[web] Add shared tests for ui.Path (flutter/engine#37222)

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/path_metrics.dart

@@ -20,7 +20,7 @@ class CkPathMetrics extends IterableBase<ui.PathMetric>
 
   /// The [CkPath.isEmpty] case is special-cased to avoid booting the WASM machinery just to find out there are no contours.
   @override
-  Iterator<ui.PathMetric> get iterator => _path.isEmpty
+  late final Iterator<ui.PathMetric> iterator = _path.isEmpty
       ? const CkPathMetricIteratorEmpty._()
       : CkContourMeasureIter(this);
 }
@@ -42,7 +42,7 @@ class CkContourMeasureIter extends ManagedSkiaObject<SkContourMeasureIter>
     if (currentMetric == null) {
       throw RangeError(
           'PathMetricIterator is not pointing to a PathMetric. This can happen in two situations:\n'
-          '- The iteration has not started yet. If so, call "moveNext" to start iteration.'
+          '- The iteration has not started yet. If so, call "moveNext" to start iteration.\n'
           '- The iterator ran out of elements. If so, check that "moveNext" returns true prior to calling "current".');
     }
     return currentMetric;

engine/src/flutter/lib/web_ui/lib/src/engine/html/path/path.dart

@@ -1170,10 +1170,10 @@ class SurfacePath implements ui.Path {
         points[p] += offsetX;
         points[p + 1] += offsetY;
       } else {
-        final double x = offsetX + points[p];
-        final double y = offsetY + points[p + 1];
-        points[p] = (matrix4[0] * x) + (matrix4[4] * y) + matrix4[12];
-        points[p + 1] = (matrix4[1] * x) + (matrix4[5] * y) + matrix4[13];
+        final double x = points[p];
+        final double y = points[p + 1];
+        points[p] = (matrix4[0] * x) + (matrix4[4] * y) + (matrix4[12] + offsetX);
+        points[p + 1] = (matrix4[1] * x) + (matrix4[5] * y) + (matrix4[13] + offsetY);
       }
     }
     _resetAfterEdit();

engine/src/flutter/lib/web_ui/lib/src/engine/html/path/path_metrics.dart

@@ -34,7 +34,7 @@ class SurfacePathMetrics extends IterableBase<ui.PathMetric>
     implements ui.PathMetrics {
   SurfacePathMetrics(PathRef path, bool forceClosed)
       : _iterator =
-            SurfacePathMetricIterator._(_SurfacePathMeasure(path, forceClosed));
+            SurfacePathMetricIterator._(_SurfacePathMeasure(PathRef.shallowCopy(path), forceClosed));
 
   final SurfacePathMetricIterator _iterator;
 
@@ -497,7 +497,15 @@ class SurfacePathMetricIterator implements Iterator<ui.PathMetric> {
   final _SurfacePathMeasure _pathMeasure;
 
   @override
-  SurfacePathMetric get current => _pathMetric!;
+  SurfacePathMetric get current {
+    if (_pathMetric == null) {
+      throw RangeError(
+          'PathMetricIterator is not pointing to a PathMetric. This can happen in two situations:\n'
+          '- The iteration has not started yet. If so, call "moveNext" to start iteration.\n'
+          '- The iterator ran out of elements. If so, check that "moveNext" returns true prior to calling "current".');
+    }
+    return _pathMetric!;
+  }
 
   @override
   bool moveNext() {

engine/src/flutter/lib/web_ui/test/ui/README.md

@@ -0,0 +1,12 @@
+# UI Tests
+
+These tests are intended to be renderer-agnostic. These tests should not use
+APIs which only exist in either the HTML or CanvasKit renderers.
+
+In practice, this means these tests should only use `dart:ui` APIs or
+`dart:_engine` APIs which are not renderer-specific.
+
+## Notes
+
+These tests should call `setUpUiTest()` at the top level to initialize the
+renderer they are expected to run.

engine/src/flutter/lib/web_ui/test/ui/path_test.dart

@@ -0,0 +1,241 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:typed_data' show Float64List;
+
+import 'package:test/bootstrap/browser.dart';
+import 'package:test/test.dart';
+import 'package:ui/ui.dart';
+
+import 'utils.dart';
+
+void main() {
+  internalBootstrapBrowserTest(() => testMain);
+}
+
+void testMain() {
+  setUpUiTest();
+  test('path getBounds', () {
+    const Rect r = Rect.fromLTRB(1.0, 3.0, 5.0, 7.0);
+    final Path p = Path()..addRect(r);
+    expect(p.getBounds(), equals(r));
+    p.lineTo(20.0, 15.0);
+    expect(p.getBounds(), equals(const Rect.fromLTRB(1.0, 3.0, 20.0, 15.0)));
+  });
+
+  test('path combine rect', () {
+    final Rect c1 = Rect.fromCircle(center: const Offset(10.0, 10.0), radius: 10.0);
+    final Rect c2 = Rect.fromCircle(center: const Offset(5.0, 5.0), radius: 10.0);
+    final Rect c1UnionC2 = c1.expandToInclude(c2);
+    final Rect c1IntersectC2 = c1.intersect(c2);
+    final Path pathCircle1 = Path()..addRect(c1);
+    final Path pathCircle2 = Path()..addRect(c2);
+
+    final Path difference = Path.combine(PathOperation.difference, pathCircle1, pathCircle2);
+    expect(difference.getBounds(), equals(c1));
+
+    final Path reverseDifference = Path.combine(PathOperation.reverseDifference, pathCircle1, pathCircle2);
+    expect(reverseDifference.getBounds(), equals(c2));
+
+    final Path union = Path.combine(PathOperation.union, pathCircle1, pathCircle2);
+    expect(union.getBounds(), equals(c1UnionC2));
+
+    final Path intersect = Path.combine(PathOperation.intersect, pathCircle1, pathCircle2);
+    expect(intersect.getBounds(), equals(c1IntersectC2));
+
+    // the bounds on this will be the same as union - but would draw a missing inside piece.
+    final Path xor = Path.combine(PathOperation.xor, pathCircle1, pathCircle2);
+    expect(xor.getBounds(), equals(c1UnionC2));
+  // TODO(hterkelsen): Implement Path.combine in the HTML renderer, https://github.com/flutter/flutter/issues/44572
+  }, skip: isHtml);
+
+  test('path combine oval', () {
+    final Rect c1 = Rect.fromCircle(center: const Offset(10.0, 10.0), radius: 10.0);
+    final Rect c2 = Rect.fromCircle(center: const Offset(5.0, 5.0), radius: 10.0);
+    final Rect c1UnionC2 = c1.expandToInclude(c2);
+    final Rect c1IntersectC2 = c1.intersect(c2);
+    final Path pathCircle1 = Path()..addOval(c1);
+    final Path pathCircle2 = Path()..addOval(c2);
+
+    final Path difference = Path.combine(PathOperation.difference, pathCircle1, pathCircle2);
+
+    expect(difference.getBounds().top, closeTo(0.88, 0.01));
+
+    final Path reverseDifference = Path.combine(PathOperation.reverseDifference, pathCircle1, pathCircle2);
+    expect(reverseDifference.getBounds().right, closeTo(14.11, 0.01));
+
+    final Path union = Path.combine(PathOperation.union, pathCircle1, pathCircle2);
+    expect(union.getBounds(), equals(c1UnionC2));
+
+    final Path intersect = Path.combine(PathOperation.intersect, pathCircle1, pathCircle2);
+    expect(intersect.getBounds(), equals(c1IntersectC2));
+
+    // the bounds on this will be the same as union - but would draw a missing inside piece.
+    final Path xor = Path.combine(PathOperation.xor, pathCircle1, pathCircle2);
+    expect(xor.getBounds(), equals(c1UnionC2));
+  // TODO(hterkelsen): Implement Path.combine in the HTML renderer, https://github.com/flutter/flutter/issues/44572
+  }, skip: isHtml);
+
+  test('path clone', () {
+    final Path p1 = Path()..lineTo(20.0, 20.0);
+    final Path p2 = Path.from(p1);
+
+    expect(p1.getBounds(), equals(p2.getBounds()));
+
+    p1.lineTo(10.0, 30.0);
+    expect(p1.getBounds().bottom, equals(p2.getBounds().bottom + 10));
+  });
+
+  test('shift tests', () {
+    const Rect bounds = Rect.fromLTRB(0.0, 0.0, 10.0, 10.0);
+    final Path p = Path()..addRect(bounds);
+    expect(p.getBounds(), equals(bounds));
+    final Path shifted = p.shift(const Offset(10, 10));
+    expect(shifted.getBounds(), equals(const Rect.fromLTRB(10, 10, 20, 20)));
+  });
+
+  test('transformation tests', () {
+    const Rect bounds = Rect.fromLTRB(0.0, 0.0, 10.0, 10.0);
+    final Path p = Path()..addRect(bounds);
+    final Float64List scaleMatrix = Float64List.fromList(<double>[
+      2.5, 0.0, 0.0, 0.0, // first col
+      0.0, 0.5, 0.0, 0.0, // second col
+      0.0, 0.0, 1.0, 0.0, // third col
+      0.0, 0.0, 0.0, 1.0, // fourth col
+    ]);
+
+    expect(p.getBounds(), equals(bounds));
+    final Path pTransformed = p.transform(scaleMatrix);
+
+    expect(pTransformed.getBounds(),
+        equals(const Rect.fromLTRB(0.0, 0.0, 10 * 2.5, 10 * 0.5)));
+
+    final Path p2 = Path()..lineTo(10.0, 10.0);
+
+    p.addPath(p2, const Offset(10.0, 10.0));
+    expect(p.getBounds(), equals(const Rect.fromLTRB(0.0, 0.0, 20.0, 20.0)));
+
+    p.addPath(p2, const Offset(20.0, 20.0), matrix4: scaleMatrix);
+    expect(p.getBounds(),
+        equals(const Rect.fromLTRB(0.0, 0.0, 20 + (10 * 2.5), 20 + (10 * .5))));
+
+    p.extendWithPath(p2, Offset.zero);
+    expect(p.getBounds(), equals(const Rect.fromLTRB(0.0, 0.0, 45.0, 25.0)));
+
+    p.extendWithPath(p2, const Offset(45.0, 25.0), matrix4: scaleMatrix);
+    expect(p.getBounds(), equals(const Rect.fromLTRB(0.0, 0.0, 70.0, 30.0)));
+  });
+
+  test('path metrics tests', () {
+    final Path simpleHorizontalLine = Path()..lineTo(10.0, 0.0);
+
+    // basic tests on horizontal line
+    final PathMetrics simpleHorizontalMetrics = simpleHorizontalLine.computeMetrics();
+    expect(() => simpleHorizontalMetrics.iterator.current, throwsRangeError);
+    expect(simpleHorizontalMetrics.iterator.moveNext(), isTrue);
+    expect(simpleHorizontalMetrics.iterator.current, isNotNull);
+    expect(simpleHorizontalMetrics.iterator.current.length, equals(10.0));
+    expect(simpleHorizontalMetrics.iterator.current.isClosed, isFalse);
+    final Path simpleExtract = simpleHorizontalMetrics.iterator.current.extractPath(1.0, 9.0);
+    expect(simpleExtract.getBounds(), equals(const Rect.fromLTRB(1.0, 0.0, 9.0, 0.0)));
+    final Tangent posTan = simpleHorizontalMetrics.iterator.current.getTangentForOffset(1.0)!;
+    expect(posTan.position, equals(const Offset(1.0, 0.0)));
+    expect(posTan.angle, equals(0.0));
+
+    expect(simpleHorizontalMetrics.iterator.moveNext(), isFalse);
+    expect(() => simpleHorizontalMetrics.iterator.current, throwsRangeError);
+
+    // test with forceClosed
+    final PathMetrics simpleMetricsClosed = simpleHorizontalLine.computeMetrics(forceClosed: true);
+    expect(() => simpleHorizontalMetrics.iterator.current, throwsRangeError);
+    expect(simpleMetricsClosed.iterator.moveNext(), isTrue);
+    expect(simpleMetricsClosed.iterator.current, isNotNull);
+    expect(simpleMetricsClosed.iterator.current.length, equals(20.0)); // because we forced close
+    expect(simpleMetricsClosed.iterator.current.isClosed, isTrue);
+    final Path simpleExtract2 = simpleMetricsClosed.iterator.current.extractPath(1.0, 9.0);
+    expect(simpleExtract2.getBounds(), equals(const Rect.fromLTRB(1.0, 0.0, 9.0, 0.0)));
+    expect(simpleMetricsClosed.iterator.moveNext(), isFalse);
+
+    // test getTangentForOffset with vertical line
+    final Path simpleVerticalLine = Path()..lineTo(0.0, 10.0);
+    final PathMetrics simpleMetricsVertical = simpleVerticalLine.computeMetrics()..iterator.moveNext();
+    final Tangent posTanVertical = simpleMetricsVertical.iterator.current.getTangentForOffset(5.0)!;
+    expect(posTanVertical.position, equals(const Offset(0.0, 5.0)));
+    expect(posTanVertical.angle, closeTo(-1.5708, .0001)); // 90 degrees
+
+    // test getTangentForOffset with diagonal line
+    final Path simpleDiagonalLine = Path()..lineTo(10.0, 10.0);
+    final PathMetrics simpleMetricsDiagonal = simpleDiagonalLine.computeMetrics()..iterator.moveNext();
+    final double midPoint = simpleMetricsDiagonal.iterator.current.length / 2;
+    final Tangent posTanDiagonal = simpleMetricsDiagonal.iterator.current.getTangentForOffset(midPoint)!;
+    expect(posTanDiagonal.position, equals(const Offset(5.0, 5.0)));
+    expect(posTanDiagonal.angle, closeTo(-0.7853981633974483, .00001)); // ~45 degrees
+
+    // test a multi-contour path
+    final Path multiContour = Path()
+      ..lineTo(0.0, 10.0)
+      ..moveTo(10.0, 10.0)
+      ..lineTo(10.0, 15.0);
+
+    final PathMetrics multiContourMetric = multiContour.computeMetrics();
+    expect(() => multiContourMetric.iterator.current, throwsRangeError);
+    expect(multiContourMetric.iterator.moveNext(), isTrue);
+    expect(multiContourMetric.iterator.current, isNotNull);
+    expect(multiContourMetric.iterator.current.length, equals(10.0));
+    expect(multiContourMetric.iterator.moveNext(), isTrue);
+    expect(multiContourMetric.iterator.current, isNotNull);
+    expect(multiContourMetric.iterator.current.length, equals(5.0));
+    expect(multiContourMetric.iterator.moveNext(), isFalse);
+    expect(() => multiContourMetric.iterator.current, throwsRangeError);
+  // TODO(hterkelsen): forceClosed in computeMetrics is ignored in the HTML renderer, https://github.com/flutter/flutter/issues/114446
+  }, skip: isHtml);
+
+  test('PathMetrics can remember lengths and isClosed', () {
+    final Path path = Path()..lineTo(0, 10)
+                            ..close()
+                            ..moveTo(0, 15)
+                            ..lineTo(10, 15);
+    final List<PathMetric> metrics = path.computeMetrics().toList();
+    expect(metrics.length, 2);
+    expect(metrics[0].length, 20);
+    expect(metrics[0].isClosed, true);
+    expect(metrics[0].getTangentForOffset(4.0)!.vector, const Offset(0.0, 1.0));
+    expect(metrics[0].extractPath(4.0, 10.0).computeMetrics().first.length, 6.0);
+    expect(metrics[1].length, 10);
+    expect(metrics[1].isClosed, false);
+    expect(metrics[1].getTangentForOffset(4.0)!.vector, const Offset(1.0, 0.0));
+    expect(metrics[1].extractPath(4.0, 6.0).computeMetrics().first.length, 2.0);
+  // TODO(hterkelsen): isClosed always returns false in the HTML renderer, https://github.com/flutter/flutter/issues/114446
+  }, skip: isHtml);
+
+  test('PathMetrics on a mutated path', () {
+    final Path path = Path()..lineTo(0, 10);
+    final PathMetrics metrics = path.computeMetrics();
+    final PathMetric firstMetric = metrics.first;
+    // We've consumed the iterator.
+    expect(metrics, isEmpty);
+    expect(firstMetric.length, 10);
+    expect(firstMetric.isClosed, false);
+    expect(firstMetric.getTangentForOffset(4.0)!.vector, const Offset(0.0, 1.0));
+    expect(firstMetric.extractPath(4.0, 10.0).computeMetrics().first.length, 6.0);
+
+    path..lineTo(10, 10)..lineTo(10, 0)..close();
+    // mutating the path shouldn't have added anything to the iterator.
+    expect(metrics, isEmpty);
+    expect(firstMetric.length, 10);
+    expect(firstMetric.isClosed, false);
+    expect(firstMetric.getTangentForOffset(4.0)!.vector, const Offset(0.0, 1.0));
+    expect(firstMetric.extractPath(4.0, 10.0).computeMetrics().first.length, 6.0);
+
+    // getting a new iterator should update us.
+    final PathMetrics newMetrics = path.computeMetrics();
+    final PathMetric newFirstMetric = newMetrics.first;
+    expect(newMetrics, isEmpty);
+    expect(newFirstMetric.length, 40);
+    expect(newFirstMetric.isClosed, true);
+    expect(newFirstMetric.getTangentForOffset(4.0)!.vector, const Offset(0.0, 1.0));
+    expect(newFirstMetric.extractPath(4.0, 10.0).computeMetrics().first.length, 6.0);
+  // TODO(hterkelsen): isClosed always returns false in the HTML renderer, https://github.com/flutter/flutter/issues/114446
+  }, skip: isHtml);
+}

engine/src/flutter/lib/web_ui/test/ui/rect_test.dart

@@ -6,11 +6,14 @@ import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
 import 'package:ui/ui.dart';
 
+import 'utils.dart';
+
 void main() {
   internalBootstrapBrowserTest(() => testMain);
 }
 
 void testMain() {
+  setUpUiTest();
   test('rect accessors', () {
     const Rect r = Rect.fromLTRB(1.0, 3.0, 5.0, 7.0);
     expect(r.left, equals(1.0));

engine/src/flutter/lib/web_ui/test/ui/rrect_test.dart

@@ -6,11 +6,14 @@ import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart' hide TypeMatcher, isInstanceOf;
 import 'package:ui/ui.dart';
 
+import 'utils.dart';
+
 void main() {
   internalBootstrapBrowserTest(() => testMain);
 }
 
 void testMain() {
+  setUpUiTest();
   test('RRect.contains()', () {
     final RRect rrect = RRect.fromRectAndCorners(
         const Rect.fromLTRB(1.0, 1.0, 2.0, 2.0),

engine/src/flutter/lib/web_ui/test/ui/title_test.dart

@@ -7,11 +7,15 @@ import 'package:test/test.dart';
 import 'package:ui/src/engine.dart';
 import 'package:ui/ui.dart' as ui;
 
+import 'utils.dart';
+
 void main() {
   internalBootstrapBrowserTest(() => testMain);
 }
 
 void testMain() {
+  setUpUiTest();
+
   const MethodCodec codec = JSONMethodCodec();
 
   group('Title', () {

engine/src/flutter/lib/web_ui/test/ui/utils.dart

@@ -12,3 +12,9 @@ void setUpUiTest() {
     setUpCanvasKitTest();
   }
 }
+
+/// Returns [true] if this test is running in the CanvasKit renderer.
+bool get isCanvasKit => renderer is CanvasKitRenderer;
+
+/// Returns [true] if this test is running in the HTML renderer.
+bool get isHtml => renderer is HtmlRenderer;