No stars in Qt QOpenGLWidget

[GitHubCYH]

When I integrate osgEarth into QOpenGLWidget (Qt 6.9.3) on the Windows (MSVC2022) platform and use Sky_Simple, the stars fail to display correctly.

[emminizer]

I had a similar problem. It turned out to be that a core profile was not being selected in some edge cases and it was using a newer 4.5 compatibility profile. I never figured out why the compatibility profile didn't show stars, but they did show up on the 3.3 core profile once I was able to force that. The compatibility profile display issue smelled to me like a driver bug when I saw it.

[GitHubCYH]

The shader of StarNode in 'sky_simple/SimpleSky.Stars.frag.glsl' may work incorrectly.

              #pragma vp_entryPoint oe_Stars_FS
              #pragma vp_location fragment_coloring
              in float oe_Stars_visibility; 
              void oe_Stars_FS(inout vec4 color)
              { 
                  float b1 = 1.0-(2.0*abs(gl_PointCoord.s-0.5)); 
                  float b2 = 1.0-(2.0*abs(gl_PointCoord.t-0.5)); 
                  float i = b1*b1 * b2*b2; 
                  color = color * i * oe_Stars_visibility;
              }

'gl_PointCoord.s' and 'gl_PointCoord.t' are all zero.
AI's explanation for this is that the Qt OpenGL context is incompatible and so on.