Mercurial > sdl-ios-xcode
view docs/html/sdlcreatesemaphore.html @ 883:50f5a29c6a17
Date: Sat, 10 Apr 2004 02:25:33 -0400
From: Glenn Maynard
To: sdl@libsdl.org
Subject: [SDL] SDL_SetVideoMode() failing and not setting an error (patch)
Running an OpenGL SDL application off 1.2.7, at SDL_InitSubSystem(SDL_INIT_VIDEO) time:
Warning: Unable to initialize AAlib mouseUsing AAlib driver: Slang driver 1.0 (slang)
SDL_SetVideoMode then fails; SDL_GetError() returns "".
The installation problem is straightforward: X (the higher priority
driver) isn't running, so SDL is falling back on aalib. However,
no error is being set when aalib fails to initialize. This also
happens with the svgalib driver.
SDL_video.c line ~653 sets mode to NULL, since aalib didn't return an
OpenGL surface. Line ~711 ("failed setting a video mode") returns NULL.
The attached patch sets an error. It's a horrible, useless error
message--it should really say eg. "aalib does not support OpenGL"; this
should probably be done earlier in the individual drivers, too.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Sun, 11 Apr 2004 19:54:40 +0000 (2004-04-11) |
parents | 355632dca928 |
children |
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<HTML ><HEAD ><TITLE >SDL_CreateSemaphore</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="Multi-threaded Programming" HREF="thread.html"><LINK REL="PREVIOUS" TITLE="SDL_mutexV" HREF="sdlmutexv.html"><LINK REL="NEXT" TITLE="SDL_DestroySemaphore" HREF="sdldestroysemaphore.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SDL Library Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="sdlmutexv.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdldestroysemaphore.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLCREATESEMAPHORE" ></A >SDL_CreateSemaphore</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN7936" ></A ><H2 >Name</H2 >SDL_CreateSemaphore -- Creates a new semaphore and assigns an initial value to it.</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN7939" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN7940" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h" #include "SDL_thread.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >SDL_sem *<B CLASS="FSFUNC" >SDL_CreateSemaphore</B ></CODE >(Uint32 initial_value);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7946" ></A ><H2 >Description</H2 ><P ><TT CLASS="FUNCTION" >SDL_CreateSemaphore()</TT > creates a new semaphore and initializes it with the value <TT CLASS="PARAMETER" ><I >initial_value</I ></TT >. Each locking operation on the semaphore by <A HREF="sdlsemwait.html" >SDL_SemWait</A >, <A HREF="sdlsemtrywait.html" >SDL_SemTryWait</A > or <A HREF="sdlsemwaittimeout.html" >SDL_SemWaitTimeout</A > will atomically decrement the semaphore value. The locking operation will be blocked if the semaphore value is not positive (greater than zero). Each unlock operation by <A HREF="sdlsempost.html" >SDL_SemPost</A > will atomically increment the semaphore value.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7955" ></A ><H2 >Return Value</H2 ><P >Returns a pointer to an initialized semaphore or <SPAN CLASS="RETURNVALUE" >NULL</SPAN > if there was an error.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7959" ></A ><H2 >Examples</H2 ><P ><PRE CLASS="PROGRAMLISTING" >SDL_sem *my_sem; my_sem = SDL_CreateSemaphore(INITIAL_SEM_VALUE); if (my_sem == NULL) { return CREATE_SEM_FAILED; }</PRE ></P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7963" ></A ><H2 >See Also</H2 ><P ><A HREF="sdldestroysemaphore.html" ><TT CLASS="FUNCTION" >SDL_DestroySemaphore</TT ></A >, <A HREF="sdlsemwait.html" ><TT CLASS="FUNCTION" >SDL_SemWait</TT ></A >, <A HREF="sdlsemtrywait.html" ><TT CLASS="FUNCTION" >SDL_SemTryWait</TT ></A >, <A HREF="sdlsemwaittimeout.html" ><TT CLASS="FUNCTION" >SDL_SemWaitTimeout</TT ></A >, <A HREF="sdlsempost.html" ><TT CLASS="FUNCTION" >SDL_SemPost</TT ></A >, <A HREF="sdlsemvalue.html" ><TT CLASS="FUNCTION" >SDL_SemValue</TT ></A ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdlmutexv.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdldestroysemaphore.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_mutexV</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="thread.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_DestroySemaphore</TD ></TR ></TABLE ></DIV ></BODY ></HTML >