Fixes SSBO causing GL_INVALID_ENUM in Debug Mode

[MeFisto94]

Background: https://github.com/MeFisto94/test-spotbugs/runs/560327969?check_suite_focus=true#step:5:1490

On MESA with Debug Mode or Assertions on, we get a GL_INVALID_ENUM at Line 510 (getInteger(GL_MAX_GEOMETRY_SHADER_...)).

I assume this is because this device supports SSBOs as an extension while still being on OpenGL 3.1. For most non-strict-real-gpus, SSBOs are only available with a much higher GL Version.

Anyway, this is my blind poke at this, I will re-run the above test, but I'd appreciate if someone finds some official source about when the Integers can be getted.

Also note the GL_ARB_geometry_shader_4, I hope I did it right, it's not a core extension but an extension and I've read some stuff that those _4 usually had a completely different API.

[MeFisto94]

I just realized that Geometry and Compute Shaders are checked just below my code, so I can probably reorder that.

I only wonder if the extensions are always present, even when the shader type should already be in core?

i.e. we miss a bunch of if version >=s there, don't we?
Also I wonder if this is a MESA only thing, because the UBO Extension should expose all those limits, even when the specific shaders aren't available. The good thing is this patch doesn't hurt other implementations.

Edit: The second concern is not true, provided loadCapabilitiesGL2 is run before that code, see

jmonkeyengine/jme3-core/src/main/java/com/jme3/renderer/opengl/GLRenderer.java

Lines 214 to 217 in 64797f9

	if (oglVer >= 330) {
	caps.add(Caps.OpenGL33);
	caps.add(Caps.GeometryShader);
	}

When I checked that, I will reorder the other stuff.

[MeFisto94]

Green light: https://github.com/MeFisto94/test-spotbugs/runs/560492126?check_suite_focus=true#step:5:1485

So @pspeed42 and @riccardobl let's talk about the specific implementation, especially given that if you expand the diff down you see that geometry shader detection is already there. When I move that up I could use Caps.contains(GeometryShader), but I think the Geometry Shader detection misses out implementations where the extension isn't present but the GL Version supports Geom Shaders already, or is this done somewhere else already?

[MeFisto94]

When the test at https://github.com/MeFisto94/test-spotbugs/runs/560573233?check_suite_focus=true is green, I will merge this.

[MeFisto94]

Debug Mode finally works, green lights: https://github.com/MeFisto94/test-spotbugs/runs/560573233?check_suite_focus=true#step:5:1483

[stephengold]

Included in v3.3 branch at 828ca92.