Using Ada Bindings to the X Window System

Abstract : The graphical user interface has been accepted as being one of the most important parts of the user interactive software projects. Until recently, however, the design and implementation of such interfaces in Ada was a long and difficult process. A solution to this problem was found with the introduction of the X Window System in the mid 1980's. These C libraries make it relatively easy to construct sophisticated user interfaces. In the last couple of years, several organizations have developed bindings to, or implementation of, the X Window System software for use in Ada programs. Two of the more significant accomplishments were the bindings developed by the Science Applications International Corporation (SAIC) 1,2 and those developed by the boeing Aerospace Corporation 3. In 1987, SAIC developed Ada bindings to X11R4. Their work was performed under a Software Technology for Adaptable Reliable Systems (STARS) foundation contract, and is therefore in the public domain. Stephen Hyland gives an overview of these bindings in 1. In this paper we present a detailed example of how to use the SAIC and Boeing bindings to interface an Ada program to X. We discuss issues involving SAIC/Boeing binding compatibility, pixmap creation and use, connection with the X-server, creation of several different widgets, and adding appropriate callback procedures. We give a more general description of the issues involved in building Ada/X interfaces.