code: private ItemStack handleNormalClick(MalisisSlot slot, boolean fullStack)
  	{
  		if (!getPickedItemStack().isEmpty() && !slot.isItemValid(pickedItemStack))
  			return getPickedItemStack();
  
  		// already picked up an itemStack, insert/swap itemStack
  		if (!getPickedItemStack().isEmpty())
  		{
  			if (slot.isState(PLAYER_INSERT | PLAYER_EXTRACT))
  				setPickedItemStack(slot.insert(pickedItemStack, fullStack ? ItemUtils.FULL_STACK : 1, true));
  		}
  		// pick itemStack in slot
  		else if (slot.isState(PLAYER_EXTRACT))
  			setPickedItemStack(slot.extract(fullStack ? ItemUtils.FULL_STACK : ItemUtils.HALF_STACK));
  
  		return getPickedItemStack();
  	}
docs: Handles the normal left or right click.
  
  @param slot the slot
  @param fullStack the full stack
  @return the item stack