RN3DTouchGestureRecognizer

RN3DTouchGestureRecognizer.swift

//
//  RN3DTouchGestureRecognizer.swift
//
//  Created by Ryan Nystrom on 10/10/15.
//  Copyright © 2015 Ryan Nystrom. All rights reserved.
//

import UIKit.UIGestureRecognizerSubclass

class RN3DTouchGestureRecognizer: UIGestureRecognizer {

    // 0 to 1.0, reaches 1.0 when 3d touch state is active
    private(set) var progress: CGFloat = 0
    
    // roughly when "Peek" activates
    private let threshold: CGFloat = 0.22
    
    // ignore the first 10% of the touch before enabling 3D
    private let delay: CGFloat = 0.1

    private var shouldPresent: Bool {
        return progress >= 1.0
    }

    private func handleTouches(touches: Set<UITouch>, failedState: UIGestureRecognizerState, continueState: UIGestureRecognizerState) {
        guard let touch = touches.first where touches.count == 1 else {
            state = failedState
            return
        }
        let f = max(touch.force - touch.maximumPossibleForce * delay, 0)
        let p = f / (touch.maximumPossibleForce * threshold)
        progress = min(max(p, 0), 1)
        if shouldPresent {
            state = .Ended
        } else {
            state = continueState
        }
    }

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent) {
        super.touchesBegan(touches, withEvent: event)
        handleTouches(touches, failedState: .Failed, continueState: .Began)
    }

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent) {
        super.touchesMoved(touches, withEvent: event)
        handleTouches(touches, failedState: .Cancelled, continueState: .Changed)
    }

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent) {
        super.touchesEnded(touches, withEvent: event)
        handleTouches(touches, failedState: .Failed, continueState: .Cancelled)
    }

    override func touchesCancelled(touches: Set<UITouch>, withEvent event: UIEvent) {
        super.touchesCancelled(touches, withEvent: event)
        state = .Cancelled
    }

    override func reset() {
        super.reset()
        progress = 0
        state = .Possible
    }

}