# State

These functions are declared in the main Allegro header file:

     #include <allegro5/allegro.h>

## API: ALLEGRO_STATE

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.)

## API: ALLEGRO_STATE_FLAGS

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

## API: al_restore_state

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

See also: [al_store_state], [ALLEGRO_STATE_FLAGS]

## API: al_store_state

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]

## API: al_get_errno

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.

## API: al_set_errno

Set the error number for the calling thread.

