packages/flutter/lib/src/widgets/banner.dart - mirrors/flutter - Git at Google

 // 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: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
 final Rect _kRect = new Rect.fromLTWH(-_kOffset, _kOffset - _kHeight, _kOffset * 2.0, _kHeight);

 const Color _kColor = const Color(0xA0B71C1C);
 const TextStyle _kTextStyle = const TextStyle(
   color: const 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);

   /// 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 corder).
   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;

   bool _prepared = false;
   TextPainter _textPainter;
   Paint _paintShadow;
   Paint _paintBanner;

   void _prepare() {
     _paintShadow = new Paint()
       ..color = const Color(0x7F000000)
       ..maskFilter = const MaskFilter.blur(BlurStyle.normal, 4.0);
     _paintBanner = new Paint()
       ..color = color;
     _textPainter = new TextPainter(
       text: new 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 + new 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;
         }
         break;
       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;
         }
         break;
     }
     return null;
   }

   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;
     }
     return null;
   }

   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;
         }
         break;
       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;
         }
         break;
     }
     return null;
   }
 }

 /// 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({
     Key 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),
        super(key: key);

   /// The widget to show behind the banner.
   ///
   /// {@macro flutter.widgets.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 corder).
   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 new CustomPaint(
       foregroundPainter: new 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(new StringProperty('message', message, showName: false));
     properties.add(new EnumProperty<TextDirection>('textDirection', textDirection, defaultValue: null));
     properties.add(new EnumProperty<BannerLocation>('location', location));
     properties.add(new EnumProperty<TextDirection>('layoutDirection', layoutDirection, defaultValue: null));
     properties.add(new DiagnosticsProperty<Color>('color', color, showName: false));
     textStyle?.debugFillProperties(properties, prefix: 'text ');
   }
 }

 /// Displays a [Banner] saying "DEBUG" when running in checked mode.
 /// [MaterialApp] builds one of these by default.
 /// Does nothing in release mode.
 class CheckedModeBanner extends StatelessWidget {
   /// Creates a checked mode banner.
   const CheckedModeBanner({
     Key key,
     @required this.child
   }) : super(key: key);

   /// The widget to show behind the banner.
   ///
   /// {@macro flutter.widgets.child}
   final Widget child;

   @override
   Widget build(BuildContext context) {
     Widget result = child;
     assert(() {
       result = new Banner(
         child: result,
         message: 'DEBUG',
         textDirection: TextDirection.ltr,
         location: BannerLocation.topEnd,
       );
       return true;
     }());
     return result;
   }

   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     String message = 'disabled';
     assert(() {
       message = '"DEBUG"';
       return true;
     }());
     properties.add(new DiagnosticsNode.message(message));
   }
 }
	// 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: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
	final Rect _kRect = new Rect.fromLTWH(-_kOffset, _kOffset - _kHeight, _kOffset * 2.0, _kHeight);

	const Color _kColor = const Color(0xA0B71C1C);
	const TextStyle _kTextStyle = const TextStyle(
	color: const 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);

	/// 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 corder).
	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;

	bool _prepared = false;
	TextPainter _textPainter;
	Paint _paintShadow;
	Paint _paintBanner;

	void _prepare() {
	_paintShadow = new Paint()
	..color = const Color(0x7F000000)
	..maskFilter = const MaskFilter.blur(BlurStyle.normal, 4.0);
	_paintBanner = new Paint()
	..color = color;
	_textPainter = new TextPainter(
	text: new 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 + new 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;
	}
	break;
	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;
	}
	break;
	}
	return null;
	}

	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;
	}
	return null;
	}

	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;
	}
	break;
	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;
	}
	break;
	}
	return null;
	}
	}

	/// 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({
	Key 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),
	super(key: key);

	/// The widget to show behind the banner.
	///
	/// {@macro flutter.widgets.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 corder).
	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 new CustomPaint(
	foregroundPainter: new 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(new StringProperty('message', message, showName: false));
	properties.add(new EnumProperty<TextDirection>('textDirection', textDirection, defaultValue: null));
	properties.add(new EnumProperty<BannerLocation>('location', location));
	properties.add(new EnumProperty<TextDirection>('layoutDirection', layoutDirection, defaultValue: null));
	properties.add(new DiagnosticsProperty<Color>('color', color, showName: false));
	textStyle?.debugFillProperties(properties, prefix: 'text ');
	}
	}

	/// Displays a [Banner] saying "DEBUG" when running in checked mode.
	/// [MaterialApp] builds one of these by default.
	/// Does nothing in release mode.
	class CheckedModeBanner extends StatelessWidget {
	/// Creates a checked mode banner.
	const CheckedModeBanner({
	Key key,
	@required this.child
	}) : super(key: key);

	/// The widget to show behind the banner.
	///
	/// {@macro flutter.widgets.child}
	final Widget child;

	@override
	Widget build(BuildContext context) {
	Widget result = child;
	assert(() {
	result = new Banner(
	child: result,
	message: 'DEBUG',
	textDirection: TextDirection.ltr,
	location: BannerLocation.topEnd,
	);
	return true;
	}());
	return result;
	}

	@override
	void debugFillProperties(DiagnosticPropertiesBuilder properties) {
	super.debugFillProperties(properties);
	String message = 'disabled';
	assert(() {
	message = '"DEBUG"';
	return true;
	}());
	properties.add(new DiagnosticsNode.message(message));
	}
	}