SwiftUI - Fit X Circles of varying size (wrt each other) in a given frame (Packed Bubble Chart) - Ios swift

KunalVerma
January 18, 2022
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2 Answers

Is there any way to create something like this with SwiftUI (w/o using D3.js) –

// test data
    @State private var data: [DataItem] = [
        DataItem(title: "chrome", weight: 180, color: .green),
        DataItem(title: "firefox", weight: 60, color: .red),
        DataItem(title: "safari", weight: 90, color: .blue),
        DataItem(title: "edge", weight: 30, color: .orange),
        DataItem(title: "ie", weight: 50, color: .yellow),
        DataItem(title: "opera", weight: 25, color: .purple)
    ]

Here in the test data, "weight" denotes which item should be larger/smaller.

One way I can think of is to have X Circles in a given view with size relative to the parent. But that in itself creates issues for positioning and making sure that circles are not touching or overlapping each other.

Not sure about the usage of SpriteKit here? Can that be used or can this be achieved using SwiftUI components only?

Answers

This was fun, going back to school math 🙂
Here is my result. The smaller circles all align around the first large one, I didn’t solve the positioning of "opera" in your image, it seems to be accidentally.

Here is the code:
It’s a starting point, no safety checks

import SwiftUI

struct DataItem: Identifiable {
    var id = UUID()
    var title: String
    var size: CGFloat
    var color: Color
    var offset = CGSize.zero
}


struct ContentView: View {
    
    // test data
    @State private var data: [DataItem] = [
        DataItem(title: "chrome", size: 180, color: .green),
        DataItem(title: "firefox", size: 60, color: .red),
        DataItem(title: "safari", size: 90, color: .blue),
        DataItem(title: "edge", size: 30, color: .orange),
        DataItem(title: "ie", size: 50, color: .yellow),
        DataItem(title: "opera", size: 25, color: .mint)
    ]
    
            
    var body: some View {
        
        ZStack {
            ForEach(data, id: .id) { item in
                ZStack {
                    Circle()
                        .frame(width: CGFloat(item.size))
                        .foregroundColor(item.color)
                    Text(item.title)
                }
                .offset(item.offset)
            }
        }
        
        // calculate and set the offsets - could be done at other time or place in code
        .onAppear {
            data[0].offset = CGSize.zero
            data[1].offset = CGSize(width: (data[0].size + data[1].size) / 2, height: 0 )
                
            var alpha = CGFloat.zero
            
            for i in 2..<data.count {
                                
                // sides of the triangle from circle center points
                let c = (data[0].size + data[i-1].size) / 2
                let b = (data[0].size + data[i].size) / 2
                let a = (data[i-1].size + data[i].size) / 2
                
                alpha += calculateAlpha(a, b, c)
                                
                let x = cos(alpha) * b
                let y = sin(alpha) * b
                
                data[i].offset = CGSize(width: x, height: -y )
            }
        }
    }
    
    // Calculate alpha from sides - 1. Cosine theorem
    func calculateAlpha(_ a: CGFloat, _ b: CGFloat, _ c: CGFloat) -> CGFloat {
        return acos(
            ( pow(a, 2) - pow(b, 2) - pow(c, 2) )
            /
            ( -2 * b * c ) )

    }
    
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

ok you motivated me 🙂 here comes the extended version

standalone struct
adapts to parent !!
accepts the data, spacing, start angle, direction (clockwise/counterclockwise)

the frame ist just to show adapt to parent size:

you call it like this:

struct ContentView: View {
    
    // graph data
    @State private var data: [DataItem] = [
        DataItem(title: "chrome", size: 180, color: .green),
        DataItem(title: "firefox", size: 60, color: .red),
        DataItem(title: "safari", size: 90, color: .blue),
        DataItem(title: "edge", size: 30, color: .orange),
        DataItem(title: "ie", size: 50, color: .yellow),
        DataItem(title: "chrome", size: 120, color: .green),
        DataItem(title: "firefox", size: 60, color: .red),
        DataItem(title: "safari", size: 90, color: .blue),
        DataItem(title: "edge", size: 30, color: .orange),
        DataItem(title: "opera", size: 25, color: .mint)
    ]
    
    
    var body: some View {
        
        BubbleView(data: $data, spacing: 0, startAngle: 180, clockwise: true)
            .font(.caption)
            .frame(width: 300, height: 400)
            .border(Color.red)
        
    }
}

And here is the code:

struct DataItem: Identifiable {
    var id = UUID()
    var title: String
    var size: CGFloat
    var color: Color
    var offset = CGSize.zero
}

struct BubbleView: View {
    
    @Binding var data: [DataItem]
    
    // Spacing between bubbles
    var spacing: CGFloat
    
    // startAngle in degrees -360 to 360 from left horizontal
    var startAngle: Int
    
    // direction
    var clockwise: Bool
    
    struct ViewSize {
        var xMin: CGFloat = 0
        var xMax: CGFloat = 0
        var yMin: CGFloat = 0
        var yMax: CGFloat = 0
    }
    
    @State private var mySize = ViewSize()
    
    var body: some View {

        let xSize = (mySize.xMax - mySize.xMin) == 0 ? 1 : (mySize.xMax - mySize.xMin)
        let ySize = (mySize.yMax - mySize.yMin) == 0 ? 1 : (mySize.yMax - mySize.yMin)

        GeometryReader { geo in
            
            let xScale = geo.size.width / xSize
            let yScale = geo.size.height / ySize
            let scale = min(xScale, yScale)
                     
            ZStack {
                ForEach(data, id: .id) { item in
                    ZStack {
                        Circle()
                            .frame(width: CGFloat(item.size) * scale,
                                   height: CGFloat(item.size) * scale)
                            .foregroundColor(item.color)
                        Text(item.title)
                    }
                    .offset(x: item.offset.width * scale, y: item.offset.height * scale)
                }
            }
            .offset(x: xOffset() * scale, y: yOffset() * scale)
        }
        .onAppear {
            setOffets()
            mySize = absoluteSize()
        }
    }
    
    
    // taken out of main for compiler complexity issue
    func xOffset() -> CGFloat {
        let size = data[0].size
        let xOffset = mySize.xMin + size / 2
        return -xOffset
    }
    
    func yOffset() -> CGFloat {
        let size = data[0].size
        let yOffset = mySize.yMin + size / 2
        return -yOffset
    }

    
    // calculate and set the offsets
    func setOffets() {
        if data.isEmpty { return }
        // first circle
        data[0].offset = CGSize.zero
        
        if data.count < 2 { return }
        // second circle
        let b = (data[0].size + data[1].size) / 2 + spacing
        
        // start Angle
        var alpha: CGFloat = CGFloat(startAngle) / 180 * CGFloat.pi
        
        data[1].offset = CGSize(width:  cos(alpha) * b,
                                height: sin(alpha) * b)
        
        // other circles
        for i in 2..<data.count {
            
            // sides of the triangle from circle center points
            let c = (data[0].size + data[i-1].size) / 2 + spacing
            let b = (data[0].size + data[i].size) / 2 + spacing
            let a = (data[i-1].size + data[i].size) / 2 + spacing
            
            alpha += calculateAlpha(a, b, c) * (clockwise ? 1 : -1)
            
            let x = cos(alpha) * b
            let y = sin(alpha) * b
            
            data[i].offset = CGSize(width: x, height: y )
        }
    }
    
    // Calculate alpha from sides - 1. Cosine theorem
    func calculateAlpha(_ a: CGFloat, _ b: CGFloat, _ c: CGFloat) -> CGFloat {
        return acos(
            ( pow(a, 2) - pow(b, 2) - pow(c, 2) )
            /
            ( -2 * b * c ) )
        
    }
    
    // calculate max dimensions of offset view
    func absoluteSize() -> ViewSize {
        let radius = data[0].size / 2
        let initialSize = ViewSize(xMin: -radius, xMax: radius, yMin: -radius, yMax: radius)
        
        let maxSize = data.reduce(initialSize, { partialResult, item in
            let xMin = min(
                partialResult.xMin,
                item.offset.width - item.size / 2 - spacing
            )
            let xMax = max(
                partialResult.xMax,
                item.offset.width + item.size / 2 + spacing
            )
            let yMin = min(
                partialResult.yMin,
                item.offset.height - item.size / 2 - spacing
            )
            let yMax = max(
                partialResult.yMax,
                item.offset.height + item.size / 2 + spacing
            )
            return ViewSize(xMin: xMin, xMax: xMax, yMin: yMin, yMax: yMax)
        })
        return maxSize
    }
    
}

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SwiftUI – Fit X Circles of varying size (wrt each other) in a given frame (Packed Bubble Chart) – Ios swift

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