add in-memory tile cache, tile fade transitions, and performance HUD to map page

lib/pages/map/page.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:math' as math;
 
 import 'package:flutter/gestures.dart'
@@ -30,10 +31,25 @@ class MapPage extends StatefulWidget {
   State<MapPage> createState() => _MapPageState();
 }
 
-class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
+class _MapPageState extends State<MapPage> with TickerProviderStateMixin {
   static const _london = LatLng(51.5074, -0.1278);
   static const _routeColor = Color(0xFFE02425);
   static const _tileSize = 256.0;
+  static const _tileSourcePixelRatio = 2.0;
+  static const _minZoom = 2.0;
+  static const _maxZoom = 24.0;
+  static const _minTileZoom = 2;
+  static const _maxTileZoom = 22;
+  static const _tileOverscan = 1;
+  static const _tileFadeReadyRatio = 0.72;
+  static const _tileFadeDuration = Duration(milliseconds: 220);
+  static const _interactionIdleDelay = Duration(milliseconds: 280);
+  static const _prefetchDebounceDelay = Duration(milliseconds: 280);
+  static const _tilePromotionActiveInterval = Duration(seconds: 1);
+  static const _tilePromotionIdleInterval = Duration(seconds: 1);
+  static const _tilePromotionBatchSize = 28;
+  static const _fpsWindowSize = 90;
+  static const _fpsUpdateInterval = Duration(milliseconds: 240);
   static const _tileUrlTemplate =
       'https://api.mapbox.com/styles/v1/mapbox/streets-v12/tiles/256/{z}/{x}/{y}@2x?access_token=pk.eyJ1IjoiaW1iZW5qaTAzIiwiYSI6ImNtN2Rqdmw5MDA0bzEyaXM3YjE1emkzOXAifQ.cYyCPQE7OvZx0hzKX2hEiQ';
 
@@ -46,6 +62,8 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
   LatLng _mapCenter = _london;
   double _zoom = 12;
   double _targetZoom = 12;
+  int _activeTileZoom = 12;
+  double _devicePixelRatio = 2.0;
   Offset _zoomFocal = Offset.zero;
   Size _mapSize = Size.zero;
   late final Ticker _zoomTicker;
@@ -56,20 +74,105 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
   String? _routeError;
   int _routeRequestId = 0;
   int? _draggingInsertPointIndex;
-  String _lastPrefetchSignature = '';
+  int _lastPrefetchHash = 0;
+  int _lastPrefetchCount = -1;
+  List<String> _pendingPrefetchUrls = const <String>[];
+  Timer? _prefetchDebounceTimer;
+  bool _isInteractionActive = false;
+  Timer? _interactionIdleTimer;
+  Offset _pendingPanDelta = Offset.zero;
+  bool _panFrameScheduled = false;
+  Offset _pendingPanZoomDelta = Offset.zero;
+  double _pendingPanZoomZoomDelta = 0.0;
+  Offset _pendingPanZoomFocal = Offset.zero;
+  bool _panZoomFrameScheduled = false;
+  final List<double> _frameMsWindow = <double>[];
+  late final Stopwatch _fpsUpdateStopwatch;
+  double _displayFps = 0;
+  double _displayFrameMs = 0;
+  final Set<String> _readyTileUrls = <String>{};
+  final Set<String> _pendingReadyTileUrls = <String>{};
+  Timer? _tilePromotionTimer;
+  int? _fallbackTileZoom;
+  bool _fallbackSyncScheduled = false;
+  late final AnimationController _fallbackFadeController;
+
+  void _cancelPrefetchTimer() {
+    _prefetchDebounceTimer?.cancel();
+    _prefetchDebounceTimer = null;
+  }
+
+  void _cancelInteractionTimer() {
+    _interactionIdleTimer?.cancel();
+    _interactionIdleTimer = null;
+  }
+
+  void _cancelTilePromotionTimer() {
+    _tilePromotionTimer?.cancel();
+    _tilePromotionTimer = null;
+  }
 
   @override
   void initState() {
     super.initState();
     _zoomTicker = createTicker(_onZoomTick);
+    _fallbackFadeController =
+        AnimationController(
+          vsync: this,
+          duration: _tileFadeDuration,
+          lowerBound: 0,
+          upperBound: 1,
+          value: 0,
+        )..addStatusListener((status) {
+          if (status != AnimationStatus.dismissed) return;
+          if (!mounted || _fallbackTileZoom == null) return;
+          setState(() {
+            _fallbackTileZoom = null;
+          });
+        });
+    _fpsUpdateStopwatch = Stopwatch()..start();
+    SchedulerBinding.instance.addTimingsCallback(_onFrameTimings);
   }
 
   @override
   void dispose() {
+    _cancelPrefetchTimer();
+    _cancelInteractionTimer();
+    _cancelTilePromotionTimer();
+    SchedulerBinding.instance.removeTimingsCallback(_onFrameTimings);
+    _fallbackFadeController.dispose();
     _zoomTicker.dispose();
     super.dispose();
   }
 
+  void _onFrameTimings(List<FrameTiming> timings) {
+    for (final timing in timings) {
+      final frameMs = timing.totalSpan.inMicroseconds / 1000.0;
+      _frameMsWindow.add(frameMs);
+    }
+    if (_frameMsWindow.length > _fpsWindowSize) {
+      _frameMsWindow.removeRange(0, _frameMsWindow.length - _fpsWindowSize);
+    }
+    if (_fpsUpdateStopwatch.elapsed < _fpsUpdateInterval) return;
+    _fpsUpdateStopwatch.reset();
+    if (_frameMsWindow.isEmpty || !mounted) return;
+
+    var totalMs = 0.0;
+    for (final ms in _frameMsWindow) {
+      totalMs += ms;
+    }
+    final avgMs = totalMs / _frameMsWindow.length;
+    final fps = avgMs <= 0 ? 0.0 : (1000.0 / avgMs);
+    if ((fps - _displayFps).abs() < 0.2 &&
+        (avgMs - _displayFrameMs).abs() < 0.2) {
+      return;
+    }
+    setState(() {
+      _displayFps = fps;
+      _displayFrameMs = avgMs;
+    });
+  }
+
   void _addPoint(LatLng point) {
     setState(() {
       _points.add(point);
@@ -141,7 +244,8 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
     final scale = _tileSize * math.pow(2, zoom).toDouble();
     final x = (latLng.longitude + 180.0) / 360.0 * scale;
     final sinLat = math.sin(latLng.latitude * math.pi / 180.0);
-    final y = (0.5 - math.log((1 + sinLat) / (1 - sinLat)) / (4 * math.pi)) * scale;
+    final y =
+        (0.5 - math.log((1 + sinLat) / (1 - sinLat)) / (4 * math.pi)) * scale;
     return math.Point<double>(x, y);
   }
 
@@ -153,9 +257,24 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
     return LatLng(lat, lon);
   }
 
-  int get _tileZoom => _zoom.floor().clamp(2, 18);
+  int get _tileZoom => _activeTileZoom;
 
-  double get _tileZoomFactor => math.pow(2, _zoom - _tileZoom).toDouble();
+  int _idealTileZoom(double zoomValue, {required double devicePixelRatio}) {
+    final clampedDeviceRatio = devicePixelRatio.clamp(1.0, 4.0).toDouble();
+    final maxTileZoomForScreenResolution =
+        zoomValue +
+        (math.log(clampedDeviceRatio / _tileSourcePixelRatio) / math.ln2);
+    return maxTileZoomForScreenResolution.floor().clamp(
+      _minTileZoom,
+      _maxTileZoom,
+    );
+  }
+
+  math.Point<double> _clampWorldY(math.Point<double> world, double zoom) {
+    final scale = _tileSize * math.pow(2, zoom).toDouble();
+    final maxY = math.max(0.0, scale - 1);
+    return math.Point<double>(world.x, world.y.clamp(0.0, maxY).toDouble());
+  }
 
   Offset _latLngToScreen(LatLng latLng) {
     final centerWorld = _latLngToWorld(_mapCenter, _zoom);
@@ -186,7 +305,10 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
   void _panMap(Offset delta, {bool notify = true}) {
     if (_mapSize == Size.zero) return;
     final centerWorld = _latLngToWorld(_mapCenter, _zoom);
-    final nextCenter = math.Point<double>(centerWorld.x - delta.dx, centerWorld.y - delta.dy);
+    final nextCenter = _clampWorldY(
+      math.Point<double>(centerWorld.x - delta.dx, centerWorld.y - delta.dy),
+      _zoom,
+    );
     void apply() {
       _mapCenter = _worldToLatLng(nextCenter, _zoom);
     }
@@ -198,20 +320,95 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
     }
   }
 
+  void _queuePan(Offset delta) {
+    if (delta == Offset.zero) return;
+    _noteInteraction();
+    _pendingPanDelta += delta;
+    if (_panFrameScheduled) return;
+    _panFrameScheduled = true;
+    SchedulerBinding.instance.scheduleFrameCallback((_) {
+      _panFrameScheduled = false;
+      if (!mounted) return;
+      final pending = _pendingPanDelta;
+      _pendingPanDelta = Offset.zero;
+      if (pending == Offset.zero) return;
+      setState(() {
+        _panMap(pending, notify: false);
+      });
+    });
+  }
+
+  void _queuePanZoomUpdate({
+    required Offset panDelta,
+    required double zoomDelta,
+    required Offset focal,
+  }) {
+    if (panDelta == Offset.zero && zoomDelta.abs() < 0.0001) return;
+    _noteInteraction();
+    _pendingPanZoomDelta += panDelta;
+    _pendingPanZoomZoomDelta += zoomDelta;
+    _pendingPanZoomFocal = focal;
+    if (_panZoomFrameScheduled) return;
+    _panZoomFrameScheduled = true;
+    SchedulerBinding.instance.scheduleFrameCallback((_) {
+      _panZoomFrameScheduled = false;
+      if (!mounted) return;
+      final pendingPan = _pendingPanZoomDelta;
+      final pendingZoom = _pendingPanZoomZoomDelta;
+      final pendingFocal = _pendingPanZoomFocal;
+      _pendingPanZoomDelta = Offset.zero;
+      _pendingPanZoomZoomDelta = 0.0;
+      if (pendingPan == Offset.zero && pendingZoom.abs() < 0.0001) return;
+      setState(() {
+        if (pendingZoom.abs() >= 0.0001) {
+          _setZoomAroundFocal(_zoom + pendingZoom, pendingFocal);
+          _targetZoom = _zoom;
+        }
+        if (pendingPan != Offset.zero) {
+          _panMap(pendingPan, notify: false);
+        }
+      });
+    });
+  }
+
+  void _noteInteraction() {
+    _isInteractionActive = true;
+    _interactionIdleTimer?.cancel();
+    _interactionIdleTimer = Timer(_interactionIdleDelay, () {
+      _isInteractionActive = false;
+      _flushPrefetchNow();
+      _flushTilePromotions(forceAll: true);
+    });
+  }
+
   void _setZoomAroundFocal(double requestedZoom, Offset focal) {
     if (_mapSize == Size.zero) return;
-    final nextZoom = requestedZoom.clamp(2.0, 18.0);
+    final nextZoom = requestedZoom.clamp(_minZoom, _maxZoom);
     if ((nextZoom - _zoom).abs() < 0.0001) return;
 
     final focalLatLng = _screenToLatLng(focal);
     final focalWorldNext = _latLngToWorld(focalLatLng, nextZoom);
-    final centerWorldNext = math.Point<double>(
-      focalWorldNext.x - (focal.dx - _mapSize.width / 2),
-      focalWorldNext.y - (focal.dy - _mapSize.height / 2),
+    final centerWorldNext = _clampWorldY(
+      math.Point<double>(
+        focalWorldNext.x - (focal.dx - _mapSize.width / 2),
+        focalWorldNext.y - (focal.dy - _mapSize.height / 2),
+      ),
+      nextZoom,
     );
 
+    final previousTileZoom = _activeTileZoom;
     _zoom = nextZoom;
     _mapCenter = _worldToLatLng(centerWorldNext, nextZoom);
+    _activeTileZoom = _idealTileZoom(
+      _zoom,
+      devicePixelRatio: _devicePixelRatio,
+    );
+    final nextTileZoom = _activeTileZoom;
+    if (previousTileZoom != nextTileZoom) {
+      _fallbackTileZoom = previousTileZoom;
+      _fallbackFadeController.stop();
+      _fallbackFadeController.value = 1;
+    }
   }
 
   void _onZoomTick(Duration _) {
@@ -227,12 +424,18 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
   }
 
   LatLng _segmentMidpoint(LatLng a, LatLng b) {
-    return LatLng((a.latitude + b.latitude) / 2, (a.longitude + b.longitude) / 2);
+    return LatLng(
+      (a.latitude + b.latitude) / 2,
+      (a.longitude + b.longitude) / 2,
+    );
   }
 
   void _startInsertPointDrag(int segmentIndex, Offset globalPosition) {
     if (segmentIndex < 0 || segmentIndex >= _points.length - 1) return;
-    final midpoint = _segmentMidpoint(_points[segmentIndex], _points[segmentIndex + 1]);
+    final midpoint = _segmentMidpoint(
+      _points[segmentIndex],
+      _points[segmentIndex + 1],
+    );
     final insertIndex = segmentIndex + 1;
     setState(() {
       _points.insert(insertIndex, midpoint);
@@ -265,24 +468,27 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
     _resolveRoute();
   }
 
-  List<Widget> _buildTileWidgets() {
-    if (_mapSize == Size.zero) return const <Widget>[];
+  ({List<Widget> widgets, Set<String> urls, Set<String> prefetchUrls})
+  _buildTileLayer({required int tileZoom, bool prefetchChildren = false}) {
+    if (_mapSize == Size.zero) {
+      return (widgets: <Widget>[], urls: <String>{}, prefetchUrls: <String>{});
+    }
 
-    final tileZoom = _tileZoom;
-    final factor = _tileZoomFactor;
+    final factor = math.pow(2, _zoom - tileZoom).toDouble();
     final centerWorld = _latLngToWorld(_mapCenter, tileZoom.toDouble());
     final minWorldX = centerWorld.x - (_mapSize.width / 2) / factor;
     final maxWorldX = centerWorld.x + (_mapSize.width / 2) / factor;
     final minWorldY = centerWorld.y - (_mapSize.height / 2) / factor;
     final maxWorldY = centerWorld.y + (_mapSize.height / 2) / factor;
 
-    final minTileX = (minWorldX / _tileSize).floor();
-    final maxTileX = (maxWorldX / _tileSize).floor();
-    final minTileY = (minWorldY / _tileSize).floor();
-    final maxTileY = (maxWorldY / _tileSize).floor();
+    final minTileX = (minWorldX / _tileSize).floor() - _tileOverscan;
+    final maxTileX = (maxWorldX / _tileSize).floor() + _tileOverscan;
+    final minTileY = (minWorldY / _tileSize).floor() - _tileOverscan;
+    final maxTileY = (maxWorldY / _tileSize).floor() + _tileOverscan;
 
     final maxIndex = math.pow(2, tileZoom).toInt();
     final tiles = <Widget>[];
+    final urls = <String>{};
     final prefetchUrls = <String>{};
 
     for (var tileX = minTileX; tileX <= maxTileX; tileX++) {
@@ -296,6 +502,7 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
             .replaceAll('{z}', '$tileZoom')
             .replaceAll('{x}', '$wrappedX')
             .replaceAll('{y}', '$tileY');
+        urls.add(url);
 
         tiles.add(
           Positioned(
@@ -304,18 +511,19 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
             top: top,
             width: _tileSize * factor,
             height: _tileSize * factor,
-            child: HiveTileImage(url: url),
+            child: HiveTileImage(url: url, onLoaded: _markTileReady),
           ),
         );
 
-        if (tileZoom < 18) {
+        if (prefetchChildren && tileZoom < _maxTileZoom) {
           final childZoom = tileZoom + 1;
           final childMaxIndex = math.pow(2, childZoom).toInt();
           final childXBase = wrappedX * 2;
           final childYBase = tileY * 2;
           for (var dx = 0; dx < 2; dx++) {
             for (var dy = 0; dy < 2; dy++) {
-              final childX = ((childXBase + dx) % childMaxIndex + childMaxIndex) %
+              final childX =
+                  ((childXBase + dx) % childMaxIndex + childMaxIndex) %
                   childMaxIndex;
               final childY = childYBase + dy;
               if (childY < 0 || childY >= childMaxIndex) continue;
@@ -331,14 +539,105 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
       }
     }
 
-    final prefetchList = prefetchUrls.toList()..sort();
-    final signature = prefetchList.join('|');
-    if (signature != _lastPrefetchSignature) {
-      _lastPrefetchSignature = signature;
-      HiveTileCache.prefetchUrls(prefetchList);
+    return (widgets: tiles, urls: urls, prefetchUrls: prefetchUrls);
+  }
+
+  void _markTileReady(String url) {
+    if (_readyTileUrls.contains(url) || _pendingReadyTileUrls.contains(url)) {
+      return;
+    }
+    _pendingReadyTileUrls.add(url);
+    _scheduleTilePromotionTick();
+  }
+
+  void _scheduleTilePromotionTick() {
+    if (_tilePromotionTimer != null || _pendingReadyTileUrls.isEmpty) return;
+    final delay = _isInteractionActive
+        ? _tilePromotionActiveInterval
+        : _tilePromotionIdleInterval;
+    _tilePromotionTimer = Timer(delay, () {
+      _tilePromotionTimer = null;
+      _flushTilePromotions(forceAll: true);
+    });
+  }
+
+  void _flushTilePromotions({bool forceAll = false}) {
+    if (_pendingReadyTileUrls.isEmpty) return;
+    final maxPromotions = forceAll || !_isInteractionActive
+        ? _pendingReadyTileUrls.length
+        : _tilePromotionBatchSize;
+    final promoted = <String>[];
+    final iterator = _pendingReadyTileUrls.iterator;
+    while (promoted.length < maxPromotions && iterator.moveNext()) {
+      promoted.add(iterator.current);
+    }
+    if (promoted.isEmpty) return;
+
+    var changed = false;
+    for (final url in promoted) {
+      _pendingReadyTileUrls.remove(url);
+      changed = _readyTileUrls.add(url) || changed;
     }
 
-    return tiles;
+    if (changed && mounted && _fallbackTileZoom != null) {
+      setState(() {});
+    }
+    if (_pendingReadyTileUrls.isNotEmpty) {
+      _scheduleTilePromotionTick();
+    }
+  }
+
+  double _tileReadyRatio(Set<String> urls) {
+    if (urls.isEmpty) return 1;
+    var ready = 0;
+    for (final url in urls) {
+      if (_readyTileUrls.contains(url)) {
+        ready += 1;
+      }
+    }
+    return ready / urls.length;
+  }
+
+  void _syncFallbackFade(double readyRatio) {
+    if (_fallbackTileZoom == null || _fallbackSyncScheduled) return;
+    _fallbackSyncScheduled = true;
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      _fallbackSyncScheduled = false;
+      if (!mounted || _fallbackTileZoom == null) return;
+      if (readyRatio >= _tileFadeReadyRatio) {
+        if (_fallbackFadeController.status == AnimationStatus.reverse ||
+            _fallbackFadeController.value <= 0) {
+          return;
+        }
+        _fallbackFadeController.reverse(from: _fallbackFadeController.value);
+        return;
+      }
+      if (_fallbackFadeController.value != 1) {
+        _fallbackFadeController.stop();
+        _fallbackFadeController.value = 1;
+      }
+    });
+  }
+
+  void _schedulePrefetch(Set<String> urls) {
+    if (urls.isEmpty) return;
+    final hash = Object.hashAllUnordered(urls);
+    if (hash == _lastPrefetchHash && urls.length == _lastPrefetchCount) return;
+    _lastPrefetchHash = hash;
+    _lastPrefetchCount = urls.length;
+    _pendingPrefetchUrls = urls.toList(growable: false);
+    if (_isInteractionActive) return;
+    _prefetchDebounceTimer?.cancel();
+    _prefetchDebounceTimer = Timer(_prefetchDebounceDelay, _flushPrefetchNow);
+  }
+
+  void _flushPrefetchNow() {
+    _prefetchDebounceTimer?.cancel();
+    _prefetchDebounceTimer = null;
+    final pending = _pendingPrefetchUrls;
+    _pendingPrefetchUrls = const <String>[];
+    if (pending.isEmpty) return;
+    HiveTileCache.prefetchUrls(pending);
   }
 
   List<Widget> _buildPointWidgets() {
@@ -380,8 +679,10 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
           top: screen.dy - 22,
           child: GestureDetector(
             behavior: HitTestBehavior.opaque,
-            onPanStart: (details) => _startInsertPointDrag(i, details.globalPosition),
-            onPanUpdate: (details) => _updateInsertPointDrag(details.globalPosition),
+            onPanStart: (details) =>
+                _startInsertPointDrag(i, details.globalPosition),
+            onPanUpdate: (details) =>
+                _updateInsertPointDrag(details.globalPosition),
             onPanEnd: (_) => _finishInsertPointDrag(),
             onPanCancel: _finishInsertPointDrag,
             child: SizedBox(
@@ -394,9 +695,16 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
                   decoration: BoxDecoration(
                     color: Colors.white.withValues(alpha: 0.95),
                     shape: BoxShape.circle,
-                    border: Border.all(color: const Color(0xFF111827), width: 1.5),
+                    border: Border.all(
+                      color: const Color(0xFF111827),
+                      width: 1.5,
+                    ),
+                  ),
+                  child: const Icon(
+                    Icons.open_with,
+                    size: 14,
+                    color: Color(0xFF111827),
                   ),
-                  child: const Icon(Icons.open_with, size: 14, color: Color(0xFF111827)),
                 ),
               ),
             ),
@@ -409,6 +717,35 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
 
   @override
   Widget build(BuildContext context) {
+    final nextDevicePixelRatio = MediaQuery.devicePixelRatioOf(context);
+    if ((nextDevicePixelRatio - _devicePixelRatio).abs() > 0.01) {
+      _devicePixelRatio = nextDevicePixelRatio;
+      final nextTileZoom = _idealTileZoom(
+        _zoom,
+        devicePixelRatio: _devicePixelRatio,
+      );
+      if (nextTileZoom != _activeTileZoom) {
+        _fallbackTileZoom = _activeTileZoom;
+        _fallbackFadeController.stop();
+        _fallbackFadeController.value = 1;
+        _activeTileZoom = nextTileZoom;
+      }
+    }
+
+    final currentLayer = _buildTileLayer(
+      tileZoom: _tileZoom,
+      prefetchChildren: !_isInteractionActive,
+    );
+    final currentReadyRatio = _tileReadyRatio(currentLayer.urls);
+    _syncFallbackFade(currentReadyRatio);
+
+    _schedulePrefetch(currentLayer.prefetchUrls);
+
+    final fallbackLayer =
+        _fallbackTileZoom == null || _fallbackTileZoom == _tileZoom
+        ? null
+        : _buildTileLayer(tileZoom: _fallbackTileZoom!);
+
     final routePoints = _resolvedRoute.isNotEmpty ? _resolvedRoute : _points;
     final routeScreenPoints = routePoints.map(_latLngToScreen).toList();
 
@@ -423,61 +760,86 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
                 return Listener(
                   onPointerSignal: (event) {
                     if (event is PointerScaleEvent) {
+                      _noteInteraction();
                       setState(() {
-                        _setZoomAroundFocal(_zoom + math.log(event.scale) / math.ln2, event.localPosition);
+                        _setZoomAroundFocal(
+                          _zoom + math.log(event.scale) / math.ln2,
+                          event.localPosition,
+                        );
                         _targetZoom = _zoom;
                       });
                     } else if (event is PointerScrollEvent) {
                       if (event.kind == PointerDeviceKind.trackpad) {
-                        _panMap(event.scrollDelta);
+                        _queuePan(event.scrollDelta);
                       } else {
+                        _noteInteraction();
                         final zoomStep = math.log(1.1) / math.ln2;
                         _zoomFocal = event.localPosition;
-                        _targetZoom = (_targetZoom +
-                                (event.scrollDelta.dy < 0 ? zoomStep : -zoomStep))
-                            .clamp(2.0, 18.0);
+                        _targetZoom =
+                            (_targetZoom +
+                                    (event.scrollDelta.dy < 0
+                                        ? zoomStep
+                                        : -zoomStep))
+                                .clamp(_minZoom, _maxZoom);
                         if (!_zoomTicker.isTicking) _zoomTicker.start();
                       }
                     }
                   },
                   onPointerPanZoomStart: (PointerPanZoomStartEvent event) {
                     _lastPinchScale = 1.0;
+                    _pendingPanZoomDelta = Offset.zero;
+                    _pendingPanZoomZoomDelta = 0.0;
+                    _pendingPanZoomFocal = event.localPosition;
+                    _noteInteraction();
                   },
                   onPointerPanZoomUpdate: (PointerPanZoomUpdateEvent event) {
-                    setState(() {
-                      if ((_lastPinchScale - event.scale).abs() > 0.25) {
-                        _lastPinchScale = event.scale;
-                      }
-                      final scaleChange = event.scale / _lastPinchScale;
-                      _lastPinchScale = event.scale;
-                      final dz = math.log(scaleChange) / math.ln2;
-                      _setZoomAroundFocal(_zoom + dz, event.localPosition);
-                      _targetZoom = _zoom;
-                      if (event.panDelta != Offset.zero) {
-                        _panMap(event.panDelta, notify: false);
-                      }
-                    });
+                    final scaleChange = event.scale / _lastPinchScale;
+                    _lastPinchScale = event.scale;
+                    final dz = (scaleChange - 1.0).abs() > 0.001
+                        ? math.log(scaleChange) / math.ln2
+                        : 0.0;
+                    _queuePanZoomUpdate(
+                      panDelta: event.panDelta,
+                      zoomDelta: dz,
+                      focal: event.localPosition,
+                    );
+                  },
+                  onPointerPanZoomEnd: (PointerPanZoomEndEvent event) {
+                    _noteInteraction();
                   },
-                  onPointerPanZoomEnd: (PointerPanZoomEndEvent event) {},
                   child: GestureDetector(
                     key: _mapKey,
                     behavior: HitTestBehavior.opaque,
                     onPanUpdate: (details) {
                       if (_draggingInsertPointIndex != null) return;
-                      _panMap(details.delta);
+                      _queuePan(details.delta);
                     },
                     onTapUp: (details) {
-                      if (!_isAddPointArmed || _draggingInsertPointIndex != null) return;
+                      if (!_isAddPointArmed ||
+                          _draggingInsertPointIndex != null) {
+                        return;
+                      }
                       _addPoint(_screenToLatLng(details.localPosition));
                     },
                     child: ClipRect(
                       child: Stack(
                         children: [
-                          ..._buildTileWidgets(),
+                          const Positioned.fill(
+                            child: ColoredBox(color: Color(0xFFECECEC)),
+                          ),
+                          if (fallbackLayer != null)
+                            FadeTransition(
+                              opacity: _fallbackFadeController,
+                              child: Stack(children: fallbackLayer.widgets),
+                            ),
+                          ...currentLayer.widgets,
                           Positioned.fill(
                             child: IgnorePointer(
                               child: CustomPaint(
-                                painter: _RoutePainter(points: routeScreenPoints, routeColor: _routeColor),
+                                painter: _RoutePainter(
+                                  points: routeScreenPoints,
+                                  routeColor: _routeColor,
+                                ),
                               ),
                             ),
                           ),
@@ -519,7 +881,10 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
                           spreadRadius: 2,
                         ),
                       ],
-                      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 10),
+                      padding: const EdgeInsets.symmetric(
+                        horizontal: 12,
+                        vertical: 10,
+                      ),
                       child: _StatusPanel(
                         isAddPointArmed: _isAddPointArmed,
                         isResolvingRoute: _isResolvingRoute,
@@ -532,6 +897,20 @@ class _MapPageState extends State<MapPage> with SingleTickerProviderStateMixin {
               ),
             ),
           ),
+          SafeArea(
+            child: Align(
+              alignment: Alignment.topRight,
+              child: Padding(
+                padding: const EdgeInsets.all(10),
+                child: IgnorePointer(
+                  child: _PerformanceHud(
+                    fps: _displayFps,
+                    frameMs: _displayFrameMs,
+                  ),
+                ),
+              ),
+            ),
+          ),
           const SafeArea(
             child: Align(
               alignment: Alignment.bottomLeft,
@@ -615,6 +994,51 @@ class _HudCornerNotice extends StatelessWidget {
   }
 }
 
+class _PerformanceHud extends StatelessWidget {
+  const _PerformanceHud({required this.fps, required this.frameMs});
+
+  final double fps;
+  final double frameMs;
+
+  @override
+  Widget build(BuildContext context) {
+    return DecoratedBox(
+      decoration: BoxDecoration(
+        color: Colors.white.withValues(alpha: 0.9),
+        borderRadius: BorderRadius.circular(10),
+        boxShadow: const [
+          BoxShadow(color: Color(0x26000000), blurRadius: 4, spreadRadius: 2),
+        ],
+      ),
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.end,
+          children: [
+            Text(
+              '${fps.toStringAsFixed(1)} FPS',
+              style: const TextStyle(
+                fontSize: 13,
+                fontWeight: FontWeight.w700,
+                color: Color(0xFF111827),
+              ),
+            ),
+            Text(
+              '${frameMs.toStringAsFixed(1)} ms',
+              style: const TextStyle(
+                fontSize: 11,
+                fontWeight: FontWeight.w600,
+                color: Color(0xFF4B5563),
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
 class _StatusPanel extends StatelessWidget {
   const _StatusPanel({
     required this.isAddPointArmed,
@@ -675,10 +1099,7 @@ class _StatusPanel extends StatelessWidget {
             const SizedBox(height: 4),
             Text(
               routeError!,
-              style: const TextStyle(
-                fontSize: 12,
-                color: Color(0xFFB91C1C),
-              ),
+              style: const TextStyle(fontSize: 12, color: Color(0xFFB91C1C)),
             ),
           ],
           const SizedBox(height: 4),

lib/pages/map/tiles/hive_tile_cache.dart

@@ -1,3 +1,4 @@
+import 'dart:collection';
 import 'dart:typed_data';
 
 import 'package:hive/hive.dart';
@@ -8,9 +9,14 @@ class HiveTileCache {
 
   static const String _boxName = 'map_tile_cache_v1';
   static const int _maxEntries = 6000;
+  static const int _maxMemoryEntries = 1024;
   static const Duration _staleAfter = Duration(days: 14);
+  static const Duration _prefetchCooldown = Duration(seconds: 25);
   static final Map<String, Future<Uint8List?>> _inFlight =
       <String, Future<Uint8List?>>{};
+  static final LinkedHashMap<String, Uint8List> _memoryCache =
+      LinkedHashMap<String, Uint8List>();
+  static final Map<String, int> _recentPrefetches = <String, int>{};
 
   static Future<void> init() async {
     if (!Hive.isBoxOpen(_boxName)) {
@@ -27,30 +33,68 @@ class HiveTileCache {
     }
   }
 
-  static Future<Uint8List?> getOrFetch(String url) async {
-    final now = DateTime.now().millisecondsSinceEpoch;
-    final box = _boxOrNull;
-    if (box == null) return _fetchWithoutCache(url);
-    final cached = _freshCachedBytes(box, url, now);
-    if (cached != null) return cached;
+  static Uint8List? peek(String url) {
+    final inMemory = _memoryCache.remove(url);
+    if (inMemory != null) {
+      _memoryCache[url] = inMemory;
+      return inMemory;
+    }
 
-    return _fetchAndStore(box, url, now);
+    final box = _boxOrNull;
+    if (box == null) return null;
+    final now = DateTime.now().millisecondsSinceEpoch;
+    final cached = _freshCachedBytes(box, url, now);
+    if (cached == null || cached.isEmpty) return null;
+    _rememberInMemory(url, cached);
+    return cached;
   }
 
-  static void prefetchUrls(
-    Iterable<String> urls, {
-    int maxCount = 96,
-  }) {
+  static Future<Uint8List?> getOrFetch(String url) async {
+    final immediate = peek(url);
+    if (immediate != null) return immediate;
+
+    final now = DateTime.now().millisecondsSinceEpoch;
+    final box = _boxOrNull;
+    if (box == null) {
+      final bytes = await _fetchWithoutCache(url);
+      if (bytes != null && bytes.isNotEmpty) {
+        _rememberInMemory(url, bytes);
+      }
+      return bytes;
+    }
+
+    final bytes = await _fetchAndStore(box, url, now);
+    if (bytes != null && bytes.isNotEmpty) {
+      _rememberInMemory(url, bytes);
+    }
+    return bytes;
+  }
+
+  static void prefetchUrls(Iterable<String> urls, {int maxCount = 48}) {
     final box = _boxOrNull;
     if (box == null) return;
     final now = DateTime.now().millisecondsSinceEpoch;
+    _recentPrefetches.removeWhere(
+      (_, ts) => now - ts > _prefetchCooldown.inMilliseconds,
+    );
     var queued = 0;
     for (final url in urls) {
       if (queued >= maxCount) break;
-      if (_freshCachedBytes(box, url, now) != null) continue;
+      if (_memoryCache.containsKey(url)) continue;
+      if (box.containsKey(url)) continue;
+      final lastPrefetchTs = _recentPrefetches[url];
+      if (lastPrefetchTs != null &&
+          now - lastPrefetchTs < _prefetchCooldown.inMilliseconds) {
+        continue;
+      }
       if (_inFlight.containsKey(url)) continue;
+      _recentPrefetches[url] = now;
       queued += 1;
-      _fetchAndStore(box, url, now);
+      _fetchAndStore(box, url, now).then((bytes) {
+        if (bytes != null && bytes.isNotEmpty) {
+          _rememberInMemory(url, bytes);
+        }
+      });
     }
   }
 
@@ -89,6 +133,7 @@ class HiveTileCache {
       if (response.statusCode != 200) return null;
       final bytes = response.bodyBytes;
       await box.put(url, <String, dynamic>{'ts': now, 'bytes': bytes});
+      _rememberInMemory(url, bytes);
       await _pruneIfNeeded(box);
       return bytes;
     } catch (_) {
@@ -116,13 +161,30 @@ class HiveTileCache {
     }
 
     entries.sort((a, b) {
-      final ats = (a.value is Map && a.value['ts'] is int) ? a.value['ts'] as int : 0;
-      final bts = (b.value is Map && b.value['ts'] is int) ? b.value['ts'] as int : 0;
+      final ats = (a.value is Map && a.value['ts'] is int)
+          ? a.value['ts'] as int
+          : 0;
+      final bts = (b.value is Map && b.value['ts'] is int)
+          ? b.value['ts'] as int
+          : 0;
       return ats.compareTo(bts);
     });
 
     for (var i = 0; i < overflow; i++) {
-      await box.delete(entries[i].key);
+      final key = entries[i].key;
+      await box.delete(key);
+      if (key is String) {
+        _memoryCache.remove(key);
+      }
+    }
+  }
+
+  static void _rememberInMemory(String url, Uint8List bytes) {
+    if (bytes.isEmpty) return;
+    _memoryCache.remove(url);
+    _memoryCache[url] = bytes;
+    while (_memoryCache.length > _maxMemoryEntries) {
+      _memoryCache.remove(_memoryCache.keys.first);
     }
   }
 }

lib/pages/map/tiles/hive_tile_image.dart

@@ -4,9 +4,10 @@ import 'package:flutter/material.dart';
 import 'package:rra_app/pages/map/tiles/hive_tile_cache.dart';
 
 class HiveTileImage extends StatefulWidget {
-  const HiveTileImage({required this.url, super.key});
+  const HiveTileImage({required this.url, this.onLoaded, super.key});
 
   final String url;
+  final ValueChanged<String>? onLoaded;
 
   @override
   State<HiveTileImage> createState() => _HiveTileImageState();
@@ -15,18 +16,30 @@ class HiveTileImage extends StatefulWidget {
 class _HiveTileImageState extends State<HiveTileImage> {
   Uint8List? _bytes;
   String? _loadingUrl;
+  bool _reportedLoaded = false;
 
   @override
   void initState() {
     super.initState();
-    _load(widget.url);
+    _bytes = HiveTileCache.peek(widget.url);
+    if (_bytes != null && _bytes!.isNotEmpty) {
+      _reportLoaded();
+    } else {
+      _load(widget.url);
+    }
   }
 
   @override
   void didUpdateWidget(covariant HiveTileImage oldWidget) {
     super.didUpdateWidget(oldWidget);
     if (oldWidget.url != widget.url) {
-      _load(widget.url);
+      _reportedLoaded = false;
+      _bytes = HiveTileCache.peek(widget.url);
+      if (_bytes != null && _bytes!.isNotEmpty) {
+        _reportLoaded();
+      } else {
+        _load(widget.url);
+      }
     }
   }
 
@@ -38,20 +51,29 @@ class _HiveTileImageState extends State<HiveTileImage> {
       setState(() {
         _bytes = bytes;
       });
+      _reportLoaded();
     }
   }
 
+  void _reportLoaded() {
+    if (_reportedLoaded) return;
+    _reportedLoaded = true;
+    widget.onLoaded?.call(widget.url);
+  }
+
   @override
   Widget build(BuildContext context) {
     final bytes = _bytes;
     if (bytes == null || bytes.isEmpty) {
-      return const ColoredBox(color: Color(0xFFE0E0E0));
+      return const ColoredBox(color: Colors.transparent);
     }
+    _reportLoaded();
     return Image.memory(
       bytes,
+      scale: widget.url.contains('@2x') ? 2.0 : 1.0,
       fit: BoxFit.cover,
       gaplessPlayback: true,
-      filterQuality: FilterQuality.low,
+      filterQuality: FilterQuality.medium,
     );
   }
 }