what is "primary" refer to in visual

Simon Thum simon.thum at gmx.de
Tue Mar 16 09:06:33 PDT 2010

Am 16.03.2010 09:42, schrieb Zhang, Xing Z:
> Hi experts:
>          From xlib manual, here are sentences for color:
> GrayScale is treated the same way as PseudoColor except that the *primary* that drives the
> screen is undefined. Thus, the client should always store the same value for red, green, and
> blue in the colormaps.
> TrueColor is treated the same way as DirectColor except that the colormap has predefined,
> read-only RGB values. These RGB values are server dependent but provide linear or
> near-linear ramps in each *primary*.
>        I apologize for my bad English, I am confused by the word "primary". I wonder what does
> "primary" mean here? Thank you.

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