draw_handler on top of Rendered shading mode

Question

I'm using bpy.types.SpaceView3D.draw_handler_add and the gpu/bgl/blf library to draw some labels in the 3D view. The handler is created like this:

self._handle = bpy.types.SpaceView3D.draw_handler_add(self.draw_callback,
                                                      (context,),
                                                      'WINDOW',
                                                      'POST_PIXEL')

This draws everything fine when in Solid, Wireframe or LookDev shading mode, but shows nothing when in Rendered shading mode - for both Cycles and Eevee.

Is it possible to draw on top of the rendered shading mode in python? Maybe using the new Overlays system?

Answer 1

Ok, I'm an idiot.

For future googlers, if you're using POST_PIXEL it should draw on top of all shading modes no problem.

The reason it wasn't working for me was because, hiding in my code, I had:

if context.space_data.shading.type == 'RENDERED':
    return

i.e. at some point in the past I deliberately prevented it from drawing on top of rendered shading mode, probably to be consistent with other overlays in Blender 2.7.