fix(port): make shock absorbers actually absorb shock damage (#4321)

vehicles: make shock absorbers actually absorb shock damage

Add the SHOCK_ABSORBER flag to shock absorbers, and change
vehicle::damage_all() so that parts on the same tile as a
shock absorber take substantially less damage from transmitted
shock damage in collisions.

Co-authored-by: Mark Langsdorf <mark.langsdorf@gmail.com>

data/json/vehicleparts/armor.json

@@ -32,14 +32,15 @@
     "color": "dark_gray",
     "broken_color": "dark_gray",
     "durability": 340,
+    "bonus": 50,
     "description": "A system of springs and pads, intended to cushion the effects of collisions on the interior of your vehicle.",
     "breaks_into": [ { "item": "scrap", "count": [ 1, 5 ] }, { "item": "spring", "count": [ 0, 4 ] } ],
     "requirements": {
       "install": { "skills": [ [ "mechanics", 4 ] ], "time": "60 m", "using": [ [ "welding_standard", 5 ] ] },
       "removal": { "skills": [ [ "mechanics", 2 ] ], "time": "30 m", "using": [ [ "vehicle_weld_removal", 1 ] ] },
       "repair": { "skills": [ [ "mechanics", 5 ] ], "time": "60 m", "using": [ [ "welding_standard", 5 ] ] }
     },
-    "flags": [ "ARMOR" ],
-    "damage_reduction": { "all": 15, "bash": 100 }
+    "flags": [ "SHOCK_ABSORBER" ],
+    "damage_reduction": { "all": 25 }
   }
 ]

data/json/vehicleparts/vp_flags.json

@@ -22,7 +22,7 @@
     "id": "ARMOR",
     "type": "json_flag",
     "context": [ "vehicle_part" ],
-    "info": "Armor plate.  Will partially protect other components on the same frame from damage."
+    "info": "Armor plate.  Will partially protect other components on the same frame from damage from direct attacks but not from the shock damage of a distant collision."
   },
   {
     "id": "BED",
@@ -133,6 +133,12 @@
     "info": "This part will help prevent you from being thrown from the vehicle in a collision.  You will automatically enable this part when you move into a tile with it.",
     "requires_flag": "BELTABLE"
   },
+  {
+    "id": "SHOCK_ABSORBER",
+    "type": "json_flag",
+    "context": [ "vehicle_part" ],
+    "info": "Armor plate.  Will partially protect other components on the same frame from the shock damage of a distant collision but not from direct attacks."
+  },
   {
     "id": "STABLE",
     "type": "json_flag",

src/vehicle.cpp

@@ -6613,9 +6613,16 @@ void vehicle::damage_all( int dmg1, int dmg2, damage_type type, point impact )
     for( const vpart_reference &vp : get_all_parts() ) {
         const size_t p = vp.part_index();
         int distance = 1 + square_dist( vp.mount(), impact );
-        if( distance > 1 && part_info( p ).location == part_location_structure &&
-            !part_info( p ).has_flag( "PROTRUSION" ) ) {
-            damage_direct( p, rng( dmg1, dmg2 ) / ( distance * distance ), type );
+        if( distance > 1 ) {
+            int net_dmg = rng( dmg1, dmg2 ) / ( distance * distance );
+            if( part_info( p ).location != part_location_structure ||
+                !part_info( p ).has_flag( "PROTRUSION" ) ) {
+                int shock_absorber = part_with_feature( p, "SHOCK_ABSORBER", true );
+                if( shock_absorber >= 0 ) {
+                    net_dmg = std::max( 0, net_dmg - parts[ shock_absorber ].info().bonus );
+                }
+            }
+            damage_direct( p, net_dmg, type );
         }
     }
 }