Function UpdateTownGrowCounter

src/town_cmd.cpp:3804–3812

* Updates town grow counter after growth rate change. * Preserves relative house builting progress whenever it can. * @param t The town to calculate grow counter for * @param prev_growth_rate Town growth rate before it changed (one that was used with grow counter to be updated) */

 * @param prev_growth_rate Town growth rate before it changed (one that was used with grow counter to be updated)
 */
static void UpdateTownGrowCounter(Town *t, uint16_t prev_growth_rate)
{
	if (t->growth_rate == TOWN_GROWTH_RATE_NONE) return;
	if (prev_growth_rate == TOWN_GROWTH_RATE_NONE) {
		t->grow_counter = std::min<uint16_t>(t->growth_rate, t->grow_counter);
		return;
	}
	t->grow_counter = RoundDivSU((uint32_t)t->grow_counter * (t->growth_rate + 1), prev_growth_rate + 1);
}

/**
 * Calculates amount of active stations in the range of town (HZB_TOWN_EDGE).