Cache light fixture overlays (#3948)

changes:

Light fixture overlays are now cached.
BlendRGB is now cached (used by light fixture overlays)
Nightmode now only tints the bulb instead of both the bulb and the fixture itself.

code/__defines/subsystem-defines.dm

@@ -86,3 +86,7 @@
 
 // Connection prefixes for player-editable fields
 #define WP_ELECTRONICS "elec_"
+
+
+// -- SSicon_cache --
+#define LIGHT_FIXTURE_CACHE(icon,state,color) SSicon_cache.light_fixture_cache["[icon]_[state]_[color]"] || (SSicon_cache.light_fixture_cache["[icon]_[state]_[color]"] = SSicon_cache.generate_color_variant(icon,state,color))

code/_helpers/icons.dm

@@ -553,6 +553,11 @@ proc/BlendHSV(hsv1, hsv2, amount)
 	amount<0 or amount>1 are allowed
  */
 proc/BlendRGB(rgb1, rgb2, amount)
+	var/cachekey = "[rgb1]_[rgb2]_[amount]"
+	. = SSicon_cache.rgb_blend_cache[cachekey]
+	if (.)
+		return
+
 	var/list/RGB1 = ReadRGB(rgb1)
 	var/list/RGB2 = ReadRGB(rgb2)
 
@@ -566,7 +571,8 @@ proc/BlendRGB(rgb1, rgb2, amount)
 	var/b = round(RGB1[3] + (RGB2[3] - RGB1[3]) * amount, 1)
 	var/alpha = usealpha ? round(RGB1[4] + (RGB2[4] - RGB1[4]) * amount, 1) : null
 
-	return isnull(alpha) ? rgb(r, g, b) : rgb(r, g, b, alpha)
+	. = isnull(alpha) ? rgb(r, g, b) : rgb(r, g, b, alpha)
+	SSicon_cache.rgb_blend_cache[cachekey] = .
 
 proc/BlendRGBasHSV(rgb1, rgb2, amount)
 	return HSVtoRGB(RGBtoHSV(rgb1), RGBtoHSV(rgb2), amount)

code/controllers/subsystems/icon_cache.dm

@@ -63,6 +63,10 @@
 
 	var/list/ao_cache = list()
 
+	var/list/light_fixture_cache = list()
+
+	var/list/rgb_blend_cache = list()	// not an icon per-se, but this proc could be expensive so we might as well cache it.
+
 /datum/controller/subsystem/icon_cache/New()
 	NEW_SS_GLOBAL(SSicon_cache)
 
@@ -85,3 +89,8 @@
 	uniform_states = list()
 	for (var/i in icon_states('icons/mob/uniform.dmi'))
 		uniform_states[i] = TRUE
+
+/datum/controller/subsystem/icon_cache/proc/generate_color_variant(icon/icon, icon_state, color)
+	var/image/I = new(icon, icon_state)
+	I.color = color
+	return I

code/modules/power/lighting.dm

@@ -218,30 +218,21 @@
 	icon_state = "[base_state]_empty"
 	switch(status)		// set icon_states
 		if(LIGHT_OK)
-			var/image/I = image(icon, "[base_state][on]")
-			I.color = brightness_color
-			add_overlay(I)
+			var/target_color = brightness_color
 			if (supports_nightmode && nightmode && on)
-				color = "#d2d2d2"
-			else
-				color = null
+				target_color = BlendRGB("#d2d2d2", target_color, 0.25)
+
+			add_overlay(LIGHT_FIXTURE_CACHE(icon, "[base_state][on]", target_color))
 
 		if(LIGHT_EMPTY)
 			on = 0
 		if(LIGHT_BURNED)
-			var/image/I = image(icon, "[base_state]_burned")
-			I.color = brightness_color
-			add_overlay(I)
+			add_overlay(LIGHT_FIXTURE_CACHE(icon, "[base_state]_burned", brightness_color))
 			on = 0
 		if(LIGHT_BROKEN)
-			var/image/I = image(icon, "[base_state]_broken")
-			I.color = brightness_color
-			add_overlay(I)
+			add_overlay(LIGHT_FIXTURE_CACHE(icon, "[base_state]_broken", brightness_color))
 			on = 0
 
-	if (!on)
-		color = null
-
 // update the icon_state and luminosity of the light depending on its state
 /obj/machinery/light/proc/update(var/trigger = 1)
 	update_icon()