HP zx2000 Supplementary Manual page 54

configuring an X Server on HP-UX
pOVis
while (--nOVisuals >= 0)
}
XFree(pOverlayVisuals);
/*
**There might be some additional checking of the found
**transparent overlay visuals wanted; e.g., for depth.
*/
}
XFree(pVisuals);
}
This program segment is not complete; however, its main purpose is to give an idea of how to
find an overlay visual having transparency.
When the overlay planes are enabled, one colormap entry in the PseudoColor colormaps is not
available for use by clients. The server handles this entry in one of two ways depending upon the
setting of the "CountTransInOvlyVis" device option. If the option is not set, the server reports
that 256 colormap entries are available for allocation in the PseudoColor visual. This option may
be useful to applications that depend on having 256 colormap entries available in depth 8
PseudoColor visuals. However, the transparent pixel always remains transparent. The image
layer is visible wherever this pixel value is rendered in the overlay planes. Hence, applications
should not render using this pixel unless transparency is desired.
This may cause problems with some applications. Setting "CountTransInOvlyVis" causes the
server to reserve the transparent pixel index. In this case, the server reports that 255 colormap
entries are available for allocation in the PseudoColor visual. The transparent index value is
configurable through the "TransparentIndex0" device option. Setting this option changes the
transparent pixel value to 0 from the default of 255. This option may be useful to applications
that depend on the transparent pixel value being 0.
ATI Fire GL4 Colormaps Hints
ATI Fire GL4 devices have a total of 5 hardware colormaps. One colormap is reserved for
gamma correction and is not directly available to X clients. The remaining colormaps are
available for clients to use. When the default visual is in the overlay planes, one of the four
available hardware colormaps is reserved for the default colormap. This ensures that clients using
the default colormap never encounter color flashing.
The ATI Fire GL4 driver reports on the installation status of a total of 5 colormaps via the
XListInstalledColormaps() API. Four of these correspond to the actual state of the hardware
color tables used with PseudoColor visuals. Colormaps are installed in these hardware LUTs in
first-in, first-out order. The driver also keeps track of the last TrueColor colormap installed via
XInstallColormap() and includes this information whenever queried. By definition, all TrueColor
colormaps are always installed.
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= pOverlayVisuals;
{if ( pOVis->transparentType == TransparentPixel )
{/*
**Found a transparent overlay visual,
**set ident. aside.
*/
};
pOVis++;
Graphics Administration Guide