Nodes of different colours represent the following:
Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.
public function vkf_sky_style(node) bind(C, name="vkf_sky_style")
The sky's style buffer: 24 floats, the attitude (a column-major 4x4 matrix, sky frame to root frame),
then 8 parameters (lines: width in window units, 3 unused, then the color r, g, b, a; unused by stars
and the texture); call vkf_sky_style_changed after writing them. Null on failure.