ekklesiaandClaude Opus 5
de5025ad22
Teachers prepare a lesson across several tabs — the lesson, its video,
the activity — and app mode is the one thing that cannot give them that.
Chrome cannot be asked for "tabs but no omnibox". App mode has no tabs; a
normal window has an address bar and no policy, flag or extension removes
it; tabbed web apps need a manifest on a site that is not ours and push
off-origin links out into a normal browser window, which is the whole of
what this design exists to prevent. So the tab strip is ours, and the
engine is Chromium either way.
QtWebEngine, from Debian, measured before it was chosen rather than
after. The usual and correct objection is codecs: on Debian 13 it reports
H.264, AAC, MP3, VP8 and VP9 all playable, MediaSource supports avc1,
mp4a and vp9, and a 720p H.264 file decoded and played to the end in the
lab. app.wonderink.org loads, and its sign-in is an ordinary email and
password form rather than a Google flow that would mind an embedded
browser. The user agent has the QtWebEngine token stripped so a site
gating on it sees the Chromium this actually is, and Widevine is handed
over from Chrome's own bundle when the machine has Chrome, which a
classroom always does.
[ Lesson ] [ Video ] [ Activity ]
The strip appears only above one tab, so an ordinary lesson looks exactly
like the application it replaces. A tab can only come from the lesson —
target=_blank, window.open, a middle click, a Ctrl+click — and there is
no address bar, no search and no button that makes a blank tab. No
allowlist of domains either, on purpose: a list would have to be right
about every video service a lesson might ever embed.
Three bugs the lab caught and this fixes. A lesson calling window.print()
did nothing at all, which is worse than no print button because a teacher
concludes the printer is broken; printRequested is now bound to the page
that asked. Leaving fullscreen left the window 200 pixels wide in the
corner — a window that has only ever been maximised has no ordinary
geometry to return to — so the fullscreen bit is cleared rather than
maximised being re-requested. And the Present view video failure written
up in docs/wonder-ink.md is acted on at last: that investigation named
the autoplay gesture chain as the likeliest cause and declined to fix it,
because in Chrome the only lever governed the ordinary browser as well.
Here it does not — this profile is Wonder Ink and nothing else — so a
lesson may start its own video and no other page in the room may.
Reproduced both ways in the lab with an unmuted video started by a script
with no gesture: NotAllowedError at Chrome's default, playing as shipped.
That is not proof Present view is fixed; the lab has no Wonder Ink
account, and candidates 2 and 3 in that document are still open.
Measured on a rebooted machine, from the package: tabs open from a link
and from window.open, switch, and close; closing one leaves the others;
closing the last closes Wonder Ink; H.264 video plays and fills the
display in fullscreen and comes back maximised with its tabs; the print
dialog offers the room's own Elmer queue; a download lands in ~/Downloads;
back and forward work from a right-click menu that is built rather than
filtered; pressing the panel button twice raises one window rather than
starting a second on the same profile; KWin reports the window as
ekklesia-wonderink, which is one panel button and not two.
Separate from the browser as before, in its own profile, with cookies
that live only as long as the window — what the Chrome policy did for
wonderink.org, and the reason closing Wonder Ink ends a teacher's
session. Chrome's old profile directory is left untouched beside it, and
the browser's own policy is not edited by any of this.
Wonder Ink is now optional per device, through WONDERINK_ENABLED in
device.conf, because one future device is a laptop that will not have it.
It rides the mechanism the disc player already uses: one marked line in
the packaged layout, edited by classroom-desktop-layout. False takes the
launcher off the panel and makes the command refuse to start; the
browser, Parent Call and the disc player are untouched and the panel
stays balanced. Absent means yes, so every existing room is unchanged.
One scale, still. Chrome has to be handed UI_SCALE because it was
measured not to follow the compositor; Qt does follow it — devicePixelRatio
2.0 at UI_SCALE=2.0, measured — so Wonder Ink is deliberately not told,
or the room would get it twice.
Co-Authored-By: Claude Opus 5 <[email protected]>
10 KiB
Wonder Ink
Wonder Ink is a lesson application, not a browser: its own window, its own profile, and no way from it into the rest of the web.
Since 0.2.1 it has tabs.
Why it stopped being Chrome
It used to be google-chrome --app=https://app.wonderink.org/. App mode
gives exactly the window a classroom wants — no tab strip, no address bar,
reads as a program — and teacher feedback then found the thing app mode
takes away is the thing they need. A lesson is prepared across several
tabs: the lesson, its video, the activity.
Chrome cannot be asked for "tabs but no omnibox". App mode has no tabs. A
normal window has tabs and an address bar, and no policy, flag or
extension removes the address bar from it. Tabbed web apps come closest,
need a display_override in a manifest on a site that is not ours, and
push off-origin links out into a normal browser window — which is the
whole of what this design exists to prevent.
So the tab strip is the classroom's own, in classroom-wonderink, and the
engine is Chromium either way.
Why QtWebEngine
python3-pyqt6.qtwebengine, from Debian, updated with the rest of the
system.
The usual and correct objection is codecs, so it was measured before it was chosen. On Debian 13, QtWebEngine 6.8.2 (Chromium 122):
canPlayType H.264, AAC, MP3, VP8, VP9 |
all "probably" |
MediaSource.isTypeSupported avc1, mp4a, vp9 |
all true |
| a 720p H.264/AAC file | loaded, played to the end, 1280×720 |
app.wonderink.org |
loads; the sign-in is an ordinary email and password form, not a Google flow that would mind an embedded browser |
Two further things the shell does for the same reason:
- The user agent has QtWebEngine's own token stripped, leaving a plain Chrome string. The engine really is that Chromium, and a site gating on the UA should not see something it has never heard of.
- Widevine is handed to it from Chrome's own bundle when Chrome is installed, which on a classroom machine it always is. A lesson whose video service wants DRM is not stopped by the engine change. Absent, the flag is not passed and nothing else is affected.
What a teacher gets
[ Lesson ] [ Video ] [ Activity ]
The strip appears only when there is more than one tab, so a room with one lesson open looks exactly like the application this replaced. Each tab has a close button. Closing the last one closes Wonder Ink; closing any other leaves the rest alone.
A tab can only come from the lesson: a link the site opens in a new window, a middle click, a Ctrl+click, "open in a new tab" in the menu. There is no address bar, no search, and no button that makes a blank tab. That is the seam the whole design turns on — Wonder Ink can take a teacher anywhere it needs to, including a video CDN nobody told us about, and a teacher cannot take themselves anywhere.
There is deliberately no allowlist of domains. A list would have to be right about every service a lesson might ever embed, and the day it is wrong a teacher is standing in front of a class.
The right-click menu is built rather than filtered, so a future Qt cannot grow view-source or save-page back into it without somebody noticing in the code: back, forward, reload, open in a new tab when there is a link, cut/copy/paste in a text field, print.
Keys: Ctrl+W closes a tab, Alt+Left and Alt+Right navigate, Ctrl+P prints, Ctrl+Tab switches. Ctrl+T, Ctrl+N and Ctrl+L are deliberately unbound.
What stayed the same
- A separate profile from the ordinary browser. A teacher's Wonder Ink sign-in and the room's shared YouTube account are different sessions in different storage that cannot reach each other. The browser is still Chrome and nothing in this change touches it.
- Cookies live only as long as the window. This is what the Chrome
policy's
CookiesSessionOnlyForUrlsdid for wonderink.org, and it is the reason closing Wonder Ink ends the teacher's session rather than leaving the next person signed in as the last one. The whole profile rather than one domain now, because this profile only ever goes where a lesson sends it. If a room ever wants sign-ins to survive, it is the one linesetPersistentCookiesPolicyinclassroom-wonderink. - The old Chrome profile is left where it is, at
~/.local/share/ekklesia-classroom/wonderink. The new one iswonderink-shellbeside it, so rolling back to 0.2.0 finds the old one intact. - One scale for the room. Chrome has to be handed
UI_SCALEbecause it was measured not to follow the compositor on Wayland. Qt does follow it — measured atUI_SCALE=2.0, where a Qt client on that session reportsdevicePixelRatio 2.0without being told anything — so Wonder Ink is deliberately not told, or the scale would be applied twice.
Turning it off
One future device is a laptop that will not have Wonder Ink at all.
WONDERINK_ENABLED=false
in /etc/ekklesia-classroom/device.conf, then
sudo classroom-desktop-layout and a logout. The launcher comes off the
panel, the command refuses to start and says why, and nothing Wonder Ink
owns runs. The browser, Parent Call and the disc player are untouched, and
the panel stays balanced because the applications are centred rather than
placed.
The setting is read the same way the disc player's line is written: one
marked line in the packaged layout, edited by classroom-desktop-layout.
Absent, it means yes — every room that has never heard of the setting is a
room with Wonder Ink.
Present view video
Fixed in 0.2.1. The investigation below is kept because it is what found the cause, and because the second and third candidates in it were never ruled out and may still matter.
Candidate 1 — the autoplay gesture chain — is the one the new shell can
act on, and does. Chrome refuses to begin audible playback that no click
asked for, and in Chrome the only lever was AutoplayAllowlist on the
policy that governs the ordinary browser as well; allowing autoplay
everywhere on a classroom machine was a real change and was deliberately
not made on a guess.
Wonder Ink is no longer governed by that policy. Its profile is Wonder
Ink and nothing else, so PlaybackRequiresUserGesture is turned off for
that profile alone and reaches no other page in the room. The ordinary
browser is a separate application with a separate policy and is not
touched.
Measured both ways in the lab, with a page that starts an unmuted video from a script with no user gesture — which is what Present view does:
| the setting at Chrome's default | AUTOPLAY BLOCKED: NotAllowedError — the exact error predicted below |
| the setting as shipped | AUTOPLAY OK muted=false, video playing |
That is the lab reproducing the failure and then not reproducing it. It is not confirmation that Present view itself is fixed, because the lab has no Wonder Ink account: if Present view still stops after this, candidates 2 and 3 below are where to look next.
The observation
On the classroom endpoint:
- Vimeo videos embedded in Wonder Ink play correctly in the normal lesson view.
- The same videos in Wonder Ink's Present view stop immediately when Play is pressed.
What this rules out
The system's video capability is fine. The same video, the same host, the same browser and the same codecs work a click earlier in the same session. Nothing is missing from the machine.
No codecs or media packages were installed for this, and none should be. Installing packages to fix a problem that is not a missing package would leave the classroom carrying software it does not need, and would not fix Present view.
Nothing in the system was changed for this.
The decisive test
Run it once at the endpoint. This separates "Wonder Ink" from "the classroom's Chrome configuration" in one step:
sudo mv /etc/opt/chrome/policies /etc/opt/chrome/policies.off
google-chrome --user-data-dir=/tmp/plain-chrome
That is a stock Chrome with a clean profile and no classroom policy at all. Sign in, open the lesson, press Present, press Play.
- Still fails — it is Wonder Ink, and nothing here can fix it. Report it to them with the console output below.
- Works — something in the classroom configuration is responsible, and the next section is where to look.
Afterwards:
sudo mv /etc/opt/chrome/policies.off /etc/opt/chrome/policies
rm -rf /tmp/plain-chrome
If it turns out to be this end
Two candidates, in order of likelihood. Neither has been applied.
1. The autoplay gesture chain
Chrome refuses to start audible playback without a user gesture. If Present view starts the player programmatically after its own view transition, the gesture from the Present click may not carry, and Chrome rejects the play. That would look exactly like this: fine when you click the player directly, dead when the view starts it for you.
This is stock Chrome behaviour, not a classroom setting — a plain Chrome on any machine would do the same, which is what the decisive test above checks.
Diagnostic: open DevTools (F12) in Present view and press Play. A rejected autoplay logs:
NotAllowedError: play() failed because the user didn't interact
with the document first.
If that appears, the fix is a scoped policy, not a global one:
"AutoplayAllowlist": ["https://app.wonderink.org"]
AutoplayAllowlist is recognised by Chrome 152 — verified against the
installed binary. It has deliberately not been added, because
allowing autoplay everywhere on a classroom machine is a real change and
should follow evidence, not a guess.
Since 0.2.1 this no longer applies to Wonder Ink, which is not a Chrome window any more and allows its own lesson to start a video without changing anything about the browser. See the top of this section. It still applies to the ordinary browser, where nothing has changed.
2. A popup window that sway tiles
sway tiles new windows rather than floating them. If Present view opens a second browser window, it gets a tiled geometry the site did not expect, and a player that is resized or re-parented mid-start can stop.
Diagnostic, while Present view is open:
swaymsg -t get_tree | grep -c google-chrome
More than one Chrome window means this is worth pursuing.
3. Not the classroom policies
For completeness, so nobody re-audits them: the managed policy in
/etc/opt/chrome/policies/managed/ sets first-run, sign-in, password
and homepage behaviour only. None of it touches media, autoplay,
iframes, fullscreen or site permissions.