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| 1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 import '../animation/scroll_behavior.dart'; | |
| 6 import '../debug/tracing.dart'; | |
| 7 import '../fn.dart'; | |
| 8 import 'dart:math' as math; | |
| 9 import 'dart:async'; | |
| 10 import 'scrollable.dart'; | |
| 11 | |
| 12 abstract class FixedHeightScrollable extends Scrollable { | |
| 13 static final Style _style = new Style(''' | |
| 14 overflow: hidden; | |
| 15 position: relative; | |
| 16 will-change: transform;''' | |
| 17 ); | |
| 18 | |
| 19 static final Style _scrollAreaStyle = new Style(''' | |
| 20 position:relative; | |
| 21 will-change: transform;''' | |
| 22 ); | |
| 23 | |
| 24 FixedHeightScrollable({ | |
| 25 Object key | |
| 26 }) : super(key: key); | |
| 27 | |
| 28 ScrollBehavior createScrollBehavior() => new OverscrollBehavior(); | |
| 29 OverscrollBehavior get scrollBehavior => super.scrollBehavior as OverscrollBeh
avior; | |
| 30 | |
| 31 double _height = 0.0; | |
| 32 double _itemHeight; | |
| 33 | |
| 34 int _itemCount = 0; | |
| 35 int get itemCount => _itemCount; | |
| 36 void set itemCount (int value) { | |
| 37 if (_itemCount != value) { | |
| 38 _itemCount = value; | |
| 39 if (_itemHeight != null) | |
| 40 scrollBehavior.contentsHeight = _itemHeight * _itemCount; | |
| 41 } | |
| 42 } | |
| 43 | |
| 44 void _measureHeights() { | |
| 45 trace('FixedHeightScrollable::_measureHeights', () { | |
| 46 if (_itemHeight != null) | |
| 47 return; | |
| 48 var root = getRoot(); | |
| 49 if (root == null) | |
| 50 return; | |
| 51 var item = root.firstChild.firstChild; | |
| 52 if (item == null) | |
| 53 return; | |
| 54 setState(() { | |
| 55 _height = root.height; | |
| 56 assert(_height > 0); | |
| 57 _itemHeight = item.height; | |
| 58 assert(_itemHeight > 0); | |
| 59 scrollBehavior.containerHeight = _height; | |
| 60 scrollBehavior.contentsHeight = _itemHeight * _itemCount; | |
| 61 }); | |
| 62 }); | |
| 63 } | |
| 64 | |
| 65 UINode buildContent() { | |
| 66 var itemNumber = 0; | |
| 67 var drawCount = 1; | |
| 68 var transformStyle = ''; | |
| 69 | |
| 70 if (_itemHeight == null) | |
| 71 new Future.microtask(_measureHeights); | |
| 72 | |
| 73 if (_height > 0.0 && _itemHeight != null) { | |
| 74 if (scrollOffset < 0.0) { | |
| 75 double visibleHeight = _height + scrollOffset; | |
| 76 drawCount = (visibleHeight / _itemHeight).round() + 1; | |
| 77 transformStyle = | |
| 78 'transform: translateY(${(-scrollOffset).toStringAsFixed(2)}px)'; | |
| 79 } else { | |
| 80 drawCount = (_height / _itemHeight).ceil() + 1; | |
| 81 double alignmentDelta = -scrollOffset % _itemHeight; | |
| 82 if (alignmentDelta != 0.0) | |
| 83 alignmentDelta -= _itemHeight; | |
| 84 | |
| 85 double drawStart = scrollOffset + alignmentDelta; | |
| 86 itemNumber = math.max(0, (drawStart / _itemHeight).floor()); | |
| 87 | |
| 88 transformStyle = | |
| 89 'transform: translateY(${(alignmentDelta).toStringAsFixed(2)}px)'; | |
| 90 } | |
| 91 } | |
| 92 | |
| 93 return new Container( | |
| 94 style: _style, | |
| 95 children: [ | |
| 96 new Container( | |
| 97 style: _scrollAreaStyle, | |
| 98 inlineStyle: transformStyle, | |
| 99 children: buildItems(itemNumber, drawCount) | |
| 100 ) | |
| 101 ] | |
| 102 ); | |
| 103 } | |
| 104 | |
| 105 List<UINode> buildItems(int start, int count); | |
| 106 } | |
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Chromium Code Reviews
Issue 1132063007:
Rationalize Dart mojo and sky package structure (Closed)
Base URL: https://github.com/domokit/mojo.git@master