Why are monsters capable of activating without setting their Activation property explicitly?

[Jekyll Grim Payne]

So, recently I've been trying to carefully document the confusing concept that is activation/deactivation, which resulted in me rewriting this article on the wiki: https://zdoom.org/wiki/Activation

It's a deceptively complex complex, because it touches upon both actor special execution, and the Activate()/Deactivate() virtuals, which are largely unrelated, except when there's an overlap with USESPECIAL/BUMPSPECIAL.

In any case, I've figured most of it out. Except one thing: for some reason, adding, for example, USESPECIAL and an Activate() override to an actor works as-is on monsters:

Code: Select all

class DoomImp_ : DoomImp
{
	Default
	{
		+USESPECIAL
	}

	override void Activate(Actor activator)
	{
		Console.Printf("Calling Activate()");
	}

	override void Deactivate(Actor activator)
	{
		Console.Printf("Calling Deactivate()");
	}
}

...BUT on non-monster actors it requires explicitly setting Activation THINGSPEC_Activate in their default block. On monsters the above code just works, on non-monsters it doesn't unless I set up the Activation property.

For the life of me, I can't figure out why; I've looked through the related ZScript and C++ functions and I don't see where this is set up or what even the conditions are (the ISMONSTER flag? something else?)

I need help figuring it out to complete the documentation and get rid of that Need more info bit I have there for now.

[phantombeta]

I can't reproduce this on 4.11.3, nothing happens when trying to +use a DoomImp_.

[Jekyll Grim Payne]

Okay, I'm confused because now I can't reproduce this either. Apparenly I confused myself during the multiple rounds of testing with ZScript and ACS...

While researching this further, it seems I was misunderstanding some of the THINGSPEC flags. From what I see now, the only flags that deal with Activate()/Deactivate() virtuals are THINGSPEC_Activate, THINGSPEC_Deactivate and THINGSPEC_Switch. All other THINGSPEC* flags only deal with the execution of the actor's special and don't interact with the virtuals at all (except maybe modifying activator pointers, I'm not sure).