1 <HTML 2 ><HEAD 3 ><TITLE 4 >SDL_JoystickGetBall</TITLE 5 ><META 6 NAME="GENERATOR" 7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ 8 "><LINK 9 REL="HOME" 10 TITLE="SDL Library Documentation" 11 HREF="index.html"><LINK 12 REL="UP" 13 TITLE="Joystick" 14 HREF="joystick.html"><LINK 15 REL="PREVIOUS" 16 TITLE="SDL_JoystickGetButton" 17 HREF="sdljoystickgetbutton.html"><LINK 18 REL="NEXT" 19 TITLE="SDL_JoystickClose" 20 HREF="sdljoystickclose.html"></HEAD 21 ><BODY 22 CLASS="REFENTRY" 23 BGCOLOR="#FFF8DC" 24 TEXT="#000000" 25 LINK="#0000ee" 26 VLINK="#551a8b" 27 ALINK="#ff0000" 28 ><DIV 29 CLASS="NAVHEADER" 30 ><TABLE 31 SUMMARY="Header navigation table" 32 WIDTH="100%" 33 BORDER="0" 34 CELLPADDING="0" 35 CELLSPACING="0" 36 ><TR 37 ><TH 38 COLSPAN="3" 39 ALIGN="center" 40 >SDL Library Documentation</TH 41 ></TR 42 ><TR 43 ><TD 44 WIDTH="10%" 45 ALIGN="left" 46 VALIGN="bottom" 47 ><A 48 HREF="sdljoystickgetbutton.html" 49 ACCESSKEY="P" 50 >Prev</A 51 ></TD 52 ><TD 53 WIDTH="80%" 54 ALIGN="center" 55 VALIGN="bottom" 56 ></TD 57 ><TD 58 WIDTH="10%" 59 ALIGN="right" 60 VALIGN="bottom" 61 ><A 62 HREF="sdljoystickclose.html" 63 ACCESSKEY="N" 64 >Next</A 65 ></TD 66 ></TR 67 ></TABLE 68 ><HR 69 ALIGN="LEFT" 70 WIDTH="100%"></DIV 71 ><H1 72 ><A 73 NAME="SDLJOYSTICKGETBALL" 74 ></A 75 >SDL_JoystickGetBall</H1 76 ><DIV 77 CLASS="REFNAMEDIV" 78 ><A 79 NAME="AEN6433" 80 ></A 81 ><H2 82 >Name</H2 83 >SDL_JoystickGetBall -- Get relative trackball motion</DIV 84 ><DIV 85 CLASS="REFSYNOPSISDIV" 86 ><A 87 NAME="AEN6436" 88 ></A 89 ><H2 90 >Synopsis</H2 91 ><DIV 92 CLASS="FUNCSYNOPSIS" 93 ><A 94 NAME="AEN6437" 95 ></A 96 ><P 97 ></P 98 ><PRE 99 CLASS="FUNCSYNOPSISINFO" 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, &delta_x, &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 181 ></DIV 182 ><DIV 183 CLASS="REFSECT1" 184 ><A 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 196 ></P 197 ></DIV 198 ><DIV 199 CLASS="NAVFOOTER" 200 ><HR 201 ALIGN="LEFT" 202 WIDTH="100%"><TABLE 203 SUMMARY="Footer navigation table" 204 WIDTH="100%" 205 BORDER="0" 206 CELLPADDING="0" 207 CELLSPACING="0" 208 ><TR 209 ><TD 210 WIDTH="33%" 211 ALIGN="left" 212 VALIGN="top" 213 ><A 214 HREF="sdljoystickgetbutton.html" 215 ACCESSKEY="P" 216 >Prev</A 217 ></TD 218 ><TD 219 WIDTH="34%" 220 ALIGN="center" 221 VALIGN="top" 222 ><A 223 HREF="index.html" 224 ACCESSKEY="H" 225 >Home</A 226 ></TD 227 ><TD 228 WIDTH="33%" 229 ALIGN="right" 230 VALIGN="top" 231 ><A 232 HREF="sdljoystickclose.html" 233 ACCESSKEY="N" 234 >Next</A 235 ></TD 236 ></TR 237 ><TR 238 ><TD 239 WIDTH="33%" 240 ALIGN="left" 241 VALIGN="top" 242 >SDL_JoystickGetButton</TD 243 ><TD 244 WIDTH="34%" 245 ALIGN="center" 246 VALIGN="top" 247 ><A 248 HREF="joystick.html" 249 ACCESSKEY="U" 250 >Up</A 251 ></TD 252 ><TD 253 WIDTH="33%" 254 ALIGN="right" 255 VALIGN="top" 256 >SDL_JoystickClose</TD 257 ></TR 258 ></TABLE 259 ></DIV 260 ></BODY 261 ></HTML 262 >