perf: expose isPointInPolygon and make 40% faster (at least in JIT mode) (#1907)

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

Author: ignatz

benchmark/point_in_polygon.dart

@@ -0,0 +1,76 @@
+import 'dart:async';
+import 'dart:math' as math;
+import 'dart:ui';
+
+import 'package:flutter_map/src/misc/point_in_polygon.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);
+}
+
+List<Offset> makeCircle(int points, double radius, double phase) {
+  final slice = math.pi * 2 / (points - 1);
+  return List.generate(points, (i) {
+    // Note the modulo is only there to deal with floating point imprecision
+    // and ensure first == last.
+    final angle = slice * (i % (points - 1)) + phase;
+    return Offset(radius * math.cos(angle), radius * math.sin(angle));
+  }, growable: false);
+}
+
+// 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;
+
+  final circle = makeCircle(1000, 1, 0);
+
+  results.add(await timedRun('In circle', () {
+    const point = math.Point(0, 0);
+
+    bool yesPlease = true;
+    for (int i = 0; i < N; ++i) {
+      yesPlease = yesPlease && isPointInPolygon(point, circle);
+    }
+
+    assert(yesPlease, 'should be in circle');
+    return yesPlease;
+  }));
+
+  results.add(await timedRun('Not in circle', () {
+    const point = math.Point(4, 4);
+
+    bool noSir = false;
+    for (int i = 0; i < N; ++i) {
+      noSir = noSir || isPointInPolygon(point, circle);
+    }
+
+    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

@@ -39,42 +39,41 @@ base class _PolygonPainter<R extends Object>
     required LatLng coordinate,
   }) {
     final polygon = projectedPolygon.polygon;
-
-    if (!polygon.boundingBox.contains(coordinate)) return false;
+    if (!polygon.boundingBox.contains(coordinate)) {
+      return false;
+    }
 
     final projectedCoords = getOffsetsXY(
       camera: camera,
       origin: hitTestCameraOrigin,
       points: projectedPolygon.points,
-    ).toList();
+    );
 
     if (projectedCoords.first != projectedCoords.last) {
       projectedCoords.add(projectedCoords.first);
     }
+    final isInPolygon = isPointInPolygon(point, projectedCoords);
 
     final hasHoles = projectedPolygon.holePoints.isNotEmpty;
-    late final List<List<Offset>> projectedHoleCoords;
-    if (hasHoles) {
-      projectedHoleCoords = projectedPolygon.holePoints
-          .map(
-            (points) => getOffsetsXY(
+    final isInHole = hasHoles &&
+        () {
+          for (final points in projectedPolygon.holePoints) {
+            final projectedHoleCoords = getOffsetsXY(
               camera: camera,
               origin: hitTestCameraOrigin,
               points: points,
-            ).toList(),
-          )
-          .toList();
+            );
 
-      if (projectedHoleCoords.firstOrNull != projectedHoleCoords.lastOrNull) {
-        projectedHoleCoords.add(projectedHoleCoords.first);
-      }
-    }
+            if (projectedHoleCoords.first != projectedHoleCoords.last) {
+              projectedHoleCoords.add(projectedHoleCoords.first);
+            }
 
-    final isInPolygon = _isPointInPolygon(point, projectedCoords);
-    final isInHole = hasHoles &&
-        projectedHoleCoords
-            .map((c) => _isPointInPolygon(point, c))
-            .any((e) => e);
+            if (isPointInPolygon(point, projectedHoleCoords)) {
+              return true;
+            }
+          }
+          return false;
+        }();
 
     // Second check handles case where polygon outline intersects a hole,
     // ensuring that the hit matches with the visual representation
@@ -361,24 +360,6 @@ 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/offsets.dart

@@ -25,15 +25,15 @@ List<Offset> getOffsets(MapCamera camera, Offset origin, List<LatLng> points) {
 
   // Optimization: monomorphize the Epsg3857-case to avoid the virtual function overhead.
   if (crs case final Epsg3857 epsg3857) {
-    final v = List<Offset>.filled(len, Offset.zero);
+    final v = List<Offset>.filled(len, Offset.zero, growable: true);
     for (int i = 0; i < len; ++i) {
       final (x, y) = epsg3857.latLngToXY(points[i], zoomScale);
       v[i] = Offset(x + ox, y + oy);
     }
     return v;
   }
 
-  final v = List<Offset>.filled(len, Offset.zero);
+  final v = List<Offset>.filled(len, Offset.zero, growable: true);
   for (int i = 0; i < len; ++i) {
     final (x, y) = crs.latLngToXY(points[i], zoomScale);
     v[i] = Offset(x + ox, y + oy);
@@ -63,7 +63,7 @@ List<Offset> getOffsetsXY({
   // Optimization: monomorphize the CrsWithStaticTransformation-case to avoid
   // the virtual function overhead.
   if (crs case final CrsWithStaticTransformation crs) {
-    final v = List<Offset>.filled(len, Offset.zero);
+    final v = List<Offset>.filled(len, Offset.zero, growable: true);
     for (int i = 0; i < len; ++i) {
       final p = realPoints.elementAt(i);
       final (x, y) = crs.transform(p.x, p.y, zoomScale);
@@ -72,7 +72,7 @@ List<Offset> getOffsetsXY({
     return v;
   }
 
-  final v = List<Offset>.filled(len, Offset.zero);
+  final v = List<Offset>.filled(len, Offset.zero, growable: true);
   for (int i = 0; i < len; ++i) {
     final p = realPoints.elementAt(i);
     final (x, y) = crs.transform(p.x, p.y, zoomScale);

lib/src/misc/point_in_polygon.dart

@@ -0,0 +1,29 @@
+import 'dart:math' as math;
+import 'dart:ui';
+
+/// Checks whether point [p] is within the specified closed [polygon]
+///
+/// Uses the even-odd algorithm and requires closed loop polygons, i.e.
+/// `polygon.first == polygon.last`.
+bool isPointInPolygon(math.Point p, List<Offset> polygon) {
+  final len = polygon.length;
+  assert(len >= 3, 'not a polygon');
+  assert(polygon.first == polygon.last, 'polygon not closed');
+  final double px = p.x.toDouble();
+  final double py = p.y.toDouble();
+
+  bool isInPolygon = false;
+  for (int i = 0, j = len - 1; i < len; 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;
+}

test/misc/point_in_polygon_test.dart

@@ -0,0 +1,41 @@
+import 'dart:math' as math;
+
+import 'package:flutter_map/src/misc/point_in_polygon.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+List<Offset> makeCircle(int points, double radius, double phase) {
+  final slice = math.pi * 2 / (points - 1);
+  return List.generate(points, (i) {
+    // Note the modulo is only there to deal with floating point imprecision
+    // and ensure first == last.
+    final angle = slice * (i % (points - 1)) + phase;
+    return Offset(radius * math.cos(angle), radius * math.sin(angle));
+  }, growable: false);
+}
+
+void main() {
+  test('Smoke test for points in and out of polygons', () {
+    final circle = makeCircle(100, 1, 0);
+
+    // Inside points
+    for (final point in makeCircle(32, 0.8, 0.0001)) {
+      final p = math.Point(point.dx, point.dy);
+      expect(isPointInPolygon(p, circle), isTrue);
+    }
+
+    // Edge-case: check origin
+    expect(isPointInPolygon(const math.Point(0, 0), circle), isTrue);
+
+    // Outside points: small radius
+    for (final point in makeCircle(32, 1.1, 0.0001)) {
+      final p = math.Point(point.dx, point.dy);
+      expect(isPointInPolygon(p, circle), isFalse);
+    }
+
+    // Outside points: large radius
+    for (final point in makeCircle(32, 100000, 0.0001)) {
+      final p = math.Point(point.dx, point.dy);
+      expect(isPointInPolygon(p, circle), isFalse);
+    }
+  });
+}