Add:创建 flutter go web 版

packages/flutter_web/test/rendering/slivers_layout_test.dart

@@ -0,0 +1,77 @@
+// Copyright 2015 The Chromium 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 'package:flutter_web/rendering.dart';
+import '../flutter_test_alternative.dart';
+
+import 'rendering_tester.dart';
+
+int layouts = 0;
+
+class RenderLayoutWatcher extends RenderProxyBox {
+  RenderLayoutWatcher(RenderBox child) : super(child);
+  @override
+  void performLayout() {
+    layouts += 1;
+    super.performLayout();
+  }
+}
+
+void main() {
+  test('RenderViewport basic test - impact of layout', () {
+    RenderSliverToBoxAdapter sliver;
+    RenderViewport viewport;
+    RenderBox box;
+    final RenderObject root = RenderLayoutWatcher(
+      viewport = RenderViewport(
+        crossAxisDirection: AxisDirection.right,
+        offset: ViewportOffset.zero(),
+        children: <RenderSliver>[
+          sliver = RenderSliverToBoxAdapter(
+              child: box = RenderSizedBox(const Size(100.0, 400.0))),
+        ],
+      ),
+    );
+    expect(layouts, 0);
+    layout(root);
+    expect(layouts, 1);
+    expect(box.localToGlobal(box.size.center(Offset.zero)),
+        const Offset(400.0, 200.0));
+
+    sliver.child = box = RenderSizedBox(const Size(100.0, 300.0));
+    expect(layouts, 1);
+    pumpFrame();
+    expect(layouts, 1);
+    expect(box.localToGlobal(box.size.center(Offset.zero)),
+        const Offset(400.0, 150.0));
+
+    viewport.offset = ViewportOffset.fixed(20.0);
+    expect(layouts, 1);
+    pumpFrame();
+    expect(layouts, 1);
+    expect(box.localToGlobal(box.size.center(Offset.zero)),
+        const Offset(400.0, 130.0));
+
+    viewport.offset = ViewportOffset.fixed(-20.0);
+    expect(layouts, 1);
+    pumpFrame();
+    expect(layouts, 1);
+    expect(box.localToGlobal(box.size.center(Offset.zero)),
+        const Offset(400.0, 170.0));
+
+    viewport.anchor = 20.0 / 600.0;
+    expect(layouts, 1);
+    pumpFrame();
+    expect(layouts, 1);
+    expect(box.localToGlobal(box.size.center(Offset.zero)),
+        const Offset(400.0, 190.0));
+
+    viewport.axisDirection = AxisDirection.up;
+    expect(layouts, 1);
+    pumpFrame();
+    expect(layouts, 1);
+    expect(box.localToGlobal(box.size.center(Offset.zero)),
+        const Offset(400.0, 600.0 - 190.0));
+  });
+}