Multiple Criteria Sets

XSolarisOvlSelectPartner supports a degradation sequence of criteria sets. This means that multiple criteria sets can be specified in a single call. First, the routine attempts to find a visual matching the first criteria set. If a visual is found that meets all of the hard criteria of the first set, this visual is chosen. If no visual meets all hard criteria of the first set, the routine performs a search using the second criteria set. This process continues until either a visual is found that meets the hard criteria of some criteria set, or all sets have been used to search. This degradation sequence allows clients to specify the criteria for the most preferred visual as the first criteria set. Visuals that are acceptable but are less desirable can be specified in criteria sets following the first criteria set. This allows the search to proceed through a progressive relaxation in the client's requirements for the visual with a single subroutine call.

Any of the possible criteria can be specified either as a hard or soft criteria for a particular criteria set. For a given set, hardCriteriaMask is the logical OR of the criteria bitmasks that are to be applied as hard criteria during the search. Likewise, softCriteriaMask is the logical OR of the soft criteria bitmasks.

Some criteria have values associated with them. These values are provided by other data members in the XSolarisOvlVisualCriteria structure. In the criteria descriptions that follow, these data members are mentioned where applicable.

• XSolarisOvlVisualClass specifies that the client wants the selected visual to have a specific visual class. The required class is specified in c_class.

• The following criteria interact within one another: XSolarisOvlDepth, XSolarisOvlMinColors, XSolarisOvlMinRed, XSolarisOvlMinGreen, and XSolarisOvlMinBlue. Typically only some subset of these should be specified.

• XSolarisOvlDepth specifies that the depth of the selected visual is to be equal to depth.

• XSolarisOvlMinColors specifies that the selected visual is to have at least minColors number of total displayable colors.

• XSolarisOvlMinRed, XSolarisOvlMinGreen, and XSolarisOvlMinBlue can be used to indicate more specific color requirements for DirectColor or TrueColor visuals. Their corresponding values are specified in minRed, minGreen, and minBlue, respectively. These indicate that the selected visual must have at least the specified number of reds, greens, and/or blues.

• XSolarisOvlMinBitsPerRGB specifies that the selected visual is to have at least minBitsPerRGB of color channel output from colormaps created on that visual.

• XSolarisOvlMinBuffers specifies that the client wants the selected visual to be able to be assigned at least minBuffers number of accelerated MBX image buffers.

• XSolarisOvlUnsharedPixels selects partner visuals whose window pixels don't lie in the same drawing plane groups as the window pixels of the argument visual vid. If a visual uses the same drawing plane group as the argument visual, it is not matched by this criterion.

• XSolarisOvlUnsharedColors selects partner visuals whose window pixel colors can be displayed simultaneously when the overlay/underlay window pair has the colormap focus. If a visual shares the same color LUT pool and that pool has only one color LUT in it as the argument visual, the visual is not matched by this criterion.

If either hardCriteriaMask of a criteria set is to 0, any visual will match that criteria set with a hard match. Likewise, setting the softCriteriaMask of a criteria set to 0, is sufficient to guarantee at least a soft match for that criteria set.