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// Copyright 2014 The Flutter 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 'package:engine/ui.dart' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle, TextStyle;
import 'box.dart';
import 'object.dart';
const double _kMaxWidth = 100000.0;
const double _kMaxHeight = 100000.0;
/// 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, if the parent has left the constraints
/// unbounded, 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);
builder.pushStyle(textStyle);
builder.addText(message);
_paragraph = builder.build();
} else {
_paragraph = null;
}
} catch (error) {
// If an error happens here we're in a terrible state, so we really should
// just forget about it and let the developer deal with the already-reported
// errors. It's unlikely that these errors are going to help with that.
}
}
/// The message to attempt to display at paint time.
final String message;
late final 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
Size computeDryLayout(BoxConstraints constraints) {
return constraints.constrain(const Size(_kMaxWidth, _kMaxHeight));
}
/// The distance to place around the text.
///
/// This is intended to ensure that if the [RenderErrorBox] is placed at the top left
/// of the screen, under the system's status bar, the error text is still visible in
/// the area below the status bar.
///
/// The padding is ignored if the error box is smaller than the padding.
///
/// See also:
///
/// * [minimumWidth], which controls how wide the box must be before the
/// horizontal padding is applied.
static EdgeInsets padding = const EdgeInsets.fromLTRB(64.0, 96.0, 64.0, 12.0);
/// The width below which the horizontal padding is not applied.
///
/// If the left and right padding would reduce the available width to less than
/// this value, then the text is rendered flush with the left edge.
static double minimumWidth = 200.0;
/// The color to use when painting the background of [RenderErrorBox] objects.
///
/// Defaults to red in debug mode, a light gray otherwise.
static Color backgroundColor = _initBackgroundColor();
static Color _initBackgroundColor() {
Color result = const Color(0xF0C0C0C0);
assert(() {
result = const Color(0xF0900000);
return true;
}());
return result;
}
/// The text style to use when painting [RenderErrorBox] objects.
///
/// Defaults to a yellow monospace font in debug mode, and a dark gray
/// sans-serif font otherwise.
static ui.TextStyle textStyle = _initTextStyle();
static ui.TextStyle _initTextStyle() {
ui.TextStyle result = ui.TextStyle(
color: const Color(0xFF303030),
fontFamily: 'sans-serif',
fontSize: 18.0,
);
assert(() {
result = ui.TextStyle(
color: const Color(0xFFFFFF66),
fontFamily: 'monospace',
fontSize: 14.0,
fontWeight: FontWeight.bold,
);
return true;
}());
return result;
}
/// The paragraph style to use when painting [RenderErrorBox] objects.
static ui.ParagraphStyle paragraphStyle = ui.ParagraphStyle(
textDirection: TextDirection.ltr,
textAlign: TextAlign.left,
);
@override
void paint(PaintingContext context, Offset offset) {
try {
context.canvas.drawRect(offset & size, Paint() .. color = backgroundColor);
if (_paragraph != null) {
double width = size.width;
double left = 0.0;
double top = 0.0;
if (width > padding.left + minimumWidth + padding.right) {
width -= padding.left + padding.right;
left += padding.left;
}
_paragraph!.layout(ui.ParagraphConstraints(width: width));
if (size.height > padding.top + _paragraph!.height + padding.bottom) {
top += padding.top;
}
context.canvas.drawParagraph(_paragraph!, offset + Offset(left, top));
}
} catch (error) {
// If an error happens here we're in a terrible state, so we really should
// just forget about it and let the developer deal with the already-reported
// errors. It's unlikely that these errors are going to help with that.
}
}
}