Function MoveWaypointsToBaseStations

src/saveload/waypoint_sl.cpp:68–162

* Perform all steps to upgrade from the old waypoints to the new version * that uses station. This includes some old saveload mechanics. */

 * that uses station. This includes some old saveload mechanics.
 */
void MoveWaypointsToBaseStations()
{
	/* In version 17, ground type is moved from m2 to m4 for depots and
	 * waypoints to make way for storing the index in m2. The custom graphics
	 * id which was stored in m4 is now saved as a grf/id reference in the
	 * waypoint struct. */
	if (IsSavegameVersionBefore(SLV_17)) {
		for (OldWaypoint &wp : _old_waypoints) {
			if (wp.delete_ctr != 0) continue; // The waypoint was deleted

			/* Waypoint indices were not added to the map prior to this. */
			Tile tile = wp.xy;
			tile.m2() = wp.index;

			if (HasBit(tile.m3(), 4)) {
				wp.spec = StationClass::Get(STAT_CLASS_WAYP)->GetSpec(tile.m4() + 1);
			}
		}
	} else {
		/* As of version 17, we recalculate the custom graphic ID of waypoints
		 * from the GRF ID / station index. */
		for (OldWaypoint &wp : _old_waypoints) {
			const auto specs = StationClass::Get(STAT_CLASS_WAYP)->Specs();
			auto found = std::ranges::find_if(specs, [&wp](const StationSpec *spec) { return spec != nullptr && spec->grf_prop.grfid == wp.grfid && spec->grf_prop.local_id == wp.localidx; });
			if (found != std::end(specs)) wp.spec = *found;
		}
	}

	if (!Waypoint::CanAllocateItem(_old_waypoints.size())) SlError(STR_ERROR_TOO_MANY_STATIONS_LOADING);

	/* All saveload conversions have been done. Create the new waypoints! */
	for (OldWaypoint &wp : _old_waypoints) {
		TileIndex t = wp.xy;
		/* Sometimes waypoint (sign) locations became disconnected from their actual location in
		 * the map array. If this is the case, try to locate the actual location in the map array */
		if (!IsTileType(t, MP_RAILWAY) || GetRailTileType(t) != RailTileType{2} /* RAIL_TILE_WAYPOINT */ || Tile(t).m2() != wp.index) {
			Debug(sl, 0, "Found waypoint tile {} with invalid position", t);
			t = INVALID_TILE;
			for (auto tile : Map::Iterate()) {
				if (IsTileType(tile, MP_RAILWAY) && GetRailTileType(tile) == RailTileType{2} /* RAIL_TILE_WAYPOINT */ && tile.m2() == wp.index) {
					t = TileIndex(tile);
					Debug(sl, 0, "Found actual waypoint position at {}", TileIndex(tile));
					break;
				}
			}
		}
		if (t == INVALID_TILE) {
			SlErrorCorrupt("Waypoint with invalid tile");
		}

		Waypoint *new_wp = new Waypoint(t);
		new_wp->town       = wp.town;
		new_wp->town_cn    = wp.town_cn;
		new_wp->name       = wp.name;
		new_wp->delete_ctr = 0; // Just reset delete counter for once.
		new_wp->build_date = wp.build_date;
		new_wp->owner      = wp.owner;
		new_wp->string_id  = STR_SV_STNAME_WAYPOINT;