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1. The Layer Tree

Core Animation's original name is Layer Kit

Core Animation is a compositing engine; its job is to compose different pieces of visual content on the screen, and to do so as fast as possible. The content in question is divided into individual layers stored in a hierarchy known as the layer tree. This tree forms the underpinning for all of UIKit, and for everything that you see on the screen in an iOS application.

In UIView, tasks such as rendering, layout and animation are all managed by a Core Animation class called CALayer. The only major feature of UIView that isn’t handled by CALayer is user interaction.

There are four hierarchies, each performing a different role:

	/**
	* Don't use this in production!
	*
	* Screenshot of it working: https://user-images.githubusercontent.com/2466893/27601666-f65159f0-5b24-11e7-969d-fe86103c21de.png
	*/

	/**
	* This is real, private CA API. Valid as of iOS 10.
	*/
	typedef enum {

	#!/bin/sh

	exec > /tmp/${PROJECT_NAME}_archive.log 2>&1

	UNIVERSAL_OUTPUTFOLDER=${BUILD_DIR}/${CONFIGURATION}-universal

	if [ "true" == ${ALREADYINVOKED:-false} ]
	then
	echo "RECURSION: Detected, stopping"
	else

	/*
	* This is an example provided by Facebook are for non-commercial testing and
	* evaluation purposes only.
	*
	* Facebook reserves all rights not expressly granted.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
	* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT. IN NO EVENT SHALL
	* FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN

	//
	// ViewController.m
	// AVPlayerCaching
	//
	// Created by Anurag Mishra on 5/19/14.
	// Sample code to demonstrate how to cache a remote audio file while streaming it with AVPlayer
	//

	#import "ViewController.h"
	#import <AVFoundation/AVFoundation.h>

	********************************************************
	* STEPS TO SYMBOLIZE A CRASH DUMP OR EXCEPTION LOG *
	********************************************************

	1) Move/copy both the crashing .app and the relevant.dSYM files into the same directory.

	2) If the crash was in a framework, dynamic library, or bundle, you have position-independent code and must work out the slide. Otherwise, skip up to step 9 and use slide=0.

	3a) If you have a crash dump, look in the Binary Images part of the crash log and find the framework, dynamic libray or bundle in which the crash occurred. Read the first column of the output. This is the address at which the __TEXT segment was loaded. We call it the Actual Load Address and denote it as A.

	// Taken from the commercial iOS PDF framework http://pspdfkit.com.
	// Copyright (c) 2014 Peter Steinberger, PSPDFKit GmbH. All rights reserved.
	// Licensed under MIT (http://opensource.org/licenses/MIT)
	//
	// You should only use this in debug builds. It doesn't use private API, but I wouldn't ship it.

	// PLEASE DUPE rdar://27192338 (https://openradar.appspot.com/27192338) if you would like to see this in UIKit.

	#import <objc/runtime.h>
	#import <objc/message.h>

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