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1 // Copyright 2014 The Flutter Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 6 import 'dart:math' as math; 7 8 import 'basic_types.dart'; 9 import 'borders.dart'; 10 11 /// A shape with a notch in its outline. 12 /// 13 /// Typically used as the outline of a 'host' widget to make a notch that 14 /// accommodates a 'guest' widget. e.g the [BottomAppBar] may have a notch to 15 /// accommodate the [FloatingActionButton]. 16 /// 17 /// See also: 18 /// 19 /// * [ShapeBorder], which defines a shaped border without a dynamic notch. 20 /// * [AutomaticNotchedShape], an adapter from [ShapeBorder] to [NotchedShape]. 21 abstract class NotchedShape { 22 /// Abstract const constructor. This constructor enables subclasses to provide 23 /// const constructors so that they can be used in const expressions. 24 const NotchedShape(); 25 26 /// Creates a [Path] that describes the outline of the shape. 27 /// 28 /// The `host` is the bounding rectangle of the shape. 29 /// 30 /// The `guest` is the bounding rectangle of the shape for which a notch will 31 /// be made. It is null when there is no guest. 32 Path getOuterPath(Rect host, Rect? guest); 33 } 34 35 /// A rectangle with a smooth circular notch. 36 /// 37 /// See also: 38 /// 39 /// * [CircleBorder], a [ShapeBorder] that describes a circle. 40 class CircularNotchedRectangle extends NotchedShape { 41 /// Creates a [CircularNotchedRectangle]. 42 /// 43 /// The same object can be used to create multiple shapes. 44 const CircularNotchedRectangle(); 45 46 /// Creates a [Path] that describes a rectangle with a smooth circular notch. 47 /// 48 /// `host` is the bounding box for the returned shape. Conceptually this is 49 /// the rectangle to which the notch will be applied. 50 /// 51 /// `guest` is the bounding box of a circle that the notch accommodates. All 52 /// points in the circle bounded by `guest` will be outside of the returned 53 /// path. 54 /// 55 /// The notch is curve that smoothly connects the host's top edge and 56 /// the guest circle. 57 // TODO(amirh): add an example diagram here. 58 @override 59 Path getOuterPath(Rect host, Rect? guest) { 60 if (guest == null || !host.overlaps(guest)) 61 return Path()..addRect(host); 62 63 // The guest's shape is a circle bounded by the guest rectangle. 64 // So the guest's radius is half the guest width. 65 final double notchRadius = guest.width / 2.0; 66 67 // We build a path for the notch from 3 segments: 68 // Segment A - a Bezier curve from the host's top edge to segment B. 69 // Segment B - an arc with radius notchRadius. 70 // Segment C - a Bezier curve from segment B back to the host's top edge. 71 // 72 // A detailed explanation and the derivation of the formulas below is 73 // available at: https://goo.gl/Ufzrqn 74 75 const double s1 = 15.0; 76 const double s2 = 1.0; 77 78 final double r = notchRadius; 79 final double a = -1.0 * r - s2; 80 final double b = host.top - guest.center.dy; 81 82 final double n2 = math.sqrt(b * b * r * r * (a * a + b * b - r * r)); 83 final double p2xA = ((a * r * r) - n2) / (a * a + b * b); 84 final double p2xB = ((a * r * r) + n2) / (a * a + b * b); 85 final double p2yA = math.sqrt(r * r - p2xA * p2xA); 86 final double p2yB = math.sqrt(r * r - p2xB * p2xB); 87 88 final List<Offset?> p = List<Offset?>.filled(6, null, growable: false); 89 90 // p0, p1, and p2 are the control points for segment A. 91 p[0] = Offset(a - s1, b); 92 p[1] = Offset(a, b); 93 final double cmp = b < 0 ? -1.0 : 1.0; 94 p[2] = cmp * p2yA > cmp * p2yB ? Offset(p2xA, p2yA) : Offset(p2xB, p2yB); 95 96 // p3, p4, and p5 are the control points for segment B, which is a mirror 97 // of segment A around the y axis. 98 p[3] = Offset(-1.0 * p[2]!.dx, p[2]!.dy); 99 p[4] = Offset(-1.0 * p[1]!.dx, p[1]!.dy); 100 p[5] = Offset(-1.0 * p[0]!.dx, p[0]!.dy); 101 102 // translate all points back to the absolute coordinate system. 103 for (int i = 0; i < p.length; i += 1) 104 p[i] = p[i]! + guest.center; 105 106 return Path() 107 ..moveTo(host.left, host.top) 108 ..lineTo(p[0]!.dx, p[0]!.dy) 109 ..quadraticBezierTo(p[1]!.dx, p[1]!.dy, p[2]!.dx, p[2]!.dy) 110 ..arcToPoint( 111 p[3]!, 112 radius: Radius.circular(notchRadius), 113 clockwise: false, 114 ) 115 ..quadraticBezierTo(p[4]!.dx, p[4]!.dy, p[5]!.dx, p[5]!.dy) 116 ..lineTo(host.right, host.top) 117 ..lineTo(host.right, host.bottom) 118 ..lineTo(host.left, host.bottom) 119 ..close(); 120 } 121 } 122 123 /// A [NotchedShape] created from [ShapeBorder]s. 124 /// 125 /// Two shapes can be provided. The [host] is the shape of the widget that 126 /// uses the [NotchedShape] (typically a [BottomAppBar]). The [guest] is 127 /// subtracted from the [host] to create the notch (typically to make room 128 /// for a [FloatingActionButton]). 129 class AutomaticNotchedShape extends NotchedShape { 130 /// Creates a [NotchedShape] that is defined by two [ShapeBorder]s. 131 /// 132 /// The [host] must not be null. 133 /// 134 /// The [guest] may be null, in which case no notch is created even 135 /// if a guest rectangle is provided to [getOuterPath]. 136 const AutomaticNotchedShape(this.host, [ this.guest ]); 137 138 /// The shape of the widget that uses the [NotchedShape] (typically a 139 /// [BottomAppBar]). 140 /// 141 /// This shape cannot depend on the [TextDirection], as no text direction 142 /// is available to [NotchedShape]s. 143 final ShapeBorder host; 144 145 /// The shape to subtract from the [host] to make the notch. 146 /// 147 /// This shape cannot depend on the [TextDirection], as no text direction 148 /// is available to [NotchedShape]s. 149 /// 150 /// If this is null, [getOuterPath] ignores the guest rectangle. 151 final ShapeBorder? guest; 152 153 @override 154 Path getOuterPath(Rect hostRect, Rect? guestRect) { // ignore: avoid_renaming_method_parameters, the 155 // parameters are renamed over the baseclass because they would clash 156 // with properties of this object, and the use of all four of them in 157 // the code below is really confusing if they have the same names. 158 final Path hostPath = host.getOuterPath(hostRect); 159 if (guest != null && guestRect != null) { 160 final Path guestPath = guest!.getOuterPath(guestRect); 161 return Path.combine(PathOperation.difference, hostPath, guestPath); 162 } 163 return hostPath; 164 } 165 }