this bites me every single time

src/player/InventoryWindow.php

@@ -0,0 +1,50 @@
+<?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\player;
+
+use pocketmine\inventory\Inventory;
+
+abstract class InventoryWindow{
+
+	public function __construct(
+		protected Player $viewer,
+		protected Inventory $inventory
+	){}
+
+	public function getViewer() : Player{
+		return $this->viewer;
+	}
+
+	public function getInventory() : Inventory{
+		return $this->inventory;
+	}
+
+	public function onOpen() : void{
+		$this->inventory->onOpen($this->viewer);
+	}
+
+	public function onClose() : void{
+		$this->inventory->onClose($this->viewer);
+	}
+}

src/player/PlayerInventoryWindow.php

@@ -0,0 +1,51 @@
+<?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\player;
+
+use pocketmine\inventory\Inventory;
+
+/**
+ * Window for player-owned inventories. The player can access these at all times.
+ */
+final class PlayerInventoryWindow extends InventoryWindow{
+
+	public const TYPE_INVENTORY = 0;
+	public const TYPE_OFFHAND = 1;
+	public const TYPE_ARMOR = 2;
+	public const TYPE_CURSOR = 3;
+	public const TYPE_CRAFTING = 4;
+
+	public function __construct(
+		Player $viewer,
+		Inventory $inventory,
+		private int $type
+	){
+		parent::__construct($viewer, $inventory);
+	}
+
+	/**
+	 * Returns the type of player inventory in this window.
+	 */
+	public function getType() : int{ return $this->type; }
+}