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| >SDL_JoystickGetBall</H1 |
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| >Name</H2 |
| >SDL_JoystickGetBall -- Get relative trackball motion</DIV |
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| >#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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| >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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| >Return Value</H2 |
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| >Returns <SPAN |
| CLASS="RETURNVALUE" |
| >0</SPAN |
| > on success or <SPAN |
| CLASS="RETURNVALUE" |
| >-1</SPAN |
| > on failure</P |
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| >int delta_x, delta_y; |
| SDL_Joystick *joy; |
| . |
| . |
| . |
| SDL_JoystickUpdate(); |
| if(SDL_JoystickGetBall(joy, 0, &delta_x, &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 |
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| HREF="sdljoysticknumballs.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_JoystickNumBalls</TT |
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