timetable performance optimization

lib/extensions/date_time.dart

@@ -36,6 +36,11 @@ extension CalendarDayArithmetic on DateTime {
       );
 
   DateTime subtractDays(int days) => addDays(-days);
+
+  DateTime get dateOnly => DateTime(year, month, day);
+
+  /// Monday 00:00 of this date's week.
+  DateTime get mondayOfWeek => subtractDays(weekday - 1).dateOnly;
 }
 
 /// Formatting helpers backed by Jiffy. Centralises the patterns that previously

lib/state/app/modules/foreign_timetable/bloc/foreign_timetable_bloc.dart

@@ -45,7 +45,7 @@ class ForeignTimetableBloc
   TimetableState fromNothing() {
     final reference = DateTime.now().addDays(2);
     return TimetableState(
-      startDate: _startOfWeek(reference),
+      startDate: reference.mondayOfWeek,
       endDate: _endOfWeek(reference),
     );
   }
@@ -101,7 +101,7 @@ class ForeignTimetableBloc
 
   void resetWeek() {
     final reference = DateTime.now().addDays(2);
-    changeWeek(_startOfWeek(reference), _endOfWeek(reference));
+    changeWeek(reference.mondayOfWeek, _endOfWeek(reference));
   }
 
   void refresh() => fetch();
@@ -180,19 +180,7 @@ class ForeignTimetableBloc
   }
 
   void _writeWeekToCache(DateTime weekStart, TimetableGetWeekResponse week) {
-    final key = weekStart.weekKey();
-    add(
-      Emit((s) {
-        final updated = Map<String, TimetableGetWeekResponse>.of(s.weekCache);
-        updated[key] = week;
-        return s.copyWith(weekCache: updated, dataVersion: s.dataVersion + 1);
-      }),
-    );
-  }
-
-  static DateTime _startOfWeek(DateTime reference) {
-    final monday = reference.subtractDays(reference.weekday - 1);
-    return DateTime(monday.year, monday.month, monday.day);
+    add(Emit((s) => s.withFetchedWeek(weekStart, week)));
   }
 
   static DateTime _endOfWeek(DateTime reference) {

lib/state/app/modules/timetable/bloc/timetable_bloc.dart

@@ -36,7 +36,7 @@ class TimetableBloc
   TimetableState fromNothing() {
     final reference = DateTime.now().addDays(2);
     return TimetableState(
-      startDate: _startOfWeek(reference),
+      startDate: reference.mondayOfWeek,
       endDate: _endOfWeek(reference),
     );
   }
@@ -49,7 +49,7 @@ class TimetableBloc
     final stored = TimetableState.fromJson(json);
     final reference = DateTime.now().addDays(2);
     return stored.copyWith(
-      startDate: _startOfWeek(reference),
+      startDate: reference.mondayOfWeek,
       endDate: _endOfWeek(reference),
       accessibleStartDate: null,
       accessibleEndDate: null,
@@ -99,7 +99,7 @@ class TimetableBloc
 
   void resetWeek() {
     final reference = DateTime.now().addDays(2);
-    changeWeek(_startOfWeek(reference), _endOfWeek(reference));
+    changeWeek(reference.mondayOfWeek, _endOfWeek(reference));
   }
 
   void refresh() => fetch();
@@ -245,19 +245,7 @@ class TimetableBloc
   }
 
   void _writeWeekToCache(DateTime weekStart, TimetableGetWeekResponse week) {
-    final key = weekStart.weekKey();
-    add(
-      Emit((s) {
-        final updated = Map<String, TimetableGetWeekResponse>.of(s.weekCache);
-        updated[key] = week;
-        return s.copyWith(weekCache: updated, dataVersion: s.dataVersion + 1);
-      }),
-    );
-  }
-
-  static DateTime _startOfWeek(DateTime reference) {
-    final monday = reference.subtractDays(reference.weekday - 1);
-    return DateTime(monday.year, monday.month, monday.day);
+    add(Emit((s) => s.withFetchedWeek(weekStart, week)));
   }
 
   static DateTime _endOfWeek(DateTime reference) {

lib/state/app/modules/timetable/bloc/timetable_state.dart

@@ -7,6 +7,7 @@ import '../../../../../api/marianumconnect/queries/timetable_get_subjects/timeta
 import '../../../../../api/marianumconnect/queries/timetable_get_timegrid/timetable_get_timegrid_response.dart';
 import '../../../../../api/marianumconnect/queries/timetable_get_week/timetable_get_week_response.dart';
 import '../../../../../api/mhsl/custom_timetable_event/get/get_custom_timetable_event_response.dart';
+import 'week_cache.dart';
 
 part 'timetable_state.freezed.dart';
 part 'timetable_state.g.dart';
@@ -40,6 +41,23 @@ abstract class TimetableState with _$TimetableState {
   Iterable<McTimetableEntry> getAllKnownLessons() =>
       weekCache.values.expand((response) => response.entries);
 
+  /// This state with [week] cached, or `this` when its content is unchanged
+  /// (so the emit is dropped as equal).
+  TimetableState withFetchedWeek(
+    DateTime weekStart,
+    TimetableGetWeekResponse week,
+  ) {
+    final updated = mergeWeekIntoCache(
+      weekCache,
+      weekStart,
+      week,
+      viewedWeekStart: startDate,
+      now: DateTime.now(),
+    );
+    if (updated == null) return this;
+    return copyWith(weekCache: updated, dataVersion: dataVersion + 1);
+  }
+
   bool get hasReferenceData =>
       rooms != null &&
       subjects != null &&

lib/state/app/modules/timetable/bloc/week_cache.dart

@@ -0,0 +1,45 @@
+import 'package:collection/collection.dart';
+
+import '../../../../../api/marianumconnect/queries/timetable_get_week/timetable_get_week_response.dart';
+import '../../../../../extensions/date_time.dart';
+
+/// Weeks kept around the viewed week and around today's week. Everything
+/// further away is dropped: every state emit re-serializes the whole cache for
+/// HydratedBloc and the calendar rebuilds its appointments from all of it, so
+/// an unbounded cache makes week swipes slower the longer the app is used.
+const int kWeekCacheRadius = 4;
+
+/// Returns the cache with [week] stored under [weekStart], pruned to the
+/// weeks near [viewedWeekStart] or [now]. Returns null when the stored week
+/// already has identical content, so callers can skip the emit entirely.
+Map<String, TimetableGetWeekResponse>? mergeWeekIntoCache(
+  Map<String, TimetableGetWeekResponse> cache,
+  DateTime weekStart,
+  TimetableGetWeekResponse week, {
+  required DateTime viewedWeekStart,
+  required DateTime now,
+}) {
+  final key = weekStart.weekKey();
+  final existing = cache[key];
+  if (existing != null &&
+      const DeepCollectionEquality().equals(existing.toJson(), week.toJson())) {
+    return null;
+  }
+
+  final viewedMonday = viewedWeekStart.mondayOfWeek;
+  final todayMonday = now.mondayOfWeek;
+  bool isNear(DateTime monday, DateTime anchor) =>
+      monday.difference(anchor).inDays.abs() <= kWeekCacheRadius * 7 + 1;
+
+  final updated = <String, TimetableGetWeekResponse>{};
+  for (final entry in cache.entries) {
+    final monday = DateTime.tryParse(entry.key);
+    if (monday == null ||
+        isNear(monday, viewedMonday) ||
+        isNear(monday, todayMonday)) {
+      updated[entry.key] = entry.value;
+    }
+  }
+  updated[key] = week;
+  return updated;
+}

lib/view/pages/timetable/data/timetable_appointment_factory.dart

@@ -213,10 +213,12 @@ class TimetableAppointmentFactory {
     return LessonColor.forStatus(status);
   }
 
-  McSubject? _findSubject(String? subjectShort) {
-    if (subjectShort == null) return null;
-    return subjects.where((s) => s.shortName == subjectShort).firstOrNull;
-  }
+  late final Map<String, McSubject> _subjectsByShort = {
+    for (final s in subjects.reversed) s.shortName: s,
+  };
+
+  McSubject? _findSubject(String? subjectShort) =>
+      subjectShort == null ? null : _subjectsByShort[subjectShort];
 
   String _subjectName(String? subjectShort, McTimetableEntry lesson) {
     if (subjectShort != null) {

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),

lib/view/pages/timetable/widgets/calendar/outside_chips.dart

@@ -1,16 +1,14 @@
 part of '../custom_workweek_calendar.dart';
 
 class _OutsideHoursStrip extends StatelessWidget {
-  final DateTime weekStart;
-  final List<Appointment> appointments;
+  final List<List<Appointment>> outside;
   final double rulerWidth;
   final void Function(Appointment) onAppointmentTap;
   final bool Function(Appointment) isCrossedOut;
 
   const _OutsideHoursStrip({
     super.key,
-    required this.weekStart,
-    required this.appointments,
+    required this.outside,
     required this.rulerWidth,
     required this.onAppointmentTap,
     required this.isCrossedOut,
@@ -18,10 +16,6 @@ class _OutsideHoursStrip extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final outside = partitionAppointmentsForWeek(
-      appointments,
-      weekStart,
-    ).outside;
     if (outside.every((day) => day.isEmpty)) return const SizedBox.shrink();
 
     final theme = Theme.of(context);

lib/view/pages/timetable/widgets/calendar/week_grid.dart

@@ -1,10 +1,31 @@
 part of '../custom_workweek_calendar.dart';
 
+/// Per-week derived data, computed once per appointment/region set instead of
+/// on every rebuild of a week page.
+class _WeekData {
+  final List<List<Appointment>> inside;
+  final List<List<Appointment>> outside;
+  final List<List<BoundRegion>> regions;
+
+  _WeekData._(this.inside, this.outside, this.regions);
+
+  factory _WeekData.compute(
+    DateTime weekStart,
+    List<Appointment> appointments,
+    List<TimeRegion> timeRegions,
+  ) {
+    final partitioned = partitionAppointmentsForWeek(appointments, weekStart);
+    return _WeekData._(partitioned.inside, partitioned.outside, [
+      for (var d = 0; d < 5; d++)
+        expandRegionsForDay(timeRegions, weekStart.addDays(d)),
+    ]);
+  }
+}
+
 class _WeekGrid extends StatelessWidget {
   final DateTime weekStart;
   final LessonPeriodSchedule schedule;
-  final List<Appointment> appointments;
-  final List<TimeRegion> timeRegions;
+  final _WeekData data;
   final void Function(Appointment) onAppointmentTap;
   final bool Function(Appointment) isCrossedOut;
   final void Function(DateTime start, DateTime end)? onCreateEvent;
@@ -16,8 +37,7 @@ class _WeekGrid extends StatelessWidget {
   const _WeekGrid({
     required this.weekStart,
     required this.schedule,
-    required this.appointments,
-    required this.timeRegions,
+    required this.data,
     required this.onAppointmentTap,
     required this.isCrossedOut,
     required this.onCreateEvent,
@@ -29,8 +49,6 @@ class _WeekGrid extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final partitioned = partitionAppointmentsForWeek(appointments, weekStart);
-
     return Row(
       crossAxisAlignment: CrossAxisAlignment.stretch,
       children: [
@@ -48,8 +66,8 @@ class _WeekGrid extends StatelessWidget {
             child: _DayColumn(
               date: weekStart.addDays(d),
               schedule: schedule,
-              appointments: partitioned.inside[d],
-              timeRegions: timeRegions,
+              appointments: data.inside[d],
+              regions: data.regions[d],
               layout: layout,
               today: today,
               nowNotifier: nowNotifier,
@@ -195,7 +213,7 @@ class _DayColumn extends StatelessWidget {
   final DateTime date;
   final LessonPeriodSchedule schedule;
   final List<Appointment> appointments;
-  final List<TimeRegion> timeRegions;
+  final List<BoundRegion> regions;
   final PeriodLayout layout;
   final DateTime today;
   final ValueListenable<DateTime> nowNotifier;
@@ -207,7 +225,7 @@ class _DayColumn extends StatelessWidget {
     required this.date,
     required this.schedule,
     required this.appointments,
-    required this.timeRegions,
+    required this.regions,
     required this.layout,
     required this.today,
     required this.nowNotifier,
@@ -280,12 +298,10 @@ class _DayColumn extends StatelessWidget {
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
 
-    final dayAppointments = appointments;
-    final dayRegions = expandRegionsForDay(timeRegions, date);
     final isToday = date.isSameDay(today);
 
-    final isTablet = MediaQuery.of(context).size.shortestSide >= 600;
-    final laidOut = assignLanes(dayAppointments, maxLanes: isTablet ? 3 : 2);
+    final isTablet = MediaQuery.sizeOf(context).shortestSide >= 600;
+    final laidOut = assignLanes(appointments, maxLanes: isTablet ? 3 : 2);
 
     final dayName = DateFormat(
       'EEEE',
@@ -304,8 +320,7 @@ class _DayColumn extends StatelessWidget {
       sortKey: OrdinalSortKey(date.weekday.toDouble()),
       child: GestureDetector(
         behavior: HitTestBehavior.translucent,
-        onLongPressStart: (details) =>
-            _handleLongPress(details, dayAppointments),
+        onLongPressStart: (details) => _handleLongPress(details, appointments),
         child: DecoratedBox(
           decoration: BoxDecoration(
             color: isToday ? theme.colorScheme.primary.withAlpha(14) : null,
@@ -342,7 +357,7 @@ class _DayColumn extends StatelessWidget {
                         color: theme.dividerColor.withAlpha(60),
                       ),
                     ),
-                  for (final region in dayRegions)
+                  for (final region in regions)
                     Positioned(
                       top: layout.yOfDateTime(region.start),
                       height:
@@ -379,6 +394,7 @@ class _DayColumn extends StatelessWidget {
                               onTap: () => onAppointmentTap(appointment),
                               child: AppointmentTile(
                                 appointment: appointment,
+                                now: nowNotifier,
                                 crossedOut: isCrossedOut(appointment),
                               ),
                             ),

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

@@ -61,29 +61,41 @@ class CustomWorkWeekCalendarState extends State<CustomWorkWeekCalendar> {
   static const double _rulerWidth = 36;
 
   late PageController _pageController;
-  late int _currentWeekIndex;
+  // Drives header + all-day strip. Kept out of setState so a page change
+  // mid-swipe doesn't rebuild the PageView and every tile in it.
+  late final ValueNotifier<int> _visibleWeekIndex;
+  late int _reportedWeekIndex;
   late DateTime _firstMonday;
   late int _totalWeeks;
   late Timer _ticker;
   late ValueNotifier<DateTime> _nowNotifier;
-  DateTime _today = _dateOnly(DateTime.now());
+  DateTime _today = DateTime.now().dateOnly;
+
+  final Map<int, _WeekData> _weekData = {};
+  // Returning the identical widget instance lets Flutter skip rebuilding a
+  // week page when the host rebuilds for unrelated reasons (e.g. the bloc
+  // recording the new week after a swipe).
+  final Map<int, _WeekGrid> _gridCache = {};
+  Object? _cacheKey;
 
   @override
   void initState() {
     super.initState();
-    _firstMonday = _mondayOf(widget.minDate);
-    final lastMonday = _mondayOf(widget.maxDate);
+    _firstMonday = widget.minDate.mondayOfWeek;
+    final lastMonday = widget.maxDate.mondayOfWeek;
     _totalWeeks = lastMonday.difference(_firstMonday).inDays ~/ 7 + 1;
-    _currentWeekIndex =
-        _mondayOf(widget.initialDate).difference(_firstMonday).inDays ~/ 7;
-    _pageController = PageController(initialPage: _currentWeekIndex);
+    final initialIndex =
+        widget.initialDate.mondayOfWeek.difference(_firstMonday).inDays ~/ 7;
+    _visibleWeekIndex = ValueNotifier<int>(initialIndex);
+    _reportedWeekIndex = initialIndex;
+    _pageController = PageController(initialPage: initialIndex);
     _nowNotifier = ValueNotifier<DateTime>(DateTime.now());
 
     _ticker = Timer.periodic(const Duration(seconds: 30), (_) {
       if (!mounted) return;
       final now = DateTime.now();
       _nowNotifier.value = now;
-      final newToday = _dateOnly(now);
+      final newToday = now.dateOnly;
       if (newToday != _today) setState(() => _today = newToday);
     });
   }
@@ -99,11 +111,11 @@ class CustomWorkWeekCalendarState extends State<CustomWorkWeekCalendar> {
     // the initial mount with the conservative fallback). Recompute the
     // range and snap the controller to the page that still represents the
     // currently visible week so the user doesn't get yanked around.
-    final newFirstMonday = _mondayOf(widget.minDate);
-    final newLastMonday = _mondayOf(widget.maxDate);
+    final newFirstMonday = widget.minDate.mondayOfWeek;
+    final newLastMonday = widget.maxDate.mondayOfWeek;
     final newTotalWeeks =
         newLastMonday.difference(newFirstMonday).inDays ~/ 7 + 1;
-    final visibleWeekStart = _firstMonday.addDays(_currentWeekIndex * 7);
+    final visibleWeekStart = _firstMonday.addDays(_visibleWeekIndex.value * 7);
     final newIndex = visibleWeekStart.difference(newFirstMonday).inDays ~/ 7;
     final clampedIndex = newIndex.clamp(0, newTotalWeeks - 1);
     final oldController = _pageController;
@@ -112,8 +124,9 @@ class CustomWorkWeekCalendarState extends State<CustomWorkWeekCalendar> {
     setState(() {
       _firstMonday = newFirstMonday;
       _totalWeeks = newTotalWeeks;
-      _currentWeekIndex = clampedIndex;
     });
+    _visibleWeekIndex.value = clampedIndex;
+    _reportedWeekIndex = clampedIndex;
   }
 
   @override
@@ -121,13 +134,12 @@ class CustomWorkWeekCalendarState extends State<CustomWorkWeekCalendar> {
     _pageController.dispose();
     _ticker.cancel();
     _nowNotifier.dispose();
+    _visibleWeekIndex.dispose();
     super.dispose();
   }
 
-  static DateTime _dateOnly(DateTime d) => DateTime(d.year, d.month, d.day);
-
   void jumpToDate(DateTime date) {
-    final target = _mondayOf(date).difference(_firstMonday).inDays ~/ 7;
+    final target = date.mondayOfWeek.difference(_firstMonday).inDays ~/ 7;
     if (target < 0 || target >= _totalWeeks) return;
     _pageController.animateToPage(
       target,
@@ -136,16 +148,79 @@ class CustomWorkWeekCalendarState extends State<CustomWorkWeekCalendar> {
     );
   }
 
-  static DateTime _mondayOf(DateTime d) {
-    final monday = d.subtractDays(d.weekday - 1);
-    return DateTime(monday.year, monday.month, monday.day);
+  /// Drops both per-week caches when any input they were built from changed.
+  void _syncCaches() {
+    final key = (
+      widget.appointments,
+      widget.timeRegions,
+      widget.schedule,
+      widget.onCreateEvent == null,
+      _today,
+      _firstMonday,
+    );
+    if (key == _cacheKey) return;
+    _cacheKey = key;
+    _weekData.clear();
+    _gridCache.clear();
   }
 
-  @override
-  Widget build(BuildContext context) {
-    final theme = Theme.of(context);
-    final visibleWeekStart = _firstMonday.addDays(_currentWeekIndex * 7);
+  _WeekData _weekDataFor(int weekIndex) {
+    return _weekData.putIfAbsent(
+      weekIndex,
+      () => _WeekData.compute(
+        _firstMonday.addDays(weekIndex * 7),
+        widget.appointments,
+        widget.timeRegions,
+      ),
+    );
+  }
 
+  /// Tells the host about the new week only once the swipe has settled, so
+  /// the resulting bloc emit + rebuild never lands inside the page animation.
+  bool _onPageScroll(ScrollNotification notification) {
+    if (notification is! ScrollEndNotification || notification.depth != 0) {
+      return false;
+    }
+    final index = _visibleWeekIndex.value;
+    if (index == _reportedWeekIndex) return false;
+    _reportedWeekIndex = index;
+    final weekStart = _firstMonday.addDays(index * 7);
+    widget.onWeekChanged(weekStart, weekStart.addDays(4));
+    return false;
+  }
+
+  void _onAppointmentTap(Appointment appointment) =>
+      widget.onAppointmentTap(appointment);
+
+  bool _isCrossedOut(Appointment appointment) =>
+      widget.isCrossedOut(appointment);
+
+  void _onCreateEvent(DateTime start, DateTime end) =>
+      widget.onCreateEvent?.call(start, end);
+
+  _WeekGrid _weekGrid(int weekIndex, PeriodLayout layout) {
+    final cached = _gridCache[weekIndex];
+    if (cached != null && cached.layout.lessonHeight == layout.lessonHeight) {
+      return cached;
+    }
+    // Only the pages next to the visible one are ever alive.
+    _gridCache.removeWhere((i, _) => (i - weekIndex).abs() > 2);
+    return _gridCache[weekIndex] = _WeekGrid(
+      weekStart: _firstMonday.addDays(weekIndex * 7),
+      schedule: widget.schedule,
+      data: _weekDataFor(weekIndex),
+      onAppointmentTap: _onAppointmentTap,
+      isCrossedOut: _isCrossedOut,
+      onCreateEvent: widget.onCreateEvent == null ? null : _onCreateEvent,
+      today: _today,
+      nowNotifier: _nowNotifier,
+      rulerWidth: _rulerWidth,
+      layout: layout,
+    );
+  }
+
+  Widget _buildWeekHeader(int weekIndex) {
+    final visibleWeekStart = _firstMonday.addDays(weekIndex * 7);
     return Column(
       children: [
         SizedBox(
@@ -190,15 +265,29 @@ class CustomWorkWeekCalendarState extends State<CustomWorkWeekCalendar> {
                   FadeTransition(opacity: animation, child: child),
               child: _OutsideHoursStrip(
                 key: ValueKey(visibleWeekStart),
-                weekStart: visibleWeekStart,
-                appointments: widget.appointments,
+                outside: _weekDataFor(weekIndex).outside,
                 rulerWidth: _rulerWidth,
-                onAppointmentTap: widget.onAppointmentTap,
-                isCrossedOut: widget.isCrossedOut,
+                onAppointmentTap: _onAppointmentTap,
+                isCrossedOut: _isCrossedOut,
               ),
             ),
           ),
         ),
+      ],
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    _syncCaches();
+
+    return Column(
+      children: [
+        ValueListenableBuilder<int>(
+          valueListenable: _visibleWeekIndex,
+          builder: (_, weekIndex, _) => _buildWeekHeader(weekIndex),
+        ),
         Container(height: 0.5, color: theme.dividerColor.withAlpha(110)),
         Expanded(
           child: LayoutBuilder(
@@ -225,30 +314,15 @@ class CustomWorkWeekCalendarState extends State<CustomWorkWeekCalendar> {
                 physics: const AlwaysScrollableScrollPhysics(),
                 child: SizedBox(
                   height: gridHeight,
-                  child: PageView.builder(
-                    controller: _pageController,
-                    itemCount: _totalWeeks,
-                    onPageChanged: (index) {
-                      setState(() => _currentWeekIndex = index);
-                      final weekStart = _firstMonday.addDays(index * 7);
-                      widget.onWeekChanged(weekStart, weekStart.addDays(4));
-                    },
-                    itemBuilder: (_, weekIndex) {
-                      final weekStart = _firstMonday.addDays(weekIndex * 7);
-                      return _WeekGrid(
-                        weekStart: weekStart,
-                        schedule: widget.schedule,
-                        appointments: widget.appointments,
-                        timeRegions: widget.timeRegions,
-                        onAppointmentTap: widget.onAppointmentTap,
-                        isCrossedOut: widget.isCrossedOut,
-                        onCreateEvent: widget.onCreateEvent,
-                        today: _today,
-                        nowNotifier: _nowNotifier,
-                        rulerWidth: _rulerWidth,
-                        layout: layout,
-                      );
-                    },
+                  child: NotificationListener<ScrollNotification>(
+                    onNotification: _onPageScroll,
+                    child: PageView.builder(
+                      controller: _pageController,
+                      itemCount: _totalWeeks,
+                      onPageChanged: (index) => _visibleWeekIndex.value = index,
+                      itemBuilder: (_, weekIndex) =>
+                          _weekGrid(weekIndex, layout),
+                    ),
                   ),
                 ),
               );

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

@@ -55,6 +55,13 @@ class TimetableCalendarViewState extends State<TimetableCalendarView> {
   // the same identity checks the cache always used.
   (int, TimetableSettings, List<CustomTimetableEvent>, bool)? _cacheKey;
 
+  // Stable identities let the calendar reuse its per-week pages across
+  // rebuilds; rebuilding these every frame would invalidate that cache.
+  LessonPeriodSchedule? _schedule;
+  Object? _scheduleKey;
+  List<TimeRegion>? _regions;
+  Object? _regionsKey;
+
   DateTime _initialDisplayDate() => DateTime.now().addDays(2);
 
   /// Snaps the calendar back to the current week. Exposed so host pages can
@@ -90,7 +97,37 @@ class TimetableCalendarViewState extends State<TimetableCalendarView> {
     ).build();
   }
 
-  bool _isCrossedOut(Appointment appointment) {
+  LessonPeriodSchedule _scheduleFor(TimetableState state) {
+    if (_schedule != null && identical(_scheduleKey, state.timegrid)) {
+      return _schedule!;
+    }
+    _scheduleKey = state.timegrid;
+    return _schedule = LessonPeriodSchedule.fromState(state);
+  }
+
+  List<TimeRegion> _regionsFor(
+    TimetableState state,
+    LessonPeriodSchedule schedule,
+  ) {
+    final theme = Theme.of(context);
+    final key = (
+      state.schoolHolidays,
+      schedule,
+      theme.colorScheme,
+      theme.disabledColor,
+      DateTime.now().dateOnly,
+    );
+    if (_regions != null && key == _regionsKey) return _regions!;
+    _regionsKey = key;
+    return _regions = SpecialRegionsBuilder(
+      holidays: state.schoolHolidays!,
+      schedule: schedule,
+      colorScheme: theme.colorScheme,
+      disabledColor: theme.disabledColor,
+    ).build();
+  }
+
+  static bool _isCrossedOut(Appointment appointment) {
     final id = appointment.id;
     if (id is LessonAppointment) return id.entry.status == 'CANCELLED';
     return false;
@@ -104,14 +141,9 @@ class TimetableCalendarViewState extends State<TimetableCalendarView> {
     // transient null can never crash the build.
     if (state.schoolHolidays == null) return const SizedBox.shrink();
 
-    final schedule = LessonPeriodSchedule.fromState(state);
+    final schedule = _scheduleFor(state);
     final appointments = _appointments(state);
-    final regions = SpecialRegionsBuilder(
-      holidays: state.schoolHolidays!,
-      schedule: schedule,
-      colorScheme: Theme.of(context).colorScheme,
-      disabledColor: Theme.of(context).disabledColor,
-    ).build();
+    final regions = _regionsFor(state, schedule);
 
     final capabilities = context.watch<CapabilitiesCubit>();
     final (minDate, maxDate) = _scrollBounds(
@@ -171,8 +203,8 @@ class TimetableCalendarViewState extends State<TimetableCalendarView> {
               ? state.accessibleEndDate!
               : baseMax)
         : baseMax;
-    final today = _startOfDay(DateTime.now());
-    final todayMonday = _mondayOf(today);
+    final today = DateTime.now().dateOnly;
+    final todayMonday = today.mondayOfWeek;
     final currentWeekEnd = todayMonday.addDays(DateTime.daysPerWeek - 1);
     final capMin = pastDays == null
         ? null
@@ -202,11 +234,6 @@ class TimetableCalendarViewState extends State<TimetableCalendarView> {
     return (mondayMin, finalMax);
   }
 
-  static DateTime _mondayOf(DateTime d) =>
-      _startOfDay(d.subtractDays(d.weekday - 1));
-
-  static DateTime _startOfDay(DateTime d) => DateTime(d.year, d.month, d.day);
-
   static DateTime _earlier(DateTime a, DateTime b) => a.isBefore(b) ? a : b;
 
   static DateTime _later(DateTime a, DateTime b) => a.isAfter(b) ? a : b;

test/extensions/date_time_test.dart

@@ -86,6 +86,15 @@ void main() {
       final d = DateTime(2026, 5, 18, 13, 45);
       expect(d.subtractDays(5), d.addDays(-5));
     });
+
+    test('dateOnly drops the time of day', () {
+      expect(DateTime(2026, 9, 24, 13, 45).dateOnly, DateTime(2026, 9, 24));
+    });
+
+    test('mondayOfWeek returns Monday midnight for any weekday', () {
+      expect(DateTime(2026, 9, 21).mondayOfWeek, DateTime(2026, 9, 21));
+      expect(DateTime(2026, 9, 27, 23, 59).mondayOfWeek, DateTime(2026, 9, 21));
+    });
   });
 
   group('DateTimeFormatting', () {

test/state/week_cache_test.dart

@@ -0,0 +1,74 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/api/marianumconnect/queries/timetable_get_week/timetable_get_week_response.dart';
+import 'package:marianum_mobile/extensions/date_time.dart';
+import 'package:marianum_mobile/state/app/modules/timetable/bloc/week_cache.dart';
+
+TimetableGetWeekResponse _week(DateTime monday, {String room = 'A101'}) =>
+    TimetableGetWeekResponse(
+      from: monday,
+      until: monday.addDays(4),
+      entries: [
+        McTimetableEntry(
+          id: 1,
+          date: monday,
+          startTime: DateTime(1970, 1, 1, 8),
+          endTime: DateTime(1970, 1, 1, 9),
+          subjects: const ['ma'],
+          teachers: const [],
+          rooms: [room],
+          classNames: const [],
+          lessonType: 'LESSON',
+          status: 'REGULAR',
+          substitutionText: null,
+          lessonText: null,
+          infoText: null,
+        ),
+      ],
+    );
+
+void main() {
+  final monday = DateTime(2026, 9, 21);
+
+  test('returns null when the stored week has identical content', () {
+    final cache = {monday.weekKey(): _week(monday)};
+    final result = mergeWeekIntoCache(
+      cache,
+      monday,
+      _week(monday),
+      viewedWeekStart: monday,
+      now: monday,
+    );
+    expect(result, isNull);
+  });
+
+  test('stores changed content', () {
+    final cache = {monday.weekKey(): _week(monday)};
+    final changed = _week(monday, room: 'B202');
+    final result = mergeWeekIntoCache(
+      cache,
+      monday,
+      changed,
+      viewedWeekStart: monday,
+      now: monday,
+    );
+    expect(result![monday.weekKey()], same(changed));
+  });
+
+  test('drops weeks far from both the viewed week and today', () {
+    final far = monday.addDays(7 * (kWeekCacheRadius + 3));
+    final nearToday = monday.addDays(-7 * kWeekCacheRadius);
+    final viewed = monday.addDays(7 * (kWeekCacheRadius * 3));
+    final cache = {
+      far.weekKey(): _week(far),
+      nearToday.weekKey(): _week(nearToday),
+    };
+    final result = mergeWeekIntoCache(
+      cache,
+      viewed,
+      _week(viewed),
+      viewedWeekStart: viewed,
+      now: monday.addDays(2),
+    );
+    expect(result!.keys, {nearToday.weekKey(), viewed.weekKey()});
+  });
+}