Function GetScaledIndustryGenerationProbability

src/industry_cmd.cpp:2305–2325

* Compute the appearance probability for an industry during map creation. * @param it Industry type to compute. * @param water Whether to get probability of land-based, water-based, (or both, if std::nullopt), industry types. * @param[out] force_at_least_one Returns whether at least one instance should be forced on map creation. * @return Relative probability for the industry to appear. */

 * @return Relative probability for the industry to appear.
 */
static uint32_t GetScaledIndustryGenerationProbability(IndustryType it, std::optional<bool> water, bool *force_at_least_one)
{
	const IndustrySpec *ind_spc = GetIndustrySpec(it);
	if (water.has_value() && ind_spc->behaviour.Test(IndustryBehaviour::BuiltOnWater) != *water) return 0;

	uint32_t chance = ind_spc->appear_creation[to_underlying(_settings_game.game_creation.landscape)];
	if (!ind_spc->enabled || ind_spc->layouts.empty() ||
			(_game_mode != GM_EDITOR && _settings_game.difficulty.industry_density == ID_FUND_ONLY) ||
			(chance = GetIndustryProbabilityCallback(it, IACT_MAPGENERATION, chance)) == 0) {
		*force_at_least_one = false;
		return 0;
	} else {
		chance *= 16; // to increase precision
		/* We want industries appearing at coast to appear less often on bigger maps, as length of coast increases slower than map area.
		 * For simplicity we scale in both cases, though scaling the probabilities of all industries has no effect. */
		chance = (ind_spc->check_proc == CHECK_REFINERY || ind_spc->check_proc == CHECK_OIL_RIG) ? Map::ScaleBySize1D(chance) : Map::ScaleBySize(chance);

		*force_at_least_one = (chance > 0) && !ind_spc->behaviour.Test(IndustryBehaviour::NoBuildMapCreation) && (_game_mode != GM_EDITOR);
		return chance;
	}
}

/**
 * Compute the probability for constructing a new industry during game play.