2002.05_Brave Gnu World-the Monthly Gnu Column.pdf

COMMUNITY

BRAVE GNU

The monthly GNU Column

WORLD

Welcome to another

issue of Georg CF

Greve’s Brave GNU

World with a mixture

of projects that

should provide some

inspiration for most

readers. This month

will also begin by

introducing some Free

Software games

Trophy

Andrew Mustun began developing Trophy in March

2000 in order to fill the hole that quitting his

computer science studies had left. Trophy is a car-

racing game in 2D top-view, in which it’s not only

passing the finish line first which matters. More

specifically, it is also about passing the finish line at

all, since, in true James Bond style, the cars are

armed and more than willing to make use of their

gadgets.

Thanks to solid graphics and sound, Trophy is

already a fairly complete game that should allow

friends of action-heavy fun to enjoy themselves,

although a powerful computer is recommended for

smooth scrolling.

Trophy was written in C++ and Andrew releases it

under the GNU General Public License. Its biggest

weakness is probably the lack of a network play

option. Andrew plans to take care of this once he

finds time for it again, since right now his newly

taken up studies keep him quite busy.

It should be noted that whilst preparing this article,

Andrew did emphasise that he was a peace-loving

individual who disapproves of guns in general and

who also considers cars to be dangerous enough

already without heavy weaponry; although as he still

lacks a driving license at 25, he couldn’t drive a real

car anyway.

That shouldn’t take the fun out of wasting an

Cornering in Trophy

entertaining afternoon with Trophy, though. If you

seek creative relaxation through designing more tracks

with GIMP, that’s not a problem. The instructions on

how to do so are on the Trophy homepage.

Should the network option be missed overly much,

interested developers are of course welcome to

implement it themselves. Andrew would definitely

appreciate help in this direction.

Adonthell

The Adonthell project is busy creating a Free 2D role

playing game similar to those on the early consoles

like the SNES, although it is intended to have a much

higher degree of freedom.

Many games consist of two connected parts

where each part can be understood individually. The

importance of content like story, graphics, music

and so on is immediately obvious. The technical

component, which does the actual interfacing with

the player, for instance, is commonly referred to as

the “engine”. Usable analogies seem to be the

relationship between programs and operating

system or scores and musical instruments. This

separation allows games to be written in an abstract

form with language and possibilities determined by

the engine.

The Adonthell project not only develops a game

with a fixed story, it also develops an engine for role

playing games along with stories that are being

Choosing tracks in Trophy

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Bathtime in Adonthell

World questionnaire, said the next step is to rewrite

big parts of the code based on experience gathered.

The team is also still looking for people willing to

help with porting the project to other platforms. The

game is known to run on GNU/Linux, FreeBSD,

OpenBSD and BeOS, but in the long term, it is also

planned to support proprietary operating systems in

order to give their users a first taste of freedom.

Internally development is moving towards a more

client/server based architecture to allow networked

playing. Even though it isn’t planned to support very

large numbers of players, Adonthell should eventually

be capable of allowing a medium number of players

to interact in a persistent world.

Since its first steps in 1999, Adonthell has come a fair

way already and further development provides hope for

more. Those with the right skills who are too impatient

to wait are encouraged to help the process along. The

Adonthell team welcomes all kind of support. All others

can already spend one or two afternoons with “Waste’s

Edge”, the first playable release.

interpreted by this engine. It is planned that all

releases will not only contain code fragments but also

complete little games.

Taking the usual fluctuations into account, the

permanent team of Adonthell are Kai Sterker,

Alexandre Courbot, James Nash, Benjamin Walther-

Franks, Joel Vennin, Joseph Toscano and Mike

Nieforth. Only three of these are programmers, the

others are musicians, graphic artists or authors.

Thanks to this combination and the fact that all

members insist on meeting in person once a year, the

game has a professional feel to it and gives a good

example of lively cooperation over the Internet.

The code and graphics of Adonthell are released

under the GNU General Public License. The

programming language used for the engine is C++.

For game control, expansions and in-game scripting,

the Python interpreter was embedded into the

engine. This makes it possible to write games for the

Adonthell engine without ever touching C++. For

music, OGG Vorbis is being used.

One of the priorities was to be able to package

engine and games separately. You only need to install

the engine and with some help of tools like map and

dialogue editors, as well as a little Python, it is

possible to create a complete game. To make this

even more interesting, the Adonthell group also

works on a complete world with its own history,

customs and peculiarities.

Alexandre Courbot, who answered the Brave GNU

XBindKeys

Philippe Brochard wrote the program XBindKeys, which

makes it possible to assign shell commands to keys

under X11. This way frequently used programs like the

mailer, browser or xterm can be launched by a single

key combination without having to take a detour via

the menu. Once you get used to being able to do

certain things without having to take the hands off the

keyboard, you won’t want to miss this capability.

Some window managers support keybindings

natively, but you’ll frequently find that not all of the

available keys are freely assignable – like special keys

only present on some keyboards. Philippe himself

uses XBindKeys to bring up a shutdown menu when

pressing the “power” key that his keyboard has.

Everyone who tries out new window managers or

Unhelpful help in Adonthell

Config file for XBindKeys

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uses different window managers from time to time

knows the problems associated with teaching the new

window manager your favourite key combinations.

XBindKeys solves both problems, and in combination

with the mini-program MoveMouse, also written by

Philippe, it can even be used to bring the mouse to

previously specified positions with a single key press.

XBindKeys and MoveMouse were both written in C

and are available under the GNU General Public

License, as Philippe feels them to be his contribution

to the GNU System. The configuration of XBindKeys

is done by directly editing the easily understood plain

ASCII configuration file, or by using the GTK front-

end XBindKeys-Config, written by Laurent Vuibert.

As a side note it should be said that one should

make sure XBindKeys gets started before the

window manager; this ensures key presses reach

XBindKeys instead of being intercepted by the

window manager.

There are no plans for further development since

XBindKeys is stable and Philippe believes it should

remain small and useful. This clearly sets a good

example in the fight against the spread of “featureism.”

hand is to design a system in a way that necessary

usage is possible, while abuse becomes impossible.

Since the conception of such systems is done by

humans there is always a significant potential for

error. Access Road by Patrick Thazard tries to model

the complex environment of information systems and

visualise it for the administrator. This does not increase

security in itself, but it offers help in finding security

problems that may have gone unnoticed otherwise.

Patrick Thazard himself has been working as a

computer security consultant since 1987 and wrote

Access Road in Java under the GNU General Public

License. The documentation is released under the

GNU Free Documentation License.

At the moment Access Road supports GNU/Linux-

like systems, simple routers and Solaris-like systems.

Even though no data update has been made before

the last release, Patrick is convinced it will already

provide a very useful structure for other developers.

Further plans including adding the interaction

between GNU/Linux and Apache and then adding the

interactions between operating system and the

employed database management system. In the long-

term expansions for modelling systems like CORBA or

Windows 2000/XP should complete the system.

Until then there is still quite a bit of work to do

and Patrick is looking for other developers willing to

support his work. Even if the approach of graphical

modelling in general does have some potential

weaknesses, this project seems to be quite fascinating

and allows exploration in new ways.

Access Road

The area of IT security is without question complex

but also important. Awareness of the possibility of

bugs in programs is reasonably good by now, but it is

also possible to create security problems by combining

programs that are working and “bug free.”

Complex environments and tasks sometimes

require pretty complex and obscure information

systems. Without access limitations, data could be

abused or modified secretly. The problem of this

becomes immediately apparent when thinking about

computer-based hospitals, for instance. The opposite,

a complete limitation of all access, is also not a good

idea since it makes all work impossible. So the task at

GNU Cons

GNU Cons offers an alternative to one of the senior

programs, GNU Make. Anyone who has ever

downloaded software as source code, or recompiled

the Linux kernel, has already used GNU Make simply

by entering the command make .

Make was written in a time when it was still

normal to compile programs by hand or with bash

shell scripts and at the time it was a big step

forward. If you’ve ever tried writing a makefile

yourself, you will most certainly have found the

syntax to be pretty hard to understand. This is why

most developers copy working makefiles from other

projects to modify them for their current purpose,

or have makefiles automatically generated by

programs like GNU Automake. On top of this,

make tries to detect modifications by the time of

their last modification only, which is problematic

and fails for sure when trying to recompile with

new compiler options.

The name GNU Cons was chosen because with its

help, programs can be “Cons-tructed” and its goal is

to do the jobs done by make the way they should be

done. A very central component for this is a good

mechanism to detect whether files have been

modified. As a result, GNU Cons does not only look at

Controling access

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COMMUNITY

access times, but also works with MD5 file signatures,

allowing a very good means of identification.

A good example of these capabilities is the

behaviour of GNU Cons in the following scenario: the

program “test” consists of the object files “test1.o”,

“test2.o” and “test3.o”. After the first compilation

of the program, the object file “test2.o” is

damaged/corrupted deliberately. The next call of GNU

Cons will rebuild “test2.o”. This will not re-link the

program “test” again, since GNU Cons realised that

the generated version of “test2.o” is identical to the

one previously linked-in.

Should GNU Cons be called with different

computer options, all parts are recompiled and linked,

since not only the results but also the parameters used

to create them are part of the comparison.

GNU Cons was written in Perl by Bob Sidebotham,

who has since retired from working on it. Rajesh

Vaidheeswarran and Steven Knight took over as

maintainers of the stable (Rajesh) and development

(Steven) versions. Being part of the GNU Project, GNU

Cons is released under the GNU General Public License.

Thanks to the use of Perl, GNU Cons runs on both

Windows and Unix-derivates and its configuration

files, the equivalent of the commonly used makefiles,

allow the use of very dynamic and complex

expressions to customise a program to a certain

system as much as possible.

GNU Cons is fully usable although it is rather C/C++

heavy. Other programming languages can be accessed

with the Cons::Plus module by Johan Holmberg. Also

configuration files are of course rather Perl-heavy,

which is not exactly a plus for many people.

At the end of this feature I would like to express

my thanks to the GNU Cons team for coming up

with extremely verbose answers to the standard Brave

GNU World questions.

Rajesh Vaidheeswarran and Erich Waelde

provided huge amounts of information with many

examples, which was very interesting for me even if

I was only able to put small parts of it into the

issue. I can only hope some of the most important

advantages got across well enough to give

interested developers an idea of why they ought to

give Cons a try.

modifications and resolving dependencies, but its

configuration files are based on Python. Also SCons

already supports parallel compilation with the

ability to specify the number of threads by a

command line option.

SCons is still a fairly young project – the first alpha

was released on December 13 2001 – which is why

releases are still happening at very short intervals,

often containing additional functions. So even

though the project has been working with a strong

regressive test-infrastructure to maintain backwards-

compatibility and quality since day one, one may still

experience roughness in everyday use.

The list of planned expansions is still rather long

and contains not only good support for Java, C# and

Fortran, but also the ability to generate

documentation in several formats (PDF, PostScript,

TeX and more) and archival.

SCons is being released under an X11-type of

license, which is known not to protect the freedoms.

It is possible that the GPL would have been the better

choice for the long-term perspective, but SCons

clearly qualifies as Free Software and taking a look at

it or participating is clearly a good idea.

Finish

Alright, so much for the Brave GNU World for this

month. For the next issue I already have one project

stowed up that I’m already looking forward to

introducing, since it has my life much easier and I

hope it’ll do the same for you.

Until then I wish you all a good time and please don’t

hold back on suggestions, ideas, comments, feedback

and project introductions; preferrably by email.

Info

Send ideas, comments and

column@brave-gnu-world.org

questions to Brave GNU World

Homepage of the GNU Project http://www.gnu.org

Homepage of Georg’s Brave GNU World http://brave-gnu-world.org

“We run GNU” initiative

http://www.gnu.org/brave-gnu-

world/rungnu/rungnu.en.html

Trophy homepage

http://trophy.sourceforge.net

Adonthell homepage

http://adonthell.linuxgames.com

OGG Vorbis homepage

http://www.xiph.org/ogg/vorbis

SCons

The obvious similarities in name between GNU Cons

and SCons are not coincidental. The design of SCons

is largely based on GNU Cons and was written in

August 2000 by Steven Knight, maintainer of the

GNU Cons development version, for the Software

Carpentry competition.

After being a maintainer of Cons for some time

already, he pursued the goal of combining the ideas

of Cons with the power of Python for the

competition. SCons is based on this work. Like

Cons, it provides superior capabilities for detecting

Join Adonthell

http://adonthell.linuxgames.com/

development/join.shtml

Xbindkeys homepage

http://hocwp.free.fr/xbindkeys/

xbindkeys.html

MoveMouse homepage

http://hocwp.free.fr/movemouse.html

Xbindkeys-Config homepage

http://www.netchampagne.com/

xbindkeys_config

Access Road homepage

http://accessroad.sourceforge.net

GNU Cons homepage

http://www.gnu.org/software/cons

GNU Make homepage

http://www.gnu.org/software/make

SCons homepage

http://www.scons.org

Issue 20 • 2002

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