This interview was originally published in Linux Magazine France n47, Feb. 2003
Remarks ganthered by Nicolas Roard and Fabien Vallon, translation : Gerold Rupprecht

Core GNUstep developers interview

What is the role of the GNUstep project, and on what are you working on at the moment?

Richard Frith-Macdonald: Main developer for the base library, I've also done a lot of work on other parts of the GNUstep system ... infrastructure (library) programming rather than applications (with the exception of Gorm). I am mostly working on software maintenance, improving documentation, and optimising the base library for performance (it already compares well with the Apple Foundation library).

Alexander Malmberg: I'm just another core developer: I fix bugs and implement missing things all over the project. My major isolated contributions are my work on the freetype/libart based backend, back-art, and the implementation of the text system, which is what I'm currently working on. In the GNUstep "project" at large, I've also written several applications and tools, most importantly Terminal (a terminal emulator) [1] and LuserNET (a newsreader) [2].

Ludovic Marcotte: I am on of the developers on the project mainly on the application [3] (which is part of the GNUstep project). I also work on other application such as Affiche and PlopFolio as well as on an application framework allowing the complete management of email: Pantomime. Presently, I am finalising the next version and Pantomime. This version will have several functional improvements , its stability as well as overal application performance.

Why are you interested in Objective-C and the GNUstep platform?

Richard Frith-Macdonald: This was largely a move away from C++, which was much too inflexible for building large real-life (ie constantly changing specifications) projects. ObjC allowed me to build software much more rapidly than C++, and I liked NeXTstep, but couldn't afford to roll out NeXTstep on customer systems, so GNustep was an obvious choice. I particularly liked (and like) the simplicity and power of the distributed objects system ... it let me easily develop highly distributed systems sharing load over many machines.

Alexander Malmberg: Because objective-c is a wonderful language, and GNUstep is a wonderful system built on it. :) I had heard good things about NeXTSTEP and OPENSTEP from many sources for a long time, and I knew that GNUstep was a free implementation of it. Eventually I got around to having a closer look at it, and I really liked what I saw.

What is the difference between the GNUstep approach and that of KDE or GNOME?

Richard Frith-Macdonald: GNUstep has the advantage that it is based on the OpenStep API ... a design which was produced, implemented, and polished by some highly talented people at NeXT, then cleaned up in the light of experience and with a fresh viewpoint provided by the people at Sun. As a result, we have a strongly object-oriented and much more consistent API which is both proven and combines power/flexibility with simplicity. It is therefore much easier to learn to use effectively.

What is the current state of GNUstep?

Richard Frith-Macdonald: It has something for everyone -
Rock-solid 24*7 backend server type applications with distributed messaging. I've been using the make package, base library, and java bridge (jigs) for this purpose for some years.
Generally usable gui applications, with inter-application services and other cool features.
Cutting edge features like object oriented database access and automated gui layout features in advanced development.

Alexander Malmberg: Most things work. There are still many issues that still need to be sorted out, and there are many minor bugs and annoyances. It's good enough to use and develop for, but if you do, you should be prepared to fix bugs in the core libraries as you find them.

What are the specifics of the GNUstep graphic rendering?

Alexander Malmberg: GNUstep's rendering system is very similar to OPENSTEP's; both use the Display PostScript rendering model, and they have the same api to it. This api is used by the GNUstep's AppKit implementation and applications both when displaying on the screen and when printing. All actual rendering is done by a backend. There are several backends available, with varying capabilities and requirements, and implementing. For example, there is backend for X using xlib, or for X using the X server's native DPS support (a rare thing), or for Win32. back-art implements large parts of the DPS and provides fast and pretty rendering to buffers in general; it can be used with great success when running X locally. There has also been experimental work on backends based on OpenGL and DirectFB.

Alex, what makes up the text system that you are working on?

Alexander Malmberg: To save developers from having to reinvent the wheel, GNUstep has a very powerful and extensible text system. Behind each visible text view is a network of supporting objects.
At the bottom, there's a text storage object that stores Unicode text and attributes (like font and color).
Above it is a "layout manager". It stores glyphs generated from the Unicode text and layout information for the glyphs. Glyphs are laid out in text containers. Normally, there's only one infinitely large, rectangular container that the user scrolls around in, but multi-page or multi-column layouts can be done by using several small containers. By changing the shapes of the containers, text can be made to flow around eg. pictures.
The actual layout of glyphs is done by a "typesetter". The typesetter interprets the attributes of the text, looks at the text containers, and determines where glyphs should be placed. The current default typesetter does standard left-to-right layout (including things like ligatures and automatic kerning), but by substituting a different typesetter, vertical layouts and other advanced script features can be handled
Normally, though, all the complexity is hidden from the developer: creating a word processor is (almost :) ) as easy as putting a text view in a window.

Ludovic,, Affiche and PlopFolio run both on Cocoa/MacOS X and GNUstep, what are your recommendations for a successful port?

Ludovic Marcotte: Firstly, you must understand that GNUstep is a project that is now following the trail of Apple with Cocoa. Because of this, certain classes present in Cocoa do not actually have a GNUstep implementation (such as NSToolbar, NSDrawer classes as well as all the services provided by CoreFoundation). A developer wanting to port a Mac OS X application to GNUstep must note these particularities. You can compensate for these problems by using conditional compilation or even implementing the missing classes and contributing them to the GNUstep project! In other respects, the develop must in general redo the user interfaces if he wants to port his GNUstep application to Osx (or vise-versa). Under GNUstep, GORM is the tool of choice for building user interfaces while under OSX, you need to use Interface Builder. The Rennaissance project may in the future make this difference unnecessary.

Pantomime is already being used in certain other software (of which certain proprietary ones). Do you think that when GNUstep/Windows is operational, GNUstep will become a favorite development platform for the multi-platform software publishers (at the same level as Java for example)?

Ludovic Marcotte: GNUstep will definitely be an alternative to consider for multi-platform software. Althought Qt and Java already allow complex application development running under Windows, Mac OS X and Linux (or other variants of UNIX) GNUstep has the advantage of the Objective-C language as well as a light weight and efficient application framework (OpenStep).

Richard, where are we with the GNUstep for Windows port? And the bridges to the other languages such as Java/Ruby?

Richard Frith-Macdonald: underway. base and make compile and work; as for the AppKit, it is really alpha. As for the bridges to other languages, Java works really well. The Ruby bridge is good as well. Python is slightly broken actually and could need some volunteers. (The bridge towards Python also works on the MacOS X platform). Guile 1.4 also works, but could need an update to the 1.6 version of guile. There also exists a scripting framework [4] with which you can add the languages you want.

Apple is now using an OpenStep implementation (which GNUstep is) as their main system, what are the relations between the two platforms?

Richard Frith-Macdonald: GNUstep and Apple/Cocoa share the OpenStep roots. GNUstep also implements many Apple additions (though not those specific to some apple technologies) but maintains the NeXTstep look. For many purposes the two systems are source-code compatible.

Alexander Malmberg: As far as I can tell, Apple is simply ignoring GNUstep. The GNUstep community is somewhat divided, but for the most part, GNUstep tries to be compatible with both OPENSTEP and sane Apple extensions.

What is the future of GNUstep?

Alexander Malmberg: The first step is to finish the core libraries (stable interfaces and behavior and complete implementations). Once that's done, we'll have a wonderful set of libraries we can build eg. applications from. What happens then is a bit outside GNUstep's scope, but there are people working on building larger things of it, eg. LinuxSTEP [5].

Thank you Richard, Alexander and Ludovic for having responded to our questions, as well as Vincent Ricard for reviewing and Gerold Rupprecht for the translation !

[1] Terminal : a terminal emulator
[2] LuserNET : a newsreader
[3] GNUMail : a mail application
[4] StepTalk : a scripting framework
[5] LinuxSTEP