Function retro_keyboard_callback_fn 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn retro_keyboard_callback_fn(
    down: bool,
    keycode: c_uint,
    character: u32,
    key_modifiers: u16,
)

If enabled by the Core, notifies it when a keyboard button has been pressed or released.

Parameters

• down: true if the key has been pressed, false if it has been released
• keycode: retro_key value
• character: The text character of the pressed key, encoded as UTF-32.
• key_modifiers: retro_mod value