Hi I'm trying to figure out what par3 in   

public ItemStack slotClick(int par1, int par2, int par3, EntityPlayer player) in Container class does.

I know it returns 1 when shiftclicking a slot and 3 when middlemouseclicking, but it sometimes randomly returns 5?

And par2 already returns 2 when middlemouseclicking, so it's actually giving this information twice, wich is quiet useless? So, what i wanna know is what par3 does, and why its not all done with par2?

Thanks in advance

Par2 and Par3 are a mishmash of various states of slot stransfer types (origins and destinations and such). Par3's value depends on par2 and sometimes even par1 for valid arguments.

Look at and study GuiContainer class at all the calls to handleMouseClick(Slot slot, int slotNum, int argument, int function) to get an idea.