[timetable] display week header for a while when user turned pages in…

… preview

lib/design/animation/marquee.dart

@@ -0,0 +1,204 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
+
+class AnimatedMarquee extends StatefulWidget {
+  final List<Widget> children;
+  final Duration transitionDuration;
+  final Duration marqueeDuration;
+
+  const AnimatedMarquee({
+    super.key,
+    required this.children,
+    this.transitionDuration = Duration.zero,
+    required this.marqueeDuration,
+  });
+
+  @override
+  State<AnimatedMarquee> createState() => _AnimatedMarqueeState();
+}
+
+class _AnimatedMarqueeState extends State<AnimatedMarquee> {
+  var curIndex = 0;
+  late Timer marqueeTimer;
+
+  @override
+  void initState() {
+    super.initState();
+    marqueeTimer = startTimer(widget.marqueeDuration);
+  }
+
+  Timer startTimer(Duration duration) {
+    return Timer.periodic(duration, (timer) {
+      if (widget.children.isEmpty) {
+        setIndex(0);
+      } else {
+        setState(() {
+          setIndex((curIndex + 1) % widget.children.length);
+        });
+      }
+    });
+  }
+
+  void setIndex(int newIndex) {
+    if (newIndex != curIndex) {
+      setState(() {
+        curIndex = newIndex;
+      });
+    }
+  }
+
+  @override
+  void dispose() {
+    super.dispose();
+    marqueeTimer.cancel();
+  }
+
+  @override
+  void didUpdateWidget(covariant AnimatedMarquee oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    if (oldWidget.marqueeDuration != widget.marqueeDuration) {
+      marqueeTimer.cancel();
+      marqueeTimer = startTimer(widget.marqueeDuration);
+    }
+    setState(() {
+      setIndex(curIndex % widget.children.length);
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AnimatedSwitcher(
+      duration: widget.transitionDuration,
+      child: widget.children[curIndex],
+    );
+  }
+}
+
+class AnimatedDualSwitcherController {
+  _AnimatedDualSwitcherState? _attached;
+
+  void switchTo(bool state) {
+    final attached = _attached!;
+    attached.$state = state;
+    final alwaysSwitchTo = attached.widget.alwaysSwitchTo;
+    if (alwaysSwitchTo == null) return;
+    if (attached.$state != alwaysSwitchTo) {
+      attached.passed = Duration.zero;
+    }
+    attached.passed = Duration.zero;
+  }
+
+  void _attach(_AnimatedDualSwitcherState state) {
+    if (_attached != null) {
+      throw FlutterError("$AnimatedDualSwitcherController should be attached only one at the same time.");
+    }
+    _attached = state;
+  }
+
+  void dispose() {
+    _attached = null;
+  }
+}
+
+class AnimatedDualSwitcher extends StatefulWidget {
+  final Duration transitionDuration;
+  final Duration switchDuration;
+  final Widget trueChild;
+  final Widget falseChild;
+  final AnimatedDualSwitcherController? controller;
+  final bool? alwaysSwitchTo;
+  final bool initial;
+
+  const AnimatedDualSwitcher({
+    super.key,
+    required this.transitionDuration,
+    required this.switchDuration,
+    required this.trueChild,
+    required this.falseChild,
+    this.controller,
+    this.alwaysSwitchTo,
+    required this.initial,
+  });
+
+  Widget _getWidget(bool state) {
+    return state ? trueChild : falseChild;
+  }
+
+  @override
+  State<AnimatedDualSwitcher> createState() => _AnimatedDualSwitcherState();
+}
+
+class _AnimatedDualSwitcherState extends State<AnimatedDualSwitcher> with SingleTickerProviderStateMixin {
+  late Ticker marqueeTicker;
+  var lastElapsed = Duration.zero;
+  var passed = Duration.zero;
+  late var _state = widget.initial;
+
+  bool get $state => _state;
+
+  set $state(bool newV) {
+    if (newV != _state) {
+      setState(() {
+        _state = newV;
+      });
+    }
+  }
+
+  late var controller = widget.controller ?? AnimatedDualSwitcherController();
+
+  @override
+  void initState() {
+    super.initState();
+    startTicker();
+    controller._attach(this);
+  }
+
+  @override
+  void dispose() {
+    marqueeTicker.dispose();
+    super.dispose();
+  }
+
+  void startTicker() {
+    marqueeTicker = createTicker((elapsed) {
+      final alwaysSwitchTo = widget.alwaysSwitchTo;
+      final delta = elapsed - lastElapsed;
+      lastElapsed = elapsed;
+      assert(elapsed >= lastElapsed);
+      if ($state != alwaysSwitchTo) {
+        passed += delta;
+      }
+      if (passed >= widget.switchDuration) {
+        passed = Duration.zero;
+        if (alwaysSwitchTo == null) {
+          $state = !$state;
+        } else {
+          $state = alwaysSwitchTo;
+        }
+      }
+    });
+    marqueeTicker.start();
+  }
+
+  @override
+  void didUpdateWidget(covariant AnimatedDualSwitcher oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    if (widget.controller != controller) {
+      controller.dispose();
+      controller = (widget.controller ?? AnimatedDualSwitcherController()).._attach(this);
+    }
+    if (oldWidget.switchDuration != widget.switchDuration) {
+      passed = Duration.zero;
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AnimatedSwitcher(
+      duration: widget.transitionDuration,
+      child: widget._getWidget($state),
+    );
+  }
+}

lib/timetable/page/preview.dart

@@ -1,6 +1,8 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_platform_widgets/flutter_platform_widgets.dart';
+import 'package:rettulf/rettulf.dart';
 import 'package:sit/design/adaptive/foundation.dart';
+import 'package:sit/design/animation/marquee.dart';
 import 'package:text_scroll/text_scroll.dart';
 
 import '../entity/background.dart';
@@ -13,6 +15,9 @@ import '../entity/pos.dart';
 import '../widgets/style.dart';
 import '../widgets/timetable/board.dart';
 
+import '../i18n.dart';
+import 'timetable.dart';
+
 class TimetablePreviewPage extends StatefulWidget {
   final SitTimetableEntity entity;
 
@@ -32,6 +37,15 @@ class _TimetablePreviewPageState extends State<TimetablePreviewPage> {
   late final $currentPos = ValueNotifier(timetable.locate(DateTime.now()));
   final scrollController = ScrollController();
   late SitTimetableEntity entity = widget.entity;
+  final $showWeekHeader = AnimatedDualSwitcherController();
+
+  @override
+  void initState() {
+    $currentPos.addListener(() {
+      $showWeekHeader.switchTo(true);
+    });
+    super.initState();
+  }
 
   @override
   void dispose() {
@@ -45,7 +59,15 @@ class _TimetablePreviewPageState extends State<TimetablePreviewPage> {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: TextScroll(timetable.name),
+        title: AnimatedDualSwitcher(
+          transitionDuration: Durations.medium4,
+          switchDuration: const Duration(milliseconds: 2000),
+          trueChild: $currentPos >> (ctx, pos) => i18n.weekOrderedName(number: pos.weekIndex + 1).text(),
+          falseChild: TextScroll(timetable.name),
+          alwaysSwitchTo: false,
+          initial: false,
+          controller: $showWeekHeader,
+        ),
         actions: [
           PlatformIconButton(
             icon: const Icon(Icons.swap_horiz),
@@ -60,6 +82,11 @@ class _TimetablePreviewPageState extends State<TimetablePreviewPage> {
         $displayMode: $displayMode,
         $currentPos: $currentPos,
       ),
+      floatingActionButton: TimetableJumpButton(
+        $displayMode: $displayMode,
+        $currentPos: $currentPos,
+        timetable: timetable,
+      ),
     );
   }
 }