Function UpdateTrainGroupID

src/group_cmd.cpp:793–809

* Recalculates the groupID of a train. Should be called each time a vehicle is added * to/removed from the chain,. * @note this needs to be called too for 'wagon chains' (in the depot, without an engine) * @note Called in CmdBuildRailVehicle, CmdBuildRailWagon, CmdMoveRailVehicle, CmdSellRailWagon * @param v First vehicle of the chain. */

 * @param v First vehicle of the chain.
 */
void UpdateTrainGroupID(Train *v)
{
	assert(v->IsFrontEngine() || v->IsFreeWagon());

	GroupID new_g = v->IsFrontEngine() ? v->group_id : (GroupID)DEFAULT_GROUP;
	for (Vehicle *u = v; u != nullptr; u = u->Next()) {
		if (u->IsEngineCountable()) UpdateNumEngineGroup(u, u->group_id, new_g);

		u->group_id = new_g;
		u->colourmap = PAL_NONE;
		u->InvalidateNewGRFCache();
	}

	/* Update the Replace Vehicle Windows */
	GroupStatistics::UpdateAutoreplace(v->owner);
	SetWindowDirty(WC_REPLACE_VEHICLE, VEH_TRAIN);
}

/**
 * Get the number of engines with EngineID id_e in the group with GroupID