Rotating an actor around an arbitrary axis

[Moritz Renftle <clutter renftles de>]

Hi clutter devs,

is there a possibility to rotate an actor around a custom axis or a
vector?

The axis I need is the same as the x-axis turned by 30° around the
y-axis.

This could of course also be achieved using the standard axes, but would
require some quite complex mathematics. Has someone ever done this
before? Seems quite an important thing to me.

Thank you,
Moritz