Rework of wall damage visuals (#21032)

# Summary

Wall damage visuals had two issue for a longer time.
The first issue is that applied visual damage was permanent and
non-revertable, additionally it was too overwhelming.
The second issue was that the wall damage inspect descriptions ignored
the added health of reinforcing materials, as a result, all wall types
received the same damage descriptions even though their actual health
was different.

## Changes

This PR fixes both issues by fixing the stacking of damage overlays,
refactoring the alpha calculation of said overlays, adding additional
inspect-descriptions and lastly by adding the additional strength of
walls to their inspect calculation.

## Additional notes

Thanks to @Batrachophreno for assisting and suggesting to refactor
visual damage layers calculation.

code/game/turfs/simulated/wall_icon.dm

@@ -103,6 +103,9 @@
 		damage_image = damage_overlays[overlay]
 		overlays_to_add += damage_image
 
+	// Remove the existing damage overlay entirely and replace it with the newly-calculated one.
+	CutOverlays(damage_overlays)
+
 	AddOverlays(overlays_to_add)
 	UNSETEMPTY(reinforcement_images)
 	QUEUE_SMOOTH(src)
@@ -110,10 +113,11 @@
 		get_underlays(cached_adjacency)
 
 /turf/simulated/wall/proc/generate_overlays()
-	var/alpha_inc = 256 / damage_overlays.len
+	for(var/damage_level = 1; damage_level <= damage_overlays.len; damage_level++) // Generate damage overlay for each placeholder (16 in array)
+		var/image/damage_overlay = image(icon = 'icons/turf/walls.dmi', icon_state = "overlay_damage")
+		damage_overlay.blend_mode = BLEND_MULTIPLY
 
-	for(var/i = 1; i <= damage_overlays.len; i++)
-		var/image/img = image(icon = 'icons/turf/walls.dmi', icon_state = "overlay_damage")
-		img.blend_mode = BLEND_MULTIPLY
-		img.alpha = (i * alpha_inc) - 1
-		damage_overlays[i] = img
+		// The actual difference in each damage overlay is represented with a different alpha value, higher alpha = higher visible damage
+		damage_overlay.alpha = damage_level * 18 + 32; // Linear scale with inital offset
+
+		damage_overlays[damage_level] = damage_overlay

code/game/turfs/simulated/walls.dm

@@ -54,13 +54,23 @@
 	if(!damage)
 		. += SPAN_NOTICE("It looks fully intact.")
 	else
-		var/dam = damage / material.integrity
-		if(dam <= 0.3)
-			. += SPAN_WARNING("It looks slightly damaged.")
-		else if(dam <= 0.6)
+		// Total damage is based of base material integrity and optionally, if reinforced, reinforcement material integrity on top
+		var/integrity = material.integrity
+		if(reinf_material)
+			integrity += reinf_material.integrity
+
+		var/relative_damage = damage / integrity
+
+		if(relative_damage <= 0.25)
+			. += SPAN_NOTICE("It looks slightly damaged.")
+		else if(relative_damage <= 0.5)
+			. += SPAN_WARNING("It looks damaged.")
+		else if(relative_damage <= 0.75)
 			. += SPAN_WARNING("It looks moderately damaged.")
-		else
+		else if(relative_damage <= 0.9)
 			. += SPAN_DANGER("It looks heavily damaged.")
+		else
+			. += SPAN_DANGER("It looks critically damaged and on the verge of structural collapse.")
 
 /turf/simulated/wall/mechanics_hints(mob/user, distance, is_adjacent)
 	. += ..()

html/changelogs/fabiank3-rework-wall-damage-visuals.yml

@@ -0,0 +1,9 @@
+author: FabianK3
+
+delete-after: True
+
+changes:
+  - bugfix: "Fixed permanently stuck wall damage overlays. Walls now properly display the correct damage visually according to their state and the damaged look vanishes when they get repaired."
+  - rscadd: "Added new informative descriptions when inspecting damaged walls to get a better feeling for their state."
+  - bugfix: "Fixed wall damage descriptions ignoring added strength of reinforced materials. Reinforced wall descriptions will now show damage later as their additional health is considered properly."
+  - balance: "Changed levels of visual damage to walls to scale more linear. Thanks to Batrachophrenoboocosmomachia."