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view docs/man3/SDL_LockSurface.3 @ 2359:b70b96e615d2 gsoc2008_iphone

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These files are the OpenGL ES render driver. You should be able to use them on any platform that supports OpenGL ES -- not just iPhone. The driver is based off the OpenGL render driver. There are a few differences between OpenGL and OpenGL ES that present difficulties for this driver: - OpenGL ES does NOT support many pixel formats (for example, no GL_BGR). Also, when using texture functions format and internalFormat must be the same -- this means 32 bit packed formats like SDL_PIXELFORMAT_BGR888 cannot be automatically converted to GL_RGB (which is 24bpp). - OpenGL ES doesn't have GL_PACK_ROW_LENGTH, which means data must be reformatted before uploading changes to dirty rects. This change has been added. - OpenGL ES doesn't support paletted textures, though there is an extension. I'm looking into this. Some other notable differences: - OpenGL ES has an extension called GL_OES_draw_texture which allows for quicker 2D sprite-type drawing. I use this in GL_RenderCopy when it is available. The iPhone supports the extension, but the iPhone Simulator does not (presently). - No glBegin() / glEnd() and no GL_QUADS! I'm using glDrawArrays with GL_TRIANGLE_STRIP instead!
author Holmes Futrell <hfutrell@umail.ucsb.edu>
date Thu, 17 Jul 2008 23:31:42 +0000
parents 546f7c1eb755
children 1238da4a7112
line wrap: on
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.TH "SDL_LockSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_LockSurface \- Lock a surface for directly access\&.
.SH "SYNOPSIS"
.PP
\fB#include "SDL\&.h"
.sp
\fBint \fBSDL_LockSurface\fP\fR(\fBSDL_Surface *surface\fR);
.SH "DESCRIPTION"
.PP
\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\&.
.PP
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\&. 
.PP
No operating system or library calls should be made between lock/unlock pairs, as critical system locks may be held during this time\&.
.PP
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\&. 
.PP
.nf
\f(CW    \&.
    \&.
    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 */
    \&.
    \&.\fR
.fi
.PP
.SH "RETURN VALUE"
.PP
\fBSDL_LockSurface\fP returns \fB0\fR, or \fB-1\fR if the surface couldn\&'t be locked\&.
.SH "SEE ALSO"
.PP
\fI\fBSDL_UnlockSurface\fP\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01