Custom blocks can block item interaction, prevents blocks being placed when opening containers

src/main/java/fr/themode/demo/blocks/StoneBlock.java

@@ -25,8 +25,8 @@ public class StoneBlock extends CustomBlock {
     }
 
     @Override
-    public void onInteract(Player player, Player.Hand hand, BlockPosition blockPosition, Data data) {
+    public boolean onInteract(Player player, Player.Hand hand, BlockPosition blockPosition, Data data) {
-
+        return false;
     }
 
     @Override

src/main/java/fr/themode/demo/blocks/UpdatableBlockDemo.java

@@ -33,8 +33,8 @@ public class UpdatableBlockDemo extends CustomBlock {
     }
 
     @Override
-    public void onInteract(Player player, Player.Hand hand, BlockPosition blockPosition, Data data) {
+    public boolean onInteract(Player player, Player.Hand hand, BlockPosition blockPosition, Data data) {
-
+        return false;
     }
 
     @Override

src/main/java/net/minestom/server/event/PlayerBlockInteractEvent.java

@@ -8,11 +8,25 @@ public class PlayerBlockInteractEvent extends CancellableEvent {
     private BlockPosition blockPosition;
     private Player.Hand hand;
 
+    /**
+     * Does this interaction block the normal item use?
+     * True for containers which open an inventory instead of letting blocks be placed
+     */
+    private boolean blocksItemUse;
+
     public PlayerBlockInteractEvent(BlockPosition blockPosition, Player.Hand hand) {
         this.blockPosition = blockPosition;
         this.hand = hand;
     }
 
+    public boolean isBlockingItemUse() {
+        return blocksItemUse;
+    }
+
+    public void setBlockingItemUse(boolean blocks) {
+        this.blocksItemUse = blocks;
+    }
+
     public BlockPosition getBlockPosition() {
         return blockPosition;
     }

src/main/java/net/minestom/server/instance/block/CustomBlock.java

@@ -33,7 +33,16 @@ public abstract class CustomBlock {
 
     public abstract void onDestroy(Instance instance, BlockPosition blockPosition, Data data);
 
-    public abstract void onInteract(Player player, Player.Hand hand, BlockPosition blockPosition, Data data);
+    /**
+     * Handles interactions with this block. Can also block normal item use (containers should block when opening the
+     * menu, this prevents the player from placing a block when opening it for instance)
+     * @param player the player interacting
+     * @param hand the hand used to interact
+     * @param blockPosition the position of this block
+     * @param data the data at this position
+     * @return true if this block blocks normal item use, false otherwise
+     */
+    public abstract boolean onInteract(Player player, Player.Hand hand, BlockPosition blockPosition, Data data);
 
     public abstract UpdateOption getUpdateOption();
 

src/main/java/net/minestom/server/listener/BlockPlacementListener.java

@@ -42,10 +42,17 @@ public class BlockPlacementListener {
             CustomBlock customBlock = instance.getCustomBlock(blockPosition);
             if (customBlock != null) {
                 Data data = instance.getBlockData(blockPosition);
-                customBlock.onInteract(player, hand, blockPosition, data);
+                boolean blocksItem = customBlock.onInteract(player, hand, blockPosition, data);
+                if(blocksItem) {
+                    playerBlockInteractEvent.setBlockingItemUse(true);
+                }
             }
         });
 
+        if(playerBlockInteractEvent.isBlockingItemUse()) {
+            return;
+        }
+
         // Check if item at hand is a block
         ItemStack usedItem = hand == Player.Hand.MAIN ? playerInventory.getItemInMainHand() : playerInventory.getItemInOffHand();
         Material material = Material.fromId(usedItem.getMaterialId());