Function ConvertBooleanCallback

src/newgrf_commons.cpp:543–551

* Converts a callback result into a boolean. * For grf version < 8 the result is checked for zero or non-zero. * For grf version >= 8 the callback result must be 0 or 1. * @param grffile NewGRF returning the value. * @param cbid Callback returning the value. * @param cb_res Callback result. * @return Boolean value. True if cb_res != 0. */

 * @return Boolean value. True if cb_res != 0.
 */
bool ConvertBooleanCallback(const GRFFile *grffile, uint16_t cbid, uint16_t cb_res)
{
	assert(cb_res != CALLBACK_FAILED); // We do not know what to return

	if (grffile->grf_version < 8) return cb_res != 0;

	if (cb_res > 1) ErrorUnknownCallbackResult(grffile->grfid, cbid, cb_res);
	return cb_res != 0;
}

/**
 * Converts a callback result into a boolean.