al_show_native_file_dialog - Allegro 5 API

       Show the dialog window.  The display may be NULL, otherwise the given display is treated as the parent if
       possible.

       This  function  blocks  the  calling  thread  until  it  returns,  so you may want to spawn a thread with
       al_create_thread(3alleg5) and call it from inside that thread.

       Returns true on success, false on failure.

              Note:         On         Android,         ALLEGRO_EVENT_DISPLAY_HALT_DRAWING(3alleg5)          and
              ALLEGRO_EVENT_DISPLAY_RESUME_DRAWING(3alleg5)  need  to  be  handled before this function returns.
              This means that you must call it from a different thread.

Allegro reference manual                                                     al_show_native_file_dialog(3alleg5)

       al_show_native_file_dialog - Allegro 5 API

              #include <allegro5/allegro_native_dialog.h>

              bool al_show_native_file_dialog(ALLEGRO_DISPLAY *display,
                 ALLEGRO_FILECHOOSER *dialog)