feat: Presentations, for a teacher who downloaded tonight's session

PRESENTATIONS_ENABLED, off by default, independent of everything else. A
teacher downloads a session in ordinary Chrome and it is on the
Presentations screen a few seconds later, ready for the television. No
file manager, no import button, no Impress.

WHY NOTHING LAUNCHES A DOCUMENT APPLICATION. The brief was to use
existing presentation software, so the existing software was tried
first, on Debian 13, before any of this was designed. `soffice --show`
does start a real fullscreen slideshow — and needs XDG_SESSION_TYPE plus
a VCL plugin or it dies with "Failed to open display", shows a splash,
opened a "Tip of the Day: 1/225" dialog over the slides, and leaves the
Impress editor when the show ends. `okular --presentation` opens THREE
windows: the presentation, the ordinary document window behind it, and
an information dialog. zathura is not a presenter. pdfpc is the closest
and is another dependency with a presenter-console model. Every one of
them leaves an application on screen that can open any file on the
machine, and none of them knows there is a library to go back to.

So LibreOffice converts once, headless, at import, with no window on any
screen; poppler renders the pages; the classroom shows the pictures.
Measured: 0.34s for a ten-slide PPTX, 0.03s for its ten thumbnails,
0.10s for one slide at 1920px. That is not a new renderer — it is the
same engine Impress would have used live — and it means Escape is ours,
presenting is instant, and a PDF exported from Google Slides skips the
conversion entirely and keeps the appearance Google gave it.

THE THREE THINGS KEPT APART. The library thumbnail, the starting slide
and the retention clock are independent, because the first slide of a
Bible study session is a generic opening shared by every session and the
one that names it is usually the second. Quick Look chooses the picture;
it does not change where the slideshow starts and it does not count as
having presented anything. mark_presented() is called when a slide is
actually drawn, not when Present is pressed: an intention is not a
presentation, and a viewer that failed to start must not buy another
thirty days.

IMPORTING. The teacher's download is copied, never moved, renamed or
deleted. A file with a .crdownload beside it is still arriving. Wonder
Ink's own folder is not looked at. Two downloads of the same name are
two presentations, the second titled (2) — found in the lab, where a PDF
and a PPTX of one session both came out with the same name because the
import being named was excluded from the taken-titles set BY TITLE, and
a set holds one copy of a repeated string.

Metadata is written saying "importing" before any work, so a reboot
mid-conversion leaves a directory the next startup sweeps and imports
again. A file that cannot be converted gets a card saying so, offering
only Remove, with the teacher's download untouched.

Retention: 180 days never presented, 30 days from the last presentation,
every presentation starting the thirty over. The cleanup never touches a
presentation being shown, never leaves the library directory, and never
looks at Downloads.

The dock order is unchanged: Presentations is appended after the disc
player, so Wonder Ink, the browser and the player keep the places
teachers have been reaching for. There is a test for exactly that.

classroom-wonderink now asks feature() rather than carrying its own copy
of the default, so the panel and the command cannot disagree.

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

config/plasma/applications/ekklesia-presentations.desktop

@@ -0,0 +1,28 @@
+[Desktop Entry]
+Type=Application
+Name=Presentations
+GenericName=Slides
+Comment=Show a presentation that was downloaded in the browser
+# Drawn for this: a screen with a slide on it and a corner turned, which
+# is a presentation rather than a document or a photograph. Breeze's
+# view-presentation is a chart on a board, which in a church reads as a
+# business meeting. Uses ColorScheme-Text like the classroom's other two
+# marks, so it recolours with the session and needs no light-theme twin.
+Icon=ekklesia-presentations
+Exec=/usr/local/bin/classroom-presentations
+Terminal=false
+Categories=Office;Presentation;
+StartupNotify=true
+# How the panel matches the window on screen to this launcher. GTK sets
+# the Wayland app id from GLib.set_prgname, which classroom-presentations
+# sets to exactly this. A mismatch here is not an error anywhere — it is
+# silently two buttons on the panel instead of one.
+StartupWMClass=ekklesia-presentations
+# One window. Pressing the panel button again brings the library forward
+# rather than opening a second copy of it.
+X-GNOME-SingleWindow=true
+# Deliberately visible to the applications index, like the disc player and
+# Parent Call: the panel resolves its launcher through that index, and an
+# entry hidden from it gives the bar a blank page instead of the mark.
+# There is no application menu in this classroom for it to clutter.
+NoDisplay=false

config/plasma/lookandfeel/contents/layouts/org.kde.plasma.desktop-layout.js

@@ -12,19 +12,22 @@
 
 // WHICH APPLICATIONS THIS DEVICE OFFERS.
 //
-// classroom-desktop-layout rewrites the three lines between the markers
-// to match device.conf and this machine's hardware, and nothing else in
+// classroom-desktop-layout rewrites the lines between the markers to
+// match device.conf and this machine's hardware, and nothing else in
 // this file. Each application is its own line because each is its own
 // setting: a laptop taking children's church needs Wonder Ink and a tower
 // used for Bible study does not, so the shape of the machine is never
 // allowed to decide what it is for.
 //
-// All true here is the shipped default, which is what an existing
-// classroom must come up as.
+// The first three are true here, which is what an existing classroom must
+// come up as. PRESENTATIONS is false, which is what an existing classroom
+// must come up as too: no room has ever had it, and an upgrade may not
+// put a button on a bar nobody asked for.
 /* CLASSROOM-FEATURES-BEGIN */
 var WONDERINK = true;
 var DVD = true;
 var PARENT_CALL = true;
+var PRESENTATIONS = false;
 /* CLASSROOM-FEATURES-END */
 
 var WALLPAPER = "/usr/share/backgrounds/ekklesia/classroom-calm.png";
@@ -84,6 +87,27 @@ if (PARENT_CALL) {
     parentCall.writeConfig("maxSectionCount", 1);
 }
 
+// HELP, beside Parent Call and not in the row with the applications.
+//
+// Every room gets it: the manual is the one thing that is never optional,
+// because a teacher who needs it is by definition a teacher who does not
+// know where to look. It shows only the pages for the features THIS
+// device has — see classroom-manual — so the button means the same thing
+// in every room while what it opens does not.
+//
+// On the left, with Parent Call, for the same reason Parent Call is
+// there: it is not one of the room's applications, and putting it in the
+// middle row would move buttons teachers reach for without looking.
+var help = panel.addWidget("org.kde.plasma.quicklaunch");
+help.currentConfigGroup = ["General"];
+help.writeConfig(
+    "launcherUrls",
+    "file:///usr/share/applications/ekklesia-manual.desktop"
+);
+help.writeConfig("showLauncherNames", false);
+help.writeConfig("enablePopup", false);
+help.writeConfig("maxSectionCount", 1);
+
 var leftGap = panel.addWidget("org.kde.plasma.panelspacer");
 leftGap.currentConfigGroup = ["General"];
 leftGap.writeConfig("expanding", true);
@@ -114,6 +138,17 @@ if (DVD) {
     launchers.push("applications:ekklesia-dvd.desktop");
 }
 
+// LAST, AND THAT IS THE WHOLE REASON IT IS HERE.
+//
+// Every existing room has Wonder Ink, the browser and the disc player in
+// that order, and teachers have been pressing them in that order for
+// months. Appending keeps all three exactly where they are on every
+// machine that upgrades; putting Presentations anywhere else in the row
+// would move a button somebody reaches for without looking.
+if (PRESENTATIONS) {
+    launchers.push("applications:ekklesia-presentations.desktop");
+}
+
 tasks.writeConfig("launchers", launchers.join(","));
 
 // THE ORDER STAYS PUT WHEN AN APPLICATION OPENS.