Function TileLoopClearAlps

src/clear_cmd.cpp:188–216

Convert to or from snowy tiles. */

/** Convert to or from snowy tiles. */
static void TileLoopClearAlps(TileIndex tile)
{
	int k = GetTileZ(tile) - GetSnowLine() + 1;

	if (!IsSnowTile(tile)) {
		/* Below the snow line, do nothing if no snow. */
		/* At or above the snow line, make snow tile if needed. */
		if (k >= 0) {
			/* Snow density is started at 0 so that it can gradually reach the required density. */
			MakeSnow(tile, 0);
			MarkTileDirtyByTile(tile);
		}
		return;
	}

	/* Update snow density. */
	uint current_density = GetClearDensity(tile);
	uint req_density = (k < 0) ? 0u : std::min<uint>(k, 3u);

	if (current_density == req_density) {
		/* Density at the required level. */
		if (k >= 0) return;
		ClearSnow(tile);
	} else {
		AddClearDensity(tile, current_density < req_density ? 1 : -1);
	}

	MarkTileDirtyByTile(tile);
}

/**
 * Tests if at least one surrounding tile is non-desert