RGBwritemask(3G)					      RGBwritemask(3G)

NAME    [Toc]    [Back]

     RGBwritemask - grants write access	to a subset of available bitplanes

C SPECIFICATION    [Toc]    [Back]

     void RGBwritemask(red, green, blue)
     short red,	green, blue;

PARAMETERS    [Toc]    [Back]

     red     expects the mask for the corresponding red	bitplanes.

     green   expects the mask for the corresponding green bitplanes.

     blue    expects the mask for the corresponding blue bitplanes.

DESCRIPTION    [Toc]    [Back]

     RGBwritemask sets the red,	green, and blue	write mask components of the
     currently active GL framebuffer, one of normal, popup, overlay, or
     underlay as specified by drawmode,	to the specified values.  The alpha
     mask component is set to enable writing to	all alpha bitplanes.  The
     current framebuffer must be in RGB	mode for the RGBwritemask command to
     be	applicable.  All drawing into the color	bitplanes of the current
     framebuffer is masked by the current write	mask.  Write mask components
     are retained in each draw mode, so	when a draw mode is re-entered,	the
     red, green, blue, and alpha masks are reset to the	last values specified
     in	that draw mode.

     Each write	mask component is an 8-bit mask, which allows changes only to
     bitplanes corresponding to	ones in	the mask.  For example,
     RGBwritemask(0xF0,0x00,0x00) allows changes only to the 4 most
     significant bits of red, and to all the bits of alpha.  Bits 8 through 15
     of	each component specification are ignored, only bits 0 through 7	are
     significant.

     It	is an error to call RGBwritemask while the current framebuffer is in
     color map mode.

     The write mask components of all framebuffers in RGB mode are set to 0xFF
     when gconfig is called.

SEE ALSO    [Toc]    [Back]

     drawmode, gRGBmask, RGBmode, wmpack

NOTE    [Toc]    [Back]

     On	Impact and Infinite Reality individual bits within a component cannot
     be	masked.


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