timetable performance optimization

lib/view/pages/timetable/widgets/appointment_tile.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:syncfusion_flutter_calendar/calendar.dart';
 
@@ -11,16 +12,19 @@ class AppointmentTile extends StatelessWidget {
   final Appointment appointment;
   final bool crossedOut;
 
+  /// Ticking clock; only the tile background listens, so a lesson fades to
+  /// the "past" look without rebuilding the text layout.
+  final ValueListenable<DateTime> now;
+
   const AppointmentTile({
     super.key,
     required this.appointment,
+    required this.now,
     this.crossedOut = false,
   });
 
   @override
   Widget build(BuildContext context) {
-    final isPast = appointment.endTime.isBefore(DateTime.now());
-    final color = appointment.color.withAlpha(isPast ? 160 : 255);
     final isCustom = appointment.id is CustomAppointment;
     final description = appointment.location ?? '';
 
@@ -29,13 +33,19 @@ class AppointmentTile extends StatelessWidget {
       child: Stack(
         children: [
           Positioned.fill(
-            child: Container(
-              padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 2),
-              alignment: Alignment.topLeft,
-              decoration: BoxDecoration(
-                shape: BoxShape.rectangle,
-                borderRadius: _radius,
-                color: color,
+            child: ValueListenableBuilder<DateTime>(
+              valueListenable: now,
+              builder: (context, now, child) => Container(
+                padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 2),
+                alignment: Alignment.topLeft,
+                decoration: BoxDecoration(
+                  shape: BoxShape.rectangle,
+                  borderRadius: _radius,
+                  color: appointment.color.withAlpha(
+                    appointment.endTime.isBefore(now) ? 160 : 255,
+                  ),
+                ),
+                child: child,
               ),
               child: _TileContent(
                 title: appointment.subject,
@@ -100,8 +110,10 @@ class _TileContent extends StatelessWidget {
         // entirely; the coloured rectangle is enough.
         if (available < titleLineHeight) return const SizedBox.shrink();
 
-        final remaining =
-            (available - titleLineHeight).clamp(0.0, double.infinity);
+        final remaining = (available - titleLineHeight).clamp(
+          0.0,
+          double.infinity,
+        );
         final bodyLineCapacity = (remaining / bodyLineHeight).floor();
 
         if (isCustom) {
@@ -187,7 +199,9 @@ class _AdaptiveTitle extends StatelessWidget {
           maxLines: 1,
           textScaler: textScaler,
         )..layout();
-        if (probe.width > constraints.maxWidth) {
+        final overflows = probe.width > constraints.maxWidth;
+        probe.dispose();
+        if (overflows) {
           return Text(
             text,
             style: baseStyle.copyWith(fontSize: minFontSize),