On Sun, 1 Jun 2003, Jon Leech wrote:
On Mon, Jun 02, 2003 at 01:09:59AM -0400, Mark Vojkovich wrote:
Extending GL to recognize a relatively unknown XFree86 format is a hard sell. I wouldn't even be able to convince my own company to dirty their code for it seeing as how relatively nobody is using XvMC.
Do you implement this without touching the GL driver code? Seems difficult to avoid touching the driver in the general case, when the format and location of pbuffer memory is intentionally opaque.
I haven't touched the GL driver at all. XvMC is direct rendered and the assumption is that it's using the same direct rendering architecture as OpenGL and should be able to get access to the pbuffer memory if it can name it, just like GL would be able to do.
You may not have touched the GL driver at all, but you are using some sort of non-public interface to it to convert a pbuffer ID to an address. That was somewhat the point of Jon's comment. I certainly don't see anything in any pbuffer documentation that I've ever seen that describes how to get the address in video memory of a pbuffer. In fact, the documentation that I have seen goes to some length to explain that at certain points in time the pbuffer may not have an address in video memory.
Instead of modifying your 3D driver, you've used an internal interface that, luckilly for you, just happened to already be there. The rest of us may not be so lucky.
Given that, I have only three comments / requests for the function.
1. Please provide a way to specify the destination buffer (i.e., GL_FRONT, GL_BACK_RIGHT, etc.) of the copy.
2. Make explicit the coordinate conversion monkey business.
3. Is there a way for apps to determine if this function is available on their hardware? Later this year when pbuffers become available in the open-source drivers, we probably won't (initially) have support for this function. I fully expect that support will follow soon, but it won't be there initially.
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