Add more comments on the internal nature of types and explicitly anno…

…tate CrsWithStaticTransformation as internal.

lib/flutter_map.dart

@@ -16,7 +16,7 @@
 /// * discord.gg: <https://discord.gg/BwpEsjqMAH>
 library flutter_map;
 
-export 'package:flutter_map/src/geo/crs.dart';
+export 'package:flutter_map/src/geo/crs.dart' hide CrsWithStaticTransformation;
 export 'package:flutter_map/src/geo/latlng_bounds.dart';
 export 'package:flutter_map/src/gestures/interactive_flag.dart';
 export 'package:flutter_map/src/gestures/latlng_tween.dart';

lib/src/geo/crs.dart

@@ -58,7 +58,9 @@ abstract class Crs {
   Bounds<double>? getProjectedBounds(double zoom);
 }
 
+/// Internal base class for CRS with a single zoom-level independent transformation.
 @immutable
+@internal
 abstract class CrsWithStaticTransformation extends Crs {
   @nonVirtual
   @protected

lib/src/misc/offsets.dart

@@ -1,6 +1,7 @@
 import 'dart:ui';
 
 import 'package:flutter_map/flutter_map.dart';
+import 'package:flutter_map/src/geo/crs.dart';
 import 'package:flutter_map/src/misc/simplify.dart';
 import 'package:latlong2/latlong.dart';
 

lib/src/misc/simplify.dart

@@ -7,13 +7,15 @@ import 'package:flutter_map/src/geo/crs.dart';
 import 'package:latlong2/latlong.dart';
 import 'package:meta/meta.dart';
 
-// Custom point due to math.Point<double> being slow. Math operations tend to
-// have 20+x penalty for virtual function overhead given the reified nature of
-// Dart generics.
+/// Internal double-precision point/vector implementation not to be used in publicly.
+///
+/// This is an optimization. Vector operations on math.Point tend to incur a 20+x
+/// penalty due to virtual function overhead caused by reified generics.
+///
+/// Further note that unlike math.Point, members are mutable to allow object reuse/pooling
+/// and therefore reduce GC pressure.
 @internal
-class DoublePoint {
-  // Note: Allow mutability for reuse/pooling to reduce GC pressure and increase performance.
-  // Geometry operations should be safe-by-default to avoid accidental bugs.
+final class DoublePoint {
   double x;
   double y;