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  75 >SDL_JoystickGetBall</H1
  76 ><DIV
  77 CLASS="REFNAMEDIV"
  78 ><A
  79 NAME="AEN6433"
  80 ></A
  81 ><H2
  82 >Name</H2
  83 >SDL_JoystickGetBall&nbsp;--&nbsp;Get relative trackball motion</DIV
  84 ><DIV
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  87 NAME="AEN6436"
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  90 >Synopsis</H2
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 100 >#include "SDL.h"</PRE
 101 ><P
 102 ><CODE
 103 ><CODE
 104 CLASS="FUNCDEF"
 105 >int <B
 106 CLASS="FSFUNC"
 107 >SDL_JoystickGetBall</B
 108 ></CODE
 109 >(SDL_Joystick *joystick, int ball, int *dx, int *dy);</CODE
 110 ></P
 111 ><P
 112 ></P
 113 ></DIV
 114 ></DIV
 115 ><DIV
 116 CLASS="REFSECT1"
 117 ><A
 118 NAME="AEN6443"
 119 ></A
 120 ><H2
 121 >Description</H2
 122 ><P
 123 >Get the <TT
 124 CLASS="PARAMETER"
 125 ><I
 126 >ball</I
 127 ></TT
 128 > axis change.</P
 129 ><P
 130 >Trackballs can only return relative motion since the last call to <TT
 131 CLASS="FUNCTION"
 132 >SDL_JoystickGetBall</TT
 133 >, these motion deltas a placed into <TT
 134 CLASS="PARAMETER"
 135 ><I
 136 >dx</I
 137 ></TT
 138 > and <TT
 139 CLASS="PARAMETER"
 140 ><I
 141 >dy</I
 142 ></TT
 143 >.</P
 144 ></DIV
 145 ><DIV
 146 CLASS="REFSECT1"
 147 ><A
 148 NAME="AEN6451"
 149 ></A
 150 ><H2
 151 >Return Value</H2
 152 ><P
 153 >Returns <SPAN
 154 CLASS="RETURNVALUE"
 155 >0</SPAN
 156 > on success or <SPAN
 157 CLASS="RETURNVALUE"
 158 >-1</SPAN
 159 > on failure</P
 160 ></DIV
 161 ><DIV
 162 CLASS="REFSECT1"
 163 ><A
 164 NAME="AEN6456"
 165 ></A
 166 ><H2
 167 >Examples</H2
 168 ><P
 169 ><PRE
 170 CLASS="PROGRAMLISTING"
 171 >int delta_x, delta_y;
 172 SDL_Joystick *joy;
 173 .
 174 .
 175 .
 176 SDL_JoystickUpdate();
 177 if(SDL_JoystickGetBall(joy, 0, &#38;delta_x, &#38;delta_y)==-1)
 178   printf("TrackBall Read Error!\n");
 179 printf("Trackball Delta- X:%d, Y:%d\n", delta_x, delta_y);</PRE
 180 ></P
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 185 NAME="AEN6460"
 186 ></A
 187 ><H2
 188 >See Also</H2
 189 ><P
 190 ><A
 191 HREF="sdljoysticknumballs.html"
 192 ><TT
 193 CLASS="FUNCTION"
 194 >SDL_JoystickNumBalls</TT
 195 ></A
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