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e8ead8bbbe
- the custom layout class in fn is removed by this patch; a new class
will be added in a later CL
- the version of layout.dart in this CL is a subset of what we're
targetting on the long run with
https://codereview.chromium.org/1093633002
- a couple of lines of dead code are removed in this CL also
R=eseidel@chromium.org
Review URL: https://codereview.chromium.org/1117143003
107 lines
2.9 KiB
Dart
107 lines
2.9 KiB
Dart
// Copyright 2015 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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import '../animation/scroll_behavior.dart';
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import '../debug/tracing.dart';
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import '../fn.dart';
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import 'dart:math' as math;
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import 'dart:async';
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import 'scrollable.dart';
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abstract class FixedHeightScrollable extends Scrollable {
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static final Style _style = new Style('''
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overflow: hidden;
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position: relative;
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will-change: transform;'''
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);
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static final Style _scrollAreaStyle = new Style('''
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position:relative;
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will-change: transform;'''
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);
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FixedHeightScrollable({
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Object key
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}) : super(key: key);
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ScrollBehavior createScrollBehavior() => new OverscrollBehavior();
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OverscrollBehavior get scrollBehavior => super.scrollBehavior as OverscrollBehavior;
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double _height = 0.0;
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double _itemHeight;
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int _itemCount = 0;
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int get itemCount => _itemCount;
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void set itemCount (int value) {
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if (_itemCount != value) {
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_itemCount = value;
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if (_itemHeight != null)
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scrollBehavior.contentsHeight = _itemHeight * _itemCount;
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}
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}
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void _measureHeights() {
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trace('FixedHeightScrollable::_measureHeights', () {
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if (_itemHeight != null)
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return;
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var root = getRoot();
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if (root == null)
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return;
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var item = root.firstChild.firstChild;
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if (item == null)
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return;
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setState(() {
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_height = root.height;
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assert(_height > 0);
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_itemHeight = item.height;
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assert(_itemHeight > 0);
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scrollBehavior.containerHeight = _height;
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scrollBehavior.contentsHeight = _itemHeight * _itemCount;
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});
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});
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}
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UINode buildContent() {
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var itemNumber = 0;
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var drawCount = 1;
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var transformStyle = '';
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if (_itemHeight == null)
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new Future.microtask(_measureHeights);
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if (_height > 0.0 && _itemHeight != null) {
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if (scrollOffset < 0.0) {
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double visibleHeight = _height + scrollOffset;
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drawCount = (visibleHeight / _itemHeight).round() + 1;
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transformStyle =
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'transform: translateY(${(-scrollOffset).toStringAsFixed(2)}px)';
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} else {
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drawCount = (_height / _itemHeight).round() + 1;
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double alignmentDelta = -scrollOffset % _itemHeight;
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if (alignmentDelta != 0.0)
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alignmentDelta -= _itemHeight;
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double drawStart = scrollOffset + alignmentDelta;
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itemNumber = math.max(0, (drawStart / _itemHeight).floor());
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transformStyle =
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'transform: translateY(${(alignmentDelta).toStringAsFixed(2)}px)';
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}
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}
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return new Container(
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style: _style,
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children: [
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new Container(
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style: _scrollAreaStyle,
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inlineStyle: transformStyle,
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children: buildItems(itemNumber, drawCount)
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)
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]
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);
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}
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List<UINode> buildItems(int start, int count);
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}
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