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ekklesiaandClaude Opus 5 f8ddfbe345 feat: make DVD playback a classroom surface, not a media player

Pressing DVD now enters DVD mode rather than opening VLC. VLC is still
the backend, because its dvdnav module is what decodes disc menus and
nothing else on Debian does that reliably, but nothing a person can see
or press belongs to it any more.

classroom-dvd-session owns the whole thing. It puts a full-screen black
layer-shell surface up the moment the button is pressed, starts VLC
behind it, and drops it once playback is actually on screen — so the
harsh cut from wallpaper to VLC's black window is gone, and no partial
VLC window or reserved dock strip is ever visible. A deadline drops the
surface regardless, because DVD mode must never leave a black screen
with nothing behind it.

The controls are a classroom bar on the overlay layer, the one layer
sway draws above a fullscreen window. It slides up when the pointer
reaches the bottom of the screen and hides again shortly after it
leaves. It is drawn from the dock's own stylesheet at the room's UI
scale, so it is the same surface, the same radius and the same white
icons. While hidden it only accepts the pointer in a thin strip along
the bottom edge, so a click on a disc menu goes to the disc.

The bar reaches VLC through an HTTP interface on loopback behind a
password generated per session, sending hotkey *actions* by name. That
is what makes the next part possible.

All 108 hotkeys VLC 3.0.23 defines are unset, then Space, Esc and the
arrow keys plus Enter are bound. Crop, aspect ratio, subtitles, audio
tracks and deinterlacing are no longer reachable by pressing a key at
random, and the arrow keys no longer change VLC's volume — the
television owns volume, and CEC will own it properly later.

Esc quits instead of leaving fullscreen. There is nothing to leave, and
leaving it was what stranded people on a black VLC window. Close, Eject
and Esc all ask VLC to quit and escalate to SIGTERM then SIGKILL if it
does not; when VLC exits by any route, including a crash, the session
ends and the classroom desktop comes back.

Verified against VLC 3.0.23 on Trixie: every argument accepted, every
control action accepted over the control interface, a wrong password
refused, and quit exiting cleanly. The surfaces were rendered under a
headless sway and screenshotted to check the bar against the dock.

Co-Authored-By: Claude Opus 5 <[email protected]>

2026-09-04 22:33:53 -05:00

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DVD support

DVD support is optional per classroom and off by default.

Enabling a room

Edit /etc/ekklesia-classroom/device.conf on that endpoint:

DVD_ENABLED=true

Then restart the session (reboot, or restart classroom-dock).

With DVD_ENABLED=false, or the key absent, the DVD button is not built at all and no drive polling happens. Older endpoints get a commented DVD_ENABLED=false appended on upgrade so the option is discoverable, which leaves their behaviour unchanged.

Behaviour

The dock polls the drive every two seconds with the CDROM_DRIVE_STATUS ioctl. That is a status query, so it does not spin the disc up.

State	Dock icon	Clicking the button
No drive connected	DVD logo held back at 55%	"No DVD drive is connected to this classroom computer."
Drive present, no disc	DVD logo held back at 55%	"No disc is in the drive. Insert a disc to get started."
Tray open	held back	"The disc tray is open. Insert a disc to get started."
Disc still being read	held back	"Reading the disc. Please try again in a moment."
Disc ready	DVD logo at full strength	Plays the disc

When a disc becomes ready, a DVD Ready notification is shown once. Discs never play on their own; playback always needs a button press.

The first poll after login only records what is already in the drive, so a disc left in over the week does not announce itself at every boot.

Playback: DVD mode

Pressing DVD does not open a media player. It enters DVD mode: a full-screen playback surface the classroom owns, with VLC decoding the disc behind it.

classroom-dvd-session runs the whole thing:

black backdrop   layer-shell TOP, covers wallpaper and dock while the
                 disc loads, hidden once VLC is on screen
VLC              fullscreen, drawn above the top layer by sway
control bar      layer-shell OVERLAY, the one layer sway draws above a
                 fullscreen window

VLC is still the backend because its dvdnav module is what decodes disc menus, and nothing else on Debian does that reliably. But nothing of VLC's own interface is exposed: no menu bar, no panels, no fullscreen controller, no cone, and no sway title bar.

The control bar

Move the mouse to the bottom of the screen and a bar slides up. It is the same dark translucent rounded surface as the dock, drawn from the same stylesheet at the same UI scale, so DVD mode feels like the same room. It hides again a second after the pointer leaves it, or after four seconds without movement.

Control	Does
⏮	Previous chapter
▶ / ⏸	Play or pause, showing which one it will do
⏭	Next chapter
☰	Back to the disc menu
⏏	Ejects the disc and leaves DVD mode
✕	Leaves DVD mode

While the bar is hidden it only accepts the pointer in a thin strip along the very bottom edge, so a click anywhere else goes to the disc menu rather than to an invisible bar.

The bar reaches VLC over an HTTP control interface on the loopback address, behind a password generated for that session alone. Commands are sent as VLC hotkey actions by name, which is why they keep working even though every key has been unbound.

The keyboard

All 108 hotkeys VLC 3.0.23 defines are unset, then these are bound:

Key	Does
Space	Play / pause
Esc	Leaves DVD mode
Arrow keys	Move around a disc menu
Enter	Choose the highlighted menu item

Nothing else responds. A volunteer cannot land on crop, aspect ratio, subtitle tracks, audio tracks or deinterlacing by pressing a key at random, and the arrow keys no longer change VLC's volume — the television owns volume.

Esc quits rather than leaving fullscreen. DVD mode is the whole screen, so there is nothing to leave, and leaving it used to strand people on a black VLC window with no way back.

There is no fullscreen toggle, because DVD mode is not a window.

Leaving

Close, Eject and Esc all do the same thing: ask VLC to quit, and if it does not, escalate to SIGTERM and then SIGKILL. When VLC exits — however it exits, including a crash — the session ends and the classroom desktop and dock come straight back. Nothing can leave a black window behind.

Only one DVD session can run at a time, however fast the button is pressed.

Commercial (CSS encrypted) discs

Most retail DVDs are CSS encrypted, and Debian cannot ship the decryption library. Unencrypted discs — curriculum discs, home-burned video — play without any extra work.

This is automatic. On any classroom with DVD_ENABLED=true, the provisioning service installs the codecs after the next boot. See provisioning.md.

To do it by hand, or to watch it happen:

sudo classroom-dvd-css-setup
classroom-dvd-css-setup --status

It enables the Debian contrib component in whichever APT source format the machine uses, installs libdvd-pkg, answers its debconf questions and builds libdvdcss. It only ever adds a missing component to an existing Debian entry, so repeated runs cannot produce a duplicate repository or a duplicate component, and third-party repositories such as Google Chrome's are never touched.

It needs the network and it compiles a package, which is why it runs from the provisioning service rather than the package postinst: the postinst executes while dpkg is still holding the apt lock.

Command line

classroom-dvd status    # drive node, drive state, whether VLC is installed
classroom-dvd toggle    # what the dock button does
classroom-dvd play      # start playback even if the drive is unsure
classroom-dvd eject     # open the tray

Permissions

Reading the drive needs group cdrom. The postinst adds the classroom user to it; that takes effect at the next login, which the OTA reboot provides. Without it the drive reads as absent.

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