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Fixed bug #166 From the autoconf obsolete macros documentation: Macro: AC_CANONICAL_SYSTEM Determine the system type and set output variables to the names of the canonical system types. See section Getting the Canonical System Type, for details about the variables this macro sets. The user is encouraged to use either AC_CANONICAL_BUILD, or AC_CANONICAL_HOST, or AC_CANONICAL_TARGET, depending on the needs. Using AC_CANONICAL_TARGET is enough to run the two other macros. From the documentation for the canonical environments: case $target in i386-*-mach* | i386-*-gnu*) obj_format=aout emulation=mach bfd_gas=yes ;; i960-*-bout) obj_format=bout ;; esac Note that the above example uses $target because it's taken from a tool which can be built on some architecture ($build), run on another ($host), but yet handle data for a third architecture ($target). Such tools are usually part of a compiler suite, they generate code for a specific $target. However $target should be meaningless for most packages. If you want to base a decision on the system where your program will be run, make sure you use the $host variable.
author Sam Lantinga <slouken@libsdl.org>
date Sun, 19 Mar 2006 05:27:22 +0000
parents 355632dca928
children
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<HTML
><HEAD
><TITLE
>SDL_LockSurface</TITLE
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><H1
><A
NAME="SDLLOCKSURFACE"
></A
>SDL_LockSurface</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1919"
></A
><H2
>Name</H2
>SDL_LockSurface&nbsp;--&nbsp;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-&#62;<TT
CLASS="STRUCTFIELD"
><I
>pixels</I
></TT
></I
></TT
>, using the pixel format stored in
<TT
CLASS="PARAMETER"
><I
>surface-&#62;<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 &#60; 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
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