gzdoom/wadsrc/static/zscript/inventory/ammo.txt

class Ammo : Inventory native
{
	native int BackpackAmount;
	native int BackpackMaxAmount;
	
	Default
	{
		+INVENTORY.KEEPDEPLETED
		Inventory.PickupSound "misc/ammo_pkup";
	}

	native Class<Actor> GetParentAmmo ();

	//===========================================================================
	//
	// AAmmo :: HandlePickup
	//
	//===========================================================================

	override bool HandlePickup (Inventory item)
	{
		let ammoitem = Ammo(item);
		if (ammoitem != null && ammoitem.GetParentAmmo() == GetClass())
		{
			if (Amount < MaxAmount || sv_unlimited_pickup)
			{
				int receiving = item.Amount;

				if (!item.bIgnoreSkill)
				{ // extra ammo in baby mode and nightmare mode
					receiving = int(receiving * G_SkillPropertyFloat(SKILLP_AmmoFactor));
				}
				int oldamount = Amount;

				if (Amount > 0 && Amount + receiving < 0)
				{
					Amount = 0x7fffffff;
				}
				else
				{
					Amount += receiving;
				}
				if (Amount > MaxAmount && !sv_unlimited_pickup)
				{
					Amount = MaxAmount;
				}
				item.bPickupGood = true;

				// If the player previously had this ammo but ran out, possibly switch
				// to a weapon that uses it, but only if the player doesn't already
				// have a weapon pending.

				if (oldamount == 0 && Owner != null && Owner.player != null)
				{
					PlayerPawn(Owner).CheckWeaponSwitch(GetClass());
				}
			}
			return true;
		}
		return false;
	}

	//===========================================================================
	//
	// AAmmo :: CreateCopy
	//
	//===========================================================================

	override Inventory CreateCopy (Actor other)
	{
		Inventory copy;
		int amount = Amount;

		// extra ammo in baby mode and nightmare mode
		if (!bIgnoreSkill)
		{
			amount = int(amount * G_SkillPropertyFloat(SKILLP_AmmoFactor));
		}

		let type = GetParentAmmo();
		if (GetClass() == type)
		{
			if (!GoAway ())
			{
				Destroy ();
			}

			copy = Inventory(Spawn (type));
			copy.Amount = amount;
			copy.BecomeItem ();
		}
		else
		{
			copy = Super.CreateCopy (other);
			copy.Amount = amount;
		}
		if (copy.Amount > copy.MaxAmount)
		{ // Don't pick up more ammo than you're supposed to be able to carry.
			copy.Amount = copy.MaxAmount;
		}
		return copy;
	}

	//===========================================================================
	//
	// AAmmo :: CreateTossable
	//
	//===========================================================================

	override Inventory CreateTossable()
	{
		Inventory copy = Super.CreateTossable();
		if (copy != null)
		{ // Do not increase ammo by dropping it and picking it back up at
		  // certain skill levels.
			copy.bIgnoreSkill = true;
		}
		return copy;
	}

	
}

class BackpackItem : Inventory native
{
	native bool bDepleted;
}