Clip geometry

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
// Copyright 2022 Esri
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import ArcGIS
import SwiftUI

struct ClipGeometryView: View {
    /// A Boolean value indicating whether the geometries are clipped.
    @State private var geometriesAreClipped = false

    /// The view model for the sample.
    @StateObject private var model = Model()

    var body: some View {
        MapView(map: model.map, graphicsOverlays: model.graphicsOverlays)
            .toolbar {
                ToolbarItem(placement: .bottomBar) {
                    Button(geometriesAreClipped ? "Reset" : "Clip") {
                        if geometriesAreClipped {
                            model.reset()
                        } else {
                            model.clipGeometries()
                        }
                        geometriesAreClipped.toggle()
                    }
                }
            }
    }
}

private extension ClipGeometryView {
    /// The model used to store the geo model and other expensive objects
    /// used in this view.
    class Model: ObservableObject {
        /// A map with a topographic basemap style and an initial viewpoint of Colorado.
        let map: Map = {
            let map = Map(basemapStyle: .arcGISTopographic)
            // Sets the initial viewpoint to Colorado and adds additional padding.
            map.initialViewpoint = Viewpoint(boundingGeometry: .coloradoEnvelope.expanded(by: 2))
            return map
        }()

        /// The graphics overlay containing an unclipped graphic of Colorado.
        private let coloradoGraphicsOverlay = GraphicsOverlay(
            graphics: [
                Graphic(geometry: .coloradoEnvelope, symbol: .coloradoFill)
            ]
        )

        /// The graphics overlay containing graphics of the other envelopes, outlined by a dotted red line.
        private let envelopesGraphicsOverlay = GraphicsOverlay(
            graphics: Geometry.envelopes.map {
                Graphic(geometry: $0, symbol: SimpleLineSymbol(style: .dot, color: .red, width: 3))
            }
        )

        /// The graphics overlay containing clipped graphics.
        private let clippedGraphicsOverlay = GraphicsOverlay()

        /// The unclipped graphic of Colorado.
        private var coloradoGraphic: Graphic { coloradoGraphicsOverlay.graphics.first! }

        /// The graphics overlays used in this sample.
        var graphicsOverlays: [GraphicsOverlay] {
            return [coloradoGraphicsOverlay, envelopesGraphicsOverlay, clippedGraphicsOverlay]
        }

        /// Clips the geometry of Colorado to the given envelope.
        /// - Parameter envelope: The envelope to clip the geometry of Colorado to.
        /// - Returns: The clipped graphic.
        private func clipColoradoGeometry(to envelope: Envelope) -> Graphic {
            // Uses the geometry engine to create a new geometry for the area of
            // Colorado that overlaps the given envelope.
            let clippedGeometry = GeometryEngine.clip(coloradoGraphic.geometry!, to: envelope)
            // Creates and returns the clipped graphic from the clipped geometry if there is an overlap.
            return Graphic(geometry: clippedGeometry, symbol: .coloradoFill)
        }

        /// Clips geometries and adds resulting graphics.
        func clipGeometries() {
            // Hides the Colorado graphic.
            coloradoGraphic.isVisible = false
            // Clips Colorado's geometry to each envelope.
            let clippedGraphics = envelopesGraphicsOverlay.graphics.map { clipColoradoGeometry(to: $0.geometry as! Envelope) }
            // Adds the clipped graphics.
            clippedGraphicsOverlay.addGraphics(clippedGraphics)
        }

        /// Removes all clipped graphics.
        func reset() {
            clippedGraphicsOverlay.removeAllGraphics()
            coloradoGraphic.isVisible = true
        }
    }
}

private extension Symbol {
    /// The simple fill symbol for Colorado graphics.
    static var coloradoFill: SimpleFillSymbol {
        SimpleFillSymbol(
            color: .blue.withAlphaComponent(0.2),
            outline: SimpleLineSymbol(
                style: .solid,
                color: .blue,
                width: 2
            )
        )
    }
}

private extension Geometry {
    /// An envelope approximating the boundary of Colorado.
    static var coloradoEnvelope: Envelope {
        Envelope(
            xMin: -11362327.1283,
            yMin: 5012861.2903,
            xMax: -12138232.0184,
            yMax: 4441198.7738,
            spatialReference: .webMercator
        )
    }
    /// An envelope inside the boundary of Colorado.
    static var containedEnvelope: Envelope {
        Envelope(
            xMin: -11655182.5952,
            yMin: 4741618.773,
            xMax: -11431488.567,
            yMax: 4593570.0683,
            spatialReference: .webMercator
        )
    }
    /// An envelope intersecting the boundary of Colorado.
    static var intersectingEnvelope: Envelope {
        Envelope(
            xMin: -11962086.4793,
            yMin: 4566553.8814,
            xMax: -12260345.1836,
            yMax: 4332053.3784,
            spatialReference: .webMercator
        )
    }
    /// An envelope outside the boundary of Colorado.
    static var outsideEnvelope: Envelope {
        Envelope(
            xMin: -11858344.3213,
            yMin: 5147942.2252,
            xMax: -12201990.2197,
            yMax: 5297071.5773,
            spatialReference: .webMercator
        )
    }
    /// The envelopes to clip the geometry of Colorado to.
    static var envelopes: [Envelope] {
        return [.containedEnvelope, .intersectingEnvelope, .outsideEnvelope]
    }
}

private extension Envelope {
    /// Expands the envelope by a given factor.
    func expanded(by factor: Double) -> Envelope {
        let builder = EnvelopeBuilder(envelope: self)
        builder.expand(by: factor)
        return builder.toGeometry()
    }
}

#Preview {
    NavigationView {
        ClipGeometryView()
    }
}