Fix #9837, 46bd2f1c: Road build with wrong half-tile ends.

src/road_cmd.cpp

@@ -989,7 +989,8 @@ CommandCost CmdBuildLongRoad(DoCommandFlag flags, TileIndex start_tile, TileInde
 	/* Swap direction, also the half-tile drag vars. */
 	if (start_tile > end_tile || (start_tile == end_tile && start_half)) {
 		dir = ReverseDiagDir(dir);
-		std::swap(start_half, end_half);
+		start_half = !start_half;
+		end_half = !end_half;
 		if (drd == DRD_NORTHBOUND || drd == DRD_SOUTHBOUND) drd ^= DRD_BOTH;
 	}
 

src/road_gui.cpp

@@ -638,14 +638,14 @@ struct BuildRoadToolbarWindow : Window {
 				case DDSP_PLACE_ROAD_X_DIR:
 				case DDSP_PLACE_ROAD_Y_DIR:
 				case DDSP_PLACE_AUTOROAD: {
-					bool start_half = _place_road_dir == AXIS_Y ? _place_road_start_half_y : _place_road_start_half_y;
+					bool start_half = _place_road_dir == AXIS_Y ? _place_road_start_half_y : _place_road_start_half_x;
 
 					if (_remove_button_clicked) {
 						Command<CMD_REMOVE_LONG_ROAD>::Post(this->rti->strings.err_remove_road, CcPlaySound_CONSTRUCTION_OTHER,
 								start_tile, end_tile, _cur_roadtype, _place_road_dir, start_half, _place_road_end_half);
 					} else {
 						Command<CMD_BUILD_LONG_ROAD>::Post(this->rti->strings.err_build_road, CcPlaySound_CONSTRUCTION_OTHER,
-								start_tile, end_tile, _cur_roadtype, _place_road_dir, _one_way_button_clicked ? DRD_NORTHBOUND : DRD_NONE, start_tile, _place_road_end_half, false);
+								start_tile, end_tile, _cur_roadtype, _place_road_dir, _one_way_button_clicked ? DRD_NORTHBOUND : DRD_NONE, start_half, _place_road_end_half, false);
 					}
 					break;
 				}