These functions are declared in the main Allegro header file:

     #include <allegro5/allegro.h>

# ALLEGRO_STATE

    typedef struct ALLEGRO_STATE ALLEGRO_STATE;

Source Code

Opaque type which is passed to al_store_state/al_restore_state.

The various state kept internally by Allegro can be displayed like this:

      global
          active system driver
              current config
      per thread
          new bitmap params
          new display params
          active file interface
          errno
          current blending mode
          current display
              deferred drawing
          current target bitmap
              current transformation
              current projection transformation
              current clipping rectangle
              bitmap locking
              current shader

In general, the only real global state is the active system driver. All other global state is per-thread, so if your application has multiple separate threads they never will interfere with each other. (Except if there are objects accessed by multiple threads of course. Usually you want to minimize that though and for the remaining cases use synchronization primitives described in the threads section or events described in the events section to control inter-thread communication.)

Examples:

- ex_blend_bench.c
- ex_blend2.cpp
- nihgui.cpp

# ALLEGRO_STATE_FLAGS

    typedef enum ALLEGRO_STATE_FLAGS

Source Code

Flags which can be passed to al_store_state/al_restore_state as bit combinations. See al_store_state for the list of flags.

# al_restore_state

    void al_restore_state(ALLEGRO_STATE const *state)

Source Code

Restores part of the state of the current thread from the given ALLEGRO_STATE object.

See also: al_store_state, ALLEGRO_STATE_FLAGS

Examples:

- ex_blend_bench.c
- ex_blend2.cpp
- nihgui.cpp

# al_store_state

    void al_store_state(ALLEGRO_STATE *state, int flags)

Source Code

Stores part of the state of the current thread in the given ALLEGRO_STATE object. The flags parameter can take any bit-combination of these flags:

- ALLEGRO_STATE_NEW_DISPLAY_PARAMETERS - new_display_format, new_display_refresh_rate, new_display_flags
- ALLEGRO_STATE_NEW_BITMAP_PARAMETERS - new_bitmap_format, new_bitmap_flags
- ALLEGRO_STATE_DISPLAY - current_display
- ALLEGRO_STATE_TARGET_BITMAP - target_bitmap
- ALLEGRO_STATE_BLENDER - blender
- ALLEGRO_STATE_TRANSFORM - current_transformation
- ALLEGRO_STATE_PROJECTION_TRANSFORM - current_projection_transformation
- ALLEGRO_STATE_NEW_FILE_INTERFACE - new_file_interface
- ALLEGRO_STATE_BITMAP - same as ALLEGRO_STATE_NEW_BITMAP_PARAMETERS and ALLEGRO_STATE_TARGET_BITMAP
- ALLEGRO_STATE_ALL - all of the above

See also: al_restore_state, ALLEGRO_STATE

Examples:

- ex_blend_bench.c
- ex_blend2.cpp
- nihgui.cpp

# al_get_errno

    int al_get_errno(void)

Source Code

Some Allegro functions will set an error number as well as returning an error code. Call this function to retrieve the last error number set for the calling thread.

Examples:

- ex_utf8.c

# al_set_errno

    void al_set_errno(int errnum)

Source Code

Set the error number for the calling thread.

Examples:

- ex_curl.c
- ex_utf8.c

Allegro version 5.2.11 - Last updated: 2026-02-09 02:00:42 UTC