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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 f12379c41042
children
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>Chapter 12. Multi-threaded Programming</H1
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><DT
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>Table of Contents</B
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><DT
><A
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>SDL_CreateThread</A
>&nbsp;--&nbsp;Creates a new thread of execution that shares its parent's properties.</DT
><DT
><A
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>SDL_ThreadID</A
>&nbsp;--&nbsp;Get the 32-bit thread identifier for the current thread.</DT
><DT
><A
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>SDL_GetThreadID</A
>&nbsp;--&nbsp;Get the SDL thread ID of a SDL_Thread</DT
><DT
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>SDL_WaitThread</A
>&nbsp;--&nbsp;Wait for a thread to finish.</DT
><DT
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>SDL_KillThread</A
>&nbsp;--&nbsp;Gracelessly terminates the thread.</DT
><DT
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>SDL_CreateMutex</A
>&nbsp;--&nbsp;Create a mutex</DT
><DT
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>SDL_DestroyMutex</A
>&nbsp;--&nbsp;Destroy a mutex</DT
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>&nbsp;--&nbsp;Lock a mutex</DT
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>SDL_mutexV</A
>&nbsp;--&nbsp;Unlock a mutex</DT
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>SDL_CreateSemaphore</A
>&nbsp;--&nbsp;Creates a new semaphore and assigns an initial value to it.</DT
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>SDL_DestroySemaphore</A
>&nbsp;--&nbsp;Destroys a semaphore that was created by <A
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>SDL_CreateSemaphore</A
>.</DT
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>SDL_SemWait</A
>&nbsp;--&nbsp;Lock a semaphore and suspend the thread if the semaphore value is zero.</DT
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>SDL_SemTryWait</A
>&nbsp;--&nbsp;Attempt to lock a semaphore but don't suspend the thread.</DT
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>SDL_SemWaitTimeout</A
>&nbsp;--&nbsp;Lock a semaphore, but only wait up to a specified maximum time.</DT
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>SDL_SemPost</A
>&nbsp;--&nbsp;Unlock a semaphore.</DT
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>SDL_SemValue</A
>&nbsp;--&nbsp;Return the current value of a semaphore.</DT
><DT
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>SDL_CreateCond</A
>&nbsp;--&nbsp;Create a condition variable</DT
><DT
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>SDL_DestroyCond</A
>&nbsp;--&nbsp;Destroy a condition variable</DT
><DT
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>SDL_CondSignal</A
>&nbsp;--&nbsp;Restart a thread wait on a condition variable</DT
><DT
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>SDL_CondBroadcast</A
>&nbsp;--&nbsp;Restart all threads waiting on a condition variable</DT
><DT
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>SDL_CondWait</A
>&nbsp;--&nbsp;Wait on a condition variable</DT
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>SDL_CondWaitTimeout</A
>&nbsp;--&nbsp;Wait on a condition variable, with timeout</DT
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>SDL provides functions for creating threads, mutexes, semphores and condition variables.</P
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>In general, you must be very aware of concurrency and data integrity issues
when writing multi-threaded programs.  Some good guidelines include:
<P
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>Don't call SDL video/event functions from separate threads</P
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>Don't use any library functions in separate threads</P
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>Don't perform any memory management in separate threads</P
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>Lock global variables which may be accessed by multiple threads</P
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>Never terminate threads, always set a flag and wait for them to quit</P
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>Think very carefully about all possible ways your code may interact</P
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>Note: </B
>SDL's threading is not implemented on MacOS, due to that lack of preemptive thread support (Mac OS X dos nt suffer from this problem)</P
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