made it worse.** The desktop reset
removes `plasma-org.kde.plasma.desktop-appletsrc` before the shell starts
so that the bar always comes from the package. With the look and feel
unresolvable, Plasma rebuilt the **Debian** default layout instead. The
reset was correct and was pointed at the wrong answer.

**3. Naming a colour scheme does not produce one.** `ColorScheme=EkklesiaDark`
is a label; KConfig reads the actual colours from `[Colors:*]` groups in
kdeglobals, and nothing was putting them there except a technician having
run `classroom-theme` once by hand. The clean-install screenshots looked
right for a reason the package did not own. A machine with no user
profile got Breeze light — confirmed here the moment a profile was
cleared.

**4. A stale user profile outranks the package.** `~/.config/kdeglobals`
sits ahead of every system directory, and `~/.config/kdedefaults` ahead of
ours. A migrated machine carried a Breeze-light palette in both.

**5. The old shell was still being started.** `waybar.service` was
activated through `graphical-session.target.wants` — and, found only by
running the crash-recovery suite on a migrated machine, **mako came back
through D-Bus**: the panel was killed, something sent a notification while
nothing owned `org.freedesktop.Notifications`, and D-Bus started mako from
the file `mako-notifier` ships. Deactivating the systemd unit would not
have been enough.

And one more that had not bitten yet: `device.conf` still said
`CHANNEL=hyprland`, so the next release published on that channel would
have handed the room the Hyprland experiment back.

### The fix

| | |
| --- | --- |
| `config/plasma/env/zz-ekklesia-classroom.sh` | new. `/etc/xdg/plasma-workspace/env/` is sourced by `startplasma` for every session; the name sorts after Debian's `env.sh`, so it appends rather than replaces, and it is a no-op if the directory is already there. This is the root fix. |
| `config/plasma/xdg/kdeglobals` | `LookAndFeelPackage[$i]` — per-entry immutability, so no leftover profile and no stray write can answer that question differently. The palette stays writable, because `classroom-theme` may change it. |
| `tools/build-kdeglobals` | new. Composes the shipped kdeglobals from the session policy **and** `EkklesiaDark.colors`, so the room is dark because the package says so. One source of truth: it composes, it does not duplicate. |
| `scripts/classroom-desktop-reset` | asserts the cascade and repairs it for the shell about to start if it is wrong; removes another desktop's look and feel defaults and a foreign palette; keeps an Ekklesia one; clears a user power profile. |
| `scripts/classroom-migrate` | new. Stops, deactivates and masks the old shell's units, removes activation from all three directories it can live in, removes hand-written unit files that no Debian package owns, clears old autostart entries, removes the login shell that used to start sway, and migrates `device.conf`. Run from `postinst` on every install. |
| `config/dbus/fr.emersion.mako.service` | new. Shadows mako's D-Bus activation from `/usr/local/share`, where the session bus looks first. `Exec=/bin/false`, which is what a machine with no notification daemon does anyway. |
| `config/plasma/xdg/powermanagementprofilesrc` | profiles immutable at the profile level, not just on the button subgroups: PowerDevil loads an idle action when it finds a group for it, so a writable profile is one a leftover user file can add a suspend to. |
| `config/systemd/logind-ekklesia-classroom.conf` | `IdleAction=ignore` as well. |
| `config/sddm/ekklesia-classroom.conf` | uid range 1000–1999. The first migrated room's classroom account was uid 1001 and would not have appeared in the greeter at all. |

### What device.conf means now

`COMPOSITOR` and `HYPR_APPEARANCE` are removed on upgrade. There is one
desktop stack and nothing left for them to choose; a stale value is an
instruction this package cannot carry out.

`CHANNEL=hyprland` becomes `CHANNEL=classroom-v2`. Not `stable` and not
`canary`: both are the sway line, and a release published there would
convert a v2 machine back. **That channel is not published yet**, so a
migrated machine takes no updates until it is — which is the honest state
of an unpublished experiment, and better than being quietly reverted.
Everything else in the file, the broker password included, is rewritten
line by line and byte-for-byte.

### The tests that would have caught it

- `tools/lab/lab plasma-up` no longer sets `XDG_CONFIG_DIRS`. The package
  has to put it there, the way it has to on a machine.
- `tools/lab/lab reboot` — a real restart of the machine under test: new
  PID 1, new user manager, every drop-in and generator read again. **SDDM
  autologin genuinely runs here**: it authenticates the classroom through
  PAM and launches the Plasma session, and then has no display hardware to
  draw on. Both scenarios now go through it.
- `tools/lab/converged-check` — 60 properties of a converged machine,
  asked of the running system and never of the repository. Both scenarios
  run the same list, because a fresh install and a migrated one have to be
  indistinguishable from a teacher's chair.
- `tools/lab/dirty-upgrade` — the Hyprland package actually installed,
  with sway, waybar and mako behind it; Waybar activated in all three
  directories; an autostart entry; a device.conf asking for a compositor
  that is gone; a Breeze-light profile in both places that outrank the
  package; a stock panel already built; and a user power profile that
  would suspend the room. Then the new package, a reboot, and the
  questions.
- `tests/test-migration.sh` — 41 source-level checks, one per reason the
  failure happened.

### Results

| | |
| --- | --- |
| dirty upgrade → converged | 60 / 60 |
| installed a second time over itself | 60 / 60, device.conf unchanged |
| clean install → converged | 60 / 60 |
| panel killed eight times | back every time, 2.2–7.4s |
| compositor killed twice | 0.1–0.4s |
| audio policy killed three times | active every time |
| the room's light theme across a logout | survived |
| every test script | 11 / 11 |

`docs/screenshots/migration-after.png` and `v2-from-package.png` are the
migrated machine and the fresh one. They are the same desktop.

### One regression this pass made and caught

The first version of the reset deleted `~/.config/kdedefaults`
unconditionally. Plasma treats that directory as the record of which look
and feel is in force, so deleting it made Plasma re-apply the look and
feel at every login — which throws away the room's chosen palette.
Measured: `classroom-theme light`, log out, and the bar came back dark.
The rule is now whose the defaults are: the classroom's are kept, another
desktop's are removed.

## Unresolved risks

In the order I would worry about them.

1. **DVD playback has never run end to end on this desktop.** The port off
   sway is done and nothing asks a compositor anything, but the lab has a
   drive with no readable disc and no libdvdcss, so VLC exits before a
   picture. A room that uses DVDs should not take this build until a real
   disc has played, the cover has dropped at the right moment, and eject
   has returned cleanly to the desktop.
2. **The loading cover is now timed, not observed.** It used to wait for
   the window manager to confirm VLC was fullscreen. It waits for a floor
   instead, because VLC's own fullscreen flag was measured to be the
   option it was given rather than a report about its window. On real
   hardware the disc is far slower than the floor, so this should not
   show — but if the cover ever drops onto a black VLC window, this is
   why, and the fix is to raise `MINIMUM_COVER_SECONDS`.
3. **Parent Call has never had a real key pressed into it.** Keyboard
   injection cannot reach the nested session in this lab at all — the
   same limit that stopped it reaching Chrome — and the one tool that
   tries disturbs the session enough to close the card. The name was
   typed through a lab-only `--child` argument. **Type a name on the
   bench before a Sunday.**
4. **SDDM has never put a picture on a screen.** More is known than
   before: in the lab it really does autologin, authenticating the
   classroom through PAM and launching the Plasma session — that is now
   one of the checks. What it cannot do in a container is find a display
   to draw on, so everything from the compositor's first frame onwards is
   still a bench test. It remains the first thing to check on a VM or a
   bench machine.
5. **No real audio hardware has been through the policy.** The decision is
   well tested; applying it is not. A wrong `pactl set-card-profile` on
   real hardware is a silent room.
6. **Plasma is a much larger surface than sway.** More code, more services,
   more that can regress in a Debian point release. The mitigations are
   that all of it is supervised, that Debian 13 is frozen apart from
   security updates, and that the OTA channel structure already lets a
   build be held back. But it is a real trade and it should be named.
7. **Performance is unmeasured on classroom hardware.** Everything here ran
   on llvmpipe, which says nothing useful about an old office machine with
   Intel graphics. Plasma with compositing is heavier than sway.
8. **Chrome remains a third-party repository.** Unchanged from today, but
   still the one part of the stack Debian does not update.
9. **The wallpaper is a stand-in.** The real illustration has not been seen
   against this palette, and is to be supplied separately.
10. **The disc launcher tracks the drive, not the disc.** A room with a
    drive shows the DVD button whether or not anything is in it.
11. **The power button has never been pressed.** Both layers are
    configured, packaged, and read back correctly, but nothing in a
    container has a power button.
12. **The maintenance chord has never been typed.** The shortcut is
    registered from the packaged entry and its action opens a shell —
    verified over D-Bus — but key injection cannot reach the nested
    session, so `Meta+Ctrl+Alt+Shift+K` itself is unpressed.
13. **Idle behaviour is configured and unobserved.** No suspend, no dim,
    no blank and no lock are all now in the package, immutable, and read
    back correctly from a migrated session. Nothing in a container goes
    idle, so none of it has been watched not happening. **Leave a bench
    machine alone for an hour.**
14. **The v2 channel does not exist yet.** A migrated machine is moved to
    `CHANNEL=classroom-v2` so that a stable or Hyprland release cannot
    take it back, and nothing is published there. Until it is, a v2
    machine takes no updates at all. That is deliberate; it is also a
    thing to remember before leaving one in a room.
15. **Ctrl+Alt+T is still registered.** Konsole's own entry declares it
    and the registration survives being shadowed. It is inert, because
    Konsole refuses to open a shell under the classroom's
    `shell_access=false` — measured — but it rests on that one
    restriction rather than on the chord not existing.

## Would I trust it on a classroom computer, unattended, for a Sunday?

**For a room that does not use DVDs: yes, after the checks below.** The
reasoning is not that Plasma is nicer. It is that the four failures the
church actually reported are all failures of code we wrote, three of them
are gone because the code is gone, and the fourth — the panel disappearing
— went from *reproducible on the third crash* to *survived eight kills* and
is now a supervised system service rather than a process started by a
compositor and forgotten.

**For a room that uses DVDs: not yet.** Finish the focus port and play a
real disc first.

Before any room:

1. Boot a bench machine from the package and confirm SDDM autologins, and
   that killing the session brings it back rather than a shell.
2. Put a television on HDMI, switch it on after the computer, and confirm
   sound arrives without touching anything, with the browser already
   open. The full procedure is under *Audio: how to test it on the
   hardware*.
3. Press Parent Call and **type a name with a real keyboard**. Then do it
   with the coordinator's mode off, and with the broker stopped.
4. **Press the power button.** Nothing should happen. Then hold it, and
   confirm the machine still dies — that is the recovery path and it
   must stay.
5. **Type Meta+Ctrl+Alt+Shift+K.** A terminal should open. Then try
   Ctrl+Alt+T and confirm nothing does.
6. Print to Elmer.
7. Play a DVD, if that room uses them: cover, picture, controls, eject.
8. Leave it running from Friday to Sunday.

## Alternate operating systems

None is required. The recommendation stays on Debian 13, which the classroom
already runs and already packages for.

If the church later wants Fedora KDE or Arch compared on real hardware, that
needs a VM this session could not create:

> **Recommended next candidate: none.**
> Debian 13 + Plasma 6.3 was actually tested, in a container, on this branch.
> A disposable VM is needed only for what a container cannot show:
> 4 vCPU, 8 GiB RAM, 60 GiB disk, a real GPU or working virtio-gpu,
> an HDMI-capable audio device, and an optical drive — to test DVD
> playback, audio switching against real hardware, SDDM autologin,
> display hotplug, and performance on classroom-class hardware.

The existing Debian classroom test VM should be kept.

## Checkpoint log

* Branch opened at `aadb1b8`; host recorded as unable to create a VM.
* Lab built; Plasma 6.3.6 running software-rendered at 1920×1080.
* Panel supervision measured, failure reproduced, drop-in written, re-measured.
* Classroom desktop written: colours, layout, window rules, Kiosk, launchers.
* Task states measured; minimise removed as a route.
* Secondary windows, print dialog, notifications, fullscreen, themes, lockdown
  all verified on a running session.
* Audio policy written with the failing room as a test.
* Cold starts repeated: eleven, identical.
* Package built, and the file conflict and the stale `postinst` it exposed
  both fixed.
* `tools/lab/from-package` run: fresh machine, `.deb`, session up, both
  applications launched, one button each.
* **Parent Call built** against the coordinator's own frozen contract,
  and proven end to end on a rig that rejects the church's networks
  before it starts.
* **Parent Call's mark** replaced twice and judged on a real panel.
* **The last of sway removed**: the DVD player asks no compositor
  anything, and `classroom-window`, `classroom_sway` and
  `classroom_chrome` are gone.
* **DVD moved out of the status row** into the applications, and the
  launcher now follows the machine's drive rather than `DVD_ENABLED`.
* **The panel is rebuilt from the package at every login**, so an update
  can reach a room that has already run.
* **Recovery re-measured against the packaged build**, not a hand-edited
  session.
* **The power button disabled at both layers**, packaged, and read back
  from logind after a reload that did not disturb the session.
* **A maintenance terminal behind one obscure chord**, declared in the
  package, hidden from every application list, granting no privilege.
* **Long-Escape investigated and recommended against**, with the two
  clean alternatives written down.
* **The migration failure found on a real room and fixed in the package**:
  the settings directory now reaches the session the way Plasma delivers
  it, the look and feel cannot be answered for by a stale profile, the
  palette is in the package rather than in somebody's home directory, and
  the old shell is stopped, deactivated, masked and — the one that was
  only found by killing the panel — unable to come back through D-Bus.
* **The lab stopped flattering the package**: it no longer sets the
  session's configuration path by hand, it restarts the machine, and it
  asks a fresh install and a machine upgraded from the Hyprland
  experiment the same sixty questions. Both answer them identically.

**Next**, in order:

0. **The thirty-second Escape test**, before anything is built on the
   gesture: bind a probe entry to `Escape`, press it in a fullscreen
   video, and see whether the video leaves fullscreen. That settles the
   one thing this pass could not measure.
1. **On the bench, tonight.** Type a name into Parent Call with a real
   keyboard. Switch a television on after the computer and listen. Play a
   disc. These three are the only things left that a container cannot
   answer, and each of them is a Sunday-morning path. Add the power
   button and the maintenance chord to that list.
2. Publish the v2 channel. `classroom-migrate` already moves a migrated
   room onto `CHANNEL=classroom-v2`, and nothing serves that manifest
   yet, so those machines are taking no updates at all. This is now the
   first packaging job rather than a tidy-up.
3. Take the upgraded VM through the same list by hand:
   `tools/lab/converged-check` is the shape of it, and the things a
   container cannot answer are the lock screen never appearing after an
   hour alone, and the machine still being there on Monday.
4. Bench-test SDDM on hardware: autologin all the way to a picture, and
   that ending the session brings the classroom back rather than a shell.
5. When the CEC adapters have been exercised, replace the computer volume
   applet with a television control, behind the service boundary in
   *Television control, and where CEC will fit*.
6. Live View, when the rest is quiet.