Tweaks turf add overlay logic (#23071)

## About PR

Makes it so when a turf calls the overlay subsystem (if overlay layer
was left as default) it'll add overlays slightly above the turf layer.
With this we'll no longer have the silly issue where turf smoothing
overlays appear under the adjacent turfs depending on turf load order

In short, here's what it fixes

Before:

<img width="396" height="601" alt="Screenshot_10"
src="https://github.com/user-attachments/assets/91708402-c6c6-433f-af9f-5293ce926731"
/>

After:

<img width="391" height="598" alt="Screenshot_9"
src="https://github.com/user-attachments/assets/556d48dd-d463-4f76-b075-f0d77340e837"
/>

---

to-do:
- [x] Figure out whether to change `is_plating()` check method or add
the missing `initial_flooring` for every exoplanet turf type since this
plays a role in deciding decal layer, suffer as both paths are equally
agonizing

code/controllers/subsystems/overlays.dm

@@ -98,25 +98,40 @@ SUBSYSTEM_DEF(overlays)
 	var/list/result = list()
 	var/icon/icon = subject.icon
 	var/atom/entry
+	var/overlay_appearance
 	for (var/i = 1 to length(sources))
 		entry = sources[i]
 		if (!entry)
 			continue
 		else if (istext(entry))
-			result += GetStateAppearance(icon, entry)
+			overlay_appearance = GetStateAppearance(icon, entry)
 		else if (isicon(entry))
-			result += GetIconAppearance(entry)
+			overlay_appearance = GetIconAppearance(entry)
 		else if (istype(entry, /mutable_appearance))
-			result += entry
+			overlay_appearance = entry
 		else
 			if (isloc(entry))
 				if (entry.atom_flags & ATOM_AWAITING_OVERLAY_UPDATE)
 					entry.UpdateOverlays()
 			if (!ispath(entry))
-				result += entry.appearance
+				overlay_appearance = entry.appearance
 			else
 				var/image/image = entry
-				result += image.appearance
+				overlay_appearance = image.appearance
+
+		// If the caller is a turf, we put the overlay's layer slightly above it.
+		// So this way overlays extending over to neighbouring turfs don't appear under them depending on load order.
+		// We only apply this if source hasn't explictly provided a layer (think the FLOAT_LAYER as a default layer for overlays).
+		// For more info see overlays doc. in byond ref.
+		var/turf/T = subject
+		if(istype(T))
+			var/mutable_appearance/turf_overlay = new()
+			turf_overlay.appearance = overlay_appearance
+			if(turf_overlay.layer == FLOAT_LAYER)
+				turf_overlay.layer = T.is_plating() ? ABOVE_PLATING_LAYER : TURF_DETAIL_LAYER
+				overlay_appearance = turf_overlay.appearance
+
+		result += overlay_appearance
 	return result
 
 
@@ -306,4 +321,3 @@ SUBSYSTEM_DEF(overlays)
 		overlays |= other.atom_protected_overlay_cache
 	if (cache_target & ATOM_ICON_CACHE_NORMAL)
 		overlays |= other.atom_overlay_cache
-

code/game/turfs/flooring/flooring_.dm

@@ -15,18 +15,21 @@
 	var/icon_base
 	var/color
 
-	var/has_base_range // basically if you want your turf to have variants, e.g. snow and grass. this number sets upper bound, starts at 0.
+	/// Basically if you want your turf to have variants, e.g. snow and grass. this number sets upper bound, starts at 0.
+	var/has_base_range
 	var/has_damage_range = 7
-	var/has_damage_state // if you've got unique damage sprites, hard-baked, not overlays. if you use overlays use the range system.
+	/// If you've got unique damage sprites, hard-baked, not overlays. if you use overlays use the range system.
+	var/has_damage_state
 	var/has_burn_range = 4
-	var/has_burn_state // same as damage state for burn.
+	/// Ssame as damage state for burn.
+	var/has_burn_state
 	var/damage_uses_color = FALSE // see wood.
 	var/damage_temperature
 	var/apply_thermal_conductivity
 	var/apply_heat_capacity
 
-	///The type of floor that can make this, if it's not set (`null`), this flooring is unbuildable
-	var/obj/item/stack/build_type      // Unbuildable if not set. Must be /obj/item/stack.
+	/// The type of floor that can make this, if it's not set (`null`), this flooring is unbuildable.
+	var/obj/item/stack/build_type
 	var/build_cost = 1  // Stack units.
 	var/build_time = 0  // BYOND ticks.
 
@@ -38,14 +41,16 @@
 	//How we smooth with other flooring
 	var/decal_layer = DECAL_LAYER
 	var/floor_smooth = SMOOTH_ALL
-	var/list/flooring_whitelist = list() //Smooth with nothing except the contents of this list
-	var/list/flooring_blacklist = list() //Smooth with everything except the contents of this list
+	/// Smooth with nothing except the contents of this list.
+	var/list/flooring_whitelist = list()
+	/// Smooth with everything except the contents of this list.
+	var/list/flooring_blacklist = list()
 
-	//How we smooth with walls
+	/// How we smooth with walls.
 	var/wall_smooth = SMOOTH_ALL
 	//There are no lists for walls at this time
 
-	//How we smooth with space and openspace tiles
+	/// How we smooth with space and openspace tiles.
 	var/space_smooth = SMOOTH_ALL
 	//There are no lists for spaces
 

code/modules/mining/mine_turfs.dm

@@ -768,8 +768,10 @@ GLOBAL_LIST_INIT(mineral_can_smooth_with, list(
 
 GLOBAL_LIST_INIT(asteroid_floor_smooth, list(
 	/turf/simulated/floor/exoplanet/asteroid/ash,
+	/turf/simulated/wall,
+	/turf/unsimulated/wall,
 	/turf/simulated/mineral,
-	/turf/simulated/wall
+	/turf/unsimulated/mineral
 ))
 
 // Copypaste parent for performance.

code/modules/overmap/exoplanets/decor/_turfs.dm

@@ -91,6 +91,9 @@
 			if(away_site.exoplanet_lightlevel && is_outside())
 				set_light(MINIMUM_USEFUL_LIGHT_RANGE, away_site.exoplanet_lightlevel, away_site.exoplanet_lightcolor)
 
+/turf/simulated/floor/exoplanet/is_plating()
+	return FALSE
+
 /turf/simulated/floor/exoplanet/update_icon(var/update_neighbors)
 	if(initial_flooring)
 		. = ..()

code/modules/overmap/exoplanets/decor/turfs/plating.dm

@@ -5,6 +5,9 @@
 	footstep_sound = SFX_FOOTSTEP_PLATING
 	has_resources = FALSE
 
+/turf/simulated/floor/exoplanet/plating/is_plating()
+	return TRUE
+
 /turf/simulated/floor/exoplanet/plating/asteroid
 	icon_state = "asteroidplating"
 

code/modules/overmap/exoplanets/decor/turfs/snow.dm

@@ -11,7 +11,9 @@
 	canSmoothWith = list(
 		/turf/simulated/floor/exoplanet/snow,
 		/turf/simulated/wall,
-		/turf/unsimulated/wall
+		/turf/unsimulated/wall,
+		/turf/simulated/mineral,
+		/turf/unsimulated/mineral
 	) //Smooths with walls but not the inverse. This way to avoid layering over walls.
 
 /turf/simulated/floor/exoplanet/snow/Initialize()

code/modules/overmap/exoplanets/decor/turfs/water.dm

@@ -144,7 +144,11 @@
 /turf/simulated/floor/exoplanet/water/shallow/konyang/beach
 	icon = 'icons/turf/flooring/exoplanet/konyang/konyang_beach.dmi'
 	smoothing_flags = SMOOTH_MORE | SMOOTH_BORDER | SMOOTH_NO_CLEAR_ICON
-	canSmoothWith = list(/turf/simulated/floor/exoplanet/water/shallow/konyang, /turf/simulated/floor/exoplanet/water/konyang, /turf/simulated/floor/exoplanet/water/shallow/konyang/beach)
+	canSmoothWith = list(
+		/turf/simulated/floor/exoplanet/water/shallow/konyang,
+		/turf/simulated/floor/exoplanet/water/konyang,
+		/turf/simulated/floor/exoplanet/water/shallow/konyang/beach
+	)
 
 /turf/simulated/floor/exoplanet/water/shallow/sewage//What horror.
 	name = "putrid sewage"

html/changelogs/kano-overlay-insanity.yml

@@ -0,0 +1,4 @@
+author: kano
+delete-after: True
+changes:
+  - bugfix: "Fixed the smooth icon overlays appearing under the adjacent turfs."