perf: pre-project polylines, and improve simplification & culling

lib/src/layer/polygon_layer/polygon_layer.dart

@@ -84,7 +84,7 @@ class _PolygonLayerState extends State<PolygonLayer> {
 
     final projected = _cachedProjectedPolygons ??= List.generate(
       widget.polygons.length,
-      (i) => _ProjectedPolygon.fromPolygon(
+      (i) => _ProjectedPolygon._fromPolygon(
         camera.crs.projection,
         widget.polygons[i],
       ),

lib/src/layer/polygon_layer/projected_polygon.dart

@@ -12,7 +12,7 @@ class _ProjectedPolygon {
     this.holePoints,
   });
 
-  _ProjectedPolygon.fromPolygon(Projection projection, Polygon polygon)
+  _ProjectedPolygon._fromPolygon(Projection projection, Polygon polygon)
       : this._(
           polygon: polygon,
           points: List<DoublePoint>.generate(

lib/src/layer/polyline_layer/painter.dart

@@ -3,7 +3,7 @@ part of 'polyline_layer.dart';
 /// [CustomPainter] for [Polygon]s.
 class _PolylinePainter<R extends Object> extends CustomPainter {
   /// Reference to the list of [Polyline]s.
-  final List<Polyline<R>> polylines;
+  final List<_ProjectedPolyline> polylines;
 
   /// Reference to the [MapCamera].
   final MapCamera camera;
@@ -20,18 +20,6 @@ class _PolylinePainter<R extends Object> extends CustomPainter {
     required this.minimumHitbox,
   });
 
-  List<Offset> getOffsets(Offset origin, List<LatLng> points) => List.generate(
-        points.length,
-        (index) => getOffset(origin, points[index]),
-        growable: false,
-      );
-
-  Offset getOffset(Offset origin, LatLng point) {
-    // Critically create as little garbage as possible. This is called on every frame.
-    final projected = camera.project(point);
-    return Offset(projected.x - origin.dx, projected.y - origin.dy);
-  }
-
   @override
   bool? hitTest(Offset position) {
     if (hitNotifier == null) return null;
@@ -41,8 +29,11 @@ class _PolylinePainter<R extends Object> extends CustomPainter {
     final origin =
         camera.project(camera.center).toOffset() - camera.size.toOffset() / 2;
 
-    for (final polyline in polylines.reversed) {
-      if (polyline.hitValue == null) continue;
+    for (final projectedPolyline in polylines.reversed) {
+      final polyline = projectedPolyline.polyline as Polyline<R>;
+      if (polyline.hitValue == null) {
+        continue;
+      }
 
       // TODO: For efficiency we'd ideally filter by bounding box here. However
       // we'd need to compute an extended bounding box that accounts account for
@@ -51,11 +42,11 @@ class _PolylinePainter<R extends Object> extends CustomPainter {
       //   continue;
       // }
 
-      final offsets = getOffsets(origin, polyline.points);
+      final offsets = getOffsetsXY(camera, origin, projectedPolyline.points);
       final strokeWidth = polyline.useStrokeWidthInMeter
           ? _metersToStrokeWidth(
               origin,
-              polyline.points.first,
+              _unproject(projectedPolyline.points.first),
               offsets.first,
               polyline.strokeWidth,
             )
@@ -141,8 +132,9 @@ class _PolylinePainter<R extends Object> extends CustomPainter {
     final origin =
         camera.project(camera.center).toOffset() - camera.size.toOffset() / 2;
 
-    for (final polyline in polylines) {
-      final offsets = getOffsets(origin, polyline.points);
+    for (final projectedPolyline in polylines) {
+      final polyline = projectedPolyline.polyline;
+      final offsets = getOffsetsXY(camera, origin, projectedPolyline.points);
       if (offsets.isEmpty) {
         continue;
       }
@@ -159,7 +151,7 @@ class _PolylinePainter<R extends Object> extends CustomPainter {
       if (polyline.useStrokeWidthInMeter) {
         strokeWidth = _metersToStrokeWidth(
           origin,
-          polyline.points.first,
+          _unproject(projectedPolyline.points.first),
           offsets.first,
           polyline.strokeWidth,
         );
@@ -281,10 +273,13 @@ class _PolylinePainter<R extends Object> extends CustomPainter {
     double strokeWidthInMeters,
   ) {
     final r = _distance.offset(p0, strokeWidthInMeters, 180);
-    final delta = o0 - getOffset(origin, r);
+    final delta = o0 - getOffset(camera, origin, r);
     return delta.distance;
   }
 
+  LatLng _unproject(DoublePoint p0) =>
+      camera.crs.projection.unprojectXY(p0.x, p0.y);
+
   @override
   bool shouldRepaint(_PolylinePainter<R> oldDelegate) => false;
 }

lib/src/layer/polyline_layer/polyline.dart

@@ -52,21 +52,6 @@ class Polyline<R extends Object> {
     this.hitValue,
   });
 
-  Polyline<R> copyWithNewPoints(List<LatLng> points) => Polyline<R>(
-        points: points,
-        strokeWidth: strokeWidth,
-        color: color,
-        borderStrokeWidth: borderStrokeWidth,
-        borderColor: borderColor,
-        gradientColors: gradientColors,
-        colorsStop: colorsStop,
-        isDotted: isDotted,
-        strokeCap: strokeCap,
-        strokeJoin: strokeJoin,
-        useStrokeWidthInMeter: useStrokeWidthInMeter,
-        hitValue: hitValue,
-      );
-
   @override
   bool operator ==(Object other) =>
       identical(this, other) ||