New skin API, add support for custom capes & custom geometry (#1416)

* Added support for changing skins ingame, custom capes & geometry
* Use PlayerSkinPacket for setting Human skin instead of PlayerList hack

src/pocketmine/event/player/PlayerChangeSkinEvent.php

@@ -0,0 +1,78 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\event\player;
+
+use pocketmine\entity\Skin;
+use pocketmine\event\Cancellable;
+use pocketmine\Player;
+
+/**
+ * Called when a player changes their skin in-game.
+ */
+class PlayerChangeSkinEvent extends PlayerEvent implements Cancellable{
+	public static $handlerList = null;
+
+	/** @var Skin */
+	private $oldSkin;
+	/** @var Skin */
+	private $newSkin;
+
+	/**
+	 * @param Player $player
+	 * @param Skin   $oldSkin
+	 * @param Skin   $newSkin
+	 */
+	public function __construct(Player $player, Skin $oldSkin, Skin $newSkin){
+		$this->player = $player;
+		$this->oldSkin = $oldSkin;
+		$this->newSkin = $newSkin;
+	}
+
+	/**
+	 * @return Skin
+	 */
+	public function getOldSkin() : Skin{
+		return $this->oldSkin;
+	}
+
+	/**
+	 * @return Skin
+	 */
+	public function getNewSkin() : Skin{
+		return $this->newSkin;
+	}
+
+	/**
+	 * @param Skin $skin
+	 * @throws \InvalidArgumentException if the specified skin is not valid
+	 */
+	public function setNewSkin(Skin $skin) : void{
+		if(!$skin->isValid()){
+			throw new \InvalidArgumentException("Skin format is invalid");
+		}
+
+		$this->newSkin = $skin;
+	}
+
+}