Make isPointInPolygon 40% faster (at least in JIT mode).

I mostly looked at the function because I wanted to use it myself but it
was private. So I thought, if I expose it then I could at least put a
ribbon on it by adding a benchmark.

Before:

  (duration: 0:00:05.998949, name: In circle)
  (duration: 0:00:06.866919, name: Not in circle)

After:

  (duration: 0:00:03.649496, name: In circle)
  (duration: 0:00:04.611599, name: Not in circle)

Note, I opportunistically touched crs to remove the dart:ui dependency.
This way it can be compiled with dart (w/o flutter) rendering the
instructions in the benchmark correct again. Unfortunately,
pointInPolygon is not so fortunate and needs flutter due to
the dependency on ui.Offset. That's why I could only run it with
"flutter test" in JIT mode.

benchmark/point_in_polygon.dart

@@ -0,0 +1,76 @@
+import 'dart:async';
+import 'dart:ui';
+import 'dart:math' as math;
+
+import 'package:flutter_map/src/misc/point_in_polygon.dart';
+import 'package:latlong2/latlong.dart';
+import 'package:logger/logger.dart';
+
+class NoFilter extends LogFilter {
+  @override
+  bool shouldLog(LogEvent event) => true;
+}
+
+typedef Result = ({
+  String name,
+  Duration duration,
+});
+
+Future<Result> timedRun(String name, dynamic Function() body) async {
+  Logger().i('running $name...');
+  final watch = Stopwatch()..start();
+  await body();
+  watch.stop();
+
+  return (name: name, duration: watch.elapsed);
+}
+
+// NOTE: to have a more prod like comparison, run with:
+//     $ dart compile exe benchmark/crs.dart && ./benchmark/crs.exe
+//
+// If you run in JIT mode, the resulting execution times will be a lot more similar.
+Future<void> main() async {
+  Logger.level = Level.all;
+  Logger.defaultFilter = NoFilter.new;
+  Logger.defaultPrinter = SimplePrinter.new;
+
+  final results = <Result>[];
+  const N = 3000000;
+  const POINTS = 1000;
+
+  results.add(await timedRun('In circle', () {
+    final polygon = List.generate(POINTS, (i) {
+      final angle = math.pi * 2 / POINTS * i;
+      return Offset(math.cos(angle), math.sin(angle));
+    });
+
+    const point = math.Point(0, 0);
+
+    bool yesPlease = true;
+    for (int i = 0; i < N; ++i) {
+      yesPlease = yesPlease && pointInPolygon(point, polygon);
+    }
+
+    assert(yesPlease, 'should be in circle');
+    return yesPlease;
+  }));
+
+  results.add(await timedRun('Not in circle', () {
+    final polygon = List.generate(POINTS, (i) {
+      final angle = math.pi * 2 / POINTS * i;
+      return Offset(math.cos(angle), math.sin(angle));
+    });
+
+    const point = math.Point(4, 4);
+
+    bool noSir = false;
+    for (int i = 0; i < N; ++i) {
+      noSir = noSir || pointInPolygon(point, polygon);
+    }
+
+    assert(!noSir, 'should not be in circle');
+    return noSir;
+  }));
+
+  Logger().i('Results:\n${results.map((r) => r.toString()).join('\n')}');
+}

lib/src/geo/crs.dart

@@ -1,7 +1,7 @@
 import 'dart:math' as math hide Point;
 import 'dart:math' show Point;
 
-import 'package:flutter_map/flutter_map.dart';
+import 'package:flutter_map/src/misc/bounds.dart';
 import 'package:latlong2/latlong.dart';
 import 'package:meta/meta.dart';
 import 'package:proj4dart/proj4dart.dart' as proj4;

lib/src/layer/polygon_layer/painter.dart

@@ -70,10 +70,10 @@ base class _PolygonPainter<R extends Object>
       }
     }
 
-    final isInPolygon = _isPointInPolygon(point, projectedCoords);
+    final isInPolygon = pointInPolygon(point, projectedCoords);
     final isInHole = hasHoles &&
         projectedHoleCoords
-            .map((c) => _isPointInPolygon(point, c))
+            .map((c) => pointInPolygon(point, c))
             .any((e) => e);
 
     // Second check handles case where polygon outline intersects a hole,
@@ -361,24 +361,6 @@ base class _PolygonPainter<R extends Object>
     );
   }
 
-  /// Checks whether point [p] is within the specified closed [polygon]
-  ///
-  /// Uses the even-odd algorithm.
-  static bool _isPointInPolygon(math.Point p, List<Offset> polygon) {
-    bool isInPolygon = false;
-
-    for (int i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
-      if ((((polygon[i].dy <= p.y) && (p.y < polygon[j].dy)) ||
-              ((polygon[j].dy <= p.y) && (p.y < polygon[i].dy))) &&
-          (p.x <
-              (polygon[j].dx - polygon[i].dx) *
-                      (p.y - polygon[i].dy) /
-                      (polygon[j].dy - polygon[i].dy) +
-                  polygon[i].dx)) isInPolygon = !isInPolygon;
-    }
-    return isInPolygon;
-  }
-
   @override
   bool shouldRepaint(_PolygonPainter<R> oldDelegate) =>
       polygons != oldDelegate.polygons ||

lib/src/layer/polygon_layer/polygon_layer.dart

@@ -9,6 +9,7 @@ import 'package:flutter_map/flutter_map.dart';
 import 'package:flutter_map/src/layer/shared/layer_interactivity/internal_hit_detectable.dart';
 import 'package:flutter_map/src/layer/shared/line_patterns/pixel_hiker.dart';
 import 'package:flutter_map/src/misc/offsets.dart';
+import 'package:flutter_map/src/misc/point_in_polygon.dart';
 import 'package:flutter_map/src/misc/simplify.dart';
 import 'package:latlong2/latlong.dart' hide Path;
 import 'package:polylabel/polylabel.dart';

lib/src/misc/point_in_polygon.dart

@@ -0,0 +1,25 @@
+import 'dart:math' as math;
+import 'dart:ui';
+
+/// Checks whether point [p] is within the specified closed [polygon]
+///
+/// Uses the even-odd algorithm.
+bool pointInPolygon(math.Point p, List<Offset> polygon) {
+  final double px = p.x.toDouble();
+  final double py = p.y.toDouble();
+
+  bool isInPolygon = false;
+  for (int i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
+    final double poIx = polygon[i].dx;
+    final double poIy = polygon[i].dy;
+
+    final double poJx = polygon[j].dx;
+    final double poJy = polygon[j].dy;
+
+    if ((((poIy <= py) && (py < poJy)) || ((poJy <= py) && (py < poIy))) &&
+        (px < (poJx - poIx) * (py - poIy) / (poJy - poIy) + poIx)) {
+      isInPolygon = !isInPolygon;
+    }
+  }
+  return isInPolygon;
+}