Display PostScript

NeXT Computer Inc. designed Display PostScript for their series of Unix-based personal computers starting around 1987. Display PostScript was developed with (or given to) Adobe, and made an official Adobe product with its own standards documents and licensing requirements.

Display PostScript is a fairly limited expansion on the original PostScript language. The main addition is the ability to map coordinate systems and update the display "on the fly", which is needed in an interactive enviornment. Normal PostScript only updates when the PS code calls showPage, typically at the end of a document. It also introduced the concept of a "pswrap", which allowed developers to wrap PostScript code into a C language function which could then be called from an application.

DPS did not, however, add a windowing system. That was left to the implementation to provide, and DPS was meant to be used in conjunction with an existing windowing engine. This was often the X Window System, and in this form Display PostScript was later adopted by companies such as IBM and SGI for their workstations.

On the NeXT system a completely new windowing engine was written, to take full advantage of their object-based operating system. The windowing system itself used PostScript to draw items like titlebars and scrollers. This, in turn, made extensive use of pswraps, which were in turn wrapped in objects and presented to the programmer in object form.