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<HTML><HEAD><TITLE>SDL_JoyBallEvent</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+"><LINKREL="HOME"TITLE="SDL Library Documentation"HREF="index.html"><LINKREL="UP"TITLE="SDL Event Structures."HREF="eventstructures.html"><LINKREL="PREVIOUS"TITLE="SDL_JoyHatEvent"HREF="sdljoyhatevent.html"><LINKREL="NEXT"TITLE="SDL_ResizeEvent"HREF="sdlresizeevent.html"></HEAD><BODYCLASS="REFENTRY"BGCOLOR="#FFF8DC"TEXT="#000000"LINK="#0000ee"VLINK="#551a8b"ALINK="#ff0000"><DIVCLASS="NAVHEADER"><TABLESUMMARY="Header navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">SDL Library Documentation</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><AHREF="sdljoyhatevent.html"ACCESSKEY="P">Prev</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom"></TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><AHREF="sdlresizeevent.html"ACCESSKEY="N">Next</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><H1><ANAME="SDLJOYBALLEVENT"></A>SDL_JoyBallEvent</H1><DIVCLASS="REFNAMEDIV"><ANAME="AEN4396"></A><H2>Name</H2>SDL_JoyBallEvent -- Joystick trackball motion event structure</DIV><DIVCLASS="REFSECT1"><ANAME="AEN4399"></A><H2>Structure Definition</H2><PRECLASS="PROGRAMLISTING">typedef struct{ Uint8 type; Uint8 which; Uint8 ball; Sint16 xrel, yrel;} SDL_JoyBallEvent;</PRE></DIV><DIVCLASS="REFSECT1"><ANAME="AEN4402"></A><H2>Structure Data</H2><DIVCLASS="INFORMALTABLE"><ANAME="AEN4404"></A><P></P><TABLEBORDER="0"CLASS="CALSTABLE"><TBODY><TR><TDALIGN="LEFT"VALIGN="TOP"><TTCLASS="STRUCTFIELD"><I>type</I></TT></TD><TDALIGN="LEFT"VALIGN="TOP"><TTCLASS="LITERAL">SDL_JOYBALLMOTION</TT></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"><TTCLASS="STRUCTFIELD"><I>which</I></TT></TD><TDALIGN="LEFT"VALIGN="TOP">Joystick device index</TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"><TTCLASS="STRUCTFIELD"><I>ball</I></TT></TD><TDALIGN="LEFT"VALIGN="TOP">Joystick trackball index</TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"><TTCLASS="STRUCTFIELD"><I>xrel</I></TT>, <TTCLASS="STRUCTFIELD"><I>yrel</I></TT></TD><TDALIGN="LEFT"VALIGN="TOP">The relative motion in the X/Y direction</TD></TR></TBODY></TABLE><P></P></DIV></DIV><DIVCLASS="REFSECT1"><ANAME="AEN4425"></A><H2>Description</H2><P><SPANCLASS="STRUCTNAME">SDL_JoyBallEvent</SPAN> is a member of the <AHREF="sdlevent.html"><SPANCLASS="STRUCTNAME">SDL_Event</SPAN></A> union and is used when an event of type <TTCLASS="LITERAL">SDL_JOYBALLMOTION</TT> is reported.</P><P>A <TTCLASS="LITERAL">SDL_JOYBALLMOTION</TT> event occurs when a user moves a trackball on the joystick. The field <TTCLASS="STRUCTFIELD"><I>which</I></TT> is the index of the joystick that reported the event and <TTCLASS="STRUCTFIELD"><I>ball</I></TT> is the index of the trackball (for a more detailed explaination see the <AHREF="joystick.html">Joystick section</A>). Trackballs only return relative motion, this is the change in position on the ball since it was last polled (last cycle of the event loop) and it is stored in <TTCLASS="STRUCTFIELD"><I>xrel</I></TT> and <TTCLASS="STRUCTFIELD"><I>yrel</I></TT>.</P></DIV><DIVCLASS="REFSECT1"><ANAME="AEN4439"></A><H2>See Also</H2><P><AHREF="sdlevent.html"><SPANCLASS="STRUCTNAME">SDL_Event</SPAN></A>,<AHREF="joystick.html">Joystick Functions</A>,<AHREF="sdljoystickeventstate.html"><TTCLASS="FUNCTION">SDL_JoystickEventState</TT></A>,<AHREF="sdljoystickgetball.html"><TTCLASS="FUNCTION">SDL_JoystickGetBall</TT></A></P></DIV><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLESUMMARY="Footer navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><AHREF="sdljoyhatevent.html"ACCESSKEY="P">Prev</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="index.html"ACCESSKEY="H">Home</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><AHREF="sdlresizeevent.html"ACCESSKEY="N">Next</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">SDL_JoyHatEvent</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="eventstructures.html"ACCESSKEY="U">Up</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">SDL_ResizeEvent</TD></TR></TABLE></DIV></BODY></HTML>⌨️ 快捷键说明
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