# SDL 1.3 on Mac OS X speed hit

**URL:** <https://discourse.libsdl.org/t/sdl-1-3-on-mac-os-x-speed-hit/14730>\
**Category:** SDL Development\
**Created:** [July 22, 2007, 9:53am UTC](https://discourse.libsdl.org/t/sdl-1-3-on-mac-os-x-speed-hit/14730 "2007-07-22T09:53:32Z")\
**Posts on this page:** 2\
**Page:** 2

<div class="post-metadata">

**Author:** ![Eric\_Wing](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/e/ea5d25/32.png) [@Eric\_Wing](https://discourse.libsdl.org/u/Eric_Wing)\
**Post date:** [August 15, 2007, 7:45am UTC](https://discourse.libsdl.org/t/sdl-1-3-on-mac-os-x-speed-hit/14730/21 "2007-08-15T07:45:34Z")

</div>

Hi, I thought I would share a few tidbits of what I know.

glBegin()/glEnd():  
Interestingly, OpenGL 3 will actually eliminate glBegin()/glEnd() aka  
immediate mode stuff. So avoiding the API is not just about  
performance anymore 😛

Quick notes about the multithreaded engine:  
First it you have an older version of Xcode or OS X that predates  
10.4.7 (or was it 10.4.8), the constant kCGLCEMPEngine is not defined.  
I recommend defining it or just using the explicit number 313. (I got  
bit by this in some other projects.)

Second, the multithreaded engine performance will vary with how your  
application uses OpenGL. If you don’t dispatch enough commands to keep  
the OpenGL pipeline busy, you may actually see worse performance due  
to the extra overhead incurred by the multithreaded OpenGL engine. (I  
saw this with some trivial OpenGL programs I wrote.) So we will need  
to benchmark to figure out if it is worth activating or not, or if it  
needs to be exposed to the end user API to enable based on their own  
application.

Pixel Formats:  
As for pixel format stuff, Apple keeps stating you should use a  
particular pixel format for optimal performance (GL\_BGRA,  
GL\_UNSIGNED\_INT\_8\_8\_8\_REV plus some other stuff you have to do in the  
image loaders). I’m a little dazzled by it because I think they play a  
few games to deal with the endian differences between PowerPC and  
Intel. They do have a new developer example called OpenGLScreenShot  
online which talks about it in the code.

Also, I’ve been working on some ImageIO stuff for another project,  
though I mentioned to Sam I was interested in seeing the SDL\_image  
library for 1.3 use ImageIO as the backend also. A few interesting  
tidbits about ImageIO. They use opaque data types for the Image  
references. To actually get at the pixel data, you must “draw” the  
image to a graphics context. I noticed that for 24-bit RGB images, you  
cannot actually create a 24-bit context and it must be a 32-bit  
context. Also the Accelerate framework vImage APIs don’t really like  
dealing with RGB and want to deal with ARGB. They have one set of APIs  
that will let you convert between 24-bit to 32-bit. I have not  
experimented yet with 16-bit formats. But I’m wondering if it’s just  
better to always convert immediately to 32-bit for the image loaders.

Thanks,  
Eric

---

<div class="post-metadata">

**Author:** ![icculus](https://discourse.libsdl.org/user_avatar/discourse.libsdl.org/icculus/32/81_2.png) [@icculus](https://discourse.libsdl.org/u/icculus)\
**Post date:** [August 15, 2007, 8:53pm UTC](https://discourse.libsdl.org/t/sdl-1-3-on-mac-os-x-speed-hit/14730/22 "2007-08-15T20:53:21Z")

</div>

> saw this with some trivial OpenGL programs I wrote.) So we will need  
> to benchmark to figure out if it is worth activating or not, or if it  
> needs to be exposed to the end user API to enable based on their own  
> application.

Yeah, maybe this should be something flagged with SDL\_GL\_SetAttribute(),  
which is a no-op on most platforms.

SDL\_GL\_MULTITHREADED

As long as there’s a big warning sign next to it that says “THIS DOES  
NOT MEAN ‘MAKE THE GL THREAD SAFE’ ON ANY PLATFORM.”

–ryan.

[Previous page](https://discourse.libsdl.org/t/sdl-1-3-on-mac-os-x-speed-hit/14730.md?page=1)