fix: put the popup close button in the dock, and clear the printer location

Three things, none of them redesigns.

The close affordance for a secondary Chrome window was a separate
layer-shell surface anchored to that window's corner, repositioned by a
five-per-second poll. Any position change tore the surface down and
built another, so on real hardware it chased the window and flickered.
Removed entirely: the GTK button process, the geometry maths that placed
it, the --close-button mode that spawned it, and the poll loop that
drove it. The window helper no longer imports GTK at all.

The behaviour underneath it was right and is kept. The first Chrome
top-level is the classroom browser, tiled and borderless; later ones
float centred at about three quarters of the output. Creation order is
the only thing that can tell them apart — confirmed on a real session,
where every Chrome top-level shares app_id, shell, PID and a null
transient_for, and sway exposes no window properties for Wayland
toplevels at all. Titles are still not used. It now follows sway's own
window events instead of polling, so dragging a popup costs nothing.

Close moved into the dock, which was already on screen and does not
move, so it cannot chase anything. It appears only while a secondary
window is focused and runs kill on that one container. The helper
publishes which window that is; the dock watches the file rather than
polling. A stock sway title bar has no close button, so restoring the
border would not have solved this either.

Two bugs found by looking rather than by testing state. Chrome
renegotiates the size of a popup opened with explicit dimensions after
the resize returns, which left windows centred for a width they no
longer had; placement now settles and repeats once, at creation only, so
dragging is still free. And the dock's Close button came up empty
because show_all does not recurse into a no-show-all widget.

The printer's Location is now blank. CUPS prints it under the queue name
in every dialog, so "Ekklesia Classroom" was a second line the teacher
had to read past; the identity is one word. The already-configured check
includes Location, so a machine set up before this is corrected rather
than left as close enough.

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

scripts/classroom-dock

@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 
 import math
+import os
 import subprocess
 import sys
 from datetime import datetime
@@ -11,7 +12,7 @@ import gi
 gi.require_version("Gtk", "3.0")
 gi.require_version("GtkLayerShell", "0.1")
 
-from gi.repository import Gtk, Gdk, GdkPixbuf, GLib, GtkLayerShell
+from gi.repository import Gio, Gtk, Gdk, GdkPixbuf, GLib, GtkLayerShell
 
 sys.path.insert(0, "/usr/local/lib/ekklesia-classroom")
 
@@ -76,6 +77,11 @@ BUSY_SPINNER_SIZE = 38
 THROBBER_FRAMES = 24
 THROBBER_INTERVAL_MS = 80
 
+# Which secondary Chrome window the Close button acts on, published by
+# classroom-chrome-windows. A file rather than a socket because the dock
+# only ever reads it, and Gio can watch it without a poll.
+CLOSE_TARGET_NAME = "chrome-close-target"
+
 BUSY_POLL_MS = 500
 
 # Long enough for a cold Chrome start on classroom hardware, short enough
@@ -231,6 +237,8 @@ class ClassroomShell(Gtk.Window):
         self.dvd_image = None
         self.disc_ready = None
         self.buttons = {}
+        self.close_target = None
+        self.close_monitor = None
 
         GtkLayerShell.init_for_window(self)
         GtkLayerShell.set_layer(
@@ -355,8 +363,100 @@ class ClassroomShell(Gtk.Window):
                 0,
             )
 
+        # Only ever on screen while a secondary browser window is focused,
+        # so the ordinary dock is exactly what it has always been.
+        close = self.make_button(
+            "close",
+            custom_icon("close.svg", scaled(BROWSER_ICON_SIZE, self.scale))
+            or themed_icon("window-close-symbolic"),
+            self.close_secondary,
+        )
+        close.set_no_show_all(True)
+        close.set_visible(False)
+
+        # show_all() does not recurse into a no-show-all widget, so the
+        # icon has to be shown by hand or the button appears empty when
+        # it is finally revealed.
+        self.buttons["close"]["image"].show()
+
+        dock.pack_start(close, False, False, 0)
+
+        self.watch_close_target()
+
         return dock
 
+    # -- the close affordance for secondary browser windows ---------
+    #
+    # The button lives here rather than on the window because a surface
+    # anchored to a moving window chases it and flickers. The dock does
+    # not move.
+
+    def watch_close_target(self):
+        directory = Path(
+            os.environ.get("XDG_RUNTIME_DIR") or "/tmp"
+        ) / "ekklesia-classroom"
+
+        try:
+            directory.mkdir(parents=True, exist_ok=True)
+
+            self.close_path = directory / CLOSE_TARGET_NAME
+
+            # Watching the directory rather than the file: the state is
+            # published by rename, so the file itself is replaced.
+            self.close_monitor = Gio.File.new_for_path(
+                str(directory)
+            ).monitor_directory(Gio.FileMonitorFlags.NONE, None)
+
+            self.close_monitor.connect(
+                "changed",
+                self.on_close_target_changed,
+            )
+        except (OSError, GLib.Error) as error:
+            print(
+                f"classroom-dock: not watching for browser popups: {error}",
+                file=sys.stderr,
+            )
+            self.close_path = None
+            return
+
+        self.refresh_close_target()
+
+    def on_close_target_changed(self, monitor, changed, other, event):
+        if changed is not None and changed.get_basename() != CLOSE_TARGET_NAME:
+            return
+
+        self.refresh_close_target()
+
+    def refresh_close_target(self):
+        target = None
+
+        if self.close_path is not None:
+            try:
+                text = self.close_path.read_text().strip()
+            except OSError:
+                text = ""
+
+            if text.isdigit():
+                target = int(text)
+
+        if target == self.close_target:
+            return
+
+        self.close_target = target
+
+        entry = self.buttons.get("close")
+
+        if entry is not None:
+            entry["button"].set_visible(target is not None)
+
+    def close_secondary(self, *_):
+        if self.close_target is None or sway is None:
+            return
+
+        # Closes exactly this container. Never the main browser, and
+        # never a Chrome process.
+        sway.command(f"[con_id={self.close_target}] kill")
+
     def make_button(self, name, image, callback):
         button = Gtk.Button()
         button.set_relief(Gtk.ReliefStyle.NONE)