[MIRROR] Actually supports alpha passed into emissive stuff [MDB IGNO…

…RE] (#24481)

* Actually supports alpha passed into emissive stuff (#79117)

## About The Pull Request

Ok so like, the emissive procs have an alpha argument right? The thing
is, the thing is it doesn't fucking do anything.

Alpha is a component of the color var (at least when it's a matrix), so
when we set alpha and then set color to a matrix, the alpha gets
overriden. Inverse is also true.

I want to support alpha args, since I like the idea of dimmable
emissives. Soooooo
Let's take the alpha arg, divide it by 255, and replace everything that
cares about alpha (as an intensity thing) with it.

This lets us do transparent emissives and transparent emissive blockers.

I added some guard checks to hopefully avoid the list init most of the
time (it is in theory comprable since color sets should copy but I don't
trust byond to optimize for that)
Also modified the macros to suppport what I'm doing nicely

## Why It's Good For The Game

We should support this, and now we do

* Actually supports alpha passed into emissive stuff

---------

Co-authored-by: LemonInTheDark <[email protected]>

code/__DEFINES/lighting.dm

@@ -78,14 +78,18 @@
 /// Don't block any emissives. Useful for things like, pieces of paper?
 #define EMISSIVE_BLOCK_NONE 2
 
+#define _EMISSIVE_COLOR(val) list(0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,1, val,val,val,0)
 /// The color matrix applied to all emissive overlays. Should be solely dependent on alpha and not have RGB overlap with [EM_BLOCK_COLOR].
-#define EMISSIVE_COLOR list(0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,1, 1,1,1,0)
+#define EMISSIVE_COLOR _EMISSIVE_COLOR(1)
 /// A globaly cached version of [EMISSIVE_COLOR] for quick access.
 GLOBAL_LIST_INIT(emissive_color, EMISSIVE_COLOR)
+
+#define _EM_BLOCK_COLOR(val) list(0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,val, 0,0,0,0)
 /// The color matrix applied to all emissive blockers. Should be solely dependent on alpha and not have RGB overlap with [EMISSIVE_COLOR].
-#define EM_BLOCK_COLOR list(0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,1, 0,0,0,0)
+#define EM_BLOCK_COLOR _EM_BLOCK_COLOR(1)
 /// A globaly cached version of [EM_BLOCK_COLOR] for quick access.
 GLOBAL_LIST_INIT(em_block_color, EM_BLOCK_COLOR)
+
 /// A set of appearance flags applied to all emissive and emissive blocker overlays.
 /// KEEP_APART to prevent parent hooking, KEEP_TOGETHER for children, and we reset the color and alpha of our parent so nothing gets overriden
 #define EMISSIVE_APPEARANCE_FLAGS (KEEP_APART|KEEP_TOGETHER|RESET_COLOR|RESET_ALPHA)

code/__HELPERS/lighting.dm

@@ -1,9 +1,11 @@
 /// Produces a mutable appearance glued to the [EMISSIVE_PLANE] dyed to be the [EMISSIVE_COLOR].
 /proc/emissive_appearance(icon, icon_state = "", atom/offset_spokesman, layer = FLOAT_LAYER, alpha = 255, appearance_flags = NONE, offset_const)
-	// Note: alpha doesn't "do" anything, since it's overriden by the color set shortly after
-	// Consider removing it someday? (I wonder if we made emissives blend right we could make alpha actually matter. dreams man, dreams)
 	var/mutable_appearance/appearance = mutable_appearance(icon, icon_state, layer, offset_spokesman, EMISSIVE_PLANE, 255, appearance_flags | EMISSIVE_APPEARANCE_FLAGS, offset_const)
-	appearance.color = GLOB.emissive_color
+	if(alpha == 255)
+		appearance.color = GLOB.emissive_color
+	else
+		var/alpha_ratio = alpha/255
+		appearance.color = _EMISSIVE_COLOR(alpha_ratio)
 
 	//Test to make sure emissives with broken or missing icon states are created
 	if(PERFORM_ALL_TESTS(focus_only/invalid_emissives))
@@ -15,15 +17,17 @@
 // This is a semi hot proc, so we micro it. saves maybe 150ms
 // sorry :)
 /proc/fast_emissive_blocker(atom/make_blocker)
-	// Note: alpha doesn't "do" anything, since it's overriden by the color set shortly after
-	// Consider removing it someday?
 	var/mutable_appearance/blocker = new()
 	blocker.icon = make_blocker.icon
 	blocker.icon_state = make_blocker.icon_state
 	// blocker.layer = FLOAT_LAYER // Implied, FLOAT_LAYER is default for appearances
 	blocker.appearance_flags |= make_blocker.appearance_flags | EMISSIVE_APPEARANCE_FLAGS
 	blocker.dir = make_blocker.dir
-	blocker.color = GLOB.em_block_color
+	if(make_blocker.alpha == 255)
+		blocker.color = GLOB.em_block_color
+	else
+		var/alpha_ratio = make_blocker.alpha/255
+		blocker.color = _EM_BLOCK_COLOR(alpha_ratio)
 
 	// Note, we are ok with null turfs, that's not an error condition we'll just default to 0, the error would be
 	// Not passing ANYTHING in, key difference
@@ -32,10 +36,12 @@
 
 /// Produces a mutable appearance glued to the [EMISSIVE_PLANE] dyed to be the [EM_BLOCK_COLOR].
 /proc/emissive_blocker(icon, icon_state = "", atom/offset_spokesman, layer = FLOAT_LAYER, alpha = 255, appearance_flags = NONE, offset_const)
-	// Note: alpha doesn't "do" anything, since it's overriden by the color set shortly after
-	// Consider removing it someday?
 	var/mutable_appearance/appearance = mutable_appearance(icon, icon_state, layer, offset_spokesman, EMISSIVE_PLANE, alpha, appearance_flags | EMISSIVE_APPEARANCE_FLAGS, offset_const)
-	appearance.color = GLOB.em_block_color
+	if(alpha == 255)
+		appearance.color = GLOB.em_block_color
+	else
+		var/alpha_ratio = alpha/255
+		appearance.color = _EM_BLOCK_COLOR(alpha_ratio)
 	return appearance
 
 /// Takes a non area atom and a threshold