op_color_assign.py

import bpy
import bmesh
import operator
from mathutils import Vector
from collections import defaultdict
from math import pi

from . import utilities_color

class op(bpy.types.Operator):
    bl_idname = "uv.textools_color_assign"
    bl_label = "Assign Color"
    bl_description = "Assign color to selected objects or faces in edit mode."
    bl_options = {'REGISTER', 'UNDO'}
    
    index : bpy.props.IntProperty(description="Color Index", default=0)

    @classmethod
    def poll(cls, context):
        if not bpy.context.active_object:
            return False

        if bpy.context.active_object not in bpy.context.selected_objects:
            return False

        if bpy.context.active_object.type != 'MESH':
            return False

        #Only in UV editor mode
        if bpy.context.area.type != 'IMAGE_EDITOR':
            return False

        return True
    
    def execute(self, context):
        assign_color(self, context, self.index)
        return {'FINISHED'}



def assign_color(self, context, index):
    
    selected_obj = bpy.context.selected_objects.copy()

    previous_mode = 'OBJECT'
    if len(selected_obj) == 1:
        previous_mode = bpy.context.active_object.mode


    for obj in selected_obj:
        # Select object
        bpy.ops.object.mode_set(mode='OBJECT')
        bpy.ops.object.select_all(action='DESELECT')
        obj.select_set( state = True, view_layer = None)
        bpy.context.view_layer.objects.active = obj

        # Enter Edit mode
        bpy.ops.object.mode_set(mode='EDIT')
        bm = bmesh.from_edit_mesh(obj.data);
        faces = []

        #Assign to all or just selected faces?
        if previous_mode == 'EDIT':
            faces = [face for face in bm.faces if face.select]
        else:
            faces = [face for face in bm.faces]        

        if previous_mode == 'OBJECT':
            bpy.ops.mesh.select_all(action='SELECT')
        

        # Verify material slots
        for i in range(index+1):
            if index >= len(obj.material_slots):
                bpy.ops.object.material_slot_add()

        utilities_color.assign_slot(obj, index)

        # Assign to selection
        obj.active_material_index = index
        bpy.ops.object.material_slot_assign()


    #Change View mode to MATERIAL
    # for area in bpy.context.screen.areas:
    #     if area.type == 'VIEW_3D':
    #         for space in area.spaces:
    #             if space.type == 'VIEW_3D':
    #                 space.shading.type = 'MATERIAL'

    # restore mode
    bpy.ops.object.mode_set(mode='OBJECT')
    bpy.ops.object.select_all(action='DESELECT')
    for obj in selected_obj:
        obj.select_set( state = True, view_layer = None)
    bpy.ops.object.mode_set(mode=previous_mode)

bpy.utils.register_class(op)