Add WorldLinePreActivated to override line activation, as a counterpart to WorldLineActivated.

src/events.cpp

@@ -413,6 +413,12 @@ void E_WorldThingDestroyed(AActor* actor)
 		handler->WorldThingDestroyed(actor);
 }
 
+void E_WorldLinePreActivated(line_t* line, AActor* actor, bool* shouldactivate)
+{
+	for (DStaticEventHandler* handler = E_FirstEventHandler; handler; handler = handler->next)
+		handler->WorldLinePreActivated(line, actor, shouldactivate);
+}
+
 void E_WorldLineActivated(line_t* line, AActor* actor)
 {
 	for (DStaticEventHandler* handler = E_FirstEventHandler; handler; handler = handler->next)
@@ -548,6 +554,7 @@ DEFINE_FIELD_X(WorldEvent, FWorldEvent, DamageType);
 DEFINE_FIELD_X(WorldEvent, FWorldEvent, DamageFlags);
 DEFINE_FIELD_X(WorldEvent, FWorldEvent, DamageAngle);
 DEFINE_FIELD_X(WorldEvent, FWorldEvent, ActivatedLine);
+DEFINE_FIELD_X(WorldEvent, FWorldEvent, ShouldActivate);
 
 DEFINE_FIELD_X(PlayerEvent, FPlayerEvent, PlayerNumber);
 DEFINE_FIELD_X(PlayerEvent, FPlayerEvent, IsReturn);
@@ -634,6 +641,7 @@ DEFINE_EMPTY_HANDLER(DStaticEventHandler, WorldThingDied)
 DEFINE_EMPTY_HANDLER(DStaticEventHandler, WorldThingRevived)
 DEFINE_EMPTY_HANDLER(DStaticEventHandler, WorldThingDamaged)
 DEFINE_EMPTY_HANDLER(DStaticEventHandler, WorldThingDestroyed)
+DEFINE_EMPTY_HANDLER(DStaticEventHandler, WorldLinePreActivated)
 DEFINE_EMPTY_HANDLER(DStaticEventHandler, WorldLineActivated)
 DEFINE_EMPTY_HANDLER(DStaticEventHandler, WorldLightning)
 DEFINE_EMPTY_HANDLER(DStaticEventHandler, WorldTick)
@@ -796,6 +804,23 @@ void DStaticEventHandler::WorldThingDestroyed(AActor* actor)
 	}
 }
 
+void DStaticEventHandler::WorldLinePreActivated(line_t* line, AActor* actor, bool* shouldactivate)
+{
+	IFVIRTUAL(DStaticEventHandler, WorldLinePreActivated)
+	{
+		// don't create excessive DObjects if not going to be processed anyway
+		if (func == DStaticEventHandler_WorldLinePreActivated_VMPtr)
+			return;
+		FWorldEvent e = E_SetupWorldEvent();
+		e.Thing = actor;
+		e.ActivatedLine = line;
+		e.ShouldActivate = *shouldactivate;
+		VMValue params[2] = { (DStaticEventHandler*)this, &e };
+		VMCall(func, params, 2, nullptr, 0);
+		*shouldactivate = e.ShouldActivate;
+	}
+}
+
 void DStaticEventHandler::WorldLineActivated(line_t* line, AActor* actor)
 {
 	IFVIRTUAL(DStaticEventHandler, WorldLineActivated)

src/events.h

@@ -40,6 +40,8 @@ void E_WorldThingRevived(AActor* actor);
 void E_WorldThingDamaged(AActor* actor, AActor* inflictor, AActor* source, int damage, FName mod, int flags, DAngle angle);
 // called before AActor::Destroy of each actor.
 void E_WorldThingDestroyed(AActor* actor);
+// called in P_ActivateLine before executing special, set shouldactivate to false to prevent activation.
+void E_WorldLinePreActivated(line_t* line, AActor* actor, bool* shouldactivate);
 // called in P_ActivateLine after successful special execution.
 void E_WorldLineActivated(line_t* line, AActor* actor);
 // same as ACS SCRIPT_Lightning
@@ -141,6 +143,7 @@ public:
 	void WorldThingRevived(AActor*);
 	void WorldThingDamaged(AActor*, AActor*, AActor*, int, FName, int, DAngle);
 	void WorldThingDestroyed(AActor*);
+	void WorldLinePreActivated(line_t*, AActor*, bool*);
 	void WorldLineActivated(line_t*, AActor*);
 	void WorldLightning();
 	void WorldTick();
@@ -198,8 +201,9 @@ struct FWorldEvent
 	FName DamageType;
 	int DamageFlags = 0;
 	DAngle DamageAngle;
-	// for lineactivated
+	// for line(pre)activated
 	line_t* ActivatedLine = nullptr;
+	bool ShouldActivate = true;
 };
 
 struct FPlayerEvent

src/p_spec.cpp

@@ -189,6 +189,11 @@ bool P_ActivateLine (line_t *line, AActor *mo, int side, int activationType, DVe
 		return false;
 	}
 
+	// [MK] Use WorldLinePreActivated to decide if activation should continue
+	bool shouldactivate = true;
+	E_WorldLinePreActivated(line, mo, &shouldactivate);
+	if ( !shouldactivate ) return false;
+
 	bool remote = (line->special != 7 && line->special != 8 && (line->special < 11 || line->special > 14));
 	if (line->locknumber > 0 && !P_CheckKeys (mo, line->locknumber, remote)) return false;
 

wadsrc/static/zscript/events.txt

@@ -25,8 +25,9 @@ struct WorldEvent native play version("2.4")
     native readonly Name DamageType;
     native readonly EDmgFlags DamageFlags;
     native readonly double DamageAngle;
-    // for lineactivated
+    // for line(pre)activated
     native readonly Line ActivatedLine;
+    native bool ShouldActivate;
 }
 
 struct PlayerEvent native play version("2.4")
@@ -302,6 +303,7 @@ class StaticEventHandler : Object native play version("2.4")
     virtual native void WorldThingRevived(WorldEvent e);
     virtual native void WorldThingDamaged(WorldEvent e);
     virtual native void WorldThingDestroyed(WorldEvent e);
+    virtual native void WorldLinePreActivated(WorldEvent e);
     virtual native void WorldLineActivated(WorldEvent e);
     virtual native void WorldLightning(WorldEvent e); // for the sake of completeness.
     virtual native void WorldTick();