Actor pointer

ZScript allows to assign custom pointers to any spawned actor via casting and member classes, as well as exposes a wide range of predefined pointers to the modders. Pointers can be used as prefixes to execute functions and modify properties and flags. Some of the common pointers used in ZScript are:

• owner — used by inventory items and anything that inherits from them. This pointer refers to the actor that is holding the item.
• invoker — used by inventory items and refers to the item itself. While DECORATE functions such as A_JumpIfInventory are designed to check the player's properties/inventory by default, zscript functions used in inventory item definitions aren't attached to any pointer by default, so either invoker or owner should be used, depending on which the modder is referring to.
• player — used to get access player-specific features/pointers (listed in PlayerInfo), such as readyweapon which is a pointer to the currently selected weapon.

Pointers in ZScript can (and often need to) be stringed together. For example, to access the currently selected weapon from an inventory item, owner.player.readyweapon is needed.

When killed, this version of Imp will spawn another Imp which has 500 health, is twice as slow and appears twice as big:

Class DoomImpEnhanced : DoomImp replaces DoomImp
{
	States 
	{
	Death:
		#### # 0 
		{
			A_NoBlocking();
			let foo = Spawn("DoomImp",pos);
			if (foo) //it's important to null-check the spawned actor, just in case
			{
				foo.health = 500;
				foo.scale *= 2;
				foo.speed *= 0.5;
			}
		}
		#### # 1 A_FadeOut(0.01);
		wait;
	}
}

Several DECORATE and ACS functions support custom retrieval and assignment of pointer values. The data location or method of retrieval is specified using named pointer selectors.

All pointers are automatically supported by all implementing functions, unless the function documentation specifies otherwise.

Selectors

The following set of named values all indicate ways of retrieving an actor pointer from a source actor or a static context. The values are divided into categories, and the first selector applicable to the source actor is used. Selectors from different categories may be combined using BITWISE OR. (SELECTOR_A | SELECTOR_B)

Selector category 1: Player-only selectors

Players will use a pointer in this category if one is specified. Otherwise, a pointer from another applicable category will be used.

• AAPTR_PLAYER_GETTARGET: Get the actor in the player's line of sight. Most target-specific functions use this approach to determining the player's target. This only works if the actor has the SHOOTABLE and SOLID flags, and also lacks the NOBLOCKMAP flag, much like A_JumpIfTargetInLOS.
• AAPTR_PLAYER_GETCONVERSATION: Get the actor currently talking to the player. Best used from a Strife dialogue that gives a custom inventory item, or starts a script with ACS_ExecuteWithResult (as it processes immediately).

Selector category 2: Generic context selectors

Any actor (non-null) will use a pointer in this category if one is specified. Otherwise, a pointer from another applicable category will be used.

• AAPTR_MASTER: Access the actor's MASTER pointer. (Players normally do not have masters.)
• AAPTR_TARGET: Access the actor's TARGET pointer. (Players normally do not use this.)
• AAPTR_TRACER: Access the actor's TRACER pointer.
• AAPTR_FRIENDPLAYER: Access the actor's FRIENDPLAYER pointer.
• AAPTR_GET_LINETARGET: Get the actor in the line of sight. This is similar to AAPTR_PLAYER_GETTARGET above, except it is used for non-player actors.

Note that AAPTR_GET_LINETARGET is identified as AAPTR_LINETARGET in DECORATE.

Note on retrieving TARGET information: Most functions use a special approach to find the target of a player; checking what they are aiming/looking at. This corresponds to AAPTR_PLAYER_GETTARGET. To make a single function that conforms to this standard, use the selector combination AAPTR_TARGET|AAPTR_PLAYER_GETTARGET. The most applicable method will be used (AAPTR_PLAYER_GETTARGET for any player).

Selector category 3: Static context selectors

Any specified pointer in this category will be used.

• AAPTR_NULL: Return NULL.
• AAPTR_PLAYER# (where # is a number in the range 1 - 8):
  • A static pointer to the player of that number. NULL if the player does not exist.

Scripting tip: AAPTR_PLAYER1 points to player 1. AAPTR_PLAYER1<<X (shift bits X up) points to player (1 + X). This fact can be applied in ACS loops if you need to reference each active player in sequence.

Selector category 4: Default

This selection is always implied, and applies if no other selection was made. To fully disable this, specify one static selection (as they always apply when specified), such as AAPTR_NULL.

• AAPTR_DEFAULT: Returns the source actor itself (null if there is no source actor).

Assignment

The following selectors expose fields for manipulation: AAPTR_MASTER, AAPTR_TARGET and AAPTR_TRACER.

Assignment operations will often, but not necessarily, prevent some assignments from occuring. Examples of such events are:

• An actor pointing to itself
• An infinite chain of references (two actors referencing eachother as master or target)

Prevention may involve cancelling the operation, or setting the pointer to NULL. Details on this should be included in the documentation of the individual function.

Revision information - assigning to pointers: Significant changes to this functionality are unlikely. Functions that support a set of selectors different from AAPTR_MASTER, AAPTR_TARGET, AAPTR_TRACER should list the supported features, along with any needed revision information.