blob: d34c5f4f7b745791784136fbcdba17fd3388df06 [file] [log] [blame]
// 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 = ui.ParagraphBuilder(paragraphStyle);
_paragraph =;
} catch (e) {
// Intentionally left empty.
/// The message to attempt to display at paint time.
final String message;
ui.Paragraph _paragraph;
double computeMaxIntrinsicWidth(double height) {
return _kMaxWidth;
double computeMaxIntrinsicHeight(double width) {
return _kMaxHeight;
bool get sizedByParent => true;
bool hitTestSelf(Offset position) => true;
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 = 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 = ui.ParagraphStyle(
height: 1.0,
void paint(PaintingContext context, Offset offset) {
try {
context.canvas.drawRect(offset & size, 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(ui.ParagraphConstraints(width: width));
context.canvas.drawParagraph(_paragraph, offset);
} catch (e) {
// Intentionally left empty.