isPrintable = function isPrintable(keysym) {

        // Keysyms with Unicode equivalents are printable
        return (keysym >= 0x00 && keysym <= 0xFF)
            || (keysym & 0xFFFF0000) === 0x01000000;

    }
Returns true if the given keysym corresponds to a printable character,
false otherwise.

@param {Number} keysym
    The keysym to check.

@returns {Boolean}
    true if the given keysym corresponds to a printable character,
    false otherwise.