Liquid War 6, a unique multiplayer wargame.
Liquid War 6 is a unique multiplayer wargame. Your army is a blob of liquid and you have to try and eat your opponents. Rules are very simple yet original, they have been invented by Thomas Colcombet. It is possible to play alone against the computer but the game is really designed to be played with friends, on a single computer, on a LAN, or on Internet.
An older version: Liquid War 5, is available, but is not part of the GNU Project. Only Liquid War 6 is part of the GNU Project, it is a complete rewrite.
Liquid War 6 can be found on http://download.savannah.gnu.org/releases/liquidwar6/.
However, it is still in alpha stage, so it is not playable yet.
These files might also be mirrored, the list of all the availables downloads is accessible on http://www.ufoot.org/liquidwar/v6/download.
Check out the MD5 checksums and GnuPG signatures to verify the integrity and authenticity of the files you download.
There is no CVS repository for Liquid War 6. Instead, a GNU Arch repository is used to follow the different versions. Read the GNU Arch tutorial to learn how Arch works. Note that there are many other source control managers available, some of which provide functionnalities similar to GNU Arch / tla. GNU Arch has been chosen for Liquid War 6 because:
The repository for Liquid War 6 is accessible on http://arch.sv.gnu.org/archives/liquidwar6. This is a read-only access, but with the distributed nature of GNU Arch, it still allows you to keep track of your own changes, and submit patches. Accessing it in read/write mode with sftp requires a Savannah account and special rights on the Liquid War 6 project.
Here are typicall commands one can use to get Liquid War 6 source from the GNU Arch repository:
tla register-archive http://arch.sv.gnu.org/archives/liquidwar6
tla get -A liquidwar6@sv.gnu.org liquidwar6--alpha
All the patches in the archive are signed with GnuPG, so you can check their authenticity with my public key.
You might need to edit your $HOME/.arch-params/signing/=default.check
file and put the following text in it:
tla-gpg-check gpg_command="gpg --verify-files -"
Before installing Liquid War 6, you'll need to install the following:
Once all these libraries are installed, use the standard sequence:
./configure
make
make install
Liquid War 6 makes a heavy use of Automake and Autoconf.
Liquid War 6 requires Mesa, a 3-D library which offers a high level API similar to OpenGL. While Liquid War 6 will compile and run with theorically any Mesa configuration, it might not run fast enough with software rendering only. The frame rate will probably be well below 10 fps, which is not acceptable.
The reason for it being so slow is that the OpenGL API was not really designed for software rendering. It is possible to achieve better performance in 2-D and 3-D graphics in software mode, but not using a high-level API like OpenGL. You need to get your hands in the dirt. On the other side, using Mesa is very comfortable, and when it is configured to use the 3-D features of the hardware, it runs faster than any pure software solution.
Therefore Liquid War 6 requires some sort of hardware acceleration. And it will probably do for some time. The reason for using a 3-D library to provide acceleration is that fundamentaly, most recent hardware provide acceleration functions through their 3-D interfaces, and barely anything is done on the pure 2-D side.
The good news is that while Liquid War 6 requires acceleration, it does not require any fast, recent or expensive video card. It can reasonnably be run on video cards which date from the last century. If not from the last millenium.
It is important, if you want to run Liquid War 6 in the best conditions, to have a hardware which provides acceleration, and for which a free (as in speech) driver is available. As GNU/Linux is the platform Liquid War 6 is being developped on, it is also the platform it is being designed for.
In a general manner, knowing which hardware devices support GNU/Linux is important not only for practical reasons—you want your hardware to work with the software that you want to use—but also for ethical and political reasons. You can help the free software movement by purchasing hardware from manufacturers who support our goals and not purchasing from those who don't.
See the list of hardware devices that support GNU/Linux for more informations.
Keep in mind that owning a hardware which has no driver for it will make Liquid War 6 and possibly any 3-D game simply unplayable.
The following list describes some hardware configurations which are capable of running Liquid War 6 in correct conditions. This list obviously does not pretend to be perfect or exhaustive. If you know any other hardware capable of sufficient 3-D acceleration (fast enough to run Liquid War 6) with a free (as in speech) driver, please inform the maintainer.
This card is fully supported under GNU/Linux.
You need to load the `mga' driver into the Linux kernel, and the XFree86 configuration file should contain a section like:
Section "Device"
Identifier "G450"
Driver "mga"
Option "AGPMode" "2"
VideoRam 32768
EndSection
This card is supported under GNU/Linux. It is typically shipped with notebooks. Make sure to use the free (as in speech) driver. It exists and works.
Note that the ATI Radeon 9200 is the latest ATI card to be fully supported by a free driver. There is an effort to develop a free driver for recent ATI cards, but this is done through reverse engineering, for ATI do not give the specs of these recent cards. It is therefore extremely hard to write drivers for this hardware.
You need to load the `radeon' driver into the Linux kernel, and the XFree86 configuration file should contain a section like:
Section "Device"
Identifier "ATI9000"
Driver "ati"
EndSection
The main discussion list is <help-liquidwar6@gnu.org>, and is used to discuss all aspects of Liquid War 6, including installation, development, game strategies, and whatever subject players and hackers might want to talk about, provided it is Liquid War 6 related.
To subscribe to it, please send an empty mail with a Subject: header line of just "subscribe" to the -request list, that is
<help-liquidwar6-request@gnu.org>.
You can also subscribe to the list and view its archives using the Mailman web interface for liquidwar6-help.
Announcements about LiquidWar 6 are made on <info-liquidwar6@gnu.org>. Subscribe to it to be informed of major releases, and other significant news.
To subscribe to it, please send an empty mail with a Subject: header line of just "subscribe" to the -request list, that is
<info-liquidwar6-request@gnu.org>.
You can also subscribe to the list and view its archives using the Mailman web interface for liquidwar6-info.
Please also consider reading the latest news on Savannah.
There is also a special list used for reporting bugs, <bug-liquidwar6@gnu.org>. Please try and describe the bug as precisely as possible. The more accurate the description, the more chances it will get to be fixed.
It is also possible, and also more convenient, to directly report bugs on Savannah.
Liquid War 6 uses the services provided by Savannah.
Starting from http://savannah.gnu.org/projects/liquidwar6/ you'll get links to various informations related to Liquid War 6 development.
The list of Liquid War 6 bugs is accessible on: http://savannah.gnu.org/bugs/?group=liquidwar6. It should be updated on a regular basis and reflect the current status of outstanding bugs.
While this Savannah interface allows you to view the list of existing bugs, it also allows you to report new bugs. Of course bugs can still be reported using the bug mailing list, but any such reported bug will end up as an entry on Savannah's bugtracker. Therefore it saves time to submit the bug on Savannah directly.
Latest Liquid War 6 news should be available on: http://savannah.gnu.org/news/?group=liquidwar6.
The news mailing list is another way to get the latest news, however Savannah has the advantage to offer a dedicated interface.
Currently, there's nothing playable. However all the technical framework has been set up. The program already uses both Guile and OpenGL, has i18n support through gettext, and so on. It is capable of loading maps, store configuration options in a config file, and the menus are interactive.
For now it seems a very complicated piece of software for what it does, but the point is that the fundations are here, and now it's possible to build something solid.
If you want to play Liquid War right now, use Liquid War 5.
Here's my .plan file, which describes what I (Christian Mauduit) have planned for Liquid War 6. There's no garantee that what's written here is a precise description of the real future, however it should give a good idea of what I have in mind.
Note that the information here was written in summer 2005, it might or not be accurate now, as the main reason for plans to exist is that people never follow them. I'm no exception.
Liquid War 6 will be an almost complete rewrite. I mean that common code between branches 5 and 6 might end up in representing 0% of the total code. I think this is a wise decision, for the current code is really hard to maintain, and would not survive any serious cleanup. LW5 was first written in 1998, for DOS, when I had much less experience in programming. In 7 years I - and other people as well - hacked major enhancements in it such as cross-platform support, network games, and if you compare release 5.0 with the latest 5.x.x release, you'll see that a bunch of things have changed. I had never expected I would patch and fix this game for so long, and it's no surprise that it's bloated today.
FYI, here's a list of what makes LW5 unsuitable for major improvements without a complete rewrite:
Liquid War 6 will use a different technical framework than Liquid War 5.
It happens that coding a large project in pure C is a waist of time, if possible at all.
If one applies the standard 80/20 rule to a computer game, one might state that 80% of the code eat up 20% of the CPU and the other 20% of the code eat up 80% of the CPU, the former being high-level glue code and the latter being low-level algorithmic code.
With Liquid War, one could speak of the 99/01 rule. I mean that 99% of the CPU time concerns only 1% of the code, and vice-versa. Basically, Liquid War has a very CPU-greedy core algorithm, still spends a fair amount of CPU displaying stuff (but this is delegated to the low-level game programming library) and the rest is totally unsignificant, in terms of CPU. Point is this "rest" represents the vast majority of the code, and also represents the very same buggy code I spend nights to patch on Liquid War 5. I'm talking about network code, GUI, and other high-level glue-code which are currently being written in C.
This idea is to write all this in a convenient scripting language. There won't be any impact on performances. I can't garantee Liquid War 6 will be blazingly fast, but for sure it won't be the scripting language fault. And of course if, as in Liquid War 3 and 5, I feel the need to implement some stuff in assembly for performances issues, I will do it.
We end up with a multi-language architecture: script + C + assembly.
My guess is that I'll use Scheme as an extension language. Python would be a good choice too. Let's say I'll give Scheme a chance, and if it's really not adapted, I'll switch back to Python. The point is that today I know Python and don't really know Scheme, but, well, it's always a pleasure for me to learn new things. It's fun.
So what is planned today is that Liquid War 6 will be a Scheme program, which will call callbacks functions written in C and/or assembly. These functions will do all the low-level time consuming algorithmic and graphical stuff. The rest of the code being entirely scripted.
Liquid War is not a 3D game, so why use OpenGL?
This choice implies that I won't use Allegro anymore. Allegro stays a very convenient library and I would recommend it for it's excellent, easy to learn, powerfull, and stable. But for the needs of Liquid War 6 I'll use something else (because of OpenGL). I first thought of using GLUT but I might end up simply using SDL. The idea is just fo have an OpenGL wrapper which sets up OpenGL in a similar manner on all platforms, and handles basic things such as mouse or keyboard.
I've got two excellent books on Csound, and the will to learn how to use this tool.
I'll probably use Csound for a number of things, ranging from "bubbling sounds" to full blown music. Stay tuned 8-)
Of course Liquid War 6 will look nicer than Liquid War 5, blah blah blah. What do you think?
Maybe I'll try to use some OpenGL features to make it possible to play on a ball, on a Moebius ring, or other fancy things. I have zillion of ideas, future will decide which ones will be implemented first.
To make it clear, visual enhancements aren't my top-level priority. However I'll try and make room for these enhancements, and prepare the terrain correctly. So it's possible that the first releases of Liquid War 6 won't be that much better than Liquid War 5, but at least Liquid War 6 will have the possibility to evolve. Something Liquid War 5 doesn't have.
There are many things that could be done easily:
As for graphical improvements, this is not my top-level priority. Simply, I'll make the game ready-to-improve. Again, all these enhancements are very hard to code in Liquid War 5, else I would already have coded them. Network enhancements
That's my top-level prioriry.
Why is that? Well, think of Liquid War in terms of "what makes it a good game?" and "what makes it a poor game?".
It's a good game because:
It's a poor game because:
For the ugliness, well, OpenGL and some artwork should make it. But for the network, what's the real problem?
The real problem is that in the current situation, the server needs to have all "keystrokes" before doing anything, and all players must be connected before a game starts. Here's what I plan to do to fix this:
This third point will be the real enhancement of Liquid War with version 6. It's one of the very points which drives me to rewrite it completely. First because it's impossible to implement it without some heavy work. Then because I find it very motivating.
Many gamers submitted suggestions, either by mail or by posting messages on the mailing list.
Don't worry, I keep them. Not reading them here does not mean I won't implement them. It simply means I won't implement them first. I first need the game basically function before enhancing it with fancy stuff.
As I stated on the mailing list, when thinking about Liquid War 6, think of years rather than months (unless I get fired, jobless, or spend several months in a hospital with a laptop).
Note that this road map takes it for granted that I'll be the lone coder on the project. It's unlikely that someone is going to help me for the first stages, until there's at least something real, something playable. Something that proves that the concept is valid. Besides, (real) team work implies a significant overhead, especially at project start. It's hard to figure out how to distribute tasks when the tasks themselves are not clearly identified. But for the rest (starting in 2007 or 2008), it's possible that external help might greatly... ...help!
Please remember that development of Liquid War 6 is a volunteer effort, and you can also contribute to its development. For information about contributing to the GNU Project, please read How to help GNU.
According to the current road map, I (Christian Mauduit) will need to work for some time on setting up the basis of the game. Basically the game must be at least playable in some demo mode for people to start hacking efficiently on it.
Meanwhile, there are always tasks which can save me a lot of time:
As of Liquid War 5, most levels have been contributed by players. While the maintainer of Liquid War 6 has technical knowledge to develop the game, artistic talent and taste might not be his domain of excellence 8-)
Therefore contribution are truely welcomed when they take the form of a new, original, fun and good looking level.
Note that this manual might refer to levels and maps: they are just two different names to describe the very same thing. It's an alias.
Liquid War 6 stores level information in a plain directory.
There is no such thing as an opaque .dat binary file.
The name of the level is the name of the directory itself,
and its elements are the files contained in it.
Files must follow a precise naming scheme. For instance
Liquid War 6 expects a map.png file to be present
in each map directory.
All image files in a level use the Portable Network Graphics format.
It is possible that in the long term, Liquid War 6 will
be able to handle levels as .tar.gz or .zip
files. In that case these files will only be a compressed
image of the actual level directory.
See the ./data/map/ directory of the source Liquid War 6
distribution to see example of maps.
This is the only required file in a level.
In fact, the existence of map.png makes a
directory a level. When checking wether a directory
is a correct level, Liquid War 6 simply tests the
existence and validity of map.png.
This image is a simple black & white area, where white zones are the background, the sea, the places where fighters can move, and black zones are the foreground, the walls, the places where fighters can't go.
This informations can be stored in a 2-color indexed file, or in a grayscaled or even truecolor RGB file, but color information won't be used. Internally, Liquid War 6 will read the color of every point. If it is over 127 on a 0 to 255 scale, it will be considered as background, if it is below 127, it will be considered as foreground.
Todo...
Todo...
Todo...
Todo...
Todo...
A README which describes the map. Should contain a short description, and copyright information.
It is a deliberate choice not to use specific fields to store these informations and use a global README instead. It makes both program code and map design simpler.
Todo...
Many Free Software games come with a free game engine, but without free data. A very good example of this is Doom. While the engine of this game is free, released under the GNU GPL, the data required by it is still proprietary. The Freedoom project addresses this issue, and aims at creating a complete Doom-based game which is Free Software. This requires time and energy, and it is very usefull since a Free Software game without free data to run with is not really usable.
All the data in Liquid War 6 are released under the GNU GPL, along with the source code. Data is considered as being part of the game, since running Liquid War 6 without any level makes no sense.
While the act of running Liquid War 6 is not restricted (see the complete terms of the GNU GPL), no non-free levels or graphics will be distributed with the game.
Here are some points you should think about before designing new maps:
Liquid War 6 is developped on GNU/Linux and other platforms are not supported yet. However there is no reason that would prevent it from running on other platforms, such as Microsoft Windows, Mac OS/X, FreeBSD and in a general manner any *NIX system.
Liquid War 6 uses libraries which are cross-platform (OpenGL, Guile...) so porting it is merely taking the time to fix makefiles and build tools for the given platform. This does not mean it is immediate, but it's a feasible task.
Liquid War 6 uses OpenGL to handle all the video rendering. It is a deliberate option to use this high-level API. The advantages are that it is cross-platform and uses the acceleration features of modern video hardware.
The major drawback is that without accelerated hardware, the game will still run using a software renderer such as Mesa, but it will definitely be too slow to be playable. The option for players who do not own such hardware, or who do not have a correct driver - many vendors keep their specifications secret, which forbids Free Software developpers to create free (as in speech) drivers for them - is to use Liquid War 5 instead, which does not require fancy hardware and accelerated drivers.
Liquid War 6 uses SDL to set up the OpenGL environment. Indeed, OpenGL itself does not handle keyboard or mouse input, and requires some platform dependant glue code to be initialized. SDL provides all this.
One of the lessons learned from Liquid War 5 is that standard C is very convenient for some tasks, but is plainly inadapted in many cases. Handling menus with a high-level API is one example of something really painfull to do with C, whereas it is child's play with a scripting language.
For this reason, Liquid War 6 is a C program which embeds a script interpreter. The C routines provide low-level routines which requires speed and/or are interfaced with C libraries, while the script interpreter handles all the game logic and high-level aspects.
The script interpreter used is Guile, which is recommended by the GNU project. Note that many other scripting languages could have been used, including Python, Perl or Lua. Still, the needs of Liquid War 6 are sufficiently simple that any scripting language can do the job. This is not to say that Scheme is inferior to any language - it might on the contrary be more powerfull - but for Liquid War 6, it was powerfull enough, and no other language had that very special feature which could have justified their used instead of Guile/scheme.
The liquidwar6 executable itself is fairly small. In fact most of the C code - not even speaking of Scheme code - is located in a set of libraries/modules which are installed with the main program. This is different from the external libraries (libGL, libguile...). Here we are speaking of libraries which are very Liquid War 6 specific.
However, they might prove usefull in other games or applications, and after all, they are ready to use. Moreover, splitting the program into libraries makes modularity a reality. Experience shows than when a program is a monolithic C program, the temptation of putting everything in the same place is very strong, and this leads to spaghetti code.
Each library exports a public interface and hides its internal.
Since Liquid War 6 uses standard C and no C++, there's no
real standard way to handle public/private features. The
convention used in Liquid War 6 is to show internal structures
as opaque pointers (void *) whenever some function needs
to operate on a structure which has possibly private fields.
This way the caller function has no way to access the internals,
and we are sure that no reference to any internal implementation
specific feature will appear.
Here's a code excerpt from src/gfx/setup.c:
void _lw6gfx_quit(_LW6GFX_CONTEXT *context) {
/*
* Implementation here.
*/
[...]
}
void lw6gfx_quit(void *context) {
_lw6gfx_quit((_LW6GFX_CONTEXT *) context);
}
The function _lw6gfx_quit (note the “_”) is internal,
declared in internal.h whereas the function lw6gfx_quit
is public, and is therefore exported in gfx.h.
This way, functions in the program using lw6gfx_quit
do not know what is in the _LW6GFX_CONTEXT structure,
and they need not know it.
This does not mean it is not possible to have public structures, only these structures must reflect some truely public, accessible and safe to access structures.
For now, linking on any of the internal library will pull down
all the Liquid War 6 dependencies, including Guile, OpenGL, and
the rest, even when it is not needed. This is due to automake/autoconf
which automatically set these dependencies when a corresponding
AC_CHECK_LIB call is present in configure.ac.
This might be fixed in the future, spending time on this would require that there is actually a real project planning to use one of Liquid War 6 internal libraries.
One of the purposes of Liquid War 6 is to make a cleaner implementation of Liquid War than the previous one, namely Liquid War 5. While the latter has achieved the practical goal of providing a playable implementation of the game, it failed at providing an evolutive platform. Network capabilities where finally added to Liquid War 5, but anyone who played on Internet with someone a few hundreds of milliseconds away would agree that it's far from being perfect. The main reason for this is that it is really had to hack on Liquid War 5, especially when you are not the core developper. The core developper himself, even knowing all the various hacks in the game, is very quickly lost when trying to implement major changes.
To put it short, Liquid War 5 is a global variable hell, a pile of hacks on top of a quick and dirty implementation. Still, it works.
With Liquid War 6, the idea is to take the time to make something stable, something nice which will enable developpers to implement the cool features, and have fun along the way.
Here are a few guidelines which I think are common sense advice, but they are still worth mentionning:
strcpy or sprintf anywhere in the code,
use their equivalent strncpy and snprintf systematically,
as they are part of the glibc and are an order of magnitude safer,
Each of the internal libraries in Liquid War has a “test” program
associated with it. For instance liquidwar6sys-test is
associated to libliquidwar6sys, and its purpose is to
test the features of this library.
While it is fairly easy to test out unitary functions which require no peculiar context, testing high-level functions which requires files, graphical and possibly network contexts to exist is obviously harder to achieve. There's no easy way to draw the line, but the idea is to put in these test executables as much features as possible, to be sure that what is tested in them is rock solid, bullet proof, and that one can safety rely on it and trust that code when running it in a more complex environnement.
These test executables are also very good places to see a library API in action, find code fragments, and make experiments.
The libliquidwar6sys provides macros to allocate and
free memory. One should use them systematically, except when
trying to free something allocated by another library.
See the documentation for module libliquidwar6sys for
more information on how to use the macros.
System functions. Provides access to various utilities which can be used by any other module.
A basic log API is provided. The idea is not to try
and make better than syslog or any existing standard
log API, but simply to wrap log calls so that they
are handled in a uniform manner in the application,
and that it is trivial to change logs behaviors.
Using this API is pretty straightforward:
lw6sys_log_info("abc",_("this is %s"),"ABC");
Using lw6sys_log_info means the message is purely
informative. Other options are lw6sys_log_debug,
lw6sys_log_warning and lw6sys_log_error.
Second argument uses a call to function _ which
means the text is i18n enabled with gettext.
Third argument is just to show that the functions can
handle string formatting the way printf does.
Dynamic memory allocation is a common pitfall in C programming. One advantage of higher level languages such as Scheme, Perl or Python is that they handle memory management for you and therefore avoid many bugs, and consequently many hours of debugging.
The module provides two macros, LW6SYS_MALLOC
and LW6SYS_FREE. Both work the way you think
they should, that is like malloc and free.
Still, there's some magic happening under the hood.
Indeed, these functions:
To implement this, some global variables (to hold
the global memory allocation/freeing counters) need
to be declared, the macro LW6SYS_MALLOC_WIZARDRY
does this for you. See the unitary test programs
(for instance src/sys/test.c) to see how this
work in practice (also check the use of
LW6SYS_CHECK_MALLOC_FREE_COUNT).
Concerning performance, calling these macros will obviously be slower than calling directly their glibc equivalents. The choice in Liquid War 6 is to renounce to this form of optimization and prefer the comfort of handy debugging tools to the risk of memory leaks.
The module contains utility functions which ease up file handling, for instance it allows you to read a whole file in one call, or test the existence of a file.
The module also contains utilities to handle strings,
that is 0 terminated char * pointers.
Most of the time these are only simple wrappers which call three and sometime only one standard glibc function, but it's convenient to use them to:
A good example is string copy. There is a builtin
glibc function which is strdup. But we prefer
using lw6sys_str_copy for it will allocate
memory using LW6SYS_MALLOC and therefore
keep track of the call, and expect and check for
the matching call to LW6SYS_FREE.
The module provides tools to handle chained lists.
Again, the idea is to be consistent with the use
of LW6SYS_MALLOC.
While one might argue that chained list handling is typically Scheme's domain of excellence, and that it's akward to do this manually in a Guile enabled program, the answer is that:
The implementation is very basic, no fancy list handling,
only push, pop, is_empty and that's
about it.
The data is stored in a void * pointer which should
point to your data. You'll need to cast it manually when
you want to read your data.
A free_func attribute can be defined, which is
called when list nodes are deleted. This enable the chained
list tools to handle objects which have been allocated
dynamically and free them properly through a callback system.
A side effect of
having LW6SYS_MALLOC defined as a macro is that
it can't be used directly as a callback. Use the function
lw6sys_free_callback for this. But do not use it
systematically instead of the LW6SYS_FREE macro,
as the macro gives more debugging informations when it fails,
including source file and line number for instance.
See the test program ./src/sys/test.c to see
the API in action.
This is very similar to the chained list API, it provides a way to handle associative arrays, AKA dictionnaries.
Note that the code here is highly unoptimized, and that
handling large associative arrays with it will be a
performance killer. There is no hash-table, and when you query
an object all the keys are read and compared with strcmp
to figure which key is the right one.
Still, having this is convenient for it avoids limitating the program with hardcoded limits. You can fit any number of items in these associative arrays, if there are too much of them it will be slow, but it will still work.
Liquid War 6 does not make an intensive use of this, it is just here to handle things like representing options in memory after they have been loaded from disk or interpreted from the command line.
The void * pointer on the data, the value of the key/value
pair which forms the dictionnary, is handled the same way
than data in chained lists. That is it can be freed automatically
with the free_func attribute, which is a callback, and
can be set to NULL if you do not need that feature.
The char * pointer on the key, which is a string, is handle
in a different manner. In fact, it is automatically duplicated
when you create an entry, and automatically deleted when you
delete an entry. Therefore using a freeing callback for this
makes no sense.
See the test program ./src/sys/test.c to see
the API in action.
Todo...
The module provides a simple wrapper over expat functions. It is used to parse primitive XML files with a general key -> value scheme of the following form:
<element key="foo" value="bar" />
While the use of XML for storing such simple informations is questionnable, it makes no doubt it's safer to rely on the well tested routines of expat rather than code a home-made parser. Additionnally, using XML will make the transition easier the day we need to store more complex and structured information.
Configuration routines. Provides a high-level API to read, update, and save configuration options.
Command-line options and file-based options are handled in a uniform manner.
Graphics functions. Also provides input functions. This is logical since input is related to the video output system. For instance using OpenGL with SDL implies that SDL handles the input. The keyboard input is not handled the same way when running X11 and when running in console mode.
The current implementation of libiquidwar6gfx relies on SDL and OpenGL, but this is not mandatory. It is theorically possible to implement a new target (plain X11, ncurses, ...), without changing a single line of code in the other modules. However this is obviously not a priority.
Depends on libliquidwar6sys and libliquidwar6ker.
Loads maps into memory. Basically this module is used to transform .png files located on the file system to a workable memory structure.
This has been separated from the rest since it's a little special, for it requires access to functions which are typically found in graphical libraries (read a .png file) so we need to link it to some graphics related .so files. But it does not do any actual video work. We use graphics formats as a well known easy-to-use storage backend.
Depends on libliquidwar6sys.
The core algorithm. This is where all the interesting and definitely Liquid Warish code is kept. It contains the shortest path algorithm imagined by Thomas Colcombet back in 1995. It tries to have as few dependencies as possible, to ease its reuse in other software.
Not implemented yet.
Ideally, depends on nothing, might depend on libliquidwar6sys.
Handles everything related to sound and music. What is planned is the use of CSound. It would allow the writing of cool music, and even contextualize the use of music - making it faster, slower, louder, scarier, whatever... - depending on what's happening within the game.
Not implemented yet.
Depends on libliquidwar6sys.
Will handle all the network stuff. Using a simple POSIX socket API won't be enough, Liquid War 6 has an ambitious goal of getting rid of the server/client mode of connecting to games. Ideally, there would be no server, simply join a game and whenever the person who initialized the game quits, then another player's computer takes the responsability to handle the game. This way one could imagine a never-ending Liquid War game. Wether this will be implemented from scratch, or if a peer to peer enabling library such as GNUnet will be used, is not decided yet.
Will depend on libliquidwar6sys, maybe also libliquidwar6ker.
This is not, like the other modules, a shared library, but rather a collection of scheme scripts which contain all the logic of the game. These scripts call the other libraries API, and are the core of the game.
This is probably where hackers would like to start. The scripts
are in the ./src/script directory of the source tarball, and installed
in /usr/local/share/liquidwar6/script/ by default.
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