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112 lines
3.9 KiB
Dart
112 lines
3.9 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 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle, TextStyle;
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import 'box.dart';
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import 'object.dart';
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const double _kMaxWidth = 100000.0;
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const double _kMaxHeight = 100000.0;
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/// A render object used as a placeholder when an error occurs.
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///
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/// The box will be painted in the color given by the
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/// [RenderErrorBox.backgroundColor] static property.
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///
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/// A message can be provided. To simplify the class and thus help reduce the
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/// likelihood of this class itself being the source of errors, the message
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/// cannot be changed once the object has been created. If provided, the text
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/// will be painted on top of the background, using the styles given by the
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/// [RenderErrorBox.textStyle] and [RenderErrorBox.paragraphStyle] static
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/// properties.
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///
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/// Again to help simplify the class, this box tries to be 100000.0 pixels wide
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/// and high, to approximate being infinitely high but without using infinities.
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class RenderErrorBox extends RenderBox {
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/// Creates a RenderErrorBox render object.
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///
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/// A message can optionally be provided. If a message is provided, an attempt
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/// will be made to render the message when the box paints.
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RenderErrorBox([ this.message = '' ]) {
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try {
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if (message != '') {
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// This class is intentionally doing things using the low-level
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// primitives to avoid depending on any subsystems that may have ended
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// up in an unstable state -- after all, this class is mainly used when
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// things have gone wrong.
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//
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// Generally, the much better way to draw text in a RenderObject is to
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// use the TextPainter class. If you're looking for code to crib from,
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// see the paragraph.dart file and the RenderParagraph class.
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ui.ParagraphBuilder builder = new ui.ParagraphBuilder(paragraphStyle);
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builder.pushStyle(textStyle);
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builder.addText(message);
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_paragraph = builder.build();
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}
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} catch (e) { }
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}
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/// The message to attempt to display at paint time.
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final String message;
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ui.Paragraph _paragraph;
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@override
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double computeMaxIntrinsicWidth(double height) {
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return _kMaxWidth;
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}
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@override
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double computeMaxIntrinsicHeight(double width) {
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return _kMaxHeight;
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}
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@override
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bool get sizedByParent => true;
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@override
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bool hitTestSelf(Point position) => true;
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@override
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void performResize() {
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size = constraints.constrain(const Size(_kMaxWidth, _kMaxHeight));
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}
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/// The color to use when painting the background of [RenderErrorBox] objects.
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static Color backgroundColor = const Color(0xF0900000);
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/// The text style to use when painting [RenderErrorBox] objects.
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static ui.TextStyle textStyle = new ui.TextStyle(
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color: const Color(0xFFFFFF00),
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fontFamily: 'monospace',
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fontSize: 7.0
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);
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/// The paragraph style to use when painting [RenderErrorBox] objects.
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static ui.ParagraphStyle paragraphStyle = new ui.ParagraphStyle(
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lineHeight: 0.25 // TODO(ianh): https://github.com/flutter/flutter/issues/2460 will affect this
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);
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@override
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void paint(PaintingContext context, Offset offset) {
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try {
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context.canvas.drawRect(offset & size, new Paint() .. color = backgroundColor);
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double width;
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if (_paragraph != null) {
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// See the comment in the RenderErrorBox constructor. This is not the
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// code you want to be copying and pasting. :-)
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if (parent is RenderBox) {
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RenderBox parentBox = parent;
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width = parentBox.size.width;
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} else {
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width = size.width;
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}
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_paragraph.layout(new ui.ParagraphConstraints(width: width));
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context.canvas.drawParagraph(_paragraph, offset);
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}
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} catch (e) { }
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}
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}
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