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Fixed bug #611 From Tim Angus 2008-08-12 11:18:06 I'm one of the maintainers of ioquake3.org, an updated version of the Quake 3 engine. Relatively recently, we moved ioq3 to use SDL as a replacement for 95% of the platform specific code that was there. On the whole it's doing a great job but unfortunately since the move we've been getting complaints about the quality of the mouse input on the Windows platform to the point where for many the game is unplayable. Put in other terms, the current stable SDL 1.2 is basically not fit for purpose if you need high quality mouse input as you do in a first person shooter. Over the weekend I decided to pull my finger out and actually figure out what's going on. There are basically two major problems. Firstly, when using the "windib" driver, mouse input is gathered via the WM_MOUSEMOVE message. Googling for this indicates that often this is known to result in "spurious" and/or "missing" mouse movement events; this is the primary cause of the poor mouse input. The second problem is that the "directx" driver does not work at all in combination with OpenGL meaning that you can't use DirectInput if your application also uses OpenGL. In other words you're locked into using the "windib" driver and its poor mouse input. In order to address these problems I've done the following: * Remove WM_MOUSEMOVE based motion event generation and replace with calls to GetCursorPos which seems much more reliable. In order to achieve this I've moved mouse motion out into a separate function that is called once per DIB_PumpEvents. * Remove the restriction on the "directx" driver being inoperable in combination with OpenGL. There is a bug for this issues that I've hijacked to a certain extent (http://bugzilla.libsdl.org/show_bug.cgi?id=265). I'm the first to admit I don't really understand why this restriction is there in the first place. The commit message for the bug fix that introduced this restriction (r581) isn't very elaborate and I couldn't see any other bug tracking the issue. If anyone has more information on the bug that was avoided by r581 it would be helpful as I/someone could then look into addressing the problem without disabling the "directx" driver. * I've also removed the restriction on not being allowed to use DirectInput in windowed mode. I couldn't see any reason for this, at least not from our perspective. I have my suspicions that it'll be something like matching up the cursor with the mouse coordinates... * I bumped up the DirectInput API used to version 7 in order to get access to mouse buttons 4-7. I've had to inject a little bit of the DX7 headers into SDL there as the MinGW ones aren't up to date in this respect.
author Sam Lantinga <slouken@libsdl.org>
date Thu, 02 Apr 2009 04:43:36 +0000
parents 60fa95a89846
children
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>SDL_Event</H1
><DIV
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><A
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><H2
>Name</H2
>SDL_Event&nbsp;--&nbsp;General event structure</DIV
><DIV
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><A
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></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
></DIV
><DIV
CLASS="REFSECT1"
><A
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><H2
>Structure Data</H2
><DIV
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><TABLE
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><TR
><TD
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><TT
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><I
>type</I
></TT
></TD
><TD
ALIGN="LEFT"
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>The type of event</TD
></TR
><TR
><TD
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><TT
CLASS="STRUCTFIELD"
><I
>active</I
></TT
></TD
><TD
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><A
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>Activation event</A
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><TT
CLASS="STRUCTFIELD"
><I
>key</I
></TT
></TD
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><A
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>Keyboard event</A
></TD
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><TR
><TD
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><TT
CLASS="STRUCTFIELD"
><I
>motion</I
></TT
></TD
><TD
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><A
HREF="sdlmousemotionevent.html"
>Mouse motion event</A
></TD
></TR
><TR
><TD
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><TT
CLASS="STRUCTFIELD"
><I
>button</I
></TT
></TD
><TD
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><A
HREF="sdlmousebuttonevent.html"
>Mouse button event</A
></TD
></TR
><TR
><TD
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><TT
CLASS="STRUCTFIELD"
><I
>jaxis</I
></TT
></TD
><TD
ALIGN="LEFT"
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><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"
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><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
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><A
HREF="sdljoyhatevent.html"
>Joystick hat motion event</A
></TD
></TR
><TR
><TD
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><TT
CLASS="STRUCTFIELD"
><I
>jbutton</I
></TT
></TD
><TD
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><A
HREF="sdljoybuttonevent.html"
>Joystick button event</A
></TD
></TR
><TR
><TD
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><TT
CLASS="STRUCTFIELD"
><I
>resize</I
></TT
></TD
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><A
HREF="sdlresizeevent.html"
>Application window resize event</A
></TD
></TR
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><TT
CLASS="STRUCTFIELD"
><I
>expose</I
></TT
></TD
><TD
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><A
HREF="sdlexposeevent.html"
>Application window expose event</A
></TD
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><TT
CLASS="STRUCTFIELD"
><I
>quit</I
></TT
></TD
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>Application quit request event</A
></TD
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><TT
CLASS="STRUCTFIELD"
><I
>user</I
></TT
></TD
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><A
HREF="sdluserevent.html"
>User defined event</A
></TD
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><TT
CLASS="STRUCTFIELD"
><I
>syswm</I
></TT
></TD
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HREF="sdlsyswmevent.html"
>Undefined window manager event</A
></TD
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><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"
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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"
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><TT
CLASS="LITERAL"
>SDL_ACTIVEEVENT</TT
></TD
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><A
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><SPAN
CLASS="STRUCTNAME"
>SDL_ActiveEvent</SPAN
></A
></TD
></TR
><TR
><TD
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><TT
CLASS="LITERAL"
>SDL_KEYDOWN/UP</TT
></TD
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><A
HREF="sdlkeyboardevent.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_KeyboardEvent</SPAN
></A
></TD
></TR
><TR
><TD
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><TT
CLASS="LITERAL"
>SDL_MOUSEMOTION</TT
></TD
><TD
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><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
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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"
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><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"
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><TT
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>SDL_VIDEOEXPOSE</TT
></TD
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><SPAN
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>SDL_ExposeEvent</SPAN
></A
></TD
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><TR
><TD
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><TT
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>SDL_USEREVENT</TT
></TD
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HREF="sdluserevent.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_UserEvent</SPAN
></A
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><P
></P
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><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
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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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