gdk:visual-red-pixel-details (visual)

visual -- a gdk:visual object

mask -- an unsigned integer, or nil
shift -- an integer, or nil
precision -- an integer, or nil

Obtains values that are needed to calculate red pixel values in TrueColor and DirectColor. The mask argument is the significant bits within the pixel. shift is the number of bits left we must shift a primary for it to be in position according to mask. Finally, precision refers to how much precision the pixel value contains for a particular primary.