tools-make/FAQ

GNUstep Frequently Asked Questions with Answers
***********************************************

   Last updated 1 January 2002 Please send corrections to
<gnustep-maintainer@gnu.org>.

GNUstep General Information
===========================

What is GNUstep?
----------------

   GNUstep is the Free Software Foundation's effort to implement NeXT
Software Inc.'s (now Apple Inc.) OpenStep Standard.  The project is not
finished, however some components are useable now.

   The GNUstep project consists of the following sub-projects:

   * GNU Objective C Compiler and Objective C Runtime Library -
     Although not actually a component of GNUstep, GCC and the GNU
     Objective C Runtime Library are integral to GNUstep, since they
     are used to make every GNU Objective C program.

   * GNUstep Base Library - Code for non-graphical objects, such as
     strings, collections, archiving support and distributed objects
     messaging.  (Including functionality similar to OpenStep's
     `FoundationKit'.)

   * GNUstep GUI Library - Code for graphical objects used in making a
     Graphical User Interface (GUI).  This includes buttons, sliders,
     text fields, windows, menus, etc.  (Including functionality
     similar to OpenStep's `AppKit'.)

   * GNUstep DisplayGhostscript Server - A server that draws PostScript
     graphics to the screen, and receives events from the keyboard and
     mouse.  It is based on GNU GhostScript. There is also an DPS
     extension to Xfree*6 that is usable.

   * Various Tools and applications, including GORM, The GNUstep
     interface builder for graphically assembling application
     interfaces, and ProjectCenter, a project manager.


What is the OpenStep standard?
------------------------------

   OpenStep is an Application Programming Interface (API) for creating
applications using the Objective C language.  It was published by NeXT
Computer Inc. in 1994.

   OpenStep consists of three parts: the `FoundationKit', a library of
non-graphical objects; the `AppKit', a library of objects usful in
creating graphical applications; and `Display Postscript', an interface
for drawing to the screen using the PostScript graphics language.

   You can obtain a copy of the OpenStep standard from the GNUstep web
site <http://www.gnustep.org> or it's mirror sites.

What platforms does GNUstep run on?
-----------------------------------

   See the list of supported platforms at
<http://www.gnustep.org/information/machines_toc.html> for information
on what machines GNUstep builds on and what the status of the ports is.
Probably a few days porting to any other Unix system where current
gcc/egcs compilers and gdb debugger work.

Does GNUstep run on Windows?
----------------------------

   The primary targets for GNUstep are free 'Unix' platforms such as
GNU/Linux.

   That being said, the base library should run on Windows-NT,98 with
the Cygwin unix emulation library from Cygnus
(http://sourceware.cygnus.com/cygwin/) or the MinGW libraries.  At
present there are a few problems with networking (Distributed Objects)
support, but the library is believed to work.

   The gui library needs a win32 backend library to work under
Windows-NT.  The backend library is a thin layer that converts the
GNUstep methods to handle drawing of GUI elements to calls to the win32
api.  This is a project looking for a volunteer.

   The application-wrapper used for GNUstep already allows for multiple
binaries to be stored for different systems, so you should be able to
write once, deploy anywhere.

What is GNUstep's position towards KDE and the GNOME project?
-------------------------------------------------------------

   You can use GNUstep with GNOME and/or KDE.  GNUstep displays on top
of X11. You can still do programming in C (since Objective-C is just a
superset of C), and when (if?) GCC gets around to it, you'll be able to
mix C++ and Objective-C code in the SAME file.

   GNUstep, is much more than a window manager or desktop environment.
It frees you to develop cross-platform applications without the work of
developing an OS independent framework from scratch. It gives you lots
of basic functionality, from Font Panels to Unicode strings to
Distributed Objects.

Is the Objective C API for GTK related?
---------------------------------------

   No.  GNUstep applications provide their GUI via the OpenStep API,
which provides fully object-oriented access to GUI manipulation.

   The object-oriented nature of the libraries and language make it
much easier for new users to create their own subclasses rather than
simply using the supplied widgets as in other frameworks.

How about implementing parts of the Application Kit with GTK?
-------------------------------------------------------------

   Yes and No - The GNUstep architecture provides a single,
platform-independent, API for handling all aspects of GUI interaction
(implemented in the gstep-gui library), with a backend architecture
that permits you to have different display models (display postscript,
X-windows, win32, berlin ...) while letting you use the same code for
printing as for displaying. Use of GTK in the frontend gui library
would remove some of those advantages without adding any.

   That being said, a backend library could be implemented using gtk if
anyone wanted to do so.  Since the frontend library handles most of the
work involved in implementing the OpenStep API, the backend is a
relatively thin layer and the advantages of GTK over direct xlib or
win32 calls is likely to be minimal.  If/when GTK is ported to more
systems, a backend written using it could be a valuable asset -
volunteers are, as always, wecome.

Which compiler can I use? Where can I get it?
---------------------------------------------

   Use gcc-2.8.1 or later, from any GNU ftp site or, on some platforms
you must use egcs-1.1.1 or later, from http://egcs.cygnus.com/

Which Foundation Library can I use?
-----------------------------------

   That depends ...

   If you only want to use the database package - gnustep-db, you can
use either the gnustep base library or libFoundation.

   If you want to develop/use GNUstep gui applications, you must use
the gnustep-base library since libFoundation is (13-Feb-2000) missing
much essential functionality.

How do you use the gnustep-make package?
----------------------------------------

   Good question.  Read the tutorials at the GNUstep web site. Also,
use the makefiles in the libraries, tool directories, and test
applications as examples.

How can I get GNUstep?
----------------------

   Get the HOWTO from
<http://www.gnustep.org/resources/documentation/GNUstep-HOWTO> Get the
latest release from <ftp://ftp.gnustep.org>. If you're really
adventurous, get the latest snapshot by anonymous ftp from
<ftp://ftp.gnustep.org:/pub/daily-snapshots>

   Use anonymous CVS to keep up to date - instructions are in the HOWTO.

How do you run GNUstep?
-----------------------

   You are presumably under the misapprehension that GNUstep is some
sort of window manager.

   It isn't.

   GNUstep is a whole load of things - primarily a set of libraries for
developing software.

   At present, it's those libraries, plus various command-line based
support tools and service providing daemons.  In the future, it will be
the libraries, plus the support tools, plus various GUI development
tools, a GUI desktop/workspace application etc.

   At no stage will you ever 'run' GNUstep - you will run applications
and tools and will make use of it's services (though at some point you
may well find packages distributed as 'GNUstep' systems in the way that
you get 'Linux' systems packaged today).

   Current tools are -

     The makefiles package
       To make building GNUstep tools and apps simple.
     The 'openapp' script
       To start up a GUI application from the command line.
     The defaults tools
       To read, create, delete, and modify user defaults from the command
       line.
     The name server
       To permit applications and tools to locate each other and
       communicate.
     The pasteboard server
       To permit cut-and-paste, drag-and-drop, and to let applicationsm
       and tools transparently provide services to each other.
     The distributed notification center
       To permit applications and tools to be notified of arbitrary
       external events.
     The 'make_services' program
       To locate (and cache information about) applications that are
       willing to provide services to other applications.
     The 'set_show_service' program
       A command-line utility to determine what services an application
       should be permitted to offer on it's 'services' menu.

   If you want to see a sample GUI application running you need to build
GNUstep and look at the example applications in the gstep-examples
package.  Build 'Finger' or 'Ink' and start it with 'openapp Finger.app'
or 'openapp Ink.app'

   To look best - use WindowMaker (the currently preferred GNUstep
window manager) as your window manager.

Is there a web site?
--------------------

   See <http://www.gnustep.org/>.

When is GNUstep intended to be available?
-----------------------------------------

   It's usable now. Releases are made about every six months. However,
if you are a serious developer, it's probably best to use the latest
snapshots.  See the GNUstep web site for a release schedule.

What is usable?
---------------

   * gstep-make does pretty much what the makefiles in NeXTstep do.

   * gstep-base (Foundation) stuff should work fine for almost all
     projects.

   * gstep-db is only EOF-1.0 compatible but should work ok.

   * gstep-gui (AppKit) has a lot working but there is still stuff
     missing.

   * DGS (Display Ghostscript) is usable but slow.

Compatibility with OPENSTEP/Cocoa/MacOSX
========================================

Can I run NeXT OPENSTEP or Apple Rhapsody programs on GNUstep?
--------------------------------------------------------------

   You can't run these programs on GNUstep, but if you have the source
code for the programs, you should be able to port them to GNUstep and
compile them. Whether or not you will be able to run them depends on how
complete GNUstep is at the time.

Is it easy to port OPENSTEP and Rhapsody programs to GNUstep?
-------------------------------------------------------------

   It is probably easy for simple programs. There are some portability
tools to make this easier
(<http://www.gnustep.org/resources/source_port.html>), or rewrite the
Makefiles yourself.  You will also have to translate the NIB files (if
there are any) to GNUstep model files using the nib2gmodel program
(from <ftp://ftp.gnustep.org/pub/gnustep/dev-apps>).

Can I transfer archived data from GNUstep to Cocoa?
---------------------------------------------------

   Apple's archiving format is proprietary and not documented, so this
poses a problem for anyone wanting to implement compatibility with it.
However, even if we reverse engineered the format, there are enough
differences between the class and ivar layouts to make this sort of
compatibility difficult. Not to mention the fact that we would
constantly have to keep up with the changes Apple made. Also Apple's
archiving format, as far as we know, would not be compatible between
different machines because of endiness issues, although GNUstep doesn't
have this problem.

   Your best bet is to implement your own archiving format that would
work both with GNUstep and Cocoa. Fortuneatly, you don't have to start
from scratch, since this has been essentially done for you in the
nib2gmodel tool, which has an archiver that works both on GNUstep and
Cocoa. It might be nice to split this off into a separate project to
make it easier for other people to do the same thing.

Does distributed objects work between GNUstep and Cocoa?
--------------------------------------------------------

   See the answer to the previous question (on archive compatibility)
for why this won't work either.

Is there an Interface Builder for GNUstep?
------------------------------------------

   There is an Interface Builder for GNUstep called Gorm, but it is in
alpha release, so it may not work perfectly. You can download it from
the ftp site or via http.  The Project Manager ProjectCenter is also
available.

Can I use my original NIB files?
--------------------------------

   No - NeXT/Apple never documented their nib format, so GNUstep
supports both the 'gmodel' format (which stores information as text
(property-lists) and can therefore be edited 'by hand') and binary
archive format (which can be edited by Gorm).  There IS a conversion
tool called nib2gmodel that can be compiled under OPENSTEP to convert
OPENSTEP nib files to GNUstep gmodel files.

Will code without NIB files work?
---------------------------------

   Well, GNUstep implements the OpenStep API, not the old NeXTstep API
but, Yes - once the gui library is complete, OpenStep or MacOS-X code
should work without translation under GNUstep.

Is GNUstep following Apple's Changes to OpenStep?
-------------------------------------------------

   Yes - gstep-base already contains the documented changes in the
Foundation library.  GNUstep aims to be compatible with both the
OpenStep specification and with MacOS-X It should be easy to write an
application that compiles cleanly under both GNUstep and Yellow Box.

Do we have to have the NeXTstep look and feel?
----------------------------------------------

   Gnustep is aiming for something like the NeXTstep-3.3 look and feel.
This is mostly determined by the gui backend library. In the case of
the two existing backends (xdps and xgps), both are designed to look
like NeXTstep/OPENSTEP.  If someone wants to write a backend with a
different look, they can.  This would only be a few man-months work.

Can one use the hybrid "Objective-C++"
--------------------------------------

   that one could on the NeXT?

   No - at present the GNU compiler (gcc) does not support
"Objective-C++" There are no specific plans to make it do so, but any
volunteers to do it would be welcome.

Is there a plan to support the Java/YellowBox Bindings?
-------------------------------------------------------

   Yes. The GNustep Java library/bridge called JIGS is available now.
JIGS is a free (LGPL) Java Interface for GNUstep; it can automatically
wrap Objective-C libraries based on GNUstep, making them accessible
directly to the Java programmer as if they were Java libraries. As a
side effect, it is also possible to use the whole engine in the reverse
way: JIGS provides a high level API to allow Objective-C programmers to
start java virtual machines inside GNUstep Objective-C code and access
java objects in the java virtual machine transparently, as if they were
objective-C objects.

What if I compile GNUstep under OPENSTEP/MacOS X Server?
--------------------------------------------------------

   No - GNUstep uses the X-windows display postscript extension - the
interface to that is not the same as the interface to the
OPENSTEP/MacOS-X windows server.  While someone could write a backend
library to provide the interface, nobody has bothered to date.

   Also, the GNUstep base library is still being ported to Darwin.

Compiling and Developing
========================

How can I help with GNUstep?
----------------------------

  1. Write/debug library code

  2. Write documentation

  3. Update the TODO list and library headers

  4. Write applications

   Let people know what you are doing.  Break your project up into the
smallest units you can.  Feed back frequent updates to the maintainers.
Ask questions in the discussion mailing list.

   Do remember that any changes beyond a few lines of code (or
documentation) require a disclaimer or copyright assignment to the Free
Software Foundation before they can be incorporated into the project.
Get in touch with the maintainer of the library you are working on
about this.

   Don't start with large-scale reorganisation of anything - instead,
get a general idea in mind of what you want to do, and proceed as much
as possible with incremental changes that don't break anything - that
way you can make those incremental changes available to the rest of the
community at frequent intervals.

   Don't be afraid to give up - there is no shame in finding out that
you have take on too large/complex a project.  It's much better to
'resign' and take on a smaller job than to just stop without telling
anyone.

How do I start writing code?
----------------------------

   There is plenty of unimplemented stuff in the gui library and
backend libraries that volunteers can work on - just browse through the
code and see if it conforms to the documentation.

   Specific tasks are noted in the developers section on the GNUstep
website.

   Once you have coded something, you could always write a testcase and
documentation for it :-)

How do I start writing documentation?
-------------------------------------

   All class documentation is written directly in the source code itself
and translated using the autogsdoc program. See the source code and
documentation for autogsdoc for information on documenting the classes.

   Newcomers could write documentation for individual classes by
comparing the OpenStep specification, the MacOS-X documentation, and
the GNUstep source.  Documentation should clearly note where individual
methods are specific to OpenStep, MacOS-X or are GNustep extensions.

   More experienced people could write documentation on general
programming topics, and tutorials for new users.

   Anyone willing to write documentation, either tutorials for using
GNUstep, or reference documentation for individual classes, should
either write it in gsdoc or as plain ascii text for someone else to
format into gsdoc.

   GNUstep documentation should have copyright assigned to the Free
Software Foundation.

How do I update the task list?
------------------------------

   The task list (<http://www.gnustep.org/developers/tasks.html>) is
supposed to tell people what jobs are waiting to be done.

   One job of major importance that pretty much anyone can do is to
look for jobs to add to the task list.  In the case of methods from the
OpenStep specification or the MacOS-X documentation not being present
in the GNustep libraries, it is also helpful to add the method
prototypes to the library header files.

   Send any changes or additions to <bug-gnustep@gnu.org>.

   A beginner can look through the MacOS-X documentation, the OpenStep
specification and the GNUstep source and contribute TODO items.

   If a class or method is in MacOS-X and OpenStep but is not in
GNUstep - it's a high priority TODO and should at least be added to the
GNUstep headers and a dummy version added to the source with a FIXME
comment.

   If a class or method is in MacOS-X but not OpenStep or GNUstep -
it's a low priority TODO.  It should be added to the GNUstep headers
bracketed in `#ifndef STRICT_OPENSTEP'

   If a class or method is in OpenStep but not in MacOS-X or GNUstep -
it's a low priority TODO.  It should be added to the GNUstep headers
bracketed in `#ifndef STRICT_MACOS_X'

   There are a couple of people working on this already, so it's a good
idea to get in touch with Adam or Richard to coordinate efforts.

How do I start writing tests?
-----------------------------

   You can write testcases - where the libraries fail tests, you could
either fix the problem, or add it to the task list.

   To write testcases, you need to use anonymous CVS to install the
latest GNUstep snapshots you can find. Then checkout the 'tests' module
from CVS.  In the 'tests' directory, you will find a regression testing
framework.  In order to use this you will also need a recent (v 1.3.2
or later) copy of Guile (you can get this from a GNU ftp site) and will
need to hacke checked out, built, and installed the 'guile' package
from the GNUstep CVS repository.

How do I start writing applications?
------------------------------------

   You can either look at the links on the GNUstep website for
applications that have been started, and email their owners to
volunteer to help, or you can start your own project.

How can I help with the GNUstep website?
----------------------------------------

   Talk to Adam Fedor <fedor@gnu.org>, the maintainer.

   The GNUstep website is kept as a CVS module, but the largest portions
of it (the FAQ, the TODO list, and the Documentation) are actually
generated from files in the individual GNUstep packages.

   If you want to update the FAQ or TODO list or documentation  - grab
the latest snapshot of the GNUstep core you can find, update it from
the CVS repository, and work with the contents of the appropriate
documentation directory.

   If you want to work on other parts of the website, you can grab a
copy of the website via anonymous CVS. See
<http://savannah.gnu.org/cvs/?group_id=99> for instructions on how to
do that.

   The main task with the website is to figure out which bits are
out-of-date (or wrong) and update/mark-as-outdated as required.

How do I compile GNUstep on my machine?
---------------------------------------

   Read the file `GNUstep-HOWTO', which comes with the GNUstep
distribution, and also is available separately on the GNUstep web site.

Are there any precompiled packages available?
---------------------------------------------

   Check <http://www.gnustep.org/resources/sources.html> for links to
sites with RPMS, and perhaps in the future, Debian packages.  In some
cases. You can check the debian site for preconfigured GNUstep
packages. Also check the BSD sites for GNUstep ports.

What are these type and size warnings?
--------------------------------------

   These warnings:
     /usr/bin/ld: warning: type and size of dynamic symbol
     `__objc_class_name_NSConstantString' are not defined

   are a common occurence and are due to a mismatch between gcc and ld.
They don't do any harm so they can be safely ignored. Apparently no one
has bothered to fix them yet.

GNU Objective C Compiler and Objective C Runtime Library
========================================================

What is the Objective C Runtime Library?
----------------------------------------

   The Objective C Runtime Library provides C functions and data
structures required to execute an Objective C program.

   The GNU Objective C Runtime Library offers everything NeXT's runtime
does, including Categories, Protocols, `+poseAs:', thread-safety, class
initialization on demand, delayed loading of classes, and
initialization of static instances (such as @""-style string objects).

   It also has several improvements over NeXT's implementation:

   * NeXT's runtime requires an extra function call (objc_msgSend) for
     each message that is sent; (the function looks up the receiving
     instance's implementation of the method).  GNU's implementation is
     faster because it does not use an extra function call.  Instead, it
     inlines a short piece of code that makes two pointer hops into a
     method dispatch table; because the code is inlined, it does not
     incur the overhead of a function call.

   * When running in thread-safe mode, NeXT's runtime must aquire a
     global mutual exclusion lock every time a message is sent; this is
     extremely slow.  GNU's runtime, amazingly, sends messages just as
     fast in thread-safe mode as it does in single-thread mode--the
     code path does not contain even a single extra instruction!  The
     GNU runtime only needs locks when certainly structures are
     written, not read; the structures are written relatively
     infrequently: only at class initialization and when `+poseAs:' is
     called.

   * GNU's runtime provides "selector-types" along with each selector;
     NeXT's does not.  A selector-type is a string that describes the C
     variable types for the method's return and argument values.  Among
     other uses, selector-types is extrememly helpful for fast
     distributed objects implementations, (see GNUstep Base Library
     Section, below).

   * Many of the GNU functions have different names than their
     corresponding NeXT functions; the GNU names conform to the GNU
     coding standards.

   * NeXT's compiler, `cc', is based on an old version of `gcc'.  GNU's
     compiler is, of course, the latest version of `gcc', and therefore
     contains all the latest enhancements.


Does it allow a mixture of Objective C and C++?
-----------------------------------------------

   No.  Unlike NeXT's `cc', GNU GCC does not support source files
containing both Objective C and C++.  Apple seems to be willing to
merge their code back into the main GCC project, but this may take some
convincing of the GCC maintainers due to the large number of changes
necessary. Send email to `discuss-gnustep@gnu.org' if you are
interesting in pushing this issue, so that the efforts of all those
people interested can be coordinated.

   Also, unlike NeXT's `cc', GNU GCC does not support the `extern
"Objective-C"' construct.

Where can I find more information?
----------------------------------

   The FAQ associated with the newsgroup `comp.lang.objective-c'
contains more information about GNU Objective C.

GNUstep Base Library
====================

What is the GNUstep Base Library?
---------------------------------

   The GNUstep Base Library is a library of general-purpose,
non-graphical Objective C objects.  For example, it includes classes
for strings, object collections, byte streams, typed coders,
invocations, notifications, notification dispatchers, moments in time,
network ports, remote object messaging support (distributed objects),
event loops, and random number generators.

   It provides functionality that aims to implement the non-graphical
portion of the OpenStep standard (the Foundation library).

What is its current state of development?
-----------------------------------------

   GNUstep base is currently stable and implements probably 99% of the
functionality of the OpenStep classes and most all of the new Carbon
classes.  Normal work can already be done using the library since the
missing 1 percent are the least-often-used features or are simply not
up to date with the latest Carbon spec.

What are the features of GNU Distributed Objects?
-------------------------------------------------

   GNU Distributed Objects has many of the features of other distributed
objects implementations, but, since it is free software, it can be
ported to platforms for which other distributed objects implementations
are not available.

   [NOTE: The GNU distributed object facilities have the same
ease-of-use as NeXT's; be warned, however, that they are not compatible
with each other.  They have different class heirarchies, different
instance variables, different method names, different implementation
strategies and different network message formats.  You cannot
communicate with a NeXT NSConnection using a GNU Connection.

   Here are some differences between GNU distributed objects and NeXT's
distributed objects: NeXT NSDistantObject asks it's remote target for
the method encoding types and caches the results; GNU NSDistantObject
gets the types directly from the local GNU "typed selector" mechanism
if the information is known locally and only queries the remote target
or caching encoding types when using a method that is not known to the
local process.  The NSProxy for the remote root object always has name 0
and, once set, you cannot change the root object of a NSConnection; the
GNU Proxy for the remote root object has a target address value just
like all other Proxy's, and you can change the root object as many
times as you like. ].

GNUstep GUI Library
===================

What is the GUI Library?
------------------------

   The GNUstep GUI Library is a library of objects useful for writing
graphical applications.  For example, it includes classes for drawing
and manipulating graphics objects on the screen: windows, menus,
buttons, sliders, text fields, and events.  There are also many
peripheral classes that offer operating-system-independent interfaces to
images, cursors, colors, fonts, pasteboards, printing.  There are also
workspace support classes such as data links, open/save panels,
context-dependent help, spell checking.

   It provides functionality that aims to implement the `AppKit'
portion of the OpenStep standard.  However the implementation has been
written to take advantage of GNUstep enhancements wherever possible.

Explain the organization of the front- and back-ends
----------------------------------------------------

   The GNUstep GUI Library is divided into a front- and back-end.  The
front-end contains the majority of implementation, but leaves out the
low-level drawing and event code.  A back-end can override whatever
methods necessary in order to implement low-level drawing event
receiving.  Different back-ends will make GNUstep available on various
platforms.  The default GNU back-end will run on top of X Windows and
the DisplayGhostScript Server.  Other back-ends could allow GNUstep to
run on OpenGL, OS/2, and WIN32 graphics/event platforms.  Much work
will be saved by this clean separation between front- and back-end,
because it allows different platforms to share the large amount of
front-end code.

What is the current state of development of the front-end?
----------------------------------------------------------

   Many of the classes are well implemented, if not thouroughly tested.
See the GNUstep web sites and read status information contained in the
distribution for the most up-to-date information.

What is the current state of development of the X/DPS back-end?
---------------------------------------------------------------

   It works, but is slow and buggy. A lot of work could be done.

GNUstep DisplayGhostScript Server
=================================

What is the Display Ghostscript Server?
---------------------------------------

   It is a free implementation of a Display PostScript server based on
the GNU Ghostscript program developed by Aladdin Enterprises and now
owned by artofcode LLC.

What is its current state of development?
-----------------------------------------

   GNU contracted with Aladdin Enterprises to add some key features to
GNU Ghostscript so it could be used as a DPS server. This work has
mostly been done, although Aladdin did not completely finish the work
that they were contracted for.  (Because the work took longer than
specified and was not completed, Aladdin agreed to waive approximately
$10,000 in promised fees for the work that was actually done and
delivered.)  DGS works fairly well with a single context.  Alpha
channel and compositing currently doesn't work.

What is the relationship between the Display Ghostscript Server and X Windows?
------------------------------------------------------------------------------

   Display Ghostscript runs on top of X Windows.

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