catch and correct possible bad values for lat/lon, add tests

lib/services/coordinate_validation.dart

@@ -0,0 +1,23 @@
+/// Shared validation helpers for geographic coordinates and zoom levels.
+///
+/// Used anywhere a [LatLng]-like value or zoom level comes from an external
+/// or platform source (GPS fixes, persisted preferences, live map camera
+/// state) that isn't guaranteed to be finite/in-range. Centralizing this
+/// avoids subtly inconsistent validation logic being duplicated across the
+/// GPS controller, map position persistence, and live camera guards.
+library;
+
+/// Validate that a latitude or longitude value is finite and within the
+/// valid range for geographic coordinates (-180 to 180).
+///
+/// Note: this intentionally uses the wider +/-180 range (rather than +/-90
+/// for latitude) so a single helper can validate both latitude and
+/// longitude values without the caller needing to track which is which.
+bool isValidCoordinate(double value) {
+  return !value.isNaN && !value.isInfinite && value >= -180.0 && value <= 180.0;
+}
+
+/// Validate that a zoom level is finite and within a sane range.
+bool isValidZoom(double zoom, {double min = 0.0, double max = 25.0}) {
+  return !zoom.isNaN && !zoom.isInfinite && zoom >= min && zoom <= max;
+}

lib/widgets/map/gps_controller.dart

@@ -8,9 +8,11 @@ import 'package:flutter/foundation.dart' show defaultTargetPlatform, TargetPlatf
 import '../../dev_config.dart';
 import '../../app_state.dart' show FollowMeMode;
 import '../../services/proximity_alert_service.dart';
+import '../../services/coordinate_validation.dart';
 import '../../models/osm_node.dart';
 import '../../models/node_profile.dart';
 
+
 /// Simple GPS controller that handles precise location permissions only.
 /// Key principles: 
 /// - Respect "denied forever" - stop trying
@@ -187,6 +189,21 @@ class GpsController {
 
   /// Handle incoming GPS position
   void _onPositionReceived(Position position) {
+    // Guard against malformed fixes from the platform location stack (some
+    // OEM/fused location providers occasionally emit NaN/Infinite lat/lng,
+    // especially while a fix is still being acquired). An unvalidated bad
+    // value here can crash the app at launch (via initialCenter) or corrupt
+    // the live map camera (via follow-me animateTo), so treat it like any
+    // other transient location error rather than trusting it.
+    if (!isValidCoordinate(position.latitude) || !isValidCoordinate(position.longitude)) {
+      debugPrint(
+        '[GpsController] Ignoring invalid GPS position: '
+        'lat=${position.latitude}, lng=${position.longitude}',
+      );
+      return;
+    }
+
+
     final newLocation = LatLng(position.latitude, position.longitude);
     _currentLocation = newLocation;
     
@@ -209,6 +226,7 @@ class GpsController {
   }
 
   /// Handle GPS stream errors
+
   void _onPositionError(dynamic error) {
     debugPrint('[GpsController] Position stream error: $error');
     if (_hasLocation) {

lib/widgets/map/map_position_manager.dart

@@ -3,6 +3,9 @@ import 'package:flutter_map_animations/flutter_map_animations.dart';
 import 'package:latlong2/latlong.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
+import '../../services/coordinate_validation.dart' as coord_validation;
+
+
 
 /// Manages map position persistence and initial positioning.
 /// Handles saving/loading last map position and moving to initial locations.
@@ -30,7 +33,8 @@ class MapPositionManager {
       final zoom = prefs.getDouble('last_map_zoom');
       
       if (lat != null && lng != null && 
-          _isValidCoordinate(lat) && _isValidCoordinate(lng)) {
+          coord_validation.isValidCoordinate(lat) && coord_validation.isValidCoordinate(lng)) {
+
         final validZoom = zoom != null && _isValidZoom(zoom) ? zoom : 15.0;
         _initialLocation = LatLng(lat, lng);
         _initialZoom = validZoom;
@@ -50,9 +54,10 @@ class MapPositionManager {
       try {
         final zoom = _initialZoom ?? 15.0;
         // Double-check coordinates are valid before moving
-        if (_isValidCoordinate(_initialLocation!.latitude) && 
-            _isValidCoordinate(_initialLocation!.longitude) && 
+        if (coord_validation.isValidCoordinate(_initialLocation!.latitude) &&
+            coord_validation.isValidCoordinate(_initialLocation!.longitude) &&
             _isValidZoom(zoom)) {
+
           controller.mapController.move(_initialLocation!, zoom);
           _hasMovedToInitialLocation = true;
           debugPrint('[MapPositionManager] Moved to initial location: ${_initialLocation!.latitude}, ${_initialLocation!.longitude}');
@@ -70,9 +75,10 @@ class MapPositionManager {
   Future<void> saveMapPosition(LatLng location, double zoom) async {
     try {
       // Validate coordinates and zoom before saving
-      if (!_isValidCoordinate(location.latitude) || 
-          !_isValidCoordinate(location.longitude) || 
+      if (!coord_validation.isValidCoordinate(location.latitude) ||
+          !coord_validation.isValidCoordinate(location.longitude) ||
           !_isValidZoom(zoom)) {
+
         debugPrint('[MapPositionManager] Invalid map position, not saving: lat=${location.latitude}, lng=${location.longitude}, zoom=$zoom');
         return;
       }
@@ -102,15 +108,8 @@ class MapPositionManager {
     }
   }
 
-  /// Validate that a coordinate value is valid (not NaN, not infinite, within bounds)
-  bool _isValidCoordinate(double value) {
-    return !value.isNaN && 
-           !value.isInfinite && 
-           value >= -180.0 && 
-           value <= 180.0;
-  }
-
   /// Validate that a zoom level is valid
+
   bool _isValidZoom(double zoom) {
     return !zoom.isNaN && 
            !zoom.isInfinite && 

lib/widgets/map_view.dart

@@ -26,9 +26,12 @@ import 'node_limit_indicator.dart';
 import 'proximity_alert_banner.dart';
 import '../dev_config.dart';
 import '../services/proximity_alert_service.dart';
+import '../services/coordinate_validation.dart';
 import 'sheet_aware_map.dart';
+
 import 'custom_scale_bar.dart';
 
+
 class MapView extends StatefulWidget {
   final AnimatedMapController controller;
   const MapView({
@@ -80,6 +83,15 @@ class MapViewState extends State<MapView> {
   
   // Track map center to clear queue on significant panning
   LatLng? _lastCenter;
+
+  // Track the last known-good (finite, in-range) camera center/zoom so we
+  // can self-heal if the camera ever gets pushed into a degenerate state
+  // (e.g. by an edge case in flutter_map's internal gesture-to-camera
+  // pipeline). This mirrors the validation used for persisted map position
+  // in MapPositionManager, applied to the *live* camera as well.
+  LatLng? _lastValidCenter;
+  double? _lastValidZoom;
+
   
   // State for proximity alert banner
   bool _showProximityBanner = false;
@@ -275,6 +287,29 @@ class MapViewState extends State<MapView> {
     return (!appState.offlineMode && appState.isInSearchMode) ? 60.0 : 0.0;
   }
 
+  /// Get a known-good fallback location for [initialCenter], preferring a
+  /// validated GPS location, then a validated persisted position, then a
+  /// hardcoded default. GpsController already validates incoming fixes, but
+  /// this extra check keeps launch resilient even if that guard is ever
+  /// bypassed (e.g. future refactor).
+  LatLng get _safeInitialCenter {
+    final gpsLocation = _gpsController.currentLocation;
+    if (gpsLocation != null &&
+        isValidCoordinate(gpsLocation.latitude) &&
+        isValidCoordinate(gpsLocation.longitude)) {
+      return gpsLocation;
+    }
+    final persisted = _positionManager.initialLocation;
+    if (persisted != null &&
+        isValidCoordinate(persisted.latitude) &&
+        isValidCoordinate(persisted.longitude)) {
+      return persisted;
+    }
+    return LatLng(37.7749, -122.4194);
+  }
+
+
+
 
   @override
   void didUpdateWidget(covariant MapView oldWidget) {
@@ -414,18 +449,55 @@ class MapViewState extends State<MapView> {
               key: ValueKey('map_${appState.selectedTileProvider?.id ?? 'none'}_${appState.selectedTileType?.id ?? 'none'}_${appState.offlineMode}_${_tileManager.mapRebuildKey}'),
               mapController: _controller.mapController,
               options: MapOptions(
-              initialCenter: _gpsController.currentLocation ?? _positionManager.initialLocation ?? LatLng(37.7749, -122.4194),
+              initialCenter: _safeInitialCenter,
             initialZoom: _positionManager.initialZoom ?? 15,
+
             minZoom: 1.0,
             maxZoom: (appState.selectedTileType?.maxZoom ?? 18).toDouble(),
             interactionOptions: _interactionManager.getInteractionOptions(editSession),
             onPositionChanged: (pos, gesture) {
+              // Self-heal if the camera has been pushed into a degenerate
+              // state (non-finite or wildly out-of-range center/zoom). This
+              // has been observed to occur silently during ordinary panning
+              // (no crash, no console output) — likely an edge case in
+              // flutter_map's internal gesture-to-camera math — leaving the
+              // map showing a blank grey view with no tiles or markers,
+              // since every subsequent gesture computes its new position as
+              // a delta from the already-broken center. Snap back to the
+              // last known-good position the moment this is detected rather
+              // than requiring the user to discover the GPS button "fixes"
+              // it (which works only because it supplies a fresh valid
+              // destination).
+              if (!isValidCoordinate(pos.center.latitude) ||
+                  !isValidCoordinate(pos.center.longitude) ||
+                  !isValidZoom(pos.zoom)) {
+
+                debugPrint(
+                  '[MapView] Detected invalid camera position '
+                  '(lat=${pos.center.latitude}, lng=${pos.center.longitude}, zoom=${pos.zoom}) '
+                  '- snapping back to last known-good position',
+                );
+                final recoveryCenter = _lastValidCenter ?? _safeInitialCenter;
+                final recoveryZoom = _lastValidZoom ?? (_positionManager.initialZoom ?? 15.0);
+                WidgetsBinding.instance.addPostFrameCallback((_) {
+                  try {
+                    _controller.mapController.move(recoveryCenter, recoveryZoom);
+                  } catch (e) {
+                    debugPrint('[MapView] Failed to recover camera position: $e');
+                  }
+                });
+                return; // Don't process this invalid position further
+              }
+              _lastValidCenter = pos.center;
+              _lastValidZoom = pos.zoom;
+
               setState(() {}); // Instant UI update for zoom, etc.
               if (gesture) {
                 widget.onUserGesture();
               }
               
               // Enforce minimum zoom level for add/edit node sheets (but not tag sheet)
+
               if ((session != null || editSession != null) && pos.zoom < kMinZoomForNodeEditingSheets) {
                 // User tried to zoom out below minimum - snap back to minimum zoom
                 _controller.animateTo(

test/services/coordinate_validation_test.dart

@@ -0,0 +1,56 @@
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:deflockapp/services/coordinate_validation.dart';
+
+void main() {
+  group('isValidCoordinate', () {
+    test('accepts normal in-range values', () {
+      expect(isValidCoordinate(0), isTrue);
+      expect(isValidCoordinate(37.7749), isTrue);
+      expect(isValidCoordinate(-122.4194), isTrue);
+      expect(isValidCoordinate(180), isTrue);
+      expect(isValidCoordinate(-180), isTrue);
+    });
+
+    test('rejects NaN', () {
+      expect(isValidCoordinate(double.nan), isFalse);
+    });
+
+    test('rejects positive and negative infinity', () {
+      expect(isValidCoordinate(double.infinity), isFalse);
+      expect(isValidCoordinate(double.negativeInfinity), isFalse);
+    });
+
+    test('rejects out-of-range values', () {
+      expect(isValidCoordinate(180.1), isFalse);
+      expect(isValidCoordinate(-180.1), isFalse);
+      expect(isValidCoordinate(1000), isFalse);
+    });
+  });
+
+  group('isValidZoom', () {
+    test('accepts normal in-range values', () {
+      expect(isValidZoom(0), isTrue);
+      expect(isValidZoom(15), isTrue);
+      expect(isValidZoom(25), isTrue);
+    });
+
+    test('rejects NaN and Infinite', () {
+      expect(isValidZoom(double.nan), isFalse);
+      expect(isValidZoom(double.infinity), isFalse);
+      expect(isValidZoom(double.negativeInfinity), isFalse);
+    });
+
+    test('rejects out-of-range values with default bounds', () {
+      expect(isValidZoom(-1), isFalse);
+      expect(isValidZoom(26), isFalse);
+    });
+
+    test('respects custom min/max bounds', () {
+      expect(isValidZoom(0.5, min: 1.0, max: 20.0), isFalse);
+      expect(isValidZoom(1.0, min: 1.0, max: 20.0), isTrue);
+      expect(isValidZoom(20.0, min: 1.0, max: 20.0), isTrue);
+      expect(isValidZoom(20.1, min: 1.0, max: 20.0), isFalse);
+    });
+  });
+}