HP Workstation zx6000 HP Graphics Administration Guide for HP-UX 11.X (IPF ver - Page 54
ATI Fire GL4 Colormaps Hints
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configuring an X Server on HP-UX pOVis = pOverlayVisuals; while (--nOVisuals >= 0) {if ( pOVis->transparentType == TransparentPixel ) {/* **Found a transparent overlay visual, **set ident. aside. */ }; pOVis++; } 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. 4-42 Graphics Administration Guide