Display PostScript

Display PostScript was developed by Adobe Systems in the mid-1980s as an extension of the PostScript page description language, which had been designed for printing. The goal was to bring the same imaging model to interactive displays, allowing screen rendering to match printed output precisely. The system was first demonstrated in 1987 and became a cornerstone of the NeXT computer, launched in 1988, where it handled all on-screen drawing. Adobe also licensed DPS to other vendors, including Sun Microsystems and Silicon Graphics, for use in their Unix workstations. The implementation included a PostScript interpreter that ran as a separate process, communicating with applications via a client-server protocol, which allowed multiple programs to share the display server.

Display PostScript operates as a client-server system: applications send PostScript code to a server process that interprets and renders it to the screen. This design provided a consistent imaging model, including anti-aliased text, arbitrary rotations, and transparency, which were advanced for the time. The server managed a single display, and clients used the PostScript language to define windows, draw graphics, and handle input events. One notable feature was the ability to use the same PostScript code for both screen and printer, ensuring WYSIWYG (What You See Is What You Get) output. However, the architecture was resource-intensive, requiring significant memory and CPU, which limited its adoption on lower-end hardware.¹ The system also included a set of extensions for interactive features, such as compositing and window management, which were not part of the standard PostScript language.

Display PostScript was most prominently used in NeXT computers, where it was integrated into the NeXTSTEP operating system, providing a rich graphical user interface. It was also adopted by Sun Microsystems for its NeWS (Network extensible Window System) and later for its Solaris operating system, and by Silicon Graphics for its IRIX systems. Despite its technical sophistication, DPS faced competition from the X Window System, which was more widely adopted in the Unix world and was less resource-heavy. By the mid-1990s, the rise of OpenGL and the increasing power of graphics hardware led to a shift toward simpler, more direct rendering APIs. Adobe discontinued Display PostScript in the late 1990s, and NeXT was acquired by Apple in 1997, leading to the development of macOS, which used a different graphics architecture.² The last major release of DPS was in 1995, and it was officially deprecated by Adobe in 1998.

Display PostScript had several niche features and historical footnotes. For instance, it supported a form of display caching that allowed complex graphics to be stored and reused, improving performance. It also included a mechanism for handling multiple windows with overlapping transparency, which was unusual at the time. A lesser-known fact is that DPS was used in the development of the first web browser for NeXT, which later influenced the creation of Safari. Additionally, Adobe's DPS implementation included a debugger and a set of development tools that were ahead of their time. The system also had a variant called "Display PostScript for Windows" that was briefly available but never gained traction. Despite its decline, DPS influenced later graphics systems, such as the PDF rendering model and Apple's Quartz, which adopted similar imaging concepts.³ Some open-source projects, like Ghostscript, have implemented PostScript interpreters that can be used for display purposes, keeping the spirit alive.

PostScript

A page description language developed by Adobe Systems for printing, which DPS extends for display.

NeXT

A computer company founded by Steve Jobs that used Display PostScript in its operating system.

NeWS

Network extensible Window System, a windowing system by Sun Microsystems that used PostScript-like code.