making sure opengl is available

This troubleshooting is listed in this post:
https://init.linpro.no/pipermail/skolelinux.no/cinelerra/2010-January/016493.html

But I thought I'd repost here so that I always have this information at hand:

I have a GeForce 8800GT card installed in my box. I see glxinfo says I have OpenGL:
[sfr...@ogre my_cinelerra]$ glxinfo | head -20
name of display: :0.0
display: :0 screen: 0
direct rendering: Yes
server glx vendor string: NVIDIA Corporation
server glx version string: 1.4

I see glxgears points to the libGL.so.1 in /usr/lib64/nvidia:
[sfr...@ogre my_cinelerra]$ ldd `which glxgears`
linux-vdso.so.1 => (0x00007fff85dff000)
libGL.so.1 => /usr/lib64/nvidia/libGL.so.1 (0x00007f791fa75000)
libm.so.6 => /lib64/libm.so.6 (0x0000003f1bc00000)
libX11.so.6 => /usr/lib64/libX11.so.6 (0x0000003f1e800000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x0000003f1c400000)
libc.so.6 => /lib64/libc.so.6 (0x0000003f1b800000)

libGLcore.so.1 => /usr/lib64/nvidia/libGLcore.so.1 (0x00007f791e5a3000) libnvidia-tls.so.1 => /usr/lib64/nvidia/tls/libnvidia-tls.so.1 (0x00007f791e4a1000)

libXext.so.6 => /usr/lib64/libXext.so.6 (0x0000003f1ec00000)
libdl.so.2 => /lib64/libdl.so.2 (0x0000003f1c000000)
libxcb.so.1 => /usr/lib64/libxcb.so.1 (0x0000003f1e400000)
/lib64/ld-linux-x86-64.so.2 (0x0000003f1b400000)
libXau.so.6 => /usr/lib64/libXau.so.6 (0x0000003f1e000000


I see that the libGL.so.1 in that directory has the appropriate OpenGL hooks:
[sfr...@ogre usr]$ strings -a /usr/lib64/nvidia/libGL.so.1 | grep glDeleteShader
glDeleteShader
[sfr...@ogre usr]$ strings -a /usr/lib64/nvidia/libGL.so.1 | grep glUseProgram
glUseProgram
glUseProgramObjectARB

I've tried manually pointing configure.in to the /usr/lib64/nvidia directory:
AC_CHECK_LIB([GL], [glUseProgram],
[OPENGL_LIBS="-lGL"; libGL=yes],
# On SUSE/OpenSUSE, NVidia places the OpenGL 2.0 capable library in
/usr/X11R6/lib
# but it doesn't place a libGL.so there, so the linker won't pick it up
# we have to use the explicit libGL.so.1 path.
save_LIBS="$LIBS"
for l in /usr/lib64/nvidia /usr/X11R6/lib /usr/X11R6/lib64; do
LIBS="$l/libGL.so.1"
AC_MSG_CHECKING(for glUseProgram in $l/libGL.so.1)
AC_TRY_LINK([],[extern int glUseProgram();
glUseProgram();],
[OPENGL_LIBS="$l/libGL.so.1";
libGL=yes],[libGL=no])
AC_MSG_RESULT([$libGL])
test $libGL = yes && break
done
LIBS="$save_LIBS"

In the end, even though ./configure did not recognize that I had openGL properly installed, I had to explicitly enable opengl on my ./configure line:
./configure --enable-opengl

Who knew?
da mule