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><H1
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>SDL_JoyBallEvent</H1
><DIV
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><A
NAME="AEN4396"
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><H2
>Name</H2
>SDL_JoyBallEvent&nbsp;--&nbsp;Joystick trackball motion event structure</DIV
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><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  Uint8 type;
  Uint8 which;
  Uint8 ball;
  Sint16 xrel, yrel;
} SDL_JoyBallEvent;</PRE
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><H2
>Structure Data</H2
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><TT
CLASS="STRUCTFIELD"
><I
>type</I
></TT
></TD
><TD
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><TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
></TD
></TR
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><TT
CLASS="STRUCTFIELD"
><I
>which</I
></TT
></TD
><TD
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>Joystick device index</TD
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><TT
CLASS="STRUCTFIELD"
><I
>ball</I
></TT
></TD
><TD
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>Joystick trackball index</TD
></TR
><TR
><TD
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><TT
CLASS="STRUCTFIELD"
><I
>xrel</I
></TT
>, <TT
CLASS="STRUCTFIELD"
><I
>yrel</I
></TT
></TD
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>The relative motion in the X/Y direction</TD
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><H2
>Description</H2
><P
><SPAN
CLASS="STRUCTNAME"
>SDL_JoyBallEvent</SPAN
> is a member of the <A
HREF="sdlevent.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Event</SPAN
></A
> union and is used when an event of type <TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
> is reported.</P
><P
>A <TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
> event occurs when a user moves a trackball on the joystick. The field <TT
CLASS="STRUCTFIELD"
><I
>which</I
></TT
> is the index of the joystick that reported the event and <TT
CLASS="STRUCTFIELD"
><I
>ball</I
></TT
> is the index of the trackball (for a more detailed explaination see the <A
HREF="joystick.html"
>Joystick section</A
>). 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 <TT
CLASS="STRUCTFIELD"
><I
>xrel</I
></TT
> and <TT
CLASS="STRUCTFIELD"
><I
>yrel</I
></TT
>.</P
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><H2
>See Also</H2
><P
><A
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><SPAN
CLASS="STRUCTNAME"
>SDL_Event</SPAN
></A
>,
<A
HREF="joystick.html"
>Joystick Functions</A
>,
<A
HREF="sdljoystickeventstate.html"
><TT
CLASS="FUNCTION"
>SDL_JoystickEventState</TT
></A
>,
<A
HREF="sdljoystickgetball.html"
><TT
CLASS="FUNCTION"
>SDL_JoystickGetBall</TT
></A
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