Fixed lights stopping emitting light in some situations (#1048)

Co-authored-by: Kocma-san <[email protected]>

Author: francinum

code/__DEFINES/dcs/signals/signals_turf.dm

@@ -24,3 +24,6 @@
 #define COMSIG_TURF_PREPARE_STEP_SOUND "turf_prepare_step_sound"
 	//stops element/footstep/proc/prepare_step() from returning null if the turf itself has no sound
 	#define FOOTSTEP_OVERRIDEN (1<<0)
+
+///Called when turf no longer blocks light from passing through
+#define COMSIG_TURF_NO_LONGER_BLOCK_LIGHT "turf_no_longer_block_light"

code/modules/lighting/lighting_source.dm

@@ -90,6 +90,7 @@
 	//yes, we register the signal to the top atom too, this is intentional and ensures contained lighting updates properly
 	if(ismovable(new_atom_host))
 		RegisterSignal(new_atom_host, COMSIG_MOVABLE_MOVED, PROC_REF(update_host_lights))
+	RegisterSignal(new_atom_host, COMSIG_TURF_NO_LONGER_BLOCK_LIGHT, PROC_REF(force_update))
 	return TRUE
 
 ///remove this light source from old_atom_host's light_sources list, unsetting movement registrations
@@ -100,6 +101,7 @@
 	LAZYREMOVE(old_atom_host.light_sources, src)
 	if(ismovable(old_atom_host))
 		UnregisterSignal(old_atom_host, COMSIG_MOVABLE_MOVED)
+	UnregisterSignal(old_atom_host, COMSIG_TURF_NO_LONGER_BLOCK_LIGHT)
 	return TRUE
 
 // Yes this doesn't align correctly on anything other than 4 width tabs.

code/modules/lighting/lighting_turf.dm

@@ -80,12 +80,16 @@
 			reconsider_lights()
 		return
 	directional_opacity = NONE
-	for(var/atom/movable/opacity_source as anything in opacity_sources)
-		if(opacity_source.flags_1 & ON_BORDER_1)
-			directional_opacity |= opacity_source.dir
-		else //If fulltile and opaque, then the whole tile blocks view, no need to continue checking.
-			directional_opacity = ALL_CARDINALS
-			break
+	if(opacity_sources)
+		for(var/atom/movable/opacity_source as anything in opacity_sources)
+			if(opacity_source.flags_1 & ON_BORDER_1)
+				directional_opacity |= opacity_source.dir
+			else //If fulltile and opaque, then the whole tile blocks view, no need to continue checking.
+				directional_opacity = ALL_CARDINALS
+				break
+	else
+		for(var/atom/movable/content as anything in contents)
+			SEND_SIGNAL(content, COMSIG_TURF_NO_LONGER_BLOCK_LIGHT)
 	if(. != directional_opacity && (. == ALL_CARDINALS || directional_opacity == ALL_CARDINALS))
 		reconsider_lights() //The lighting system only cares whether the tile is fully concealed from all directions or not.