SKUIViewWrapper.swift

SKUIViewWrapper.swift

//
/// SKUIViewWrapper.swift
///
/// Created by Peter Easdown on 23/11/20.
///
/// This is an attempt to port the class CCUIViewWrapper from Cocos2D to Swift and SpriteKit for use
/// in my apps as I move them from the excellent Cocos2D (OpenGL based) to SpriteKit (Metal based).
///
/// Note that owing to the way the class manages the auto-adding and removal of the UIView, the wrapper
/// object should only be used once.  If it is removed from the node tree, then you will need another instance
/// next time you want to add the same UIView object instance.
///

import Foundation
import SpriteKit

class SKUIViewWrapper : SKNode {

    /// The UIView object being wrapped by this SKNode.
    var uiItem : UIView
    
    /// An observer used to track when the node is added and removed from the node tree.
    var observer: NSKeyValueObservation?
    
    /// Initialises the object as a wrapper around a specific UIView object.
    /// - Parameter ui: The UIView object to be wrapped.
    init(forUIView ui: UIView) {
        self.uiItem = ui
        
        super.init()
        
        // Add this observer so that the wrapper knows when it is added to the node tree, thus allowing it to also add the UIView it wraps to the underlying UIKit view hierarchy.
        //
        self.observer = self.observe(\.parent, options: [.new]) { [weak self] (wrapper, change) in
            guard let `self` = self else { return }
            
            if self.parent == nil {
                // No parent anymore, so remove the UIView from the view hierarchy.
                self.uiItem.removeFromSuperview()
            } else {
                // The node has been added to the node tree, so add the wrapped UIView to the view hierarchy, but only if it isn't already in the hierarchy.
                if self.uiItem.superview == nil {
                    self.scene?.view?.addSubview(self.uiItem)
                }
            }
        }
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    deinit {
        // Ensure the parent observer is removed.
        //
        self.observer?.invalidate()
    }
        
    /// Transform the view to match the SKNode.
    func updateUIViewTransform() {
        var transform = CGAffineTransform(translationX: 0.0, y: SKUtilities.screenHeight())
        var p : SKNode? = self
        
        while p != nil {
            if let pp = p {
                let thisAngle = pp.zRotation
                
                if let ppp = pp.parent {
                    let pAngle = ppp.zRotation
                    
                    transform = transform.translatedBy(x: (pp.position.x * CGFloat(cosf(Float(pAngle)))) + (pp.position.y * CGFloat(sinf(Float(pAngle)))),
                                                       y: (-pp.position.y * CGFloat(cosf(Float(pAngle)))) + (pp.position.x * CGFloat(sinf(Float(pAngle)))))
                } else {
                    transform = transform.translatedBy(x: pp.position.x, y: -pp.position.y)
                }
                
                transform = transform.rotated(by: thisAngle)
                transform = transform.scaledBy(x: pp.xScale, y: pp.yScale)
                transform = transform.translatedBy(x: -pp.position.x, y: -pp.position.y)
            }
            
            p = p?.parent
        }
        
        self.uiItem.transform = transform
    }
    
    override var isHidden: Bool {
        didSet {
            self.uiItem.isHidden = isHidden
        }
    }

    override var zRotation: CGFloat {
        didSet {
            self.updateUIViewTransform()
        }
    }

    override var xScale: CGFloat {
        didSet {
            self.updateUIViewTransform()
        }
    }

    override var yScale: CGFloat {
        didSet {
            self.updateUIViewTransform()
        }
    }

    override var alpha: CGFloat {
        didSet {
            self.uiItem.alpha = alpha
        }
    }

    override var position: CGPoint {
        didSet {
            self.updateUIViewTransform()
        }
    }
}