The X Public Access (XPA) mechanism is the heart of SAOtng. XPA allows an Xt program to define named public access points through which data and commands can be exchanged with external programs. The following short papers give an overview of the XPA and its use in SAOtng:
Nearly all of SAOtng's menu functions also are defined to be XPA public access points. As a result, SAOtng can be controlled directly through its menu-based GUI or externally through the xpaset and xpaget programs. For example, the scaling algorithm can be changed and the current scale value is queried:
csh> xpaget SAOtng scale linear csh> echo "scale log" | xpaset SAOtng csh> xpaget SAOtng scale log
The imset and imget programs are provided as a convenience. These programs assume that the target is SAOtng and allow a more natural command structure:
csh> imget scale linear csh> imset scale log csh> imget scale log
See also A List of SAOtng Public Access Points.