TSDL_JoyBallEvent = record
type_: UInt8; // SDL_JOYAVBALLMOTION
which: UInt8; // The joystick device index
ball: UInt8; // The joystick trackball index
xrel: Sint16; // The relative motion in the X direction
yrel: Sint16; // The relative motion in the Y direction
end;
TSDL_JoyBallEvent is a member of the TSDL_Event union and is used when an event of type SDL_JOYBALLMOTION is reported.
A SDL_JOYBALLMOTION event occurs when a user moves a trackball on the joystick. The field which is the index of the joystick that reported the event and ball is the index of the trackball (for a more detailed explaination see the Joystick section). Trackballs only return relative motion, this is the change in position on the ball since it was last polled (last cycle of the event loop) and it is stored in xrel and yrel.