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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 'dart:math' as math;
import 'package:flutter/foundation.dart';
import 'basic.dart';
import 'debug.dart';
import 'framework.dart';
const double _kOffset = 40.0; // distance to bottom of banner, at a 45 degree angle inwards
const double _kHeight = 12.0; // height of banner
const double _kBottomOffset = _kOffset + 0.707 * _kHeight; // offset plus sqrt(2)/2 * banner height
const Rect _kRect = Rect.fromLTWH(-_kOffset, _kOffset - _kHeight, _kOffset * 2.0, _kHeight);
const Color _kColor = Color(0xA0B71C1C);
const TextStyle _kTextStyle = TextStyle(
color: Color(0xFFFFFFFF),
fontSize: _kHeight * 0.85,
fontWeight: FontWeight.w900,
height: 1.0,
);
/// Where to show a [Banner].
///
/// The start and end locations are relative to the ambient [Directionality]
/// (which can be overridden by [Banner.layoutDirection]).
enum BannerLocation {
/// Show the banner in the top-right corner when the ambient [Directionality]
/// (or [Banner.layoutDirection]) is [TextDirection.rtl] and in the top-left
/// corner when the ambient [Directionality] is [TextDirection.ltr].
topStart,
/// Show the banner in the top-left corner when the ambient [Directionality]
/// (or [Banner.layoutDirection]) is [TextDirection.rtl] and in the top-right
/// corner when the ambient [Directionality] is [TextDirection.ltr].
topEnd,
/// Show the banner in the bottom-right corner when the ambient
/// [Directionality] (or [Banner.layoutDirection]) is [TextDirection.rtl] and
/// in the bottom-left corner when the ambient [Directionality] is
/// [TextDirection.ltr].
bottomStart,
/// Show the banner in the bottom-left corner when the ambient
/// [Directionality] (or [Banner.layoutDirection]) is [TextDirection.rtl] and
/// in the bottom-right corner when the ambient [Directionality] is
/// [TextDirection.ltr].
bottomEnd,
}
/// Paints a [Banner].
class BannerPainter extends CustomPainter {
/// Creates a banner painter.
///
/// The [message], [textDirection], [location], and [layoutDirection]
/// arguments must not be null.
BannerPainter({
required this.message,
required this.textDirection,
required this.location,
required this.layoutDirection,
this.color = _kColor,
this.textStyle = _kTextStyle,
}) : assert(message != null),
assert(textDirection != null),
assert(location != null),
assert(color != null),
assert(textStyle != null),
super(repaint: PaintingBinding.instance.systemFonts);
/// The message to show in the banner.
final String message;
/// The directionality of the text.
///
/// This value is used to disambiguate how to render bidirectional text. For
/// example, if the message is an English phrase followed by a Hebrew phrase,
/// in a [TextDirection.ltr] context the English phrase will be on the left
/// and the Hebrew phrase to its right, while in a [TextDirection.rtl]
/// context, the English phrase will be on the right and the Hebrew phrase on
/// its left.
///
/// See also:
///
/// * [layoutDirection], which controls the interpretation of values in
/// [location].
final TextDirection textDirection;
/// Where to show the banner (e.g., the upper right corner).
final BannerLocation location;
/// The directionality of the layout.
///
/// This value is used to interpret the [location] of the banner.
///
/// See also:
///
/// * [textDirection], which controls the reading direction of the [message].
final TextDirection layoutDirection;
/// The color to paint behind the [message].
///
/// Defaults to a dark red.
final Color color;
/// The text style to use for the [message].
///
/// Defaults to bold, white text.
final TextStyle textStyle;
static const BoxShadow _shadow = BoxShadow(
color: Color(0x7F000000),
blurRadius: 6.0,
);
bool _prepared = false;
TextPainter? _textPainter;
late Paint _paintShadow;
late Paint _paintBanner;
/// Release resources held by this painter.
///
/// After calling this method, this object is no longer usable.
void dispose() {
_textPainter?.dispose();
_textPainter = null;
}
void _prepare() {
_paintShadow = _shadow.toPaint();
_paintBanner = Paint()
..color = color;
_textPainter?.dispose();
_textPainter = TextPainter(
text: TextSpan(style: textStyle, text: message),
textAlign: TextAlign.center,
textDirection: textDirection,
);
_prepared = true;
}
@override
void paint(Canvas canvas, Size size) {
if (!_prepared) {
_prepare();
}
canvas
..translate(_translationX(size.width), _translationY(size.height))
..rotate(_rotation)
..drawRect(_kRect, _paintShadow)
..drawRect(_kRect, _paintBanner);
const double width = _kOffset * 2.0;
_textPainter!.layout(minWidth: width, maxWidth: width);
_textPainter!.paint(canvas, _kRect.topLeft + Offset(0.0, (_kRect.height - _textPainter!.height) / 2.0));
}
@override
bool shouldRepaint(BannerPainter oldDelegate) {
return message != oldDelegate.message
|| location != oldDelegate.location
|| color != oldDelegate.color
|| textStyle != oldDelegate.textStyle;
}
@override
bool hitTest(Offset position) => false;
double _translationX(double width) {
assert(location != null);
assert(layoutDirection != null);
switch (layoutDirection) {
case TextDirection.rtl:
switch (location) {
case BannerLocation.bottomEnd:
return _kBottomOffset;
case BannerLocation.topEnd:
return 0.0;
case BannerLocation.bottomStart:
return width - _kBottomOffset;
case BannerLocation.topStart:
return width;
}
case TextDirection.ltr:
switch (location) {
case BannerLocation.bottomEnd:
return width - _kBottomOffset;
case BannerLocation.topEnd:
return width;
case BannerLocation.bottomStart:
return _kBottomOffset;
case BannerLocation.topStart:
return 0.0;
}
}
}
double _translationY(double height) {
assert(location != null);
switch (location) {
case BannerLocation.bottomStart:
case BannerLocation.bottomEnd:
return height - _kBottomOffset;
case BannerLocation.topStart:
case BannerLocation.topEnd:
return 0.0;
}
}
double get _rotation {
assert(location != null);
assert(layoutDirection != null);
switch (layoutDirection) {
case TextDirection.rtl:
switch (location) {
case BannerLocation.bottomStart:
case BannerLocation.topEnd:
return -math.pi / 4.0;
case BannerLocation.bottomEnd:
case BannerLocation.topStart:
return math.pi / 4.0;
}
case TextDirection.ltr:
switch (location) {
case BannerLocation.bottomStart:
case BannerLocation.topEnd:
return math.pi / 4.0;
case BannerLocation.bottomEnd:
case BannerLocation.topStart:
return -math.pi / 4.0;
}
}
}
}
/// Displays a diagonal message above the corner of another widget.
///
/// Useful for showing the execution mode of an app (e.g., that asserts are
/// enabled.)
///
/// See also:
///
/// * [CheckedModeBanner], which the [WidgetsApp] widget includes by default in
/// debug mode, to show a banner that says "DEBUG".
class Banner extends StatelessWidget {
/// Creates a banner.
///
/// The [message] and [location] arguments must not be null.
const Banner({
super.key,
this.child,
required this.message,
this.textDirection,
required this.location,
this.layoutDirection,
this.color = _kColor,
this.textStyle = _kTextStyle,
}) : assert(message != null),
assert(location != null),
assert(color != null),
assert(textStyle != null);
/// The widget to show behind the banner.
///
/// {@macro flutter.widgets.ProxyWidget.child}
final Widget? child;
/// The message to show in the banner.
final String message;
/// The directionality of the text.
///
/// This is used to disambiguate how to render bidirectional text. For
/// example, if the message is an English phrase followed by a Hebrew phrase,
/// in a [TextDirection.ltr] context the English phrase will be on the left
/// and the Hebrew phrase to its right, while in a [TextDirection.rtl]
/// context, the English phrase will be on the right and the Hebrew phrase on
/// its left.
///
/// Defaults to the ambient [Directionality], if any.
///
/// See also:
///
/// * [layoutDirection], which controls the interpretation of the [location].
final TextDirection? textDirection;
/// Where to show the banner (e.g., the upper right corner).
final BannerLocation location;
/// The directionality of the layout.
///
/// This is used to resolve the [location] values.
///
/// Defaults to the ambient [Directionality], if any.
///
/// See also:
///
/// * [textDirection], which controls the reading direction of the [message].
final TextDirection? layoutDirection;
/// The color of the banner.
final Color color;
/// The style of the text shown on the banner.
final TextStyle textStyle;
@override
Widget build(BuildContext context) {
assert((textDirection != null && layoutDirection != null) || debugCheckHasDirectionality(context));
return CustomPaint(
foregroundPainter: BannerPainter(
message: message,
textDirection: textDirection ?? Directionality.of(context),
location: location,
layoutDirection: layoutDirection ?? Directionality.of(context),
color: color,
textStyle: textStyle,
),
child: child,
);
}
@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
properties.add(StringProperty('message', message, showName: false));
properties.add(EnumProperty<TextDirection>('textDirection', textDirection, defaultValue: null));
properties.add(EnumProperty<BannerLocation>('location', location));
properties.add(EnumProperty<TextDirection>('layoutDirection', layoutDirection, defaultValue: null));
properties.add(ColorProperty('color', color, showName: false));
textStyle.debugFillProperties(properties, prefix: 'text ');
}
}
/// Displays a [Banner] saying "DEBUG" when running in debug mode.
/// [MaterialApp] builds one of these by default.
///
/// Does nothing in release mode.
class CheckedModeBanner extends StatelessWidget {
/// Creates a const debug mode banner.
const CheckedModeBanner({
super.key,
required this.child,
});
/// The widget to show behind the banner.
///
/// {@macro flutter.widgets.ProxyWidget.child}
final Widget child;
@override
Widget build(BuildContext context) {
Widget result = child;
assert(() {
result = Banner(
message: 'DEBUG',
textDirection: TextDirection.ltr,
location: BannerLocation.topEnd,
child: result,
);
return true;
}());
return result;
}
@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
String message = 'disabled';
assert(() {
message = '"DEBUG"';
return true;
}());
properties.add(DiagnosticsNode.message(message));
}
}