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Date: Thu, 17 Apr 2003 23:27:34 -0400 From: Darrell Walisser Subject: Yet another OS X cursor bug The synopsis: 1. Call SDL_ShowCursor(0); 2. Call SDL_SetVideoMode(); 3. Call SDL_GetEvent(); 3. Call SDL_ShowCursor(1); The result: Sometimes the cursor doesn't come back! Ack! Oddly enough, it does come back when mousing over the dock or clicking in the menu bar. But that's besides the point. The reason why this is happening is a flaw in the handling of activation/deactivation events. The short explanation is that the HideCursor() and ShowCursor() calls must be balanced, but if the cursor was initially hidden, HideCursor() was called again on the activate event - so now the next ShowCursor() fails (as does the next, and the next, for some reason). So, here's the patch. All it does is keep track of the HideCursor()/ShowCursor() calls so that they will always be balanced.
author Sam Lantinga <slouken@libsdl.org>
date Sun, 20 Apr 2003 05:41:16 +0000
parents e5bc29de3f0a
children 355632dca928
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<HTML
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>Multi-threaded Programming</TITLE
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>Chapter 12. Multi-threaded Programming</A
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><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
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>SDL_CreateThread</A
> &#8212; Creates a new thread of execution that shares its parent's properties.</DT
><DT
><A
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>SDL_ThreadID</A
> &#8212; Get the 32-bit thread identifier for the current thread.</DT
><DT
><A
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>SDL_GetThreadID</A
> &#8212; Get the SDL thread ID of a SDL_Thread</DT
><DT
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>SDL_WaitThread</A
> &#8212; Wait for a thread to finish.</DT
><DT
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>SDL_KillThread</A
> &#8212; Gracelessly terminates the thread.</DT
><DT
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>SDL_CreateMutex</A
> &#8212; Create a mutex</DT
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>SDL_DestroyMutex</A
> &#8212; Destroy a mutex</DT
><DT
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>SDL_mutexP</A
> &#8212; Lock a mutex</DT
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> &#8212; Unlock a mutex</DT
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> &#8212; Creates a new semaphore and assigns an initial value to it.</DT
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>SDL_DestroySemaphore</A
> &#8212; Destroys a semaphore that was created by <A
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>SDL_CreateSemaphore</A
>.</DT
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>SDL_SemWait</A
> &#8212; Lock a semaphore and suspend the thread if the semaphore value is zero.</DT
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>SDL_SemTryWait</A
> &#8212; Attempt to lock a semaphore but don't suspend the thread.</DT
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>SDL_SemWaitTimeout</A
> &#8212; Lock a semaphore, but only wait up to a specified maximum time.</DT
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>SDL_SemPost</A
> &#8212; Unlock a semaphore.</DT
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> &#8212; Return the current value of a semaphore.</DT
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> &#8212; Create a condition variable</DT
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>SDL_DestroyCond</A
> &#8212; Destroy a condition variable</DT
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>SDL_CondSignal</A
> &#8212; Restart a thread wait on a condition variable</DT
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>SDL_CondBroadcast</A
> &#8212; Restart all threads waiting on a condition variable</DT
><DT
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>SDL_CondWait</A
> &#8212; Wait on a condition variable</DT
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>SDL_CondWaitTimeout</A
> &#8212; Wait on a condition variable, with timeout</DT
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><P
>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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><UL
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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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><P
><B
>Note: </B
>SDL's threading is not implemented on MacOS, due to that lack of preemptive thread support (MacOS X dos nt suffer from this problem)</P
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