Allegro defines a set of "Android game keys" in keycodes.h. Of the 18 defined keys, 10 never trigger keyboard events on Android after a successful call to al_install_joystick():

• The following 10 never trigger a keyboard event: ALLEGRO_KEY_BUTTON_A, ALLEGRO_KEY_BUTTON_B, ALLEGRO_KEY_BUTTON_X, ALLEGRO_KEY_BUTTON_Y, ALLEGRO_KEY_BUTTON_L1, ALLEGRO_KEY_BUTTON_R1, ALLEGRO_KEY_DPAD_UP, ALLEGRO_KEY_DPAD_DOWN, ALLEGRO_KEY_DPAD_LEFT, ALLEGRO_KEY_DPAD_RIGHT.
• The following 8 do trigger keyboard events: ALLEGRO_KEY_START, ALLEGRO_KEY_SELECT, ALLEGRO_KEY_BUTTON_L2, ALLEGRO_KEY_BUTTON_R2, ALLEGRO_KEY_THUMBL, ALLEGRO_KEY_THUMBR, ALLEGRO_KEY_DPAD_CENTER, ALLEGRO_KEY_SEARCH.
• ALLEGRO_KEY_MENU, although not defined side-by-side with the Android game keys, also never triggers a keyboard event.

The keys that never trigger keyboard events are instead mapped to joystick input. Conversely, the keys that are not mapped to joystick input trigger keyboard events.

The present state of things leads to inconsistent behavior: in order to detect if the START button has been pressed, I have to listen to keyboard input. On the other hand, if I want to detect A, B, X, Y, I have to listen to joystick input. Other buttons behave in the same way: L1/R1 are detected as joystick input only, whereas L2/R2 are detected as keyboard input only.

Since Allegro defines 18 "Android game keys", could we have them all trigger keyboard events?

• Keycodes have publicly defined names, whereas joystick button numbers do not. In my code, I remap the joystick button numbers defined in AllegroActivity to the XInput button numbers defined in src/win/wjoyxi.c for consistency.
• If multiple gamepads are connected to a device, they all trigger keyboard events. This is not an issue, as Android game keys are already defined and gamepad differentiation can be done using the joystick API.
• All 18 game keys are correctly recognized as long as you do not call al_install_joystick(). Once you do and it succeeds, Allegro blocks 10 keys (in addition to the menu key), leading to inconsistent behavior.