Okay, so invastagating led me to "how to", but I don't undestand why and where to look for answers:

 

There are 2 events for picking up items, one fired before - Forge (cancellable) one after on actual pickup (FML).

 

What I don't understand is why ItemStack in FML event is not "real" (it can't get full ItemStack data).

 

Forge:

@SubscribeEvent
public void entityPickup(EntityItemPickupEvent event)
{
	ItemStack stack = event.item.getEntityItem();
	if(stack != null)
	{
		System.out.println("EntityItemPickupEvent: " + stack + "   Size: " + stack.stackSize);
	}
}

 

FML:

@SubscribeEvent
public void itemPickup(ItemPickupEvent event)
{
	ItemStack stack = event.pickedUp.getEntityItem();
	if(stack != null)
	{
		System.out.println("ItemPickupEvent: " + stack + "   Size: " + stack.stackSize);
	}
}

(NBT is too lost in FML)

 

[16:17:44] [server thread/INFO] [sTDOUT]: [x.ForgeEvents:entityPickup:38]: EntityItemPickupEvent: 1xitem.stick@0   Size: 1
[16:17:44] [server thread/INFO] [sTDOUT]: [x.FMLEvents:itemPickup:33]: ItemPickupEvent: 0xitem.stick@0   Size: 0

[16:17:57] [server thread/INFO] [sTDOUT]: [x.ForgeEvents:entityPickup:38]: EntityItemPickupEvent: 59xitem.stick@0   Size: 59
[16:17:57] [server thread/INFO] [sTDOUT]: [x.FMLEvents:itemPickup:33]: ItemPickupEvent: 0xitem.stick@0   Size: 0

[16:18:07] [server thread/INFO] [sTDOUT]: [x.ForgeEvents:entityPickup:38]: EntityItemPickupEvent: 12xitem.stick@0   Size: 12
[16:18:07] [server thread/INFO] [sTDOUT]: [x.FMLEvents:itemPickup:33]: ItemPickupEvent: 0xitem.stick@0   Size: 0

 

I was trying to figure it out, but looking at how are they called leaves me with no explanation.

 

Also, why is this passed: (EntityItem#onCollideWithPlayer)

int hook = net.minecraftforge.event.ForgeEventFactory.onItemPickup(this, entityIn, itemstack);

...if the ForgeEventFactory#onItemPickup is not actually using that ItemStack? Asking because this is literally only difference between those two events.

net.minecraftforge.fml.common.FMLCommonHandler.instance().firePlayerItemPickupEvent(entityIn, this);

 

Asking of pure curiosity.

Yup, that explains it.

 

 

This line was long enough for me to miss adding stack to inv.

if (this.delayBeforeCanPickup <= 0 && (this.owner == null || lifespan - this.age <= 200 || this.owner.equals(entityIn.getName())) && (hook == 1 || i <= 0 || entityIn.inventory.addItemStackToInventory(itemstack)))

 

*applauds*