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4aa3756835
Cassowary doesn't have any additional dependencies and this simplifies things. Fixes #2442
87 lines
2.8 KiB
Dart
87 lines
2.8 KiB
Dart
// Copyright 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// This example shows how to use the Cassowary autolayout system directly in the
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// underlying render tree.
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import 'package:flutter/cassowary.dart' as al;
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import 'package:flutter/rendering.dart';
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class _MyAutoLayoutDelegate extends AutoLayoutDelegate {
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AutoLayoutRect p1 = new AutoLayoutRect();
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AutoLayoutRect p2 = new AutoLayoutRect();
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AutoLayoutRect p3 = new AutoLayoutRect();
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AutoLayoutRect p4 = new AutoLayoutRect();
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@override
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List<al.Constraint> getConstraints(AutoLayoutRect parent) {
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return <al.Constraint>[
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// Sum of widths of each box must be equal to that of the container
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parent.width.equals(p1.width + p2.width + p3.width),
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// The boxes must be stacked left to right
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p1.right <= p2.left,
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p2.right <= p3.left,
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// The widths of the first and the third boxes should be equal
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p1.width.equals(p3.width),
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// The width of the first box should be twice as much as that of the second
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p1.width.equals(p2.width * al.cm(2.0)),
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// The height of the three boxes should be equal to that of the container
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p1.height.equals(p2.height),
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p2.height.equals(p3.height),
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p3.height.equals(parent.height),
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// The fourth box should be half as wide as the second and must be attached
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// to the right edge of the same (by its center)
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p4.width.equals(p2.width / al.cm(2.0)),
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p4.height.equals(al.cm(50.0)),
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p4.horizontalCenter.equals(p2.right),
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p4.verticalCenter.equals(p2.height / al.cm(2.0)),
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];
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}
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@override
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bool shouldUpdateConstraints(AutoLayoutDelegate oldDelegate) => true;
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}
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void main() {
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RenderDecoratedBox c1 = new RenderDecoratedBox(
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decoration: new BoxDecoration(backgroundColor: const Color(0xFFFF0000))
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);
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RenderDecoratedBox c2 = new RenderDecoratedBox(
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decoration: new BoxDecoration(backgroundColor: const Color(0xFF00FF00))
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);
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RenderDecoratedBox c3 = new RenderDecoratedBox(
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decoration: new BoxDecoration(backgroundColor: const Color(0xFF0000FF))
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);
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RenderDecoratedBox c4 = new RenderDecoratedBox(
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decoration: new BoxDecoration(backgroundColor: const Color(0xFFFFFFFF))
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);
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_MyAutoLayoutDelegate delegate = new _MyAutoLayoutDelegate();
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RenderAutoLayout root = new RenderAutoLayout(
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delegate: delegate,
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children: <RenderBox>[c1, c2, c3, c4]
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);
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AutoLayoutParentData parentData1 = c1.parentData;
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AutoLayoutParentData parentData2 = c2.parentData;
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AutoLayoutParentData parentData3 = c3.parentData;
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AutoLayoutParentData parentData4 = c4.parentData;
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parentData1.rect = delegate.p1;
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parentData2.rect = delegate.p2;
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parentData3.rect = delegate.p3;
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parentData4.rect = delegate.p4;
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new RenderingFlutterBinding(root: root);
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}
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