refactor: share the stylesheet renderer

The DVD control bar has to look like the dock, which is best guaranteed
by drawing it from the same template with the same measurements rather
than by keeping two stylesheets in step by hand.

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

lib/classroom_style.py

@@ -0,0 +1,35 @@
+"""The classroom stylesheet, resolved at the room's UI scale.
+
+The dock and the DVD control bar share this so they cannot drift apart:
+one template, one set of measurements, one look.
+"""
+
+from pathlib import Path
+
+from classroom_config import scaled
+
+TEMPLATE = Path("/etc/ekklesia-classroom/dock/style.css.in")
+
+# Every measurement in the template, at UI_SCALE=1.0.
+MEASUREMENTS = {
+    "dock-radius": 24,
+    "dock-padding-v": 8,
+    "dock-padding-h": 10,
+    "button-radius": 16,
+    "button-padding": 6,
+    "button-size": 44,
+    "clock-radius": 16,
+    "clock-padding-v": 7,
+    "clock-padding-h": 12,
+    "clock-font": 17,
+}
+
+
+def render(scale, template=None):
+    """Resolve the measurement tokens in the stylesheet template."""
+    css = (template or TEMPLATE).read_text()
+
+    for token, value in MEASUREMENTS.items():
+        css = css.replace(f"@{token}@", str(scaled(value, scale)))
+
+    return css

scripts/classroom-dock

@@ -14,6 +14,7 @@ from gi.repository import Gtk, Gdk, GdkPixbuf, GLib, GtkLayerShell
 
 sys.path.insert(0, "/usr/local/lib/ekklesia-classroom")
 
+import classroom_style as style  # noqa: E402
 from classroom_config import (  # noqa: E402
     enabled,
     read_device_config,
@@ -30,7 +31,6 @@ except ImportError:
     optical = None
 
 
-CSS_FILE = Path("/etc/ekklesia-classroom/dock/style.css.in")
 ICON_DIR = Path("/etc/ekklesia-classroom/icons")
 
 DVD_POLL_SECONDS = 2
@@ -358,39 +358,13 @@ class ClassroomShell(Gtk.Window):
         return True
 
 
-def render_css(scale):
-    """Resolve the measurement tokens in the stylesheet template."""
-    css = CSS_FILE.read_text()
-
-    measurements = {
-        "dock-radius": 24,
-        "dock-padding-v": 8,
-        "dock-padding-h": 10,
-        "button-radius": 16,
-        "button-padding": 6,
-        "button-size": 44,
-        "clock-radius": 16,
-        "clock-padding-v": 7,
-        "clock-padding-h": 12,
-        "clock-font": 17,
-    }
-
-    for token, value in measurements.items():
-        css = css.replace(
-            f"@{token}@",
-            str(scaled(value, scale)),
-        )
-
-    return css
-
-
 def load_css(scale):
     # Styling is worth losing before the dock is. A stylesheet that will
     # not parse leaves an unstyled but working shell rather than no shell.
     try:
         provider = Gtk.CssProvider()
         provider.load_from_data(
-            render_css(scale).encode("utf-8")
+            style.render(scale).encode("utf-8")
         )
     except (OSError, GLib.Error) as error:
         print(