System routines
These functions are declared in the main Allegro header file:
#include <allegro5/allegro.h>al_install_system
bool al_install_system(int version, int (*atexit_ptr)(void (*)(void)))Initialize the Allegro system. No other Allegro functions can be called before this (with one or two exceptions).
The version field should always be set to ALLEGRO_VERSION_INT.
If atexit_ptr is non-NULL, and if hasn't been done already, al_uninstall_system will be registered as an atexit function.
Returns true if Allegro was successfully initialized by this function call (or already was initialized previously), false if Allegro cannot be used. A common reason for this function to fail is when the version of Allegro you compiled your game against is not compatible with the version of the shared libraries that were found on the system.
The version compatibility check works as follows. Let A = xa.ya.za.* be the version of Allegro you compiled with, and B = xb.yb.zb.* be the version of Allegro found in the system shared library.
If you defined ALLEGRO_UNSTABLE before including Allegro headers, then version A is compatible with B only if xa.ya.za = xb.yb.zb. Otherwise, A is compatible with B only if xa.ya = xb.yb.
See also: al_init
al_init
#define al_init() (al_install_system(ALLEGRO_VERSION_INT, atexit))Like al_install_system, but automatically passes in the version and uses the atexit function visible in the current binary.
Note: It is typically wrong to call al_init anywhere except the final game binary. In particular, do not call it inside a shared library unless you know what you're doing. In those cases, it is better to call al_install_system either with a
NULLatexit_ptr, or with a pointer to atexit provided by the user of this shared library.
See also: al_install_system
al_uninstall_system
void al_uninstall_system(void)Closes down the Allegro system.
Note: al_uninstall_system() can be called without a corresponding al_install_system call, e.g. from atexit().
al_is_system_installed
bool al_is_system_installed(void)Returns true if Allegro is initialized, otherwise returns false.
al_get_allegro_version
uint32_t al_get_allegro_version(void)Returns the (compiled) version of the Allegro library, packed into a single integer as groups of 8 bits in the form (major << 24) | (minor << 16) | (revision << 8) | release.
You can use code like this to extract them:
uint32_t version = al_get_allegro_version();
int major = version >> 24;
int minor = (version >> 16) & 255;
int revision = (version >> 8) & 255;
int release = version & 255;The release number is 0 for an unofficial version and 1 or greater for an official release. For example "5.0.2[1]" would be the (first) official 5.0.2 release while "5.0.2[0]" would be a compile of a version from the "5.0.2" branch before the official release.
al_get_standard_path
ALLEGRO_PATH *al_get_standard_path(int id)Gets a system path, depending on the id parameter. Some of these paths may be affected by the organization and application name, so be sure to set those before calling this function.
The paths are not guaranteed to be unique (e.g., SETTINGS and DATA may be the same on some platforms), so you should be sure your filenames are unique if you need to avoid naming collisions. Also, a returned path may not actually exist on the file system.
- ALLEGRO_RESOURCES_PATH
If you bundle data in a location relative to your executable, then you should use this path to locate that data. On most platforms, this is the directory that contains the executable file.
If called from an OS X app bundle, then this will point to the internal resource directory (
/Contents/Resources). To maintain consistency, if you put your resources into a directory called "data" beneath the executable on some other platform (like Windows), then you should also create a directory called "data" under the OS X app bundle's resource folder. You should not try to write to this path, as it is very likely read-only.
If you install your resources in some other system directory (e.g., in /usr/share or C:\ProgramData), then you are responsible for keeping track of that yourself.
- ALLEGRO_TEMP_PATH
Path to the directory for temporary files.
- ALLEGRO_USER_HOME_PATH
This is the user's home directory. You should not normally write files into this directory directly, or create any sub folders in it, without explicit permission from the user. One practical application of this path would be to use it as the starting place of a file selector in a GUI.
- ALLEGRO_USER_DOCUMENTS_PATH
This location is easily accessible by the user, and is the place to store documents and files that the user might want to later open with an external program or transfer to another place.
You should not save files here unless the user expects it, usually by explicit permission.
- ALLEGRO_USER_DATA_PATH
If your program saves any data that the user doesn't need to access externally, then you should place it here. This is generally the least intrusive place to store data. This path will usually not be present on the file system, so make sure to create it before writing to it.
- ALLEGRO_USER_SETTINGS_PATH
If you are saving configuration files (especially if the user may want to edit them outside of your program), then you should place them here. This path will usually not be present on the file system, so make sure to create it before writing to it.
- ALLEGRO_EXENAME_PATH
The full path to the executable.
Returns NULL on failure. The returned path should be freed with al_destroy_path.
See also: al_set_app_name, al_set_org_name, al_destroy_path, al_set_exe_name
al_set_exe_name
void al_set_exe_name(char const *path)This override the executable name used by al_get_standard_path for ALLEGRO_EXENAME_PATH and ALLEGRO_RESOURCES_PATH.
One possibility where changing this can be useful is if you use the Python wrapper. Allegro would then by default think that the system's Python executable is the current executable - but you can set it to the .py file being executed instead.
Since: 5.0.6, 5.1.0
See also: al_get_standard_path
al_set_app_name
void al_set_app_name(const char *app_name)Sets the global application name.
The application name is used by al_get_standard_path to build the full path to an application's files.
This function may be called before al_init or al_install_system.
See also: al_get_app_name, al_set_org_name
al_set_org_name
void al_set_org_name(const char *org_name)Sets the global organization name.
The organization name is used by al_get_standard_path to build the full path to an application's files.
This function may be called before al_init or al_install_system.
See also: al_get_org_name, al_set_app_name
al_get_app_name
const char *al_get_app_name(void)Returns the global application name string.
See also: al_set_app_name
al_get_org_name
const char *al_get_org_name(void)Returns the global organization name string.
See also: al_set_org_name
al_get_system_config
ALLEGRO_CONFIG *al_get_system_config(void)Returns the system configuration structure. The returned configuration should not be destroyed with al_destroy_config. This is mainly used for configuring Allegro and its addons. You may populate this configuration before Allegro is installed to control things like the logging levels and other features.
Allegro will try to populate this configuration by loading a configuration file from a few different locations, in this order:
Unix only: /etc/allegro5rc
Unix only: $HOME/allegro5rc
allegro5.cfg next to the executable
If multiple copies are found, then they are merged using al_merge_config_into.
The contents of this file are documented inside a prototypical allegro5.cfg that you can find in the root directory of the source distributions of Allegro. Note that Allegro will not look into that file unless you make a copy of it and place it next to your executable!
al_register_assert_handler
void al_register_assert_handler(void (*handler)(char const *expr,
char const *file, int line, char const *func))Register a function to be called when an internal Allegro assertion fails. Pass NULL to reset to the default behaviour, which is to do whatever the standard assert() macro does.
Since: 5.0.6, 5.1.0
al_register_trace_handler
void al_register_trace_handler(void (*handler)(char const *))Register a callback which is called whenever Allegro writes something to its log files. The default logging to allegro.log is disabled while this callback is active. Pass NULL to revert to the default logging.
This function may be called prior to al_install_system.
See the example allegro5.cfg for documentation on how to configure the used debug channels, logging levels and trace format.
Since: 5.1.5
al_get_cpu_count
int al_get_cpu_count(void)Returns the number of CPU cores that the system Allegro is running on has and which could be detected, or a negative number if detection failed. Even if a positive number is returned, it might be that it is not correct. For example, Allegro running on a virtual machine will return the amount of CPU's of the VM, and not that of the underlying system.
Furthermore even if the number is correct, this only gives you information about the total CPU cores of the system Allegro runs on. The amount of cores available to your program may be less due to circumstances such as programs that are currently running.
Therefore, it's best to use this for advisory purposes only. It is certainly a bad idea to make your program exclusive to systems for which this function returns a certain "desirable" number.
This function may be called prior to al_install_system or al_init.
Since: 5.1.12
al_get_ram_size
int al_get_ram_size(void)Returns the size in MB of the random access memory that the system Allegro is running on has and which could be detected, or a negative number if detection failed. Even if a positive number is returned, it might be that it is not correct. For example, Allegro running on a virtual machine will return the amount of RAM of the VM, and not that of the underlying system.
Furthermore even if the number is correct, this only gives you information about the total physical memory of the system Allegro runs on. The memory available to your program may be less or more than what this function returns due to circumstances such as virtual memory, and other programs that are currently running.
Therefore, it's best to use this for advisory purposes only. It is certainly a bad idea to make your program exclusive to systems for which this function returns a certain "desirable" number.
This function may be called prior to al_install_system or al_init.
Since: 5.1.12