Returns an
GLDrawable#isRealized() GLDrawable according to it's chosen
GLCapabilitiesImmutable,
which determines pixel format, on- and offscreen incl. PBuffer type.
The chosen
GLCapabilitiesImmutable are referenced within the target
NativeSurface's
AbstractGraphicsConfiguration.
An onscreen GLDrawable is created if
CapabilitiesImmutable#isOnscreen() is true.
A FBO drawable is created if both
GLCapabilitiesImmutable#isFBO()and
GLContext#isFBOAvailable(AbstractGraphicsDevice,GLProfile) is true.
A Pbuffer drawable is created if both
GLCapabilitiesImmutable#isPBuffer()and
#canCreateGLPbuffer(AbstractGraphicsDevice,GLProfile) is true.
If not onscreen and neither FBO nor Pbuffer is available,
a simple pixmap/bitmap drawable/surface is created, which is unlikely to be hardware accelerated.