Added InventoryOpenEvent

src/main/java/net/minestom/server/entity/Player.java

@@ -10,6 +10,7 @@ import net.minestom.server.effects.Effects;
 import net.minestom.server.entity.damage.DamageType;
 import net.minestom.server.entity.property.Attribute;
 import net.minestom.server.entity.vehicle.PlayerVehicleInformation;
+import net.minestom.server.event.inventory.InventoryOpenEvent;
 import net.minestom.server.event.item.ItemDropEvent;
 import net.minestom.server.event.item.ItemUpdateStateEvent;
 import net.minestom.server.event.item.PickupExperienceEvent;
@@ -873,12 +874,22 @@ public class Player extends LivingEntity {
         return Collections.unmodifiableSet(bossBars);
     }
 
-    public void openInventory(Inventory inventory) {
+    /**
+     * Open the specified Inventory
+     *
+     * @param inventory the inventory to open
+     * @return true if the inventory has been opened/sent to the player, false otherwise (cancelled by event)
+     */
+    public boolean openInventory(Inventory inventory) {
         if (inventory == null)
             throw new IllegalArgumentException("Inventory cannot be null, use Player#closeInventory() to close current");
 
+        InventoryOpenEvent inventoryOpenEvent = new InventoryOpenEvent(this, inventory);
+
+        callCancellableEvent(InventoryOpenEvent.class, inventoryOpenEvent, () -> {
+
             if (getOpenInventory() != null) {
-            getOpenInventory().removeViewer(this);
+                closeInventory();
             }
 
             OpenWindowPacket openWindowPacket = new OpenWindowPacket();
@@ -888,6 +899,10 @@ public class Player extends LivingEntity {
             playerConnection.sendPacket(openWindowPacket);
             inventory.addViewer(this);
             refreshOpenInventory(inventory);
+
+        });
+
+        return !inventoryOpenEvent.isCancelled();
     }
 
     public void closeInventory() {

src/main/java/net/minestom/server/event/inventory/InventoryOpenEvent.java

@@ -0,0 +1,24 @@
+package net.minestom.server.event.inventory;
+
+import net.minestom.server.entity.Player;
+import net.minestom.server.event.CancellableEvent;
+import net.minestom.server.inventory.Inventory;
+
+public class InventoryOpenEvent extends CancellableEvent {
+
+    private Player player;
+    private Inventory inventory;
+
+    public InventoryOpenEvent(Player player, Inventory inventory) {
+        this.player = player;
+        this.inventory = inventory;
+    }
+
+    public Player getPlayer() {
+        return player;
+    }
+
+    public Inventory getInventory() {
+        return inventory;
+    }
+}