Sticky drag modifier. This modifier adds a drag gesture to the view it modifies. This drag gesture behaves a lot like a rubber band be pulled to its breaking point.

StickyDrag.swift

// Swift toolchain version 5.0
// Running macOS version 10.15
// Created on 11/1/20.
//
// Author: Kieran Brown
//

import SwiftUI
import UIKit

// MARK: - CGSize: VectorArithmetic

extension CGSize: VectorArithmetic {
    public mutating func scale(by rhs: Double) {
        self.width = CGFloat(rhs)*self.width
        self.height = CGFloat(rhs)*self.height
    }
    
    public var magnitudeSquared: Double {
        Double(width*width+height*height)
    }
}

// MARK: - CGSize: AdditiveArithmetic

extension CGSize: AdditiveArithmetic {
    public static func - (lhs: CGSize, rhs: CGSize) -> CGSize {
        CGSize(width: lhs.width-rhs.width,
               height: lhs.height-rhs.height)
    }
    
    public static func + (lhs: CGSize, rhs: CGSize) -> CGSize {
        return CGSize(width: lhs.width+rhs.width,
                      height: lhs.height+rhs.height)
    }
}

// MARK: - Sticky Drag Modifier

struct StickyDragModifier: ViewModifier {
    @State private var offset: CGSize = .zero
    @State private var dragState: CGSize = .zero
    @State private var snapped: Bool = false
    
    /// The threshold distance a user must drag before the stickiness effect is removed.
    /// This has a snap like animated effect.
    private var snapDistance: Double
    /// A value constrained between 0(least sticky) and 1(most sticky).
    private var stickiness: Double
    
    /// Sticky drag modifier. This modifier adds a drag gesture to the view it modifies.
    /// This drag gesture behaves a lot like a rubber band be pulled to its breaking point.
    /// Upon the user dragging further than the `snapDistance`  a haptic impact is played
    /// and the view can be dragged normally until the gesture ends.
    /// - Parameters:
    ///   - stickiness: A value constrained between 0(least sticky) and 1(most sticky).
    ///   - snapDistance: The threshold distance a user must drag before the stickiness effect is removed. This has a snap like animated effect.
    public init(stickiness: Double =  0.33, snapDistance: Double = 150) {
        self.snapDistance = max(1,snapDistance)
        self.stickiness = max(min(stickiness,1), 0)
    }
    
    private func stickify(_ translation: CGSize) -> CGSize {
        let magnitude = sqrt(translation.magnitudeSquared)
        if magnitude > snapDistance || snapped {
            if !snapped {
                Self.mediumImpact()
                snapped = true
            }
            return translation
        }
        var copy = translation
        let scale = 1-log(1 + magnitude/(snapDistance*(2-stickiness))) // dont worry about this math, if it fits it ships
        copy.scale(by: scale)
        return copy
    }
    
    private static func mediumImpact() {
        let generator = UIImpactFeedbackGenerator(style: .medium)
        generator.impactOccurred()
    }
    
    func body(content: Content) -> some View {
        content
            .offset(offset+dragState)
            .gesture(
                DragGesture()
                    .onChanged({ self.dragState = stickify($0.translation) })
                    .onEnded({
                        self.offset += $0.translation
                        self.dragState = .zero
                        self.snapped = false
                    })
            )
            .animation(.linear)
    }
}

// MARK: - View Extension

extension View {
    func stickyDraggable() -> some View {
        self.modifier(StickyDragModifier())
    }
}

// MARK: - Example

struct StickyDragExample: View {
    var body: some View {
        Circle()
            .fill(Color.blue)
            .frame(width: 50, height: 50)
            .stickyDraggable()
    }
}

struct StickyDragExample_Previews: PreviewProvider {
    static var previews: some View {
        StickyDragExample()
    }
}