s a symbolic constant chosen from the list above.
            In the explanation of the logical operations,
            <span class="emphasis"><em>s</em></span> represents the incoming color and
            <span class="emphasis"><em>d</em></span> represents the color in the frame buffer.
            Standard C-language operators are used.
            As these bitwise operators suggest,
            the logical operation is applied independently to each bit pair of the
            source and destination colo