GLX 1.3 fix

GLX 1.3 fix

The base issue here is that the default GLX implementation on some Linux laptops lies about its version numbering. Code in SkNativeGLContext_unix.cpp was checking the version number to avoid using FBConfigs in versions prior to 1.3.

To resolve this I have added a configuration path using the pre-1.3 method (i.e., XGetVisualInfo and glXGetConfig). I have also removed the run-time check and added a #define to toggle between the two implementations. This allows us to use the FBConfigs with the wayward GLX implementation but have a backup plan if we ever really encounter an older implementation.

[bsalomon, 2012-03-14 14:48:11]

Is there any advantage to us of using the FBConfigs when the driver claims 1.2
support but actually supports FBConfigs?  If not it seems preferable to just
take the alternate code path. As it is now someone who had a genuine 1.2 system
would have to know to change the added #define. Or is 1.2 so old we don't care?

http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
File src/gpu/unix/SkNativeGLContext_unix.cpp (right):

http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
src/gpu/unix/SkNativeGLContext_unix.cpp:12: #define GLX_1_3 1
Is it possible to check a macro being pulled in from the system's GLX header to
know whether we're building against a 1.3 header or not?

http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
src/gpu/unix/SkNativeGLContext_unix.cpp:104: if (vi) {
Not necessary for this change, but I think we can pull out the loop that looks
at sample counts and instead just pick the first config that works. We won't
actually ever use the back buffer so its config doesn't really matter. In fact,
it  may be better to create a pbuffer-based context, assuming it runs on the
actual GPU. I don't know if this would help us run in a headless configuration
or not.

[robertphillips, 2012-03-14 15:20:10]

I believe if someone has a true 1.2 implementation the 1.3 code won't compile at
all which is why the run time check is kind of odd.

[robertphillips, 2012-03-14 15:20:20]

http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
File src/gpu/unix/SkNativeGLContext_unix.cpp (right):

http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
src/gpu/unix/SkNativeGLContext_unix.cpp:12: #define GLX_1_3 1
There are #defines in the header but I do not believe they are standard. The
glXQueryVersion entry point is the official method.

http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
src/gpu/unix/SkNativeGLContext_unix.cpp:104: if (vi) {
One thing to keep in mind is that the pre-1.3 calls can't be used for GLXPbuffer
creation (i.e., glXCreatePbuffer requires an FBConfig).

[bsalomon, 2012-03-14 15:28:00]

On 2012/03/14 15:20:20, robertphillips wrote:
>
http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
> File src/gpu/unix/SkNativeGLContext_unix.cpp (right):
> 
>
http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
> src/gpu/unix/SkNativeGLContext_unix.cpp:12: #define GLX_1_3 1
> There are #defines in the header but I do not believe they are standard. The
> glXQueryVersion entry point is the official method.
> 
>
http://codereview.appspot.com/5823049/diff/1/src/gpu/unix/SkNativeGLContext_u...
> src/gpu/unix/SkNativeGLContext_unix.cpp:104: if (vi) {
> One thing to keep in mind is that the pre-1.3 calls can't be used for
GLXPbuffer
> creation (i.e., glXCreatePbuffer requires an FBConfig).

LGTM

[robertphillips, 2012-03-14 18:09:49]

Committed as r3384