2.80 bse examples

mesh_origin_to_selected.py

bl_info = {
    "name": "Set mesh origin to selected geometry",
    "author": "batFINGER",
    "version": (1, 0),
    "blender": (2, 80, 0),
    "description": "Set mesh origin to selected geometry",
    "warning": "",
    "wiki_url": "",
    "category": "Add Mesh",
}

import bpy
import bmesh
from mathutils import Vector

class MESH_OT_origin_to_selection(bpy.types.Operator):
    """Set the mesh's origin to the selection"""
    bl_idname = "mesh.origin_to_selection"
    bl_label = "Set Origin to Selection"
    bl_options = {'REGISTER', 'UNDO'}
    @classmethod
    def poll(cls, context):
        ob = context.edit_object
        return ob and ob.type == 'MESH'
    
    def execute(self, context):
        ob = context.edit_object
        mw = ob.matrix_world
        me = ob.data
        bm = bmesh.from_edit_mesh(me)

        selverts = [v.co for v in bm.verts if v.select]
        if len(selverts):
            pt = sum(selverts, Vector()) / len(selverts)
            #T = Matrix.Translation(-pt)
            bmesh.ops.translate(bm, vec=-pt, verts=bm.verts)
            mw.translation = mw @ pt
            bmesh.update_edit_mesh(me)    
            return {'FINISHED'}
        return {'CANCELLED'}

def draw_menu(self, context):
    self.layout.operator("mesh.origin_to_selection")

def register():
    bpy.utils.register_class(MESH_OT_origin_to_selection)
    bpy.types.VIEW3D_MT_transform.append(draw_menu)

def unregister():
    bpy.utils.unregister_class(MESH_OT_origin_to_selection)
    bpy.types.VIEW3D_MT_transform.remove(draw_menu)

if __name__ == "__main__":
    register() 

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