Codechange: Implement tile proc handler to test for building bridge over tile.

src/clear_cmd.cpp

@@ -390,6 +390,11 @@ static CommandCost TerraformTile_Clear(TileIndex tile, DoCommandFlags flags, int
 	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
 }
 
+static CommandCost CheckBuildAbove_Clear(TileIndex, DoCommandFlags, Axis, int)
+{
+	return CommandCost();
+}
+
 extern const TileTypeProcs _tile_type_clear_procs = {
 	DrawTile_Clear,           ///< draw_tile_proc
 	GetSlopePixelZ_Clear,     ///< get_slope_z_proc
@@ -405,4 +410,5 @@ extern const TileTypeProcs _tile_type_clear_procs = {
 	nullptr,                     ///< vehicle_enter_tile_proc
 	GetFoundation_Clear,      ///< get_foundation_proc
 	TerraformTile_Clear,      ///< terraform_tile_proc
+	CheckBuildAbove_Clear, // check_build_above_proc
 };

src/industry_cmd.cpp

@@ -3205,6 +3205,7 @@ extern const TileTypeProcs _tile_type_industry_procs = {
 	nullptr,                        // vehicle_enter_tile_proc
 	GetFoundation_Industry,      // get_foundation_proc
 	TerraformTile_Industry,      // terraform_tile_proc
+	nullptr, // check_build_above_proc
 };
 
 bool IndustryCompare::operator() (const IndustryListEntry &lhs, const IndustryListEntry &rhs) const

src/object_cmd.cpp

@@ -929,6 +929,16 @@ static CommandCost TerraformTile_Object(TileIndex tile, DoCommandFlags flags, in
 	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
 }
 
+static CommandCost CheckBuildAbove_Object(TileIndex tile, DoCommandFlags flags, Axis, int height)
+{
+	const ObjectSpec *spec = ObjectSpec::GetByTile(tile);
+	if (spec->flags.Test(ObjectFlag::AllowUnderBridge) && GetTileMaxZ(tile) + spec->height <= height) {
+		return CommandCost();
+	}
+
+	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
+}
+
 extern const TileTypeProcs _tile_type_object_procs = {
 	DrawTile_Object,             // draw_tile_proc
 	GetSlopePixelZ_Object,       // get_slope_z_proc
@@ -944,4 +954,5 @@ extern const TileTypeProcs _tile_type_object_procs = {
 	nullptr,                        // vehicle_enter_tile_proc
 	GetFoundation_Object,        // get_foundation_proc
 	TerraformTile_Object,        // terraform_tile_proc
+	CheckBuildAbove_Object, // check_build_above_proc
 };

src/rail_cmd.cpp

@@ -3070,6 +3070,11 @@ static CommandCost TerraformTile_Track(TileIndex tile, DoCommandFlags flags, int
 	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
 }
 
+static CommandCost CheckBuildAbove_Track(TileIndex tile, DoCommandFlags flags, Axis, int)
+{
+	if (IsPlainRail(tile)) return CommandCost();
+	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
+}
 
 extern const TileTypeProcs _tile_type_rail_procs = {
 	DrawTile_Track,           // draw_tile_proc
@@ -3086,4 +3091,5 @@ extern const TileTypeProcs _tile_type_rail_procs = {
 	VehicleEnter_Track,       // vehicle_enter_tile_proc
 	GetFoundation_Track,      // get_foundation_proc
 	TerraformTile_Track,      // terraform_tile_proc
+	CheckBuildAbove_Track, // check_build_above_proc
 };

src/road_cmd.cpp

@@ -2616,6 +2616,11 @@ CommandCost CmdConvertRoad(DoCommandFlags flags, TileIndex tile, TileIndex area_
 	return found_convertible_road ? cost : error;
 }
 
+static CommandCost CheckBuildAbove_Road(TileIndex tile, DoCommandFlags flags, Axis, int)
+{
+	if (!IsRoadDepot(tile)) return CommandCost();
+	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
+}
 
 /** Tile callback functions for road tiles */
 extern const TileTypeProcs _tile_type_road_procs = {
@@ -2633,4 +2638,5 @@ extern const TileTypeProcs _tile_type_road_procs = {
 	VehicleEnter_Road,       // vehicle_enter_tile_proc
 	GetFoundation_Road,      // get_foundation_proc
 	TerraformTile_Road,      // terraform_tile_proc
+	CheckBuildAbove_Road, // check_build_above_proc
 };

src/station_cmd.cpp

@@ -5177,4 +5177,5 @@ extern const TileTypeProcs _tile_type_station_procs = {
 	VehicleEnter_Station,       // vehicle_enter_tile_proc
 	GetFoundation_Station,      // get_foundation_proc
 	TerraformTile_Station,      // terraform_tile_proc
+	nullptr, // check_build_above_proc
 };

src/tile_cmd.h

@@ -135,6 +135,8 @@ typedef Foundation GetFoundationProc(TileIndex tile, Slope tileh);
  */
 typedef CommandCost TerraformTileProc(TileIndex tile, DoCommandFlags flags, int z_new, Slope tileh_new);
 
+using CheckBuildAboveProc = CommandCost(TileIndex tile, DoCommandFlags flags, Axis axis, int height);
+
 /**
  * Set of callback functions for performing tile operations of a given tile type.
  * @see TileType
@@ -154,6 +156,7 @@ struct TileTypeProcs {
 	VehicleEnterTileProc *vehicle_enter_tile_proc; ///< Called when a vehicle enters a tile
 	GetFoundationProc *get_foundation_proc;
 	TerraformTileProc *terraform_tile_proc;        ///< Called when a terraforming operation is about to take place
+	CheckBuildAboveProc *check_build_above_proc;
 };
 
 extern const TileTypeProcs * const _tile_type_procs[16];

src/town_cmd.cpp

@@ -4130,6 +4130,7 @@ extern const TileTypeProcs _tile_type_town_procs = {
 	nullptr,                    // vehicle_enter_tile_proc
 	GetFoundation_Town,      // get_foundation_proc
 	TerraformTile_Town,      // terraform_tile_proc
+	nullptr, // check_build_above_proc
 };
 
 std::span<const DrawBuildingsTileStruct> GetTownDrawTileData()

src/tree_cmd.cpp

@@ -1031,4 +1031,5 @@ extern const TileTypeProcs _tile_type_trees_procs = {
 	nullptr,                     // vehicle_enter_tile_proc
 	GetFoundation_Trees,      // get_foundation_proc
 	TerraformTile_Trees,      // terraform_tile_proc
+	nullptr, // check_build_above_proc
 };

src/tunnelbridge_cmd.cpp

@@ -12,7 +12,6 @@
  */
 
 #include "stdafx.h"
-#include "newgrf_object.h"
 #include "viewport_func.h"
 #include "command_func.h"
 #include "town.h"
@@ -20,7 +19,6 @@
 #include "ship.h"
 #include "roadveh.h"
 #include "pathfinder/yapf/yapf_cache.h"
-#include "pathfinder/water_regions.h"
 #include "newgrf_sound.h"
 #include "autoslope.h"
 #include "tunnelbridge_map.h"
@@ -39,7 +37,6 @@
 #include "object_base.h"
 #include "water.h"
 #include "company_gui.h"
-#include "station_func.h"
 #include "tunnelbridge_cmd.h"
 #include "landscape_cmd.h"
 #include "terraform_cmd.h"
@@ -278,6 +275,16 @@ static Money TunnelBridgeClearCost(TileIndex tile, Price base_price)
 	return base_cost;
 }
 
+static CommandCost CheckBuildAbove(TileIndex tile, DoCommandFlags flags, Axis axis, int height)
+{
+	if (_tile_type_procs[GetTileType(tile)]->check_build_above_proc != nullptr) {
+		return _tile_type_procs[GetTileType(tile)]->check_build_above_proc(tile, flags, axis, height);
+	}
+
+	/* A tile without a handler must be cleared. */
+	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
+}
+
 /**
  * Build a Bridge
  * @param flags type of operation
@@ -484,43 +491,9 @@ CommandCost CmdBuildBridge(DoCommandFlags flags, TileIndex tile_end, TileIndex t
 				return CommandCost(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
 			}
 
-			switch (GetTileType(tile)) {
+			ret = CheckBuildAbove(tile, flags, direction, z_start);
-				case MP_WATER:
+			if (ret.Failed()) return ret;
-					if (!IsWater(tile) && !IsCoast(tile)) goto not_valid_below;
+			cost.AddCost(ret.GetCost());
-					break;
-
-				case MP_RAILWAY:
-					if (!IsPlainRail(tile)) goto not_valid_below;
-					break;
-
-				case MP_ROAD:
-					if (IsRoadDepot(tile)) goto not_valid_below;
-					break;
-
-				case MP_TUNNELBRIDGE:
-					if (IsTunnel(tile)) break;
-					if (direction == DiagDirToAxis(GetTunnelBridgeDirection(tile))) goto not_valid_below;
-					if (z_start < GetBridgeHeight(tile)) goto not_valid_below;
-					break;
-
-				case MP_OBJECT: {
-					const ObjectSpec *spec = ObjectSpec::GetByTile(tile);
-					if (!spec->flags.Test(ObjectFlag::AllowUnderBridge)) goto not_valid_below;
-					if (GetTileMaxZ(tile) + spec->height > z_start) goto not_valid_below;
-					break;
-				}
-
-				case MP_CLEAR:
-					break;
-
-				default:
-	not_valid_below:;
-					/* try and clear the middle landscape */
-					ret = Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
-					if (ret.Failed()) return ret;
-					cost.AddCost(ret.GetCost());
-					break;
-			}
 
 			if (flags.Test(DoCommandFlag::Execute)) {
 				/* We do this here because when replacing a bridge with another
@@ -2084,6 +2057,17 @@ static CommandCost TerraformTile_TunnelBridge(TileIndex tile, DoCommandFlags fla
 	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
 }
 
+static CommandCost CheckBuildAbove_TunnelBridge(TileIndex tile, DoCommandFlags flags, Axis axis, int height)
+{
+	if (IsTunnel(tile)) return CommandCost();
+
+	if (axis != DiagDirToAxis(GetTunnelBridgeDirection(tile)) && height >= GetBridgeHeight(tile)) {
+		return CommandCost();
+	}
+
+	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
+}
+
 extern const TileTypeProcs _tile_type_tunnelbridge_procs = {
 	DrawTile_TunnelBridge,           // draw_tile_proc
 	GetSlopePixelZ_TunnelBridge,     // get_slope_z_proc
@@ -2099,4 +2083,5 @@ extern const TileTypeProcs _tile_type_tunnelbridge_procs = {
 	VehicleEnter_TunnelBridge,       // vehicle_enter_tile_proc
 	GetFoundation_TunnelBridge,      // get_foundation_proc
 	TerraformTile_TunnelBridge,      // terraform_tile_proc
+	CheckBuildAbove_TunnelBridge, // check_build_above_proc
 };

src/void_cmd.cpp

@@ -87,4 +87,5 @@ extern const TileTypeProcs _tile_type_void_procs = {
 	nullptr,                     // vehicle_enter_tile_proc
 	GetFoundation_Void,       // get_foundation_proc
 	TerraformTile_Void,       // terraform_tile_proc
+	nullptr, // check_build_above_proc
 };

src/water_cmd.cpp

@@ -1410,6 +1410,11 @@ static CommandCost TerraformTile_Water(TileIndex tile, DoCommandFlags flags, int
 	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
 }
 
+static CommandCost CheckBuildAbove_Water(TileIndex tile, DoCommandFlags flags, Axis, int)
+{
+	if (IsWater(tile) || IsCoast(tile)) return CommandCost();
+	return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
+}
 
 extern const TileTypeProcs _tile_type_water_procs = {
 	DrawTile_Water,           // draw_tile_proc
@@ -1426,4 +1431,5 @@ extern const TileTypeProcs _tile_type_water_procs = {
 	VehicleEnter_Water,       // vehicle_enter_tile_proc
 	GetFoundation_Water,      // get_foundation_proc
 	TerraformTile_Water,      // terraform_tile_proc
+	CheckBuildAbove_Water, // check_build_above_proc
 };