packages/flutter/lib/src/material/floating_action_button.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/painting.dart';
 import 'package:flutter/widgets.dart';

 import 'button.dart';
 import 'scaffold.dart';
 import 'theme.dart';
 import 'tooltip.dart';

 const BoxConstraints _kSizeConstraints = const BoxConstraints.tightFor(
   width: 56.0,
   height: 56.0,
 );

 const BoxConstraints _kMiniSizeConstraints = const BoxConstraints.tightFor(
   width: 40.0,
   height: 40.0,
 );

 const BoxConstraints _kExtendedSizeConstraints = const BoxConstraints(
   minHeight: 48.0,
   maxHeight: 48.0,
 );

 class _DefaultHeroTag {
   const _DefaultHeroTag();
   @override
   String toString() => '<default FloatingActionButton tag>';
 }

 // TODO(amirh): update the documentation once the BAB notch can be disabled.
 /// A material design floating action button.
 ///
 /// A floating action button is a circular icon button that hovers over content
 /// to promote a primary action in the application. Floating action buttons are
 /// most commonly used in the [Scaffold.floatingActionButton] field.
 ///
 /// Use at most a single floating action button per screen. Floating action
 /// buttons should be used for positive actions such as "create", "share", or
 /// "navigate".
 ///
 /// If the [onPressed] callback is null, then the button will be disabled and
 /// will not react to touch.
 ///
 /// If the floating action button is a descendant of a [Scaffold] that also has a
 /// [BottomAppBar], the [BottomAppBar] will show a notch to accomodate the
 /// [FloatingActionButton] when it overlaps the [BottomAppBar]. The notch's
 /// shape is an arc for a circle whose radius is the floating action button's
 /// radius plus [FloatingActionButton.notchMargin].
 ///
 /// See also:
 ///
 ///  * [Scaffold]
 ///  * [RaisedButton]
 ///  * [FlatButton]
 ///  * <https://material.google.com/components/buttons-floating-action-button.html>
 class FloatingActionButton extends StatefulWidget {
   /// Creates a circular floating action button.
   ///
   /// The [elevation], [highlightElevation], [mini], [notchMargin], and [shape]
   /// arguments must not be null.
   const FloatingActionButton({
     Key key,
     this.child,
     this.tooltip,
     this.foregroundColor,
     this.backgroundColor,
     this.heroTag = const _DefaultHeroTag(),
     this.elevation = 6.0,
     this.highlightElevation = 12.0,
     @required this.onPressed,
     this.mini = false,
     this.notchMargin = 4.0,
     this.shape = const CircleBorder(),
     this.isExtended = false,
   }) :  assert(elevation != null),
         assert(highlightElevation != null),
         assert(mini != null),
         assert(notchMargin != null),
         assert(shape != null),
         assert(isExtended != null),
         _sizeConstraints = mini ? _kMiniSizeConstraints : _kSizeConstraints,
         super(key: key);

   /// Creates a wider [StadiumBorder] shaped floating action button with both
   /// an [icon] and a [label].
   ///
   /// The [label], [icon], [elevation], [highlightElevation]
   /// [notchMargin], and [shape] arguments must not be null.
   FloatingActionButton.extended({
     Key key,
     this.tooltip,
     this.foregroundColor,
     this.backgroundColor,
     this.heroTag = const _DefaultHeroTag(),
     this.elevation = 6.0,
     this.highlightElevation = 12.0,
     @required this.onPressed,
     this.notchMargin = 4.0,
     this.shape = const StadiumBorder(),
     this.isExtended = true,
     @required Widget icon,
     @required Widget label,
   }) :  assert(elevation != null),
         assert(highlightElevation != null),
         assert(notchMargin != null),
         assert(shape != null),
         assert(isExtended != null),
         _sizeConstraints = _kExtendedSizeConstraints,
         mini = false,
         child = new Row(
           mainAxisSize: MainAxisSize.min,
           children: <Widget>[
             const SizedBox(width: 16.0),
             icon,
             const SizedBox(width: 8.0),
             label,
             const SizedBox(width: 20.0),
           ],
         ),
         super(key: key);

   /// The widget below this widget in the tree.
   ///
   /// Typically an [Icon].
   final Widget child;

   /// Text that describes the action that will occur when the button is pressed.
   ///
   /// This text is displayed when the user long-presses on the button and is
   /// used for accessibility.
   final String tooltip;

   /// The default icon and text color.
   ///
   /// Defaults to [ThemeData.accentIconTheme.color] for the current theme.
   final Color foregroundColor;

   /// The color to use when filling the button.
   ///
   /// Defaults to [ThemeData.accentColor] for the current theme.
   final Color backgroundColor;

   /// The tag to apply to the button's [Hero] widget.
   ///
   /// Defaults to a tag that matches other floating action buttons.
   ///
   /// Set this to null explicitly if you don't want the floating action button to
   /// have a hero tag.
   ///
   /// If this is not explicitly set, then there can only be one
   /// [FloatingActionButton] per route (that is, per screen), since otherwise
   /// there would be a tag conflict (multiple heroes on one route can't have the
   /// same tag). The material design specification recommends only using one
   /// floating action button per screen.
   final Object heroTag;

   /// The callback that is called when the button is tapped or otherwise activated.
   ///
   /// If this is set to null, the button will be disabled.
   final VoidCallback onPressed;

   /// The z-coordinate at which to place this button. This controls the size of
   /// the shadow below the floating action button.
   ///
   /// Defaults to 6, the appropriate elevation for floating action buttons.
   final double elevation;

   /// The z-coordinate at which to place this button when the user is touching
   /// the button. This controls the size of the shadow below the floating action
   /// button.
   ///
   /// Defaults to 12, the appropriate elevation for floating action buttons
   /// while they are being touched.
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   final double highlightElevation;

   /// Controls the size of this button.
   ///
   /// By default, floating action buttons are non-mini and have a height and
   /// width of 56.0 logical pixels. Mini floating action buttons have a height
   /// and width of 40.0 logical pixels with a layout width and height of 48.0
   /// logical pixels.
   final bool mini;

   /// The margin to keep around the floating action button when creating a
   /// notch for it.
   ///
   /// The notch is an arc of a circle with radius r+[notchMargin] where r is the
   /// radius of the floating action button. This expanded radius leaves a margin
   /// around the floating action button.
   ///
   /// See also:
   ///
   ///  * [BottomAppBar], a material design elements that shows a notch for the
   ///    floating action button.
   final double notchMargin;

   /// The shape of the button's [Material].
   ///
   /// The button's highlight and splash are clipped to this shape. If the
   /// button has an elevation, then its drop shadow is defined by this
   /// shape as well.
   final ShapeBorder shape;

   /// True if this is an "extended" floating action button.
   ///
   /// Typically [extended] buttons have a [StadiumBorder] [shape]
   /// and have been created with the [FloatingActionButton.extended]
   /// constructor.
   ///
   /// The [Scaffold] animates the appearance of ordinary floating
   /// action buttons with scale and rotation transitions. Extended
   /// floating action buttons are scaled and faded in.
   final bool isExtended;

   final BoxConstraints _sizeConstraints;

   @override
   _FloatingActionButtonState createState() => new _FloatingActionButtonState();
 }

 class _FloatingActionButtonState extends State<FloatingActionButton> {
   bool _highlight = false;
   VoidCallback _clearComputeNotch;

   void _handleHighlightChanged(bool value) {
     setState(() {
       _highlight = value;
     });
   }

   @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
     final Color foregroundColor = widget.foregroundColor ?? theme.accentIconTheme.color;
     Widget result;

     if (widget.child != null) {
       result = IconTheme.merge(
         data: new IconThemeData(
           color: foregroundColor,
         ),
         child: widget.child,
       );
     }

     if (widget.tooltip != null) {
       final Widget tooltip = new Tooltip(
         message: widget.tooltip,
         child: result,
       );
       // The long-pressable area for the tooltip should always be as big as
       // the tooltip even if there is no child.
       result = widget.child != null ? tooltip : new SizedBox.expand(child: tooltip);
     }

     result = new RawMaterialButton(
       onPressed: widget.onPressed,
       onHighlightChanged: _handleHighlightChanged,
       elevation: _highlight ? widget.highlightElevation : widget.elevation,
       constraints: widget._sizeConstraints,
       outerPadding: widget.mini ? const EdgeInsets.all(4.0) : null,
       fillColor: widget.backgroundColor ?? theme.accentColor,
       textStyle: theme.accentTextTheme.button.copyWith(
         color: foregroundColor,
         letterSpacing: 1.2,
       ),
       shape: widget.shape,
       child: result,
     );

     if (widget.heroTag != null) {
       result = new Hero(
         tag: widget.heroTag,
         child: result,
       );
     }

     return result;
   }

   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
     _clearComputeNotch = Scaffold.setFloatingActionButtonNotchFor(context, _computeNotch);
   }

   @override
   void deactivate() {
     if (_clearComputeNotch != null)
       _clearComputeNotch();
     super.deactivate();
   }

   Path _computeNotch(Rect host, Rect guest, Offset start, Offset end) {
     // The FAB's shape is a circle bounded by the guest rectangle.
     // So the FAB's radius is half the guest width.
     final double fabRadius = guest.width / 2.0;
     final double notchRadius = fabRadius + widget.notchMargin;

     assert(_notchAssertions(host, guest, start, end, fabRadius, notchRadius));

     // If there's no overlap between the guest's margin boundary and the host,
     // don't make a notch, just return a straight line from start to end.
     if (!host.overlaps(guest.inflate(widget.notchMargin)))
       return new Path()..lineTo(end.dx, end.dy);

     // We build a path for the notch from 3 segments:
     // Segment A - a Bezier curve from the host's top edge to segment B.
     // Segment B - an arc with radius notchRadius.
     // Segment C - a Bezier curver from segment B back to the host's top edge.
     //
     // A detailed explanation and the derivation of the formulas below is
     // available at: https://goo.gl/Ufzrqn

     const double s1 = 15.0;
     const double s2 = 1.0;

     final double r = notchRadius;
     final double a = -1.0 * r - s2;
     final double b = host.top - guest.center.dy;

     final double n2 = math.sqrt(b * b * r * r * (a * a + b * b - r * r));
     final double p2xA = ((a * r * r) - n2) / (a * a + b * b);
     final double p2xB = ((a * r * r) + n2) / (a * a + b * b);
     final double p2yA = math.sqrt(r * r - p2xA * p2xA);
     final double p2yB = math.sqrt(r * r - p2xB * p2xB);

     final List<Offset> p = new List<Offset>(6);

     // p0, p1, and p2 are the control points for segment A.
     p[0] = new Offset(a - s1, b);
     p[1] = new Offset(a, b);
     final double cmp = b < 0 ? -1.0 : 1.0;
     p[2] = cmp * p2yA > cmp * p2yB ? new Offset(p2xA, p2yA) : new Offset(p2xB, p2yB);

     // p3, p4, and p5 are the control points for segment B, which is a mirror
     // of segment A around the y axis.
     p[3] = new Offset(-1.0 * p[2].dx, p[2].dy);
     p[4] = new Offset(-1.0 * p[1].dx, p[1].dy);
     p[5] = new Offset(-1.0 * p[0].dx, p[0].dy);

     // translate all points back to the absolute coordinate system.
     for (int i = 0; i < p.length; i += 1)
       p[i] += guest.center;

     return new Path()
       ..lineTo(p[0].dx, p[0].dy)
       ..quadraticBezierTo(p[1].dx, p[1].dy, p[2].dx, p[2].dy)
       ..arcToPoint(
         p[3],
         radius: new Radius.circular(notchRadius),
         clockwise: false,
       )
       ..quadraticBezierTo(p[4].dx, p[4].dy, p[5].dx, p[5].dy)
       ..lineTo(end.dx, end.dy);
   }

   bool _notchAssertions(Rect host, Rect guest, Offset start, Offset end,
     double fabRadius, double notchRadius) {
     if (end.dy != host.top)
       throw new FlutterError(
         'The notch of the floating action button must end at the top edge of the host.\n'
         'The notch\'s path end point: $end is not in the top edge of $host'
       );

     if (start.dy != host.top)
       throw new FlutterError(
         'The notch of the floating action button must start at the top edge of the host.\n'
         'The notch\'s path start point: $start is not in the top edge of $host'
       );

     if (guest.center.dx - notchRadius < start.dx)
       throw new FlutterError(
         'The notch\'s path start point must be to the left of the floating action button.\n'
         'Start point was $start, guest was $guest, notchMargin was ${widget.notchMargin}.'
       );

     if (guest.center.dx + notchRadius > end.dx)
       throw new FlutterError(
         'The notch\'s end point must be to the right of the floating action button.\n'
         'End point was $start, notch was $guest, notchMargin was ${widget.notchMargin}.'
       );

     return true;
   }
 }
	// 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/painting.dart';
	import 'package:flutter/widgets.dart';

	import 'button.dart';
	import 'scaffold.dart';
	import 'theme.dart';
	import 'tooltip.dart';

	const BoxConstraints _kSizeConstraints = const BoxConstraints.tightFor(
	width: 56.0,
	height: 56.0,
	);

	const BoxConstraints _kMiniSizeConstraints = const BoxConstraints.tightFor(
	width: 40.0,
	height: 40.0,
	);

	const BoxConstraints _kExtendedSizeConstraints = const BoxConstraints(
	minHeight: 48.0,
	maxHeight: 48.0,
	);

	class _DefaultHeroTag {
	const _DefaultHeroTag();
	@override
	String toString() => '<default FloatingActionButton tag>';
	}

	// TODO(amirh): update the documentation once the BAB notch can be disabled.
	/// A material design floating action button.
	///
	/// A floating action button is a circular icon button that hovers over content
	/// to promote a primary action in the application. Floating action buttons are
	/// most commonly used in the [Scaffold.floatingActionButton] field.
	///
	/// Use at most a single floating action button per screen. Floating action
	/// buttons should be used for positive actions such as "create", "share", or
	/// "navigate".
	///
	/// If the [onPressed] callback is null, then the button will be disabled and
	/// will not react to touch.
	///
	/// If the floating action button is a descendant of a [Scaffold] that also has a
	/// [BottomAppBar], the [BottomAppBar] will show a notch to accomodate the
	/// [FloatingActionButton] when it overlaps the [BottomAppBar]. The notch's
	/// shape is an arc for a circle whose radius is the floating action button's
	/// radius plus [FloatingActionButton.notchMargin].
	///
	/// See also:
	///
	/// * [Scaffold]
	/// * [RaisedButton]
	/// * [FlatButton]
	/// * <https://material.google.com/components/buttons-floating-action-button.html>
	class FloatingActionButton extends StatefulWidget {
	/// Creates a circular floating action button.
	///
	/// The [elevation], [highlightElevation], [mini], [notchMargin], and [shape]
	/// arguments must not be null.
	const FloatingActionButton({
	Key key,
	this.child,
	this.tooltip,
	this.foregroundColor,
	this.backgroundColor,
	this.heroTag = const _DefaultHeroTag(),
	this.elevation = 6.0,
	this.highlightElevation = 12.0,
	@required this.onPressed,
	this.mini = false,
	this.notchMargin = 4.0,
	this.shape = const CircleBorder(),
	this.isExtended = false,
	}) : assert(elevation != null),
	assert(highlightElevation != null),
	assert(mini != null),
	assert(notchMargin != null),
	assert(shape != null),
	assert(isExtended != null),
	_sizeConstraints = mini ? _kMiniSizeConstraints : _kSizeConstraints,
	super(key: key);

	/// Creates a wider [StadiumBorder] shaped floating action button with both
	/// an [icon] and a [label].
	///
	/// The [label], [icon], [elevation], [highlightElevation]
	/// [notchMargin], and [shape] arguments must not be null.
	FloatingActionButton.extended({
	Key key,
	this.tooltip,
	this.foregroundColor,
	this.backgroundColor,
	this.heroTag = const _DefaultHeroTag(),
	this.elevation = 6.0,
	this.highlightElevation = 12.0,
	@required this.onPressed,
	this.notchMargin = 4.0,
	this.shape = const StadiumBorder(),
	this.isExtended = true,
	@required Widget icon,
	@required Widget label,
	}) : assert(elevation != null),
	assert(highlightElevation != null),
	assert(notchMargin != null),
	assert(shape != null),
	assert(isExtended != null),
	_sizeConstraints = _kExtendedSizeConstraints,
	mini = false,
	child = new Row(
	mainAxisSize: MainAxisSize.min,
	children: <Widget>[
	const SizedBox(width: 16.0),
	icon,
	const SizedBox(width: 8.0),
	label,
	const SizedBox(width: 20.0),
	],
	),
	super(key: key);

	/// The widget below this widget in the tree.
	///
	/// Typically an [Icon].
	final Widget child;

	/// Text that describes the action that will occur when the button is pressed.
	///
	/// This text is displayed when the user long-presses on the button and is
	/// used for accessibility.
	final String tooltip;

	/// The default icon and text color.
	///
	/// Defaults to [ThemeData.accentIconTheme.color] for the current theme.
	final Color foregroundColor;

	/// The color to use when filling the button.
	///
	/// Defaults to [ThemeData.accentColor] for the current theme.
	final Color backgroundColor;

	/// The tag to apply to the button's [Hero] widget.
	///
	/// Defaults to a tag that matches other floating action buttons.
	///
	/// Set this to null explicitly if you don't want the floating action button to
	/// have a hero tag.
	///
	/// If this is not explicitly set, then there can only be one
	/// [FloatingActionButton] per route (that is, per screen), since otherwise
	/// there would be a tag conflict (multiple heroes on one route can't have the
	/// same tag). The material design specification recommends only using one
	/// floating action button per screen.
	final Object heroTag;

	/// The callback that is called when the button is tapped or otherwise activated.
	///
	/// If this is set to null, the button will be disabled.
	final VoidCallback onPressed;

	/// The z-coordinate at which to place this button. This controls the size of
	/// the shadow below the floating action button.
	///
	/// Defaults to 6, the appropriate elevation for floating action buttons.
	final double elevation;

	/// The z-coordinate at which to place this button when the user is touching
	/// the button. This controls the size of the shadow below the floating action
	/// button.
	///
	/// Defaults to 12, the appropriate elevation for floating action buttons
	/// while they are being touched.
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	final double highlightElevation;

	/// Controls the size of this button.
	///
	/// By default, floating action buttons are non-mini and have a height and
	/// width of 56.0 logical pixels. Mini floating action buttons have a height
	/// and width of 40.0 logical pixels with a layout width and height of 48.0
	/// logical pixels.
	final bool mini;

	/// The margin to keep around the floating action button when creating a
	/// notch for it.
	///
	/// The notch is an arc of a circle with radius r+[notchMargin] where r is the
	/// radius of the floating action button. This expanded radius leaves a margin
	/// around the floating action button.
	///
	/// See also:
	///
	/// * [BottomAppBar], a material design elements that shows a notch for the
	/// floating action button.
	final double notchMargin;

	/// The shape of the button's [Material].
	///
	/// The button's highlight and splash are clipped to this shape. If the
	/// button has an elevation, then its drop shadow is defined by this
	/// shape as well.
	final ShapeBorder shape;

	/// True if this is an "extended" floating action button.
	///
	/// Typically [extended] buttons have a [StadiumBorder] [shape]
	/// and have been created with the [FloatingActionButton.extended]
	/// constructor.
	///
	/// The [Scaffold] animates the appearance of ordinary floating
	/// action buttons with scale and rotation transitions. Extended
	/// floating action buttons are scaled and faded in.
	final bool isExtended;

	final BoxConstraints _sizeConstraints;

	@override
	_FloatingActionButtonState createState() => new _FloatingActionButtonState();
	}

	class _FloatingActionButtonState extends State<FloatingActionButton> {
	bool _highlight = false;
	VoidCallback _clearComputeNotch;

	void _handleHighlightChanged(bool value) {
	setState(() {
	_highlight = value;
	});
	}

	@override
	Widget build(BuildContext context) {
	final ThemeData theme = Theme.of(context);
	final Color foregroundColor = widget.foregroundColor ?? theme.accentIconTheme.color;
	Widget result;

	if (widget.child != null) {
	result = IconTheme.merge(
	data: new IconThemeData(
	color: foregroundColor,
	),
	child: widget.child,
	);
	}

	if (widget.tooltip != null) {
	final Widget tooltip = new Tooltip(
	message: widget.tooltip,
	child: result,
	);
	// The long-pressable area for the tooltip should always be as big as
	// the tooltip even if there is no child.
	result = widget.child != null ? tooltip : new SizedBox.expand(child: tooltip);
	}

	result = new RawMaterialButton(
	onPressed: widget.onPressed,
	onHighlightChanged: _handleHighlightChanged,
	elevation: _highlight ? widget.highlightElevation : widget.elevation,
	constraints: widget._sizeConstraints,
	outerPadding: widget.mini ? const EdgeInsets.all(4.0) : null,
	fillColor: widget.backgroundColor ?? theme.accentColor,
	textStyle: theme.accentTextTheme.button.copyWith(
	color: foregroundColor,
	letterSpacing: 1.2,
	),
	shape: widget.shape,
	child: result,
	);

	if (widget.heroTag != null) {
	result = new Hero(
	tag: widget.heroTag,
	child: result,
	);
	}

	return result;
	}

	@override
	void didChangeDependencies() {
	super.didChangeDependencies();
	_clearComputeNotch = Scaffold.setFloatingActionButtonNotchFor(context, _computeNotch);
	}

	@override
	void deactivate() {
	if (_clearComputeNotch != null)
	_clearComputeNotch();
	super.deactivate();
	}

	Path _computeNotch(Rect host, Rect guest, Offset start, Offset end) {
	// The FAB's shape is a circle bounded by the guest rectangle.
	// So the FAB's radius is half the guest width.
	final double fabRadius = guest.width / 2.0;
	final double notchRadius = fabRadius + widget.notchMargin;

	assert(_notchAssertions(host, guest, start, end, fabRadius, notchRadius));

	// If there's no overlap between the guest's margin boundary and the host,
	// don't make a notch, just return a straight line from start to end.
	if (!host.overlaps(guest.inflate(widget.notchMargin)))
	return new Path()..lineTo(end.dx, end.dy);

	// We build a path for the notch from 3 segments:
	// Segment A - a Bezier curve from the host's top edge to segment B.
	// Segment B - an arc with radius notchRadius.
	// Segment C - a Bezier curver from segment B back to the host's top edge.
	//
	// A detailed explanation and the derivation of the formulas below is
	// available at: https://goo.gl/Ufzrqn

	const double s1 = 15.0;
	const double s2 = 1.0;

	final double r = notchRadius;
	final double a = -1.0 * r - s2;
	final double b = host.top - guest.center.dy;

	final double n2 = math.sqrt(b * b * r * r * (a * a + b * b - r * r));
	final double p2xA = ((a * r * r) - n2) / (a * a + b * b);
	final double p2xB = ((a * r * r) + n2) / (a * a + b * b);
	final double p2yA = math.sqrt(r * r - p2xA * p2xA);
	final double p2yB = math.sqrt(r * r - p2xB * p2xB);

	final List<Offset> p = new List<Offset>(6);

	// p0, p1, and p2 are the control points for segment A.
	p[0] = new Offset(a - s1, b);
	p[1] = new Offset(a, b);
	final double cmp = b < 0 ? -1.0 : 1.0;
	p[2] = cmp * p2yA > cmp * p2yB ? new Offset(p2xA, p2yA) : new Offset(p2xB, p2yB);

	// p3, p4, and p5 are the control points for segment B, which is a mirror
	// of segment A around the y axis.
	p[3] = new Offset(-1.0 * p[2].dx, p[2].dy);
	p[4] = new Offset(-1.0 * p[1].dx, p[1].dy);
	p[5] = new Offset(-1.0 * p[0].dx, p[0].dy);

	// translate all points back to the absolute coordinate system.
	for (int i = 0; i < p.length; i += 1)
	p[i] += guest.center;

	return new Path()
	..lineTo(p[0].dx, p[0].dy)
	..quadraticBezierTo(p[1].dx, p[1].dy, p[2].dx, p[2].dy)
	..arcToPoint(
	p[3],
	radius: new Radius.circular(notchRadius),
	clockwise: false,
	)
	..quadraticBezierTo(p[4].dx, p[4].dy, p[5].dx, p[5].dy)
	..lineTo(end.dx, end.dy);
	}

	bool _notchAssertions(Rect host, Rect guest, Offset start, Offset end,
	double fabRadius, double notchRadius) {
	if (end.dy != host.top)
	throw new FlutterError(
	'The notch of the floating action button must end at the top edge of the host.\n'
	'The notch\'s path end point: $end is not in the top edge of $host'
	);

	if (start.dy != host.top)
	throw new FlutterError(
	'The notch of the floating action button must start at the top edge of the host.\n'
	'The notch\'s path start point: $start is not in the top edge of $host'
	);

	if (guest.center.dx - notchRadius < start.dx)
	throw new FlutterError(
	'The notch\'s path start point must be to the left of the floating action button.\n'
	'Start point was $start, guest was $guest, notchMargin was ${widget.notchMargin}.'
	);

	if (guest.center.dx + notchRadius > end.dx)
	throw new FlutterError(
	'The notch\'s end point must be to the right of the floating action button.\n'
	'End point was $start, notch was $guest, notchMargin was ${widget.notchMargin}.'
	);

	return true;
	}
	}