Allegro Manual: Unix specifics

# Unix specifics

- allegro_icon — Pointer to the Allegro X11 icon.
- DIGI_*/Unix — Supported Unix digital sound drivers.
- GFX_*/Linux — Supported Linux console graphic drivers.
- GFX_*/X — Supported X graphic drivers.
- JOY_TYPE_*/Linux — Supported Linux joystick drivers.
- MIDI_*/Unix — Supported Unix MIDI sound drivers.
- xwin_set_window_name — Specify the window name and group (or class).

Under Unix you usually have two ways of redistributing your binaries. You either pack everything in a single directory, even providing Allegro in binary or source form for the user to compile. Or your program is being packaged separately from Allegro and stored in different paths. For the first case of redistribution, read section "Files shared by Allegro" from the "Dos specifics" chapter to learn more about this.

For the second type, you can ignore redistributing the setup, keyboard mappings and language datafiles, because they will be already installed in the system. This, however, is problematic if you are using get_config_text() to localise your program's text strings.

The problem is that on other platforms you usually mix your program's text strings with those of Allegro (found in the ``resources'` directory) to create a special language.dat. And it is likely that the Allegro library installed on the user's system already contains a datafile.dat. You can go ahead and still provide your own language.dat file, but this will mean that if Allegro is updated, your language.dat file may not contain all the text strings used by the new version.

Given the slow paced release cycle of Allegro, this might not be a concern. However, if you want to make it easy on system administrators, instead of providing your own ``language.dat'`, you should provide the separate ``xxtext.cfg'` files it in a separate directory. Then, before showing the strings to the user you can detect the language setting and use override_config_file() with the appropriate localisation file and call reload_config_texts().

In order to locate things like the config and translation files, Allegro needs to know the path to your executable. Since there is no standard way to find that, it needs to capture a copy of your argv[] parameter, and it does this with some preprocessor macro trickery. Unfortunately it can't quite pull this off without a little bit of your help, so you will have to write END_OF_MAIN() right after your main() function. Pretty easy, really, and if you forget, you'll get a nice linker error about a missing _mangled_main function to remind you :-)

Under Unix resources are searched for in many different paths (see above). When a configuration resource is looked for, it is usually tried with the variations ``name.cfg'` or ``.namerc'` in multiple paths: the current directory, the directory pointed to by the ALLEGRO environment variable, the user's home directory, one or more global system directories which usually only the root user has access to and any custom paths set up with set_allegro_resource_path(). Text files, like the main allegro config file or a language text translation files are looked for in the following places:

>        ./allegro.cfg
>        $ALLEGRO/allegro.cfg
>        ~/allegro.cfg
>        ~/.allegrorc
>        /etc/allegro.cfg
>        /etc/allegrorc

Binary resources like the language translation files packfile (language.dat) are looked for in:

>        ./language.dat
>        $ALLEGRO/language.dat
>        ~/language.dat
>        /etc/language.dat
>        /usr/share/allegro/language.dat
>        /usr/local/share/allegro/language.dat

Note that if you have installed Allegro from the source distribution with the typical ``make install`', global files like ``language.dat'` and ``allegro.cfg'` will not have been installed. As a system administrator you are required to install them manually wherever you prefer to have them. If you suspect that an Allegro program is somehow not finding the correct configuration file, you could try using the following command:

>        strace program 2>&1|egrep "(open|stat)"

The strace program traces system calls and signals. By default it outputs the information to stderr, so that's why we redirect it to stdin with ``2>&1`'. Since we are interested only in files being (un)successfully opened, we restrict the output of the log to stat or open calls with the extended grep command. You could add another grep to filter only lines with text like ``language'` or ``allegro'`.

Drivers JOY_TYPE_*/Linux
The Linux library supports the following type parameters for the install_joystick() function:

- JOY_TYPE_AUTODETECT
  Attempts to autodetect your joystick hardware. It will use information from the configuration file if one is available (this can be created using the setup utility or by calling the save_joystick_data() function), so you can always use JOY_TYPE_AUTODETECT in your code and then select the exact hardware type from the setup program.
- JOY_TYPE_NONE
  Dummy driver for machines without any joystick.
- JOY_TYPE_LINUX_ANALOGUE
  Regular joystick interface. Joystick support needs to be enabled in your kernel.

> See also: install_joystick.

Drivers GFX_*/Linux
When running in Linux console mode, Allegro supports the following card parameters for the set_gfx_mode() function:

- GFX_TEXT
  Return to text mode.
- GFX_AUTODETECT
  Let Allegro pick an appropriate graphics driver.
- GFX_AUTODETECT_FULLSCREEN
  Autodetects a graphics driver, but will only use fullscreen drivers, failing if these are not available on current platform.
- GFX_AUTODETECT_WINDOWED
  Same as above, but uses only windowed drivers. This will always fail under Linux console mode.
- GFX_SAFE
  Special driver for when you want to reliably set a graphics mode and don't really care what resolution or color depth you get. See the set_gfx_mode() documentation for details.
- GFX_FBCON
  Use the framebuffer device (eg. /dev/fb0). This requires you to have framebuffer support compiled into your kernel, and correctly configured for your hardware. It is currently the only console mode driver that will work without root permissions, unless you are using a development version of SVGAlib.
- GFX_VBEAF
  Use a VBE/AF driver (vbeaf.drv), assuming that you have installed one which works under Linux (currently only two of the FreeBE/AF project drivers are capable of this: I don't know about the SciTech ones). VBE/AF requires root permissions, but is currently the only Linux driver which supports hardware accelerated graphics.
- GFX_SVGALIB
  Use the SVGAlib library for graphics output. This requires root permissions if your version of SVGAlib requires them.
- GFX_VGA
  GFX_MODEX
  Use direct hardware access to set standard VGA or mode-X resolutions, supporting the same modes as in the DOS versions of these drivers. Requires root permissions.

> See also: set_gfx_mode, GFX_*/X.

Drivers GFX_*/X
When running in X mode, Allegro supports the following card parameters for the set_gfx_mode() function:

- GFX_TEXT
  This closes any graphics mode previously opened with set_gfx_mode.
- GFX_AUTODETECT
  Let Allegro pick an appropriate graphics driver.
- GFX_AUTODETECT_FULLSCREEN
  Autodetects a graphics driver, but will only use fullscreen drivers, failing if these are not available on current platform.
- GFX_AUTODETECT_WINDOWED
  Same as above, but uses only windowed drivers.
- GFX_SAFE
  Special driver for when you want to reliably set a graphics mode and don't really care what resolution or color depth you get. See the set_gfx_mode() documentation for details.
- GFX_XWINDOWS
  The standard X graphics driver. This should work on any Unix system, and can operate remotely. It does not require root permissions. If the ARGB cursor extension is available, this driver is capable of displaying a hardware cursor. This needs to be enabled by calling enable_hardware_cursor() because it cannot be used reliably alongside get_mouse_mickeys().
- GFX_XWINDOWS_FULLSCREEN
  The same as above, but while GFX_XWINDOWS runs windowed, this one uses the XF86VidMode extension to make it run in fullscreen mode even without root permissions. You're still using the standard X protocol though, so expect the same low performances as with the windowed driver version. If the ARGB cursor extension is available, this driver is capable of displaying a hardware cursor. This needs to be enabled by calling enable_hardware_cursor() because it cannot be used reliably alongside get_mouse_mickeys().
- GFX_XDGA2
  Use new DGA 2.0 extension provided by XFree86 4.0.x. This will work in fullscreen mode, and it will support hardware acceleration if available. This driver requires root permissions.
- GFX_XDGA2_SOFT
  The same as GFX_XDGA2, but turns off hardware acceleration support. This driver requires root permissions.

> See also: set_gfx_mode, GFX_*/Linux.

Drivers DIGI_*/Unix
The Unix sound functions support the following digital sound cards:

>           DIGI_AUTODETECT      - let Allegro pick a digital sound driver
>           DIGI_NONE            - no digital sound
>           DIGI_OSS             - Open Sound System
>           DIGI_ESD             - Enlightened Sound Daemon
>           DIGI_ARTS            - aRts (Analog Real-Time Synthesizer)
>           DIGI_ALSA            - ALSA sound driver
>           DIGI_JACK            - JACK sound driver

> See also: detect_digi_driver, install_sound, install_sound_input.

Drivers MIDI_*/Unix
The Unix sound functions support the following MIDI sound cards:

>           MIDI_AUTODETECT      - let Allegro pick a MIDI sound driver
>           MIDI_NONE            - no MIDI sound
>           MIDI_OSS             - Open Sound System
>           MIDI_DIGMID          - sample-based software wavetable player
>           MIDI_ALSA            - ALSA RawMIDI driver

> See also: detect_midi_driver, install_sound, install_sound_input.

## Unix integration routines

void xwin_set_window_name(const char *name, const char *group);
This function is only available under X. It lets you to specify the window name and group (or class). They are important because they allow the window manager to remember the window attributes (position, layer, etc). Note that the name and the title of the window are two different things: the title is what appears in the title bar of the window, but usually has no other effects on the behaviour of the application.

> See also: set_window_title.

extern void *allegro_icon;
This is a pointer to the Allegro X11 icon, which is in the format of standard .xpm bitmap data. You do not normally have to bother with this at all: you can use the xfixicon.sh utility from the tools/x11 directory to convert a true colour bitmap to a C file that you only need to link with your own code to set the icon.

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