// Copyright 2015 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 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle, TextStyle; import 'box.dart'; import 'object.dart'; const double _kMaxWidth = 100000.0; const double _kMaxHeight = 100000.0; // Line length to fit small phones without dynamically checking size. const String _kLine = '\n\n────────────────────\n\n'; /// A render object used as a placeholder when an error occurs. /// /// The box will be painted in the color given by the /// [RenderErrorBox.backgroundColor] static property. /// /// A message can be provided. To simplify the class and thus help reduce the /// likelihood of this class itself being the source of errors, the message /// cannot be changed once the object has been created. If provided, the text /// will be painted on top of the background, using the styles given by the /// [RenderErrorBox.textStyle] and [RenderErrorBox.paragraphStyle] static /// properties. /// /// Again to help simplify the class, this box tries to be 100000.0 pixels wide /// and high, to approximate being infinitely high but without using infinities. class RenderErrorBox extends RenderBox { /// Creates a RenderErrorBox render object. /// /// A message can optionally be provided. If a message is provided, an attempt /// will be made to render the message when the box paints. RenderErrorBox([ this.message = '' ]) { try { if (message != '') { // This class is intentionally doing things using the low-level // primitives to avoid depending on any subsystems that may have ended // up in an unstable state -- after all, this class is mainly used when // things have gone wrong. // // Generally, the much better way to draw text in a RenderObject is to // use the TextPainter class. If you're looking for code to crib from, // see the paragraph.dart file and the RenderParagraph class. final ui.ParagraphBuilder builder = new ui.ParagraphBuilder(paragraphStyle); builder.pushStyle(textStyle); builder.addText( '$message$_kLine$message$_kLine$message$_kLine$message$_kLine$message$_kLine$message$_kLine' '$message$_kLine$message$_kLine$message$_kLine$message$_kLine$message$_kLine$message' ); _paragraph = builder.build(); } } catch (e) { } // ignore: empty_catches } /// The message to attempt to display at paint time. final String message; ui.Paragraph _paragraph; @override double computeMaxIntrinsicWidth(double height) { return _kMaxWidth; } @override double computeMaxIntrinsicHeight(double width) { return _kMaxHeight; } @override bool get sizedByParent => true; @override bool hitTestSelf(Offset position) => true; @override void performResize() { size = constraints.constrain(const Size(_kMaxWidth, _kMaxHeight)); } /// The color to use when painting the background of [RenderErrorBox] objects. static Color backgroundColor = const Color(0xF0900000); /// The text style to use when painting [RenderErrorBox] objects. static ui.TextStyle textStyle = new ui.TextStyle( color: const Color(0xFFFFFF66), fontFamily: 'monospace', fontSize: 14.0, fontWeight: FontWeight.bold ); /// The paragraph style to use when painting [RenderErrorBox] objects. static ui.ParagraphStyle paragraphStyle = new ui.ParagraphStyle( lineHeight: 0.85 ); @override void paint(PaintingContext context, Offset offset) { try { context.canvas.drawRect(offset & size, new Paint() .. color = backgroundColor); double width; if (_paragraph != null) { // See the comment in the RenderErrorBox constructor. This is not the // code you want to be copying and pasting. :-) if (parent is RenderBox) { final RenderBox parentBox = parent; width = parentBox.size.width; } else { width = size.width; } _paragraph.layout(new ui.ParagraphConstraints(width: width)); context.canvas.drawParagraph(_paragraph, offset); } } catch (e) { } // ignore: empty_catches } }