__init__.py

                description="Amount texture affects color of the horizon"
                            "",
                soft_min=0.0, soft_max=1.0, default=1.0)

    object: StringProperty(
                name="Object",
                description="Object to use for mapping with Object texture coordinates",
                default="")

    texture_coords: EnumProperty(
                name="Coordinates",
                description="Texture coordinates used to map the texture onto the background",
                items=(("VIEW", "View", "Use view vector for the texture coordinates"),
                       ("GLOBAL", "Global", "Use global coordinates for the texture coordinates (interior mist)"),
                       ("ANGMAP", "AngMap", "Use 360 degree angular coordinates, e.g. for spherical light probes"),
                       ("SPHERE", "Sphere", "For 360 degree panorama sky, spherical mapped, only top half"),
                       ("EQUIRECT", "Equirectangular", "For 360 degree panorama sky, equirectangular mapping"),
                       ("TUBE", "Tube", "For 360 degree panorama sky, cylindrical mapped, only top half"),
                       ("OBJECT", "Object", "Use linked object’s coordinates for texture coordinates")),
                default="VIEW")

    use_map_blend: BoolProperty(
                name="Blend Map", description="Affect the color progression of the background",
                default=True)

    use_map_horizon: BoolProperty(
                name="Horizon Map", description="Affect the color of the horizon",
                default=False)

    use_map_zenith_down: BoolProperty(
                name="", description="Affect the color of the zenith below",
                default=False)

    use_map_zenith_up: BoolProperty(
                name="Zenith Up Map", description="Affect the color of the zenith above",
                default=False)

    zenith_down_factor: FloatProperty(
                name="Zenith Down",
                description="Amount texture affects color of the zenith below",
                soft_min=0.0, soft_max=1.0, default=1.0)

    zenith_up_factor: FloatProperty(
                name="Zenith Up",
                description="Amount texture affects color of the zenith above",
                soft_min=0.0, soft_max=1.0, default=1.0)

'''
#class WORLD_TEXTURE_SLOTS_UL_layerlist(bpy.types.UIList):
#    texture_slots:
    
class WorldTextureSlots(bpy.props.PropertyGroup):
    index = bpy.prop.PropertyInt(name='index')
    #foo  = random prop

bpy.types.World.texture_slots = bpy.props.CollectionProperty(type=PropertyGroup)

for i in range(18):  # length of world texture slots
    world.texture_slots.add()
'''


###############################################################################
# Text POV properties.
###############################################################################
class RenderPovSettingsText(PropertyGroup):
    custom_code: EnumProperty(
            name="Custom Code",
            description="rendered source: Both adds text at the "
                        "top of the exported POV-Ray file",
            items=(("3dview", "View", ""),
                   ("text", "Text", ""),
                   ("both", "Both", "")),
            default="text")

###############################################################################
# Povray Preferences.
###############################################################################
class PovrayPreferences(AddonPreferences):
    bl_idname = __name__

    branch_feature_set_povray: EnumProperty(
                name="Feature Set",
                description="Choose between official (POV-Ray) or (UberPOV) "
                            "development branch features to write in the pov file",
                items= (('povray', 'Official POV-Ray', '','PLUGIN', 0),
                        ('uberpov', 'Unofficial UberPOV', '', 'PLUGIN', 1)),
                default='povray'
                )

    filepath_povray: StringProperty(
                name="Binary Location",
                description="Path to renderer executable",
                subtype='FILE_PATH',
                )
    docpath_povray: StringProperty(
                name="Includes Location",
                description="Path to Insert Menu files",
                subtype='FILE_PATH',
                )
    def draw(self, context):
        layout = self.layout
        layout.prop(self, "branch_feature_set_povray")
        layout.prop(self, "filepath_povray")
        layout.prop(self, "docpath_povray")


classes = (
    PovrayPreferences,
    RenderPovSettingsCamera,
    RenderPovSettingsLight,    
    RenderPovSettingsWorld,
    MaterialTextureSlot,
    WorldTextureSlot,
    RenderPovSettingsMaterial,
    MaterialRaytraceMirror, 
    MaterialSubsurfaceScattering,
    RenderPovSettingsObject,
    RenderPovSettingsScene,
    RenderPovSettingsText,
    RenderPovSettingsTexture,
)


def register():

    #bpy.utils.register_module(__name__) #DEPRECATED Now imported from bpy.utils import register_class

    for cls in classes:
        register_class(cls)
 
    render.register()
    ui.register()
    primitives.register()
    nodes.register()

    '''    
        bpy.types.VIEW3D_MT_add.prepend(ui.menu_func_add)
        bpy.types.TOPBAR_MT_file_import.append(ui.menu_func_import)
        bpy.types.TEXT_MT_templates.append(ui.menu_func_templates)
        bpy.types.RENDER_PT_povray_radiosity.prepend(ui.rad_panel_func)
        bpy.types.LIGHT_PT_POV_light.prepend(ui.light_panel_func)
        bpy.types.WORLD_PT_world.prepend(ui.world_panel_func)
        # was used for parametric objects but made the other addon unreachable on
        # unregister for other tools to use created a user action call instead
        #addon_utils.enable("add_mesh_extra_objects", default_set=False, persistent=True)

        #bpy.types.TEXTURE_PT_context_texture.prepend(TEXTURE_PT_povray_type)
    '''
    bpy.types.NODE_HT_header.append(ui.menu_func_nodes)
    nodeitems_utils.register_node_categories("POVRAYNODES", node_categories)
    bpy.types.Scene.pov = PointerProperty(type=RenderPovSettingsScene)
    #bpy.types.Modifier.pov = PointerProperty(type=RenderPovSettingsModifier)
    bpy.types.Material.pov = PointerProperty(type=RenderPovSettingsMaterial)
    bpy.types.Material.pov_subsurface_scattering = PointerProperty(type=MaterialSubsurfaceScattering)
    bpy.types.Material.pov_raytrace_mirror = PointerProperty(type=MaterialRaytraceMirror)
    bpy.types.Texture.pov = PointerProperty(type=RenderPovSettingsTexture)
    bpy.types.Object.pov = PointerProperty(type=RenderPovSettingsObject)
    bpy.types.Camera.pov = PointerProperty(type=RenderPovSettingsCamera)
    bpy.types.Light.pov = PointerProperty(type=RenderPovSettingsLight)
    bpy.types.World.pov = PointerProperty(type=RenderPovSettingsWorld)
    bpy.types.Material.texture_slots = CollectionProperty(type = MaterialTextureSlot)
    bpy.types.World.texture_slots = CollectionProperty(type = WorldTextureSlot)
    bpy.types.Text.pov = PointerProperty(type=RenderPovSettingsText)



def unregister():
    del bpy.types.Scene.pov
    del bpy.types.Material.pov
    del bpy.types.Material.pov_subsurface_scattering
    del bpy.types.Material.pov_raytrace_mirror
    #del bpy.types.Modifier.pov
    del bpy.types.Texture.pov
    del bpy.types.Object.pov
    del bpy.types.Camera.pov
    del bpy.types.Light.pov
    del bpy.types.World.pov    
    del bpy.types.Text.pov
    nodeitems_utils.unregister_node_categories("POVRAYNODES")
    bpy.types.NODE_HT_header.remove(ui.menu_func_nodes)
    '''
    #bpy.types.TEXTURE_PT_context_texture.remove(TEXTURE_PT_povray_type)
    #addon_utils.disable("add_mesh_extra_objects", default_set=False)
    bpy.types.WORLD_PT_POV_world.remove(ui.world_panel_func)
    bpy.types.LIGHT_PT_POV_light.remove(ui.light_panel_func)
    bpy.types.RENDER_PT_povray_radiosity.remove(ui.rad_panel_func)
    bpy.types.TEXT_MT_templates.remove(ui.menu_func_templates)
    bpy.types.TOPBAR_MT_file_import.remove(ui.menu_func_import)
    bpy.types.VIEW3D_MT_add.remove(ui.menu_func_add)
    '''
    #bpy.utils.unregister_module(__name__)

    nodes.unregister()
    primitives.unregister()
    ui.unregister()
    render.unregister()

    for cls in reversed(classes):
        unregister_class(cls)
 


if __name__ == "__main__":
    register()