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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
85 CLASS="REFSYNOPSISDIV"
86 ><A
87 NAME="AEN6436"
88 ></A
89 ><H2
90 >Synopsis</H2
91 ><DIV
92 CLASS="FUNCSYNOPSIS"
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94 NAME="AEN6437"
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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, &#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
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
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