fix: prevent infinite looping when polygon labels displayed on rotated map (#2054)

Co-authored-by: JaffaKetchup <[email protected]>

Author: monsieurtanuki

CHANGELOG.md

@@ -4,16 +4,26 @@ Please consider [donating](https://docs.fleaflet.dev/supporters#support-us) or [
 
 This CHANGELOG does not include every commit and/or PR - it is a hand picked selection of the ones that have an effect on you. For a full list of changes, please check the GitHub repository releases/tags.
 
-## [8.1.0] - 2025/02/XX
+## [8.1.1] - 2025/03/08
+
+Contains the following user-affecting bug fixes:
+
+- Prevent infinite looping when polygon labels displayed on rotated map - [#2054](https://github.com/fleaflet/flutter_map/pull/2054) for [#2052](https://github.com/fleaflet/flutter_map/issues/2052)
+
+Many thanks to these contributors (in no particular order):
+
+- @monsieurtanuki
+
+## [8.1.0] - 2025/02/25
 
 Contains the following user-affecting changes:
 
 - Added multi-world support for `Polygon`s and `Polyline`s - [#2033](https://github.com/fleaflet/flutter_map/pull/2033)
 
 Contains the following user-affecting bug fixes:
 
-- Ensure movement gestures emit events when starting - [#2035](https://github.com/fleaflet/flutter_map/pull/2035)
-- Ensure `MapController.rotateAroundPoint` does not move map when already rotated - [#2029](https://github.com/fleaflet/flutter_map/pull/2029)
+- Ensure movement gestures emit events when starting - [#2035](https://github.com/fleaflet/flutter_map/pull/2035) for [#1939](https://github.com/fleaflet/flutter_map/issues/1939)
+- Ensure `MapController.rotateAroundPoint` does not move map when already rotated - [#2029](https://github.com/fleaflet/flutter_map/pull/2029) for [#2028](https://github.com/fleaflet/flutter_map/issues/2028)
 
 Many thanks to these contributors (in no particular order):
 

example/pubspec.yaml

@@ -1,7 +1,7 @@
 name: flutter_map_example
 description: Example application for 'flutter_map' package
 publish_to: "none"
-version: 8.1.0
+version: 8.1.1
 
 environment:
   sdk: ">=3.6.0 <4.0.0"

lib/src/layer/polygon_layer/label.dart

@@ -17,13 +17,26 @@ void Function(Canvas canvas)? _buildLabelTextPainter({
   // Cull labels where the polygon is still on the map but the label would not be.
   // Currently this is only enabled when the map isn't rotated, since the placementOffset
   // is relative to the MobileLayerTransformer rather than in actual screen coordinates.
+  final double textWidth;
+  final double textHeight;
+  final double mapWidth;
+  final double mapHeight;
   if (rotationRad == 0) {
-    if (dx + width / 2 < 0 || dx - width / 2 > mapSize.width) {
-      return null;
-    }
-    if (dy + height / 2 < 0 || dy - height / 2 > mapSize.height) {
-      return null;
-    }
+    textWidth = width;
+    textHeight = height;
+    mapWidth = mapSize.width;
+    mapHeight = mapSize.height;
+  } else {
+    // lazily we imagine the worst case scenario regarding sizes, instead of
+    // computing the angles
+    textWidth = textHeight = max(width, height);
+    mapWidth = mapHeight = max(mapSize.width, mapSize.height);
+  }
+  if (dx + textWidth / 2 < 0 || dx - textWidth / 2 > mapWidth) {
+    return null;
+  }
+  if (dy + textHeight / 2 < 0 || dy - textHeight / 2 > mapHeight) {
+    return null;
   }
 
   // Note: I'm pretty sure this doesn't work for concave shapes. It would be more

lib/src/layer/shared/feature_layer_utils.dart

@@ -54,13 +54,26 @@ mixin FeatureLayerUtils on CustomPainter {
   /// Internally, the worker is invoked in the 'negative' worlds (worlds to the
   /// left of the 'primary' world) until repetition is stopped, then in the
   /// 'positive' worlds: <--||-->.
-  bool workAcrossWorlds(WorldWorkControl Function(double shift) work) {
+  bool workAcrossWorlds(
+    WorldWorkControl Function(double shift) work,
+  ) {
+    // Protection in case of unexpected infinite loop if `work` never returns
+    // `invisible`. e.g. https://github.com/fleaflet/flutter_map/issues/2052.
+    const maxShiftsCount = 10;
+    int shiftsCount = 0;
+
+    void protectInfiniteLoop() {
+      if (++shiftsCount > maxShiftsCount) throw const StackOverflowError();
+    }
+
+    protectInfiniteLoop();
     if (work(0) == WorldWorkControl.hit) return true;
 
     if (worldWidth == 0) return false;
 
     negativeWorldsLoop:
     for (double shift = -worldWidth;; shift -= worldWidth) {
+      protectInfiniteLoop();
       switch (work(shift)) {
         case WorldWorkControl.hit:
           return true;
@@ -71,6 +84,7 @@ mixin FeatureLayerUtils on CustomPainter {
     }
 
     for (double shift = worldWidth;; shift += worldWidth) {
+      protectInfiniteLoop();
       switch (work(shift)) {
         case WorldWorkControl.hit:
           return true;

pubspec.yaml

@@ -1,6 +1,6 @@
 name: flutter_map
 description: A versatile mapping package for Flutter, that's simple and easy to learn, yet completely customizable and configurable
-version: 8.1.0
+version: 8.1.1
 
 repository: https://github.com/fleaflet/flutter_map
 issue_tracker: https://github.com/fleaflet/flutter_map/issues

windowsApplicationInstallerSetup.iss

@@ -2,7 +2,7 @@
 ; SEE THE DOCUMENTATION FOR DETAILS ON CREATING INNO SETUP SCRIPT FILES!
 
 #define MyAppName "flutter_map Demo"
-#define MyAppVersion "for 8.1.0"
+#define MyAppVersion "for 8.1.1"
 #define MyAppPublisher "fleaflet"
 #define MyAppURL "https://github.com/fleaflet/flutter_map"
 #define MyAppSupportURL "https://github.com/fleaflet/flutter_map/issues"