Find the geometry of a SwiftUI View

GeometryFinder.swift

//
//  GeometryFinder.swift
//
//  Created by Timothy Costa on 2019/06/24.
//  Copyright © 2019 timothycosta.com. All rights reserved.
//

import SwiftUI

struct RectPreferenceKey: PreferenceKey {
	static var defaultValue: CGRect = CGRect.zero
	static func reduce(value: inout CGRect, nextValue: () -> CGRect) {
		value = nextValue()
	}
}

struct GeometryFinder: View {

	var coordinateSpace: CoordinateSpace = .global
	var onUpdate: (CGRect) -> Void

	var body: some View {
		GeometryReader { proxy in
			Color.clear
				.preference(key: RectPreferenceKey.self, value: proxy.frame(in: self.coordinateSpace))
		}
		.onPreferenceChange(RectPreferenceKey.self) { value in
			self.onUpdate(value)
		}
	}
}

struct GeometryBinder: View {

	@Binding var rect: CGRect
	var coordinateSpace: CoordinateSpace = .local
	// old and new rects
	var shouldChange: (CGRect, CGRect) -> Bool = { _,_ in return true }
	//{ old,new in return old.integral != new.integral }

	var body: some View {
		GeometryReader { proxy in
			Color.clear
				.preference(key: RectPreferenceKey.self, value: proxy.frame(in: self.coordinateSpace))
		}
		.onPreferenceChange(RectPreferenceKey.self) { value in
			if self.shouldChange(self.rect, value) {
				withAnimation(nil) {
					self.rect = value
				}
			}
		}
	}
}