Add:创建 flutter go web 版

packages/flutter_web/test/rendering/independent_layout_test.dart

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+// Copyright 2016 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/material.dart';
+import 'package:flutter_web/rendering.dart';
+import '../flutter_test_alternative.dart';
+
+import 'rendering_tester.dart';
+
+class TestLayout {
+  TestLayout() {
+    // incoming constraints are tight 800x600
+    root = RenderPositionedBox(
+      child: RenderConstrainedBox(
+        additionalConstraints: const BoxConstraints.tightFor(width: 800.0),
+        child: RenderCustomPaint(
+          painter: TestCallbackPainter(onPaint: () {
+            painted = true;
+          }),
+          child: child = RenderConstrainedBox(
+            additionalConstraints:
+                const BoxConstraints.tightFor(height: 10.0, width: 10.0),
+          ),
+        ),
+      ),
+    );
+  }
+  RenderBox root;
+  RenderBox child;
+  bool painted = false;
+}
+
+void main() {
+  const ViewConfiguration testConfiguration = ViewConfiguration(
+    size: Size(800.0, 600.0),
+    devicePixelRatio: 1.0,
+  );
+
+  test('onscreen layout does not affect offscreen', () {
+    final TestLayout onscreen = TestLayout();
+    final TestLayout offscreen = TestLayout();
+    expect(onscreen.child.hasSize, isFalse);
+    expect(onscreen.painted, isFalse);
+    expect(offscreen.child.hasSize, isFalse);
+    expect(offscreen.painted, isFalse);
+    // Attach the offscreen to a custom render view and owner
+    final RenderView renderView =
+        RenderView(configuration: testConfiguration, window: null);
+    final PipelineOwner pipelineOwner = PipelineOwner();
+    renderView.attach(pipelineOwner);
+    renderView.child = offscreen.root;
+    renderView.scheduleInitialFrame();
+    // Lay out the onscreen in the default binding
+    layout(onscreen.root, phase: EnginePhase.paint);
+    expect(onscreen.child.hasSize, isTrue);
+    expect(onscreen.painted, isTrue);
+    expect(onscreen.child.size, equals(const Size(800.0, 10.0)));
+    // Make sure the offscreen didn't get laid out
+    expect(offscreen.child.hasSize, isFalse);
+    expect(offscreen.painted, isFalse);
+    // Now lay out the offscreen
+    pipelineOwner.flushLayout();
+    expect(offscreen.child.hasSize, isTrue);
+    expect(offscreen.painted, isFalse);
+    pipelineOwner.flushCompositingBits();
+    pipelineOwner.flushPaint();
+    expect(offscreen.painted, isTrue);
+  });
+  test('offscreen layout does not affect onscreen', () {
+    final TestLayout onscreen = TestLayout();
+    final TestLayout offscreen = TestLayout();
+    expect(onscreen.child.hasSize, isFalse);
+    expect(onscreen.painted, isFalse);
+    expect(offscreen.child.hasSize, isFalse);
+    expect(offscreen.painted, isFalse);
+    // Attach the offscreen to a custom render view and owner
+    final RenderView renderView =
+        RenderView(configuration: testConfiguration, window: null);
+    final PipelineOwner pipelineOwner = PipelineOwner();
+    renderView.attach(pipelineOwner);
+    renderView.child = offscreen.root;
+    renderView.scheduleInitialFrame();
+    // Lay out the offscreen
+    pipelineOwner.flushLayout();
+    expect(offscreen.child.hasSize, isTrue);
+    expect(offscreen.painted, isFalse);
+    pipelineOwner.flushCompositingBits();
+    pipelineOwner.flushPaint();
+    expect(offscreen.painted, isTrue);
+    // Make sure the onscreen didn't get laid out
+    expect(onscreen.child.hasSize, isFalse);
+    expect(onscreen.painted, isFalse);
+    // Now lay out the onscreen in the default binding
+    layout(onscreen.root, phase: EnginePhase.paint);
+    expect(onscreen.child.hasSize, isTrue);
+    expect(onscreen.painted, isTrue);
+    expect(onscreen.child.size, equals(const Size(800.0, 10.0)));
+  });
+}