ZDoom

This seems to have gotten added. https://github.com/coelckers/gzdoom/commit/63277346599b6b32088864d51bce4f8ee2fac032

New PR to fix merge conflict.

Understood. That'll be something for me to think about as a separate PR, but not until after this one has been merged.

I also opened a completely new PR when I reworked it to ensure this is clean.

No, that won't help much. To pull this off you'd have to wrap the virtual Use call into another function, similar to CallTryPickup and do the check there.

Of course you have to do this for all Use calls everywhere and that's going to be a bit tricky.

//===========================================================================
//
// ACustomInventory :: Use
//
//===========================================================================

override bool Use (bool pickup)
{
	if (!pickup && Owner && !Owner.CanUseItem(self))
		return false;
	return CallStateChain (Owner, FindState('Use'));
}

I'm going to introduce [b]CanUseItem[/b] as well. I just found myself wishing that I could block certain inventory items from being usable while under a certain condition. I.e. activating powerups while morphed (at least some of them).

The only problem is, this area is a bit more sticky and I'm not entirely sure where I should place the check... Would it be best to just put this in CustomInventory's Use override?

[code]//===========================================================================
//
// ACustomInventory :: Use
//
//===========================================================================

override bool Use (bool pickup)
{
if (!pickup && Owner && !Owner.CanUseItem(self))
return false;
return CallStateChain (Owner, FindState('Use'));
}[/code]

Simplified and renamed it accordingly so it's delegated to Touch only.

Why did you add this in two places and added a special handling to CallTryPickup? Such things need commenting because it is not apparent why it is necessary.

EDIT: Reworked and renamed.
[url=https://github.com/coelckers/gzdoom/pull/775]Pull Request[/url]

Items could pick and choose whom they can enter, but never the other way around.
This PR adds functionality to fix this issue, allowing those with the +PICKUP flag the ability to filter what items they can pick up.
Simply override the CanTouchItem(Inventory item) function. Return true to signify the actor can attempt to pick up the item, false if they cannot.