Description: Returns the display or control, and button pressed/released on an external joystick device; returning 'true' interrupts normal button function in 'onJoystickButtonDown', as in 'onKeyDown'-
( https://community.bistudio.com/wiki/User_Interface_Event_Handlers#onKeyDown )

Syntax: findDisplay 46 displayAddEventHandler ["JoystickButtonUp", "hint str _this;"];
Syntax2: findDisplay 46 displayAddEventHandler ["JoystickButtonDown", if(_this select 2 == 3) then {true}];

Returns: Array

displayOrControl: Display/Control
deviceIndex: Number- Indexed number of the Joystick device (support for multiple joystick devices);
buttonNumber: Number- Number corresponding to the affected button.

Reasoning: Enables ability for scripts to use joystick buttons as keybinds, for custom keybinds, as in CBA.