Mercurial > sdl-ios-xcode
view docs/html/sdllocksurface.html @ 885:9f6ad2286011
Date: Wed, 28 Apr 2004 16:52:41 -0400
From: "Damien A"
Subject: testdyngl fix
The test program you included in the latest version of SDL crashes on startup in Window (XP). The reason for this is that OpenGL functions on Windows use the __stdcall calling convention, not the C convention. Placing APIENTRY infront of the * operator solves this problem.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Fri, 30 Apr 2004 18:33:30 +0000 (2004-04-30) |
parents | 355632dca928 |
children |
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<HTML ><HEAD ><TITLE >SDL_LockSurface</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="Video" HREF="video.html"><LINK REL="PREVIOUS" TITLE="SDL_FreeSurface" HREF="sdlfreesurface.html"><LINK REL="NEXT" TITLE="SDL_UnlockSurface" HREF="sdlunlocksurface.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="sdlfreesurface.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdlunlocksurface.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLLOCKSURFACE" ></A >SDL_LockSurface</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN1919" ></A ><H2 >Name</H2 >SDL_LockSurface -- Lock a surface for directly access.</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN1922" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN1923" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >int <B CLASS="FSFUNC" >SDL_LockSurface</B ></CODE >(SDL_Surface *surface);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN1929" ></A ><H2 >Description</H2 ><P ><TT CLASS="FUNCTION" >SDL_LockSurface</TT > sets up a surface for directly accessing the pixels. Between calls to <TT CLASS="FUNCTION" >SDL_LockSurface</TT > and <TT CLASS="FUNCTION" >SDL_UnlockSurface</TT >, you can write to and read from <TT CLASS="PARAMETER" ><I >surface-><TT CLASS="STRUCTFIELD" ><I >pixels</I ></TT ></I ></TT >, using the pixel format stored in <TT CLASS="PARAMETER" ><I >surface-><TT CLASS="STRUCTFIELD" ><I >format</I ></TT ></I ></TT >. Once you are done accessing the surface, you should use <TT CLASS="FUNCTION" >SDL_UnlockSurface</TT > to release it.</P ><P >Not all surfaces require locking. If <TT CLASS="LITERAL" >SDL_MUSTLOCK</TT >(<TT CLASS="PARAMETER" ><I >surface</I ></TT >) evaluates to <SPAN CLASS="RETURNVALUE" >0</SPAN >, then you can read and write to the surface at any time, and the pixel format of the surface will not change. </P ><P >No operating system or library calls should be made between lock/unlock pairs, as critical system locks may be held during this time.</P ><P >It should be noted, that since SDL 1.1.8 surface locks are recursive. This means that you can lock a surface multiple times, but each lock must have a match unlock. <PRE CLASS="PROGRAMLISTING" > . . SDL_LockSurface( surface ); . /* Surface is locked */ /* Direct pixel access on surface here */ . SDL_LockSurface( surface ); . /* More direct pixel access on surface */ . SDL_UnlockSurface( surface ); /* Surface is still locked */ /* Note: Is versions < 1.1.8, the surface would have been */ /* no longer locked at this stage */ . SDL_UnlockSurface( surface ); /* Surface is now unlocked */ . .</PRE ></P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN1947" ></A ><H2 >Return Value</H2 ><P ><TT CLASS="FUNCTION" >SDL_LockSurface</TT > returns <SPAN CLASS="RETURNVALUE" >0</SPAN >, or <SPAN CLASS="RETURNVALUE" >-1</SPAN > if the surface couldn't be locked.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN1953" ></A ><H2 >See Also</H2 ><P ><A HREF="sdlunlocksurface.html" ><TT CLASS="FUNCTION" >SDL_UnlockSurface</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="sdlfreesurface.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="sdlunlocksurface.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_FreeSurface</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="video.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_UnlockSurface</TD ></TR ></TABLE ></DIV ></BODY ></HTML >