let's play the optimization game featuring lighting (#12310)

* debug proc

* kinda quirky

* let's play the lighting game

* let's play the macro game

* let's play the refactor game

* let's play the optimization game

* let's play the optimization game x2

* yeehaw

* e

* let's play the memory game

* fix

* lighting fix

* sanitization and checks

* mh

* hotkeys fix

* ok

code/modules/lighting/lighting_source.dm

@@ -237,18 +237,25 @@
 		return //nothing's changed
 
 	var/list/datum/lighting_corner/corners = list()
+	var/datum/lighting_corner/C
 	var/list/turf/turfs                    = list()
 	var/thing
-	var/datum/lighting_corner/C
 	var/turf/T
 	if (source_turf)
 		var/oldlum = source_turf.luminosity
 		source_turf.luminosity = CEILING(light_range, 1)
 		for(T in view(CEILING(light_range, 1), source_turf))
-			for (thing in T.get_corners(source_turf))
-				C = thing
-				corners[C] = 0
 			turfs += T
+			if(!IS_DYNAMIC_LIGHTING(T) && !T.light_sources)
+				continue
+			if(!T.lighting_corners_initialised)
+				T.generate_missing_corners()
+			if(T.has_opaque_atom)
+				continue
+			corners[T.lc_topright] = 0
+			corners[T.lc_bottomright] = 0
+			corners[T.lc_bottomleft] = 0
+			corners[T.lc_topleft] = 0
 		source_turf.luminosity = oldlum
 
 	LAZYINITLIST(affecting_turfs)