1 .TH "SDL_LockSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 

     2 .SH "NAME"

     3 SDL_LockSurface \- Lock a surface for directly access\&.

     4 .SH "SYNOPSIS"

     5 .PP

     6 \fB#include "SDL\&.h"

     7 .sp

     8 \fBint \fBSDL_LockSurface\fP\fR(\fBSDL_Surface *surface\fR);

     9 .SH "DESCRIPTION"

    10 .PP

    11 \fBSDL_LockSurface\fP sets up a surface for directly accessing the pixels\&. Between calls to \fBSDL_LockSurface\fP and \fBSDL_UnlockSurface\fP, you can write to and read from \fBsurface->\fBpixels\fR\fR, using the pixel format stored in \fBsurface->\fBformat\fR\fR\&. Once you are done accessing the surface, you should use \fBSDL_UnlockSurface\fP to release it\&.

    12 .PP

    13 Not all surfaces require locking\&. If \fBSDL_MUSTLOCK\fP(\fBsurface\fR) evaluates to \fB0\fR, then you can read and write to the surface at any time, and the pixel format of the surface will not change\&. 

    14 .PP

    15 No operating system or library calls should be made between lock/unlock pairs, as critical system locks may be held during this time\&.

    16 .PP

    17 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\&. 

    18 .PP

    19 .nf

    20 \f(CW    \&.

    21     \&.

    22     SDL_LockSurface( surface );

    23     \&.

    24     /* Surface is locked */

    25     /* Direct pixel access on surface here */

    26     \&.

    27     SDL_LockSurface( surface );

    28     \&.

    29     /* More direct pixel access on surface */

    30     \&.

    31     SDL_UnlockSurface( surface );

    32     /* Surface is still locked */

    33     /* Note: Is versions < 1\&.1\&.8, the surface would have been */

    34     /* no longer locked at this stage                         */

    35     \&.

    36     SDL_UnlockSurface( surface );

    37     /* Surface is now unlocked */

    38     \&.

    39     \&.\fR

    40 .fi

    41 .PP

    42 .SH "RETURN VALUE"

    43 .PP

    44 \fBSDL_LockSurface\fP returns \fB0\fR, or \fB-1\fR if the surface couldn\&'t be locked\&.

    45 .SH "SEE ALSO"

    46 .PP

    47 \fI\fBSDL_UnlockSurface\fP\fR

    48 ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01