added random name gen button in .ext

node_BMeshview.py

import bpy
import bmesh
import mathutils
from mathutils import Vector, Matrix
from bpy.props import BoolProperty, FloatVectorProperty

from node_s import *
from util import *
import random


def get_random_init():
    greek_alphabet = [
        'Alpha', 'Beta', 'Gamma', 'Delta',
        'Epsilon', 'Zeta', 'Eta', 'Theta',
        'Iota', 'Kappa', 'Lamda', 'Mu',
        'Nu', 'Xi', 'Omicron', 'Pi',
        'Rho', 'Sigma', 'Tau', 'Upsilon',
        'Phi', 'Chi', 'Psi', 'Omega']
    return random.choice(greek_alphabet)


def default_mesh(name):
    verts = [(1, 1, -1), (1, -1, -1), (-1, -1, -1)]
    faces = [(0, 1, 2)]

    mesh_data = bpy.data.meshes.new(name)
    mesh_data.from_pydata(verts, [], faces)
    mesh_data.update()
    return mesh_data


def bmesh_from_pydata(verts=[], edges=[], faces=[]):
    ''' verts is necessary, edges/faces are optional '''

    bm = bmesh.new()
    add_vert = bm.verts.new
    [add_vert(co) for co in verts]
    bm.verts.index_update()

    if faces:
        add_face = bm.faces.new
        for face in faces:
            add_face(tuple(bm.verts[i] for i in face))
        bm.faces.index_update()

    if edges:
        add_edge = bm.edges.new
        for edge in edges:
            edge_seq = tuple(bm.verts[i] for i in edge)
            try:
                add_edge(edge_seq)
            except ValueError:
                # edge exists!
                pass

        bm.edges.index_update()

    return bm


def make_bmesh_geometry(context, name, verts, edges, faces, matrix):
    # no verts. no processing.
    if not verts:
        return

    scene = context.scene
    meshes = bpy.data.meshes
    objects = bpy.data.objects

    if name in objects:
        sv_object = objects[name]
    else:
        temp_mesh = default_mesh(name)
        sv_object = objects.new(name, temp_mesh)
        scene.objects.link(sv_object)
        scene.update()

    # definitely verts, definitely do something.
    bm = bmesh_from_pydata(verts, edges, faces)

    # Finish up, write the bmesh back to the mesh
    bm.to_mesh(sv_object.data)
    bm.free()  # free and prevent further access

    sv_object.hide_select = True

    # apply matrices if necessary
    if matrix:
        sv_object.matrix_local = list(zip(*matrix))


class SvBmeshViewOp(bpy.types.Operator):

    bl_idname = "node.showhide_bmesh"
    bl_label = "Sverchok bmesh showhide"
    bl_options = {'REGISTER', 'UNDO'}

    fn_name = StringProperty(default='')

    def hide_unhide(self, context, type_op):
        n = context.node
        k = n.basemesh_name + "_"

        # maybe do hash+(obj_name + treename)
        child = lambda obj: obj.type == "MESH" and obj.name.startswith(k)
        objs = list(filter(child, bpy.data.objects))

        if type_op == 'hide_view':
            for obj in objs:
                obj.hide = n.state_view
            n.state_view = not n.state_view

        elif type_op == 'hide_render':
            for obj in objs:
                obj.hide_render = n.state_render
            n.state_render = not n.state_render

        elif type_op == 'hide_select':
            for obj in objs:
                obj.hide_select = n.state_select
            n.state_select = not n.state_select

        elif type_op == 'mesh_select':
            for obj in objs:
                obj.select = n.select_state_mesh
            n.select_state_mesh = not n.select_state_mesh

        elif type_op == 'random_mesh_name':
            n.basemesh_name = get_random_init()

    def execute(self, context):
        self.hide_unhide(context, self.fn_name)
        return {'FINISHED'}


class BmeshViewerNode(Node, SverchCustomTreeNode):

    bl_idname = 'BmeshViewerNode'
    bl_label = 'Bmesh Viewer Draw'
    bl_icon = 'OUTLINER_OB_EMPTY'

    activate = BoolProperty(
        name='Show', description='Activate node?',
        default=True,
        update=updateNode)

    basemesh_name = StringProperty(default=get_random_init(), update=updateNode)
    state_view = BoolProperty(default=True)
    state_render = BoolProperty(default=True)
    state_select = BoolProperty(default=True)
    select_state_mesh = BoolProperty(default=False)

    def init(self, context):
        self.inputs.new('VerticesSocket', 'vertices', 'vertices')
        self.inputs.new('StringsSocket', 'edges', 'edges')
        self.inputs.new('StringsSocket', 'faces', 'faces')
        self.inputs.new('MatrixSocket', 'matrix', 'matrix')

    def draw_buttons(self, context, layout):
        row = layout.row(align=True)
        split = row.split()
        col1 = split.column()
        col1.prop(self, "activate", text="Update")

        def icons(button_type):
            icon = 'WARNING'
            if button_type == 'v':
                state = self.state_view
                icon = 'RESTRICT_VIEW_OFF' if state else 'RESTRICT_VIEW_ON'
            elif button_type == 'r':
                state = self.state_render
                icon = 'RESTRICT_RENDER_OFF' if state else 'RESTRICT_RENDER_ON'
            elif button_type == 's':
                state = self.state_select
                icon = 'RESTRICT_SELECT_OFF' if state else 'RESTRICT_SELECT_ON'

            return icon

        split = split.split()
        col2 = split.column()
        sh = 'node.showhide_bmesh'
        col2.operator(sh, text='', icon=icons('v')).fn_name = 'hide_view'
        col3 = split.column()
        col3.operator(sh, text='', icon=icons('s')).fn_name = 'hide_select'
        col4 = split.column()
        col4.operator(sh, text='', icon=icons('r')).fn_name = 'hide_render'

        layout.label("Base mesh name(s)", icon='OUTLINER_OB_MESH')
        row = layout.row()
        row.prop(self, "basemesh_name", text="")

    def draw_buttons_ext(self, context, layout):
        sh = 'node.showhide_bmesh'

        row = layout.row(align=True)
        row.prop(self, "basemesh_name", text="")
        row.operator(sh, text='Random Name').fn_name = 'random_mesh_name'
        row = layout.row()
        row.operator(sh, text='Select Meshes').fn_name = 'mesh_select'

    def get_corrected_data(self, socket_name, socket_type):
        inputs = self.inputs
        socket = inputs[socket_name].links[0].from_socket
        if isinstance(socket, socket_type):
            socket_in = SvGetSocketAnyType(self, inputs[socket_name])
            return dataCorrect(socket_in)
        else:
            return []

    def get_geometry_from_sockets(self):
        inputs = self.inputs
        mverts, medges, mfaces, mmatrix = [], [], [], []

        mverts = self.get_corrected_data('vertices', VerticesSocket)

        # could be looped, yielded..
        if 'matrix' in inputs and inputs['matrix'].links:
            mmatrix = self.get_corrected_data('matrix', MatrixSocket)

        if 'edges' in inputs and inputs['edges'].links:
            medges = self.get_corrected_data('edges', StringsSocket)

        if 'faces' in inputs and inputs['faces'].links:
            mfaces = self.get_corrected_data('faces', StringsSocket)

        return mverts, medges, mfaces, mmatrix

    def get_structure(self, stype, sindex):
        if not stype:
            return []

        try:
            j = stype[sindex]
        except IndexError:
            j = []
        finally:
            return j

    def update(self):

        # startup safety net
        try:
            l = bpy.data.node_groups[self.id_data.name]
        except Exception as e:
            print(self.name, "cannot run during startup, press update.")
            return

        # regular code from this point
        if self.activate and ('vertices' in self.inputs):
            if not self.inputs['vertices'].links:
                return
        else:
            return

        C = bpy.context
        mverts, *mrest = self.get_geometry_from_sockets()

        def get_edges_faces_matrices(obj_index):
            for geom in mrest:
                yield self.get_structure(geom, obj_index)

        # matrices need to define count of objects. paradigma
        maxlen = max(len(mverts), len(mrest[0]), len(mrest[1]), len(mrest[2]))
        fullList(mverts, maxlen)
        if mrest[0]:
            fullList(mrest[0], maxlen)
        if mrest[1]:
            fullList(mrest[1], maxlen)
        if mrest[2]:
            fullList(mrest[2], maxlen)

        for obj_index, Verts in enumerate(mverts):
            if not Verts:
                continue

            data = get_edges_faces_matrices(obj_index)
            mesh_name = self.basemesh_name + "_" + str(obj_index)
            make_bmesh_geometry(C, mesh_name, Verts, *data)

        self.remove_non_updated_objects(obj_index, self.basemesh_name)
        self.set_corresponding_materials()

    def remove_non_updated_objects(self, obj_index, _name):

        meshes = bpy.data.meshes
        objects = bpy.data.objects

        for i in bpy.context.selected_objects:
            i.select = False

        objs = [obj for obj in objects if obj.type == 'MESH']
        objs = [obj for obj in objs if obj.name.startswith(_name)]
        objs = [obj.name for obj in objs if int(obj.name.split("_")[-1]) > obj_index]

        # select and finally remove all excess objects
        for object_name in objs:
            objects[object_name].hide_select = False
            objects[object_name].select = True
        bpy.ops.object.delete()

        # delete associated meshes
        for object_name in objs:
            meshes.remove(meshes[object_name])

        # fingers crossed.

    def set_corresponding_materials(self):
        objs = bpy.data.objects
        first_mesh = self.basemesh_name + '_0'

        group_material = objs[first_mesh].active_material

        if group_material:
            for obj in objs:
                # if this object is made by bmesh - assign material of 'object_0'
                if obj.name.startswith(self.basemesh_name + "_"):
                    active_mat = obj.active_material
                    if (not active_mat) or not (active_mat == group_material):
                        active_mat = group_material

    def update_socket(self, context):
        self.update()


def register():
    bpy.utils.register_class(BmeshViewerNode)
    bpy.utils.register_class(SvBmeshViewOp)


def unregister():
    bpy.utils.unregister_class(BmeshViewerNode)
    bpy.utils.unregister_class(SvBmeshViewOp)