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><H1
><A
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>SDL_JoystickGetBall</A
></H1
><DIV
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><A
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><H2
>Name</H2
>SDL_JoystickGetBall&nbsp;--&nbsp;Get relative trackball motion</DIV
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>Synopsis</H2
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><P
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><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_JoystickGetBall</B
></CODE
>(SDL_Joystick *joystick, int ball, int *dx, int *dy);</CODE
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><H2
>Description</H2
><P
>Get the <TT
CLASS="PARAMETER"
><I
>ball</I
></TT
> axis change.</P
><P
>Trackballs can only return relative motion since the last call to <TT
CLASS="FUNCTION"
>SDL_JoystickGetBall</TT
>, these motion deltas a placed into <TT
CLASS="PARAMETER"
><I
>dx</I
></TT
> and <TT
CLASS="PARAMETER"
><I
>dy</I
></TT
>.</P
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><H2
>Return Value</H2
><P
>Returns <SPAN
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>0</SPAN
> on success or <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> on failure</P
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>Examples</H2
><P
><PRE
CLASS="PROGRAMLISTING"
>int delta_x, delta_y;
SDL_Joystick *joy;
.
.
.
SDL_JoystickUpdate();
if(SDL_JoystickGetBall(joy, 0, &#38;delta_x, &#38;delta_y)==-1)
  printf("TrackBall Read Error!\n");
printf("Trackball Delta- X:%d, Y:%d\n", delta_x, delta_y);</PRE
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>See Also</H2
><P
><A
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><TT
CLASS="FUNCTION"
>SDL_JoystickNumBalls</TT
></A
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author	Sam Lantinga <slouken@libsdl.org>
date	Mon, 22 Oct 2001 21:34:50 +0000
parents	e5bc29de3f0a
children	355632dca928