docs/html/sdlevent.html - third_party/sdl - Git at Google

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 >Name</H2
 >SDL_Event&nbsp;--&nbsp;General event structure</DIV
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 ><H2
 >Structure Definition</H2
 ><PRE
 CLASS="PROGRAMLISTING"
 >typedef union{
   Uint8 type;
   SDL_ActiveEvent active;
   SDL_KeyboardEvent key;
   SDL_MouseMotionEvent motion;
   SDL_MouseButtonEvent button;
   SDL_JoyAxisEvent jaxis;
   SDL_JoyBallEvent jball;
   SDL_JoyHatEvent jhat;
   SDL_JoyButtonEvent jbutton;
   SDL_ResizeEvent resize;
   SDL_ExposeEvent expose;
   SDL_QuitEvent quit;
   SDL_UserEvent user;
   SDL_SysWMEvent syswm;
 } SDL_Event;</PRE
 ></DIV
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 ></A
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 >The type of event</TD
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 ><TT
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 ><I
 >active</I
 ></TT
 ></TD
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 ><A
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 >Activation event</A
 ></TD
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 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >key</I
 ></TT
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 ><A
 HREF="sdlkeyboardevent.html"
 >Keyboard event</A
 ></TD
 ></TR
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 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >motion</I
 ></TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlmousemotionevent.html"
 >Mouse motion event</A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
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 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >button</I
 ></TT
 ></TD
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 ><A
 HREF="sdlmousebuttonevent.html"
 >Mouse button event</A
 ></TD
 ></TR
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 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >jaxis</I
 ></TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdljoyaxisevent.html"
 >Joystick axis motion event</A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >jball</I
 ></TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdljoyballevent.html"
 >Joystick trackball motion event</A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >jhat</I
 ></TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdljoyhatevent.html"
 >Joystick hat motion event</A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >jbutton</I
 ></TT
 ></TD
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 ><A
 HREF="sdljoybuttonevent.html"
 >Joystick button event</A
 ></TD
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 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >resize</I
 ></TT
 ></TD
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 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlresizeevent.html"
 >Application window resize event</A
 ></TD
 ></TR
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 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >expose</I
 ></TT
 ></TD
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 ALIGN="LEFT"
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 ><A
 HREF="sdlexposeevent.html"
 >Application window expose event</A
 ></TD
 ></TR
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 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >quit</I
 ></TT
 ></TD
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 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlquitevent.html"
 >Application quit request event</A
 ></TD
 ></TR
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 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >user</I
 ></TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdluserevent.html"
 >User defined event</A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="STRUCTFIELD"
 ><I
 >syswm</I
 ></TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlsyswmevent.html"
 >Undefined window manager event</A
 ></TD
 ></TR
 ></TBODY
 ></TABLE
 ><P
 ></P
 ></DIV
 ></DIV
 ><DIV
 CLASS="REFSECT1"
 ><A
 NAME="AEN3791"
 ></A
 ><H2
 >Description</H2
 ><P
 >The <SPAN
 CLASS="STRUCTNAME"
 >SDL_Event</SPAN
 > union is the core to all event handling is SDL, its probably the most important structure after <SPAN
 CLASS="STRUCTNAME"
 >SDL_Surface</SPAN
 >. <SPAN
 CLASS="STRUCTNAME"
 >SDL_Event</SPAN
 > is a union of all event structures used in SDL, using it is a simple matter of knowing which union member relates to which event <TT
 CLASS="STRUCTFIELD"
 ><I
 >type</I
 ></TT
 >.</P
 ><P
 ><DIV
 CLASS="INFORMALTABLE"
 ><A
 NAME="AEN3799"
 ></A
 ><P
 ></P
 ><TABLE
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 ><THEAD
 ><TR
 ><TH
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 >Event <TT
 CLASS="STRUCTFIELD"
 ><I
 >type</I
 ></TT
 ></TH
 ><TH
 ALIGN="LEFT"
 VALIGN="TOP"
 >Event Structure</TH
 ></TR
 ></THEAD
 ><TBODY
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="MIDDLE"
 ><TT
 CLASS="LITERAL"
 >SDL_ACTIVEEVENT</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="MIDDLE"
 ><A
 HREF="sdlactiveevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_ActiveEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
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 ><TT
 CLASS="LITERAL"
 >SDL_KEYDOWN/UP</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlkeyboardevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_KeyboardEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_MOUSEMOTION</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlmousemotionevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_MouseMotionEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_MOUSEBUTTONDOWN/UP</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlmousebuttonevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_MouseButtonEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_JOYAXISMOTION</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdljoyaxisevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_JoyAxisEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_JOYBALLMOTION</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdljoyballevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_JoyBallEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_JOYHATMOTION</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdljoyhatevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_JoyHatEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_JOYBUTTONDOWN/UP</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdljoybuttonevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_JoyButtonEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_QUIT</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlquitevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_QuitEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_SYSWMEVENT</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlsyswmevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_SysWMEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_VIDEORESIZE</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlresizeevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_ResizeEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_VIDEOEXPOSE</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdlexposeevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_ExposeEvent</SPAN
 ></A
 ></TD
 ></TR
 ><TR
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><TT
 CLASS="LITERAL"
 >SDL_USEREVENT</TT
 ></TD
 ><TD
 ALIGN="LEFT"
 VALIGN="TOP"
 ><A
 HREF="sdluserevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_UserEvent</SPAN
 ></A
 ></TD
 ></TR
 ></TBODY
 ></TABLE
 ><P
 ></P
 ></DIV
 ></P
 ></DIV
 ><DIV
 CLASS="REFSECT1"
 ><A
 NAME="AEN3885"
 ></A
 ><H2
 >Use</H2
 ><P
 >The <SPAN
 CLASS="STRUCTNAME"
 >SDL_Event</SPAN
 > structure has two uses</P
 ><P
 ></P
 ><UL
 COMPACT="COMPACT"
 ><LI
 ><P
 >Reading events on the event queue</P
 ></LI
 ><LI
 ><P
 >Placing events on the event queue</P
 ></LI
 ></UL
 ><P
 >Reading events from the event queue is done with either <A
 HREF="sdlpollevent.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_PollEvent</TT
 ></A
 > or <A
 HREF="sdlpeepevents.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_PeepEvents</TT
 ></A
 >. We'll use <TT
 CLASS="FUNCTION"
 >SDL_PollEvent</TT
 > and step through an example.</P
 ><P
 >First off, we create an empty <SPAN
 CLASS="STRUCTNAME"
 >SDL_Event</SPAN
 > structure.
 <PRE
 CLASS="PROGRAMLISTING"
 >SDL_Event test_event;</PRE
 >
 <TT
 CLASS="FUNCTION"
 >SDL_PollEvent</TT
 > removes the next event from the event queue, if there are no events on the queue it returns <SPAN
 CLASS="RETURNVALUE"
 >0</SPAN
 > otherwise it returns <SPAN
 CLASS="RETURNVALUE"
 >1</SPAN
 >. We use a <TT
 CLASS="FUNCTION"
 >while</TT
 > loop to process each event in turn.
 <PRE
 CLASS="PROGRAMLISTING"
 >while(SDL_PollEvent(&#38;test_event)) {</PRE
 >
 The <TT
 CLASS="FUNCTION"
 >SDL_PollEvent</TT
 > function take a pointer to an <SPAN
 CLASS="STRUCTNAME"
 >SDL_Event</SPAN
 > structure that is to be filled with event information. We know that if <TT
 CLASS="FUNCTION"
 >SDL_PollEvent</TT
 > removes an event from the queue then the event information will be placed in our <SPAN
 CLASS="STRUCTNAME"
 >test_event</SPAN
 > structure, but we also know that the <SPAN
 CLASS="emphasis"
 ><I
 CLASS="EMPHASIS"
 >type</I
 ></SPAN
 > of event will be placed in the <TT
 CLASS="STRUCTFIELD"
 ><I
 >type</I
 ></TT
 > member of <SPAN
 CLASS="STRUCTNAME"
 >test_event</SPAN
 >. So to handle each event <TT
 CLASS="STRUCTFIELD"
 ><I
 >type</I
 ></TT
 > seperately we use a <TT
 CLASS="FUNCTION"
 >switch</TT
 > statement.
 <PRE
 CLASS="PROGRAMLISTING"
 >  switch(test_event.type) {</PRE
 >
 We need to know what kind of events we're looking for <SPAN
 CLASS="emphasis"
 ><I
 CLASS="EMPHASIS"
 >and</I
 ></SPAN
 > the event <TT
 CLASS="STRUCTFIELD"
 ><I
 >type</I
 ></TT
 >'s of those events. So lets assume we want to detect where the user is moving the mouse pointer within our application. We look through our event types and notice that <TT
 CLASS="LITERAL"
 >SDL_MOUSEMOTION</TT
 > is, more than likely, the event we're looking for. A little <A
 HREF="sdlmousemotionevent.html"
 >more</A
 > research tells use that <TT
 CLASS="LITERAL"
 >SDL_MOUSEMOTION</TT
 > events are handled within the <A
 HREF="sdlmousemotionevent.html"
 ><SPAN
 CLASS="STRUCTNAME"
 >SDL_MouseMotionEvent</SPAN
 ></A
 > structure which is the <TT
 CLASS="STRUCTFIELD"
 ><I
 >motion</I
 ></TT
 > member of <SPAN
 CLASS="STRUCTNAME"
 >SDL_Event</SPAN
 >. We can check for the <TT
 CLASS="LITERAL"
 >SDL_MOUSEMOTION</TT
 > event <TT
 CLASS="STRUCTFIELD"
 ><I
 >type</I
 ></TT
 > within our <TT
 CLASS="FUNCTION"
 >switch</TT
 > statement like so:
 <PRE
 CLASS="PROGRAMLISTING"
 >    case SDL_MOUSEMOTION:</PRE
 >
 All we need do now is read the information out of the <TT
 CLASS="STRUCTFIELD"
 ><I
 >motion</I
 ></TT
 > member of <SPAN
 CLASS="STRUCTNAME"
 >test_event</SPAN
 >.
 <PRE
 CLASS="PROGRAMLISTING"
 >      printf("We got a motion event.\n");
       printf("Current mouse position is: (%d, %d)\n", test_event.motion.x, test_event.motion.y);
       break;
     default:
       printf("Unhandled Event!\n");
       break;
   }
 }
 printf("Event queue empty.\n");</PRE
 ></P
 ><P
 >It is also possible to push events onto the event queue and so use it as a two-way communication path. Both <A
 HREF="sdlpushevent.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_PushEvent</TT
 ></A
 > and <A
 HREF="sdlpeepevents.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_PeepEvents</TT
 ></A
 > allow you to place events onto the event queue. This is usually used to place a <TT
 CLASS="LITERAL"
 >SDL_USEREVENT</TT
 > on the event queue, however you could use it to post fake input events if you wished. Creating your own events is a simple matter of choosing the event type you want, setting the <TT
 CLASS="STRUCTFIELD"
 ><I
 >type</I
 ></TT
 > member and filling the appropriate member structure with information.
 <PRE
 CLASS="PROGRAMLISTING"
 >SDL_Event user_event;

 user_event.type=SDL_USEREVENT;
 user_event.user.code=2;
 user_event.user.data1=NULL;
 user_event.user.data2=NULL;
 SDL_PushEvent(&#38;user_event);</PRE
 ></P
 ></DIV
 ><DIV
 CLASS="REFSECT1"
 ><A
 NAME="AEN3942"
 ></A
 ><H2
 >See Also</H2
 ><P
 ><A
 HREF="sdlpollevent.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_PollEvent</TT
 ></A
 >,
 <A
 HREF="sdlpushevent.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_PushEvent</TT
 ></A
 >,
 <A
 HREF="sdlpeepevents.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_PeepEvents</TT
 ></A
 ></P
 ></DIV
 ><DIV
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	>SDL_Event</H1
	><DIV
	CLASS="REFNAMEDIV"
	><A
	NAME="AEN3711"
	></A
	><H2
	>Name</H2
	>SDL_Event -- General event structure</DIV
	><DIV
	CLASS="REFSECT1"
	><A
	NAME="AEN3714"
	></A
	><H2
	>Structure Definition</H2
	><PRE
	CLASS="PROGRAMLISTING"
	>typedef union{
	Uint8 type;
	SDL_ActiveEvent active;
	SDL_KeyboardEvent key;
	SDL_MouseMotionEvent motion;
	SDL_MouseButtonEvent button;
	SDL_JoyAxisEvent jaxis;
	SDL_JoyBallEvent jball;
	SDL_JoyHatEvent jhat;
	SDL_JoyButtonEvent jbutton;
	SDL_ResizeEvent resize;
	SDL_ExposeEvent expose;
	SDL_QuitEvent quit;
	SDL_UserEvent user;
	SDL_SysWMEvent syswm;
	} SDL_Event;</PRE
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	><DIV
	CLASS="REFSECT1"
	><A
	NAME="AEN3717"
	></A
	><H2
	>Structure Data</H2
	><DIV
	CLASS="INFORMALTABLE"
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	></A
	><P
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	><TABLE
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	><TT
	CLASS="STRUCTFIELD"
	><I
	>type</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	>The type of event</TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>active</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlactiveevent.html"
	>Activation event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>key</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlkeyboardevent.html"
	>Keyboard event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>motion</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlmousemotionevent.html"
	>Mouse motion event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>button</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlmousebuttonevent.html"
	>Mouse button event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>jaxis</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdljoyaxisevent.html"
	>Joystick axis motion event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>jball</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdljoyballevent.html"
	>Joystick trackball motion event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>jhat</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdljoyhatevent.html"
	>Joystick hat motion event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>jbutton</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdljoybuttonevent.html"
	>Joystick button event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>resize</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlresizeevent.html"
	>Application window resize event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>expose</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlexposeevent.html"
	>Application window expose event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>quit</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlquitevent.html"
	>Application quit request event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>user</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdluserevent.html"
	>User defined event</A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="STRUCTFIELD"
	><I
	>syswm</I
	></TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlsyswmevent.html"
	>Undefined window manager event</A
	></TD
	></TR
	></TBODY
	></TABLE
	><P
	></P
	></DIV
	></DIV
	><DIV
	CLASS="REFSECT1"
	><A
	NAME="AEN3791"
	></A
	><H2
	>Description</H2
	><P
	>The <SPAN
	CLASS="STRUCTNAME"
	>SDL_Event</SPAN
	> union is the core to all event handling is SDL, its probably the most important structure after <SPAN
	CLASS="STRUCTNAME"
	>SDL_Surface</SPAN
	>. <SPAN
	CLASS="STRUCTNAME"
	>SDL_Event</SPAN
	> is a union of all event structures used in SDL, using it is a simple matter of knowing which union member relates to which event <TT
	CLASS="STRUCTFIELD"
	><I
	>type</I
	></TT
	>.</P
	><P
	><DIV
	CLASS="INFORMALTABLE"
	><A
	NAME="AEN3799"
	></A
	><P
	></P
	><TABLE
	BORDER="1"
	CLASS="CALSTABLE"
	><THEAD
	><TR
	><TH
	ALIGN="LEFT"
	VALIGN="TOP"
	>Event <TT
	CLASS="STRUCTFIELD"
	><I
	>type</I
	></TT
	></TH
	><TH
	ALIGN="LEFT"
	VALIGN="TOP"
	>Event Structure</TH
	></TR
	></THEAD
	><TBODY
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="MIDDLE"
	><TT
	CLASS="LITERAL"
	>SDL_ACTIVEEVENT</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="MIDDLE"
	><A
	HREF="sdlactiveevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_ActiveEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_KEYDOWN/UP</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlkeyboardevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_KeyboardEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_MOUSEMOTION</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlmousemotionevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_MouseMotionEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_MOUSEBUTTONDOWN/UP</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlmousebuttonevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_MouseButtonEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_JOYAXISMOTION</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdljoyaxisevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_JoyAxisEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_JOYBALLMOTION</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdljoyballevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_JoyBallEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_JOYHATMOTION</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdljoyhatevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_JoyHatEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_JOYBUTTONDOWN/UP</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdljoybuttonevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_JoyButtonEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_QUIT</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlquitevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_QuitEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_SYSWMEVENT</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlsyswmevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_SysWMEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_VIDEORESIZE</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlresizeevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_ResizeEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_VIDEOEXPOSE</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdlexposeevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_ExposeEvent</SPAN
	></A
	></TD
	></TR
	><TR
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><TT
	CLASS="LITERAL"
	>SDL_USEREVENT</TT
	></TD
	><TD
	ALIGN="LEFT"
	VALIGN="TOP"
	><A
	HREF="sdluserevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_UserEvent</SPAN
	></A
	></TD
	></TR
	></TBODY
	></TABLE
	><P
	></P
	></DIV
	></P
	></DIV
	><DIV
	CLASS="REFSECT1"
	><A
	NAME="AEN3885"
	></A
	><H2
	>Use</H2
	><P
	>The <SPAN
	CLASS="STRUCTNAME"
	>SDL_Event</SPAN
	> structure has two uses</P
	><P
	></P
	><UL
	COMPACT="COMPACT"
	><LI
	><P
	>Reading events on the event queue</P
	></LI
	><LI
	><P
	>Placing events on the event queue</P
	></LI
	></UL
	><P
	>Reading events from the event queue is done with either <A
	HREF="sdlpollevent.html"
	><TT
	CLASS="FUNCTION"
	>SDL_PollEvent</TT
	></A
	> or <A
	HREF="sdlpeepevents.html"
	><TT
	CLASS="FUNCTION"
	>SDL_PeepEvents</TT
	></A
	>. We'll use <TT
	CLASS="FUNCTION"
	>SDL_PollEvent</TT
	> and step through an example.</P
	><P
	>First off, we create an empty <SPAN
	CLASS="STRUCTNAME"
	>SDL_Event</SPAN
	> structure.
	<PRE
	CLASS="PROGRAMLISTING"
	>SDL_Event test_event;</PRE
	>
	<TT
	CLASS="FUNCTION"
	>SDL_PollEvent</TT
	> removes the next event from the event queue, if there are no events on the queue it returns <SPAN
	CLASS="RETURNVALUE"
	>0</SPAN
	> otherwise it returns <SPAN
	CLASS="RETURNVALUE"
	>1</SPAN
	>. We use a <TT
	CLASS="FUNCTION"
	>while</TT
	> loop to process each event in turn.
	<PRE
	CLASS="PROGRAMLISTING"
	>while(SDL_PollEvent(&test_event)) {</PRE
	>
	The <TT
	CLASS="FUNCTION"
	>SDL_PollEvent</TT
	> function take a pointer to an <SPAN
	CLASS="STRUCTNAME"
	>SDL_Event</SPAN
	> structure that is to be filled with event information. We know that if <TT
	CLASS="FUNCTION"
	>SDL_PollEvent</TT
	> removes an event from the queue then the event information will be placed in our <SPAN
	CLASS="STRUCTNAME"
	>test_event</SPAN
	> structure, but we also know that the <SPAN
	CLASS="emphasis"
	><I
	CLASS="EMPHASIS"
	>type</I
	></SPAN
	> of event will be placed in the <TT
	CLASS="STRUCTFIELD"
	><I
	>type</I
	></TT
	> member of <SPAN
	CLASS="STRUCTNAME"
	>test_event</SPAN
	>. So to handle each event <TT
	CLASS="STRUCTFIELD"
	><I
	>type</I
	></TT
	> seperately we use a <TT
	CLASS="FUNCTION"
	>switch</TT
	> statement.
	<PRE
	CLASS="PROGRAMLISTING"
	> switch(test_event.type) {</PRE
	>
	We need to know what kind of events we're looking for <SPAN
	CLASS="emphasis"
	><I
	CLASS="EMPHASIS"
	>and</I
	></SPAN
	> the event <TT
	CLASS="STRUCTFIELD"
	><I
	>type</I
	></TT
	>'s of those events. So lets assume we want to detect where the user is moving the mouse pointer within our application. We look through our event types and notice that <TT
	CLASS="LITERAL"
	>SDL_MOUSEMOTION</TT
	> is, more than likely, the event we're looking for. A little <A
	HREF="sdlmousemotionevent.html"
	>more</A
	> research tells use that <TT
	CLASS="LITERAL"
	>SDL_MOUSEMOTION</TT
	> events are handled within the <A
	HREF="sdlmousemotionevent.html"
	><SPAN
	CLASS="STRUCTNAME"
	>SDL_MouseMotionEvent</SPAN
	></A
	> structure which is the <TT
	CLASS="STRUCTFIELD"
	><I
	>motion</I
	></TT
	> member of <SPAN
	CLASS="STRUCTNAME"
	>SDL_Event</SPAN
	>. We can check for the <TT
	CLASS="LITERAL"
	>SDL_MOUSEMOTION</TT
	> event <TT
	CLASS="STRUCTFIELD"
	><I
	>type</I
	></TT
	> within our <TT
	CLASS="FUNCTION"
	>switch</TT
	> statement like so:
	<PRE
	CLASS="PROGRAMLISTING"
	> case SDL_MOUSEMOTION:</PRE
	>
	All we need do now is read the information out of the <TT
	CLASS="STRUCTFIELD"
	><I
	>motion</I
	></TT
	> member of <SPAN
	CLASS="STRUCTNAME"
	>test_event</SPAN
	>.
	<PRE
	CLASS="PROGRAMLISTING"
	> printf("We got a motion event.\n");
	printf("Current mouse position is: (%d, %d)\n", test_event.motion.x, test_event.motion.y);
	break;
	default:
	printf("Unhandled Event!\n");
	break;
	}
	}
	printf("Event queue empty.\n");</PRE
	></P
	><P
	>It is also possible to push events onto the event queue and so use it as a two-way communication path. Both <A
	HREF="sdlpushevent.html"
	><TT
	CLASS="FUNCTION"
	>SDL_PushEvent</TT
	></A
	> and <A
	HREF="sdlpeepevents.html"
	><TT
	CLASS="FUNCTION"
	>SDL_PeepEvents</TT
	></A
	> allow you to place events onto the event queue. This is usually used to place a <TT
	CLASS="LITERAL"
	>SDL_USEREVENT</TT
	> on the event queue, however you could use it to post fake input events if you wished. Creating your own events is a simple matter of choosing the event type you want, setting the <TT
	CLASS="STRUCTFIELD"
	><I
	>type</I
	></TT
	> member and filling the appropriate member structure with information.
	<PRE
	CLASS="PROGRAMLISTING"
	>SDL_Event user_event;

	user_event.type=SDL_USEREVENT;
	user_event.user.code=2;
	user_event.user.data1=NULL;
	user_event.user.data2=NULL;
	SDL_PushEvent(&user_event);</PRE
	></P
	></DIV
	><DIV
	CLASS="REFSECT1"
	><A
	NAME="AEN3942"
	></A
	><H2
	>See Also</H2
	><P
	><A
	HREF="sdlpollevent.html"
	><TT
	CLASS="FUNCTION"
	>SDL_PollEvent</TT
	></A
	>,
	<A
	HREF="sdlpushevent.html"
	><TT
	CLASS="FUNCTION"
	>SDL_PushEvent</TT
	></A
	>,
	<A
	HREF="sdlpeepevents.html"
	><TT
	CLASS="FUNCTION"
	>SDL_PeepEvents</TT
	></A
	></P
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