Fix #10208: allow to use specific underlay for road/tram tunnels (#10233)

src/road.h

@@ -58,7 +58,7 @@ enum RoadTypeSpriteGroup {
 	ROTSG_CURSORS,        ///< Optional: Cursor and toolbar icon images
 	ROTSG_OVERLAY,        ///< Optional: Images for overlaying track
 	ROTSG_GROUND,         ///< Required: Main group of ground images
-	ROTSG_reserved1,      ///<           Placeholder, if we need specific tunnel sprites.
+	ROTSG_TUNNEL,         ///< Optional: Ground images for tunnels
 	ROTSG_CATENARY_FRONT, ///< Optional: Catenary front
 	ROTSG_CATENARY_BACK,  ///< Optional: Catenary back
 	ROTSG_BRIDGE,         ///< Required: Bridge surface images

src/road_cmd.cpp

@@ -1489,21 +1489,24 @@ static void DrawRoadDetail(SpriteID img, const TileInfo *ti, int dx, int dy, int
  * @param tram_rti Tram road type information
  * @param road_offset Road sprite offset (based on road bits)
  * @param tram_offset Tram sprite offset (based on road bits)
+ * @param draw_underlay Whether to draw underlays
  */
-void DrawRoadOverlays(const TileInfo *ti, PaletteID pal, const RoadTypeInfo *road_rti, const RoadTypeInfo *tram_rti, uint road_offset, uint tram_offset)
+void DrawRoadOverlays(const TileInfo *ti, PaletteID pal, const RoadTypeInfo *road_rti, const RoadTypeInfo *tram_rti, uint road_offset, uint tram_offset, bool draw_underlay)
 {
-	/* Road underlay takes precedence over tram */
-	if (road_rti != nullptr) {
-		if (road_rti->UsesOverlay()) {
-			SpriteID ground = GetCustomRoadSprite(road_rti, ti->tile, ROTSG_GROUND);
-			DrawGroundSprite(ground + road_offset, pal);
-		}
-	} else {
-		if (tram_rti->UsesOverlay()) {
-			SpriteID ground = GetCustomRoadSprite(tram_rti, ti->tile, ROTSG_GROUND);
-			DrawGroundSprite(ground + tram_offset, pal);
+	if (draw_underlay) {
+		/* Road underlay takes precedence over tram */
+		if (road_rti != nullptr) {
+			if (road_rti->UsesOverlay()) {
+				SpriteID ground = GetCustomRoadSprite(road_rti, ti->tile, ROTSG_GROUND);
+				DrawGroundSprite(ground + road_offset, pal);
+			}
 		} else {
-			DrawGroundSprite(SPR_TRAMWAY_TRAM + tram_offset, pal);
+			if (tram_rti->UsesOverlay()) {
+				SpriteID ground = GetCustomRoadSprite(tram_rti, ti->tile, ROTSG_GROUND);
+				DrawGroundSprite(ground + tram_offset, pal);
+			} else {
+				DrawGroundSprite(SPR_TRAMWAY_TRAM + tram_offset, pal);
+			}
 		}
 	}
 

src/road_func.h

@@ -158,6 +158,6 @@ void MarkDirtyAdjacentLevelCrossingTiles(TileIndex tile, Axis road_axis);
 void UpdateCompanyRoadInfrastructure(RoadType rt, Owner o, int count);
 
 struct TileInfo;
-void DrawRoadOverlays(const TileInfo *ti, PaletteID pal, const RoadTypeInfo *road_rti, const RoadTypeInfo *tram_rit, uint road_offset, uint tram_offset);
+void DrawRoadOverlays(const TileInfo *ti, PaletteID pal, const RoadTypeInfo *road_rti, const RoadTypeInfo *tram_rit, uint road_offset, uint tram_offset, bool draw_underlay = true);
 
 #endif /* ROAD_FUNC_H */

src/tunnelbridge_cmd.cpp

@@ -1307,8 +1307,28 @@ static void DrawTile_TunnelBridge(TileInfo *ti)
 			const RoadTypeInfo *road_rti = road_rt == INVALID_ROADTYPE ? nullptr : GetRoadTypeInfo(road_rt);
 			const RoadTypeInfo *tram_rti = tram_rt == INVALID_ROADTYPE ? nullptr : GetRoadTypeInfo(tram_rt);
 			uint sprite_offset = DiagDirToAxis(tunnelbridge_direction) == AXIS_X ? 1 : 0;
+			bool draw_underlay = true;
+
+			/* Road underlay takes precedence over tram */
+			if (road_rti != nullptr) {
+				if (road_rti->UsesOverlay()) {
+					SpriteID ground = GetCustomRoadSprite(road_rti, ti->tile, ROTSG_TUNNEL);
+					if (ground != 0) {
+						DrawGroundSprite(ground + tunnelbridge_direction, PAL_NONE);
+						draw_underlay = false;
+					}
+				}
+			} else {
+				if (tram_rti->UsesOverlay()) {
+					SpriteID ground = GetCustomRoadSprite(tram_rti, ti->tile, ROTSG_TUNNEL);
+					if (ground != 0) {
+						DrawGroundSprite(ground + tunnelbridge_direction, PAL_NONE);
+						draw_underlay = false;
+					}
+				}
+			}
 
-			DrawRoadOverlays(ti, PAL_NONE, road_rti, tram_rti, sprite_offset, sprite_offset);
+			DrawRoadOverlays(ti, PAL_NONE, road_rti, tram_rti, sprite_offset, sprite_offset, draw_underlay);
 
 			/* Road catenary takes precedence over tram */
 			SpriteID catenary_sprite_base = 0;