ui.py

        layout = self.layout

        cam = context.camera

        layout.active = cam.dof.use_dof
        layout.use_property_split = True # Active single-column layout

        flow = layout.grid_flow(row_major=True, columns=0, even_columns=True, even_rows=False, align=False)

        col = flow.column()
        col.label(text="F-Stop value will export as")
        col.label(text="POV-Ray aperture : " + "%.3f" % (1/cam.dof.aperture_fstop*1000))
        
        col = flow.column()
        col.prop(cam.pov, "dof_samples_min")
        col.prop(cam.pov, "dof_samples_max")
        col.prop(cam.pov, "dof_variance")        
        col.prop(cam.pov, "dof_confidence")



class CAMERA_PT_povray_cam_nor(CameraDataButtonsPanel, Panel):
    bl_label = "POV-Ray Perturbation"
    COMPAT_ENGINES = {'POVRAY_RENDER'}

    def draw_header(self, context):
        cam = context.camera

        self.layout.prop(cam.pov, "normal_enable", text="")

    def draw(self, context):
        layout = self.layout

        cam = context.camera

        layout.active = cam.pov.normal_enable

        layout.prop(cam.pov,"normal_patterns")
        layout.prop(cam.pov,"cam_normal")
        layout.prop(cam.pov,"turbulence")
        layout.prop(cam.pov,"scale")


class CAMERA_PT_povray_replacement_text(CameraDataButtonsPanel, Panel):
    bl_label = "Custom POV Code"
    COMPAT_ENGINES = {'POVRAY_RENDER'}

    def draw(self, context):
        layout = self.layout

        cam = context.camera

        col = layout.column()
        col.label(text="Replace properties with:")
        col.prop(cam.pov, "replacement_text", text="")

###############################################################################
# Text Povray Settings
###############################################################################

class TEXT_OT_povray_insert(Operator):
    """Tooltip"""
    bl_idname = "text.povray_insert"
    bl_label = "Insert"

    filepath : bpy.props.StringProperty(name="Filepath", subtype='FILE_PATH')

    @classmethod
    def poll(cls, context):
        # context.area.type == 'TEXT_EDITOR'
        return bpy.ops.text.insert.poll()

    def execute(self, context):
        if self.filepath and isfile(self.filepath):
            file = open(self.filepath, "r")
            bpy.ops.text.insert(text=file.read())

            # places the cursor at the end without scrolling -.-
            # context.space_data.text.write(file.read())
            file.close()
        return {'FINISHED'}

def validinsert(ext):
	return ext in {".txt",".inc",".pov"}

class TEXT_MT_insert(bpy.types.Menu):
    bl_label = "Insert"
    bl_idname = "TEXT_MT_insert"

    def draw(self, context):
        pov_documents = locate_docpath()
        prop = self.layout.operator("wm.path_open", text="Open folder", icon='FILE_FOLDER')
        prop.filepath = pov_documents
        self.layout.separator()

        list=[]
        for root,dirs,files in os.walk(pov_documents):
            list.append(root)
        print(list)
        self.path_menu(list,
                       "text.povray_insert",
                       #{"internal": True},
					   filter_ext= validinsert
                       )

class TEXT_PT_povray_custom_code(TextButtonsPanel, Panel):
    bl_label = "POV-Ray"
    COMPAT_ENGINES = {'POVRAY_RENDER'}

    def draw(self, context):
        layout = self.layout

        text = context.space_data.text

        pov_documents = locate_docpath()
        if not pov_documents :
            layout.label(text="Please configure ", icon="INFO")
            layout.label(text="default pov include path ")
            layout.label(text="in addon preferences")
            #layout.separator()
            layout.operator("preferences.addon_show",
                         text="Go to Render: POV-Ray addon",
                         icon="PREFERENCES").module = "render_povray"

            #layout.separator()
        else:
            #print(pov_documents)
            layout.menu(TEXT_MT_insert.bl_idname)

        if text:
            box = layout.box()
            box.label(text='Source to render:', icon='RENDER_STILL')
            row = box.row()
            row.prop(text.pov, "custom_code",expand = True)
            if text.pov.custom_code in {'3dview'}:
                box.operator("render.render", icon='OUTLINER_DATA_POSE')
            if text.pov.custom_code in {'text'}:
                rtext = bpy.context.space_data.text
                box.operator("text.run", icon='POSE_DATA')
            #layout.prop(text.pov, "custom_code")
            elif text.pov.custom_code in {'both'}:
                box.operator("render.render", icon='POSE_HLT')
                layout.label(text="Please specify declared", icon="INFO")
                layout.label(text="items in properties ")
                #layout.label(text="")
                layout.label(text="replacement fields")


###############################################
# Text editor templates from header menu

class TEXT_MT_templates_pov(bpy.types.Menu):
    bl_label = "POV-Ray"

    # We list templates on file evaluation, we can assume they are static data,
    # and better avoid running this on every draw call.
    import os
    template_paths = [os.path.join(os.path.dirname(__file__), "templates_pov")]

    def draw(self, context):
        self.path_menu(
            self.template_paths,
            "text.open",
            props_default={"internal": True},
        )

def menu_func_templates(self, context):
    # Do not depend on POV-Ray being active renderer here...
    self.layout.menu("TEXT_MT_templates_pov")

classes = (
    WORLD_PT_POV_world,
    POV_WORLD_MT_presets,
    AddPresetWorld,
    WORLD_TEXTURE_SLOTS_UL_List,
    WORLD_PT_POV_mist,    
    #RenderButtonsPanel,
    #ModifierButtonsPanel,
    #MaterialButtonsPanel,
    #TextureButtonsPanel,
    #ObjectButtonsPanel,
    #CameraDataButtonsPanel,
    #WorldButtonsPanel,
    #TextButtonsPanel,
    #PovDataButtonsPanel,
    DATA_PT_POV_normals,
    DATA_PT_POV_texture_space,
    DATA_PT_POV_vertex_groups,
    DATA_PT_POV_shape_keys,
    DATA_PT_POV_uv_texture,
    DATA_PT_POV_vertex_colors,
    DATA_PT_POV_customdata,
    #PovLampButtonsPanel,
    LIGHT_PT_POV_preview,
    LIGHT_PT_POV_light,
    POV_LIGHT_MT_presets,
    AddPresetLamp,
    OBJECT_PT_povray_obj_rainbow,
    RENDER_PT_povray_export_settings,
    RENDER_PT_povray_render_settings,
    RENDER_PT_povray_photons,
    RENDER_PT_povray_antialias,
    RENDER_PT_povray_radiosity,
    POV_RADIOSITY_MT_presets,
    AddPresetRadiosity,
    RENDER_PT_povray_media,
    MODIFIERS_PT_povray_modifiers,
    MATERIAL_PT_POV_sss,
    MATERIAL_MT_POV_sss_presets,
    AddPresetSSS,
    MATERIAL_PT_strand,
    MATERIAL_PT_povray_activate_node,
    MATERIAL_PT_povray_active_node,
    MATERIAL_PT_POV_mirror,
    MATERIAL_PT_POV_transp,
    MATERIAL_PT_povray_reflection,
    #MATERIAL_PT_POV_interior,
    MATERIAL_PT_povray_fade_color,
    MATERIAL_PT_povray_caustics,
    MATERIAL_PT_povray_replacement_text,
    TEXTURE_MT_specials,
    TEXTURE_PT_POV_context_texture,    
    TEXTURE_PT_povray_type,
    TEXTURE_PT_povray_preview,
    TEXTURE_PT_povray_parameters,
    TEXTURE_PT_povray_tex_gamma,
    OBJECT_PT_povray_obj_parameters,
    OBJECT_PT_povray_obj_sphere,
    OBJECT_PT_povray_obj_cylinder,
    OBJECT_PT_povray_obj_cone,
    OBJECT_PT_povray_obj_superellipsoid,
    OBJECT_PT_povray_obj_torus,
    OBJECT_PT_povray_obj_supertorus,
    OBJECT_PT_povray_obj_parametric,
    OBJECT_PT_povray_replacement_text,
    POVRAY_MT_primitives_add_menu,
    BasicShapesMenu,
    ImportMenu,
    NodeMapCreateMenu,
    CAMERA_PT_povray_cam_dof,
    CAMERA_PT_povray_cam_nor,
    CAMERA_PT_povray_replacement_text,
    TEXT_OT_povray_insert,
    TEXT_MT_insert,
    TEXT_PT_povray_custom_code,
    TEXT_MT_templates_pov
)


def register():
    #from bpy.utils import register_class

    for cls in classes:
        register_class(cls)

    bpy.types.VIEW3D_MT_add.prepend(menu_func_add)
    bpy.types.TOPBAR_MT_file_import.append(menu_func_import)
    bpy.types.TEXT_MT_templates.append(menu_func_templates)
    bpy.types.RENDER_PT_povray_radiosity.prepend(rad_panel_func)
    bpy.types.LIGHT_PT_POV_light.prepend(light_panel_func)
    #bpy.types.WORLD_PT_POV_world.prepend(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)

def unregister():
    #from bpy.utils import unregister_class

    #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(world_panel_func)
    bpy.types.LIGHT_PT_POV_light.remove(light_panel_func)
    bpy.types.RENDER_PT_povray_radiosity.remove(rad_panel_func)
    bpy.types.TEXT_MT_templates.remove(menu_func_templates)
    bpy.types.TOPBAR_MT_file_import.remove(menu_func_import)
    bpy.types.VIEW3D_MT_add.remove(menu_func_add)

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