Don't cancel single slot drag event click

[konradpomocny]

The problem:
When placing an item with a "drag" (the InventoryDragEvent) onto GuiStorageElement, it will always get canceled. Placing a single item with drag event is undistinguishable to a player from a regular inventory click. This creates a weird bug where sometimes item just won't get placed into storage.

This is a fix.

[Phoenix616]

Thank you for your PR and while it seems to make sense (as the single slot drag is forwarded as a click but then cancelled here by the event instance chec) I cannot reproduce any issue with the current implementation which is a bit confusing to me and I want to figure out why it's not actually causing an issue for me first before merging.

[konradpomocny]

Thanks for a quick response!
You're right! The GUI that has this problem is a multi-page storage "chest" that's using GuiElementGroup class. I simplified it as much as I could to replicate the issue:

            InventoryGui gui = new InventoryGui(this, null, "", new String[]{
                "ggggggggg",
                "ggggggggg",
                "ggggggggg",
                "ggggggggg",
                "ggggggggg",
                "ggggggggg",
            });
            GuiElementGroup group = new GuiElementGroup('g');
            Inventory inventory = Bukkit.createInventory(null, 54);
            for (int i = 0; i < 54; i++) {
                group.addElement(new GuiStorageElement('e', inventory, i));
            }
            gui.addElement(group);
            gui.show(player);

When having an itemstack on the cursor and right clicking on each slot, this happens:
Base Profile 2025.09.09 - 15.22.08.02.webm

(I clicked once on each slot, eventually the item will go through)
@Phoenix616

[Phoenix616]

Thanks for providing the additional info. My guess right now is that this is caused by using a group instead of the GuiStorageElement directly so the click would get passed through the group first which could potentially change behaviour and cause what you describe. I only tested with a direct storage element before. (your example should be able to not use a group at all as the GuiStorageElement would automatically map the slots to the slots in the inventory but of course storage inside groups should be properly fixed too)

[Phoenix616]

Can you please re-test if the latest changes to the library (1.6.5 release) fixes your issues already without this additional PR?

[konradpomocny]

Can you please re-test if the latest changes to the library (1.6.5 release) fixes your issues already without this additional PR?

Unfortunately it appears that the issue is still there. I tested it on version 1.20.4 though (added a startup flag), could that be the problem?

[Phoenix616]

I tested it on version 1.20.4 though (added a startup flag), could that be the problem?

You need to test on 1.21.9+ as server versions previous to this have a bug which makes handling inventories correctly not possible.