feat: give every room the broker, one scale, and its own panel back
Little Waders took the Plasma build and reported what a container cannot. A disc player on a machine with no optical drive, a clock nobody at the back of the room could read, a browser at half the size of the panel around it, and Parent Call with no broker to call. The broker is the same for every classroom, so it is a default now and not something to fill in room by room. classroom-migrate brings an existing room to the same place without touching its name, its username or its password, and Parent Call distinguishes a broker it cannot reach from one that was never set up: those send somebody to look at completely different things. The disc player's detection was right and ran too late — alongside the session rather than before it, and the panel is built from the layout the moment a session starts. It runs before the display manager now, and again from udev when a drive is plugged in. UI_SCALE had a ceiling of 1.5, which cannot express a 4K television; a clock pinned at 15 points, which is the same size at every scale; and a browser that was never told the number at all. All three are fixed and the room doubles together at 200%. This also brings 0.1.47's work into the repository, where it had only ever existed in a build directory under /tmp: the hidden display dialog, its authenticated writer, the polkit action, and the church's own wallpaper. One piece of it is deliberately left out. The custom volume display needed a shell package of our own, and with one selected plasmashell builds no panel at all — measured twice, with that build's own files, on a classroom that deletes its panel configuration at every login by design. The lab connected to the real church broker the moment the package defaulted to it. Nothing was left behind, which was checked, but the guard that should have stopped it had never worked: it used iptables, which the lab image does not have, and probed with /dev/tcp under dash, where that always fails. Both reported success. Co-Authored-By: Claude Opus 5 <[email protected]>
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ekklesia
co-authored by
Claude Opus 5
Claude Opus 5
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# UI scale
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# Classroom display size (Plasma v2)
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Every classroom gets the same design at a size that suits its TV. A 32"
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panel a few feet from the children and a 65" set across a hall want
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different sizes of the same room, not different rooms.
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Each room keeps its own `UI_SCALE` in `/etc/ekklesia-classroom/device.conf`.
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Package upgrades preserve the value. Plasma applies it at every classroom login.
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Native display resolution is unchanged.
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## Changing it
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## Administrator setting
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Edit `/etc/ekklesia-classroom/device.conf` on that endpoint:
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On the classroom keyboard press **Meta+Ctrl+Alt+Shift+D** to open Display size.
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It is hidden from application lists and the teacher's panel. Saving requires
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administrator authentication through polkit; the keyboard shortcut grants no
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privilege. Choose a percentage and press Save and apply. Canceling the password
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prompt leaves the saved setting unchanged.
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Start at **200% for a 4K TV**, which gives 1920×1080 logical space while retaining
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3840×2160 output. The offered values are 100, 125, 150, 175, 200, 225, 250 and 300%.
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The choice applies to all connected, enabled displays on that classroom computer.
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For SSH administration, the fixed-purpose helper can also be run as root:
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```
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UI_SCALE=1.25
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sudo /usr/local/bin/classroom-set-scale 2
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```
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Then restart the classroom shell:
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It writes only UI_SCALE, preserving room configuration, broker credentials and
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file ownership and permissions. The new size takes effect at the next classroom
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login, or by running `classroom-scale` inside the classroom's graphical session.
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The hidden window saves and applies in one operation.
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```
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sudo systemctl restart getty@tty1
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```
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## Implementation and validation limits
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That ends the session and the autologin brings it straight back at the
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new size. A reboot does the same. Nothing else needs touching, and no
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CSS or source file is ever edited to change a room's size.
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`classroom-scale` uses `kscreen-doctor`; the login autostart runs only in KDE and
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the script applies only to the classroom account. Values read from older/manual
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configurations remain clamped to 0.8–3.0; invalid/nonfinite values become 1.0.
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The helper accepts only the window's predefined choices, takes no paths, and
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writes the root-owned settings file atomically. Polkit requires auth_admin for
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every save, with no retained authorization.
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## What it scales
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Hardware checks required: shortcut registration, administrator authentication,
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200% at 4K, logout/reboot persistence, and Chrome/Parent Call/DVD sizing. XWayland
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applications may be softer than native Wayland applications when scaled.
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**Everything.** UI_SCALE is a property of the television, not of one
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program, so it is applied where it reaches the whole session: sway's
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output scale.
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## Wallpaper in the v2 package
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- Chrome's tabs, omnibox, toolbar icons and menus
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- VLC, and any other application's own interface
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- The dock, the clock, notifications and the DVD control bar
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- Mouse hit targets, because they scale with the widgets
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The approved background source is `config/wallpapers/classroom-calm.png`. The
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package installs it at `/usr/share/backgrounds/ekklesia/classroom-calm.png`, the
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path used by the packaged Plasma layout. The layout is rebuilt at login, so
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upgraded classrooms receive the package wallpaper without per-room copying.
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The display mode is **not** changed. The panel stays at its native
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1920x1080. Only the logical coordinate space shrinks, which is what
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makes everything drawn in it larger:
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## What the one number reaches
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| UI_SCALE | Logical space | Roughly |
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| --- | --- | --- |
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| 0.8 | 2400x1350 | Small or close-up panel |
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| 1.0 | 1920x1080 | Default. 32–50" classroom TV |
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| 1.25 | 1536x864 | Large room, or a set viewed from further back |
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| 1.5 | 1280x720 | 65"+ |
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`classroom-ui-scale` prints it, clamped, and everything that cannot read
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the display scale for itself asks that command rather than the file:
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Anything outside 0.8–1.5 is clamped, and anything that is not a number
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falls back to 1.0, so a typo in device.conf cannot produce an unusable
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shell.
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* **Plasma** — the panel, the clock, notifications, the volume display and
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every dialog, because `classroom-scale` sets it as the display's scale
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through `kscreen-doctor` at every login.
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* **Chrome and Wonder Ink** — `--force-device-scale-factor`, because
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Chrome on Wayland was measured not to follow the compositor's output
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scale on its own. It is the same number, not a second scaling: Chrome
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replaces its detected scale with it.
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* **The disc player's own surfaces** — they are measured in the logical
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pixels the compositor is already scaling, so they follow without being
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told.
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## Measured
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Against 1920x1080 under sway, with Chrome 152:
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| | 1.0 | 1.25 | 1.5 |
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| --- | --- | --- | --- |
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| Chrome tab strip | 40px | 49px (x1.23) | 59px (x1.48) |
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| sway title bar | 25px | 31px (x1.24) | 38px (x1.52) |
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| Classroom dock | 74px | 92px (x1.24) | 110px (x1.49) |
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Everything scales once, together.
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## Why our own surfaces do not scale themselves
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`classroom-scale` runs first in the sway config and sets the output
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scale. From then on the dock, the notifications and the DVD control bar
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are measured in the same logical pixels sway is already scaling, so they
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must render **unscaled** — `SHELL_SCALE` in `classroom_config.py` is
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`1.0`. Scaling them again would apply UI_SCALE twice and the dock would
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come out half again too big.
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The stylesheet templates still take a scale, and `SHELL_SCALE` is the
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one place it comes from. If compositor scaling ever has to be abandoned,
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setting it back to `ui_scale(config)` restores per-surface scaling
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without touching a template.
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## Tradeoffs
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**GTK 3 has no fractional scaling.** At UI_SCALE=1.5 sway advertises an
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integer scale of 2 to GTK, which renders at 2x, and sway scales the
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result down to 1.5x. The dock is the right size but very slightly softer
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than at 1.0. On a TV at classroom distance this is not visible.
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Icons have to be drawn for that themselves. `new_from_file_at_scale`
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rasterises an SVG at its *logical* size, and the compositor then
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enlarges that finished raster — which made icons visibly soft on a 24"
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monitor while the clock text beside them stayed sharp. `classroom_icons`
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renders each SVG at `size x scale_factor` physical pixels and hands GTK
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a cairo surface carrying that device scale, so the artwork lands at the
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display's real density and the layout is unchanged. Measured on the
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Chrome icon, peak edge contrast at UI_SCALE 1.5 went from 49 to 83 out
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of 255, and at 2.0 from 37 to 82; at 1.0 it is identical to before.
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**XWayland is softer at fractional scale.** X11 clients have no concept
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of a fractional output scale, so sway renders them at the logical size
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and scales the buffer. Measured on terminal text, scale 1.5 produced
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about 50% more intermediate-tone pixels than scale 1.0 — real, modest
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softening.
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VLC is the only XWayland application in the classroom, and in DVD mode
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none of its interface is on screen: only video, from a 720x480 disc
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being upscaled regardless. Chrome runs on Wayland natively and is sharp
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at every scale, which is what matters for reading.
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At UI_SCALE=1.0 nothing is scaled at all and the session is identical to
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one with no scaling.
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The clock is the one thing that used to be left behind. It was pinned at
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15 points, which is the same 15 points at every scale, and on a 4K
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television it was a clock nobody at the back of the room could read. It
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is sized by the bar now.
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