dart / external / github.com / flutter / flutter / 5ddc00cc0307a571b806a47f2b59f2265d9faf1d / . / packages / flutter / lib / src / painting / notched_shapes.dart

// 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 'basic_types.dart'; | |

import 'borders.dart'; | |

/// A shape with a notch in its outline. | |

/// | |

/// Typically used as the outline of a 'host' widget to make a notch that | |

/// accommodates a 'guest' widget. e.g the [BottomAppBar] may have a notch to | |

/// accommodate the [FloatingActionButton]. | |

/// | |

/// See also: | |

/// | |

/// * [ShapeBorder], which defines a shaped border without a dynamic notch. | |

/// * [AutomaticNotchedShape], an adapter from [ShapeBorder] to [NotchedShape]. | |

abstract class NotchedShape { | |

/// Abstract const constructor. This constructor enables subclasses to provide | |

/// const constructors so that they can be used in const expressions. | |

const NotchedShape(); | |

/// Creates a [Path] that describes the outline of the shape. | |

/// | |

/// The `host` is the bounding rectangle of the shape. | |

/// | |

/// The `guest` is the bounding rectangle of the shape for which a notch will | |

/// be made. It is null when there is no guest. | |

Path getOuterPath(Rect host, Rect? guest); | |

} | |

/// A rectangle with a smooth circular notch. | |

/// | |

/// See also: | |

/// | |

/// * [CircleBorder], a [ShapeBorder] that describes a circle. | |

class CircularNotchedRectangle extends NotchedShape { | |

/// Creates a [CircularNotchedRectangle]. | |

/// | |

/// The same object can be used to create multiple shapes. | |

const CircularNotchedRectangle(); | |

/// Creates a [Path] that describes a rectangle with a smooth circular notch. | |

/// | |

/// `host` is the bounding box for the returned shape. Conceptually this is | |

/// the rectangle to which the notch will be applied. | |

/// | |

/// `guest` is the bounding box of a circle that the notch accommodates. All | |

/// points in the circle bounded by `guest` will be outside of the returned | |

/// path. | |

/// | |

/// The notch is curve that smoothly connects the host's top edge and | |

/// the guest circle. | |

// TODO(amirh): add an example diagram here. | |

@override | |

Path getOuterPath(Rect host, Rect? guest) { | |

if (guest == null || !host.overlaps(guest)) | |

return Path()..addRect(host); | |

// The guest's shape is a circle bounded by the guest rectangle. | |

// So the guest's radius is half the guest width. | |

final double notchRadius = guest.width / 2.0; | |

// 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 curve 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 = List<Offset?>.filled(6, null); | |

// p0, p1, and p2 are the control points for segment A. | |

p[0] = Offset(a - s1, b); | |

p[1] = Offset(a, b); | |

final double cmp = b < 0 ? -1.0 : 1.0; | |

p[2] = cmp * p2yA > cmp * p2yB ? Offset(p2xA, p2yA) : 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] = Offset(-1.0 * p[2]!.dx, p[2]!.dy); | |

p[4] = Offset(-1.0 * p[1]!.dx, p[1]!.dy); | |

p[5] = 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] = p[i]! + guest.center; | |

return Path() | |

..moveTo(host.left, host.top) | |

..lineTo(p[0]!.dx, p[0]!.dy) | |

..quadraticBezierTo(p[1]!.dx, p[1]!.dy, p[2]!.dx, p[2]!.dy) | |

..arcToPoint( | |

p[3]!, | |

radius: Radius.circular(notchRadius), | |

clockwise: false, | |

) | |

..quadraticBezierTo(p[4]!.dx, p[4]!.dy, p[5]!.dx, p[5]!.dy) | |

..lineTo(host.right, host.top) | |

..lineTo(host.right, host.bottom) | |

..lineTo(host.left, host.bottom) | |

..close(); | |

} | |

} | |

/// A [NotchedShape] created from [ShapeBorder]s. | |

/// | |

/// Two shapes can be provided. The [host] is the shape of the widget that | |

/// uses the [NotchedShape] (typically a [BottomAppBar]). The [guest] is | |

/// subtracted from the [host] to create the notch (typically to make room | |

/// for a [FloatingActionButton]). | |

class AutomaticNotchedShape extends NotchedShape { | |

/// Creates a [NotchedShape] that is defined by two [ShapeBorder]s. | |

/// | |

/// The [host] must not be null. | |

/// | |

/// The [guest] may be null, in which case no notch is created even | |

/// if a guest rectangle is provided to [getOuterPath]. | |

const AutomaticNotchedShape(this.host, [ this.guest ]); | |

/// The shape of the widget that uses the [NotchedShape] (typically a | |

/// [BottomAppBar]). | |

/// | |

/// This shape cannot depend on the [TextDirection], as no text direction | |

/// is available to [NotchedShape]s. | |

final ShapeBorder host; | |

/// The shape to subtract from the [host] to make the notch. | |

/// | |

/// This shape cannot depend on the [TextDirection], as no text direction | |

/// is available to [NotchedShape]s. | |

/// | |

/// If this is null, [getOuterPath] ignores the guest rectangle. | |

final ShapeBorder? guest; | |

@override | |

Path getOuterPath(Rect hostRect, Rect? guestRect) { // ignore: avoid_renaming_method_parameters | |

// The parameters of this method are renamed over the baseclass because they | |

// would clash with properties of this object, and the use of all four of | |

// them in the code below is really confusing if they have the same names. | |

final Path hostPath = host.getOuterPath(hostRect); | |

if (guest != null && guestRect != null) { | |

final Path guestPath = guest!.getOuterPath(guestRect); | |

return Path.combine(PathOperation.difference, hostPath, guestPath); | |

} | |

return hostPath; | |

} | |

} |