move_n_grab.py

            class SverchPresetAddOperator(bpy.types.Operator):
                bl_idname = "node.sv_preset_" + get_preset_idname_for_operator(self.name)
                bl_label = "Add {} preset".format(self.name)
                bl_options = {'REGISTER', 'UNDO'}

                first_mouse_x = IntProperty()
                first_mouse_y = IntProperty()


                @classmethod
                def poll(cls, context):
                    try:
                        return context.space_data.node_tree.bl_idname in {'SverchCustomTreeType', 'SverchGroupTreeType'}
                    except:
                        return False

                def modal(operator, context, event):
                    if event.type == 'MOUSEMOVE':
                        # delta_x = operator.first_mouse_x - event.mouse_x
                        # delta_y = operator.first_mouse_y - event.mouse_y
                        # context.object.location.x = self.first_value + delta * 0.01
                        bpy.ops.node.translate_attach(TRANSFORM_OT_translate={"value":(event.mouse_x, event.mouse_y, 0)})
                        # bpy.ops.node.translate_attach(TRANSFORM_OT_translate={"value":(delta_x, -delta_y, 0)})

                    elif event.type == 'LEFTMOUSE':
                        bpy.ops.node.translate_attach(TRANSFORM_OT_translate={"value":(event.mouse_x, event.mouse_y, 0)})
                        # bpy.ops.node.translate_attach(TRANSFORM_OT_translate={"value":(delta_x, -delta_y, 0)})

                        return {'FINISHED'}

                    elif event.type in {'RIGHTMOUSE', 'ESC'}:
                        # context.object.location.x = self.first_value
                        return {'CANCELLED'}

                    return {'RUNNING_MODAL'}

                def invoke(operator, context, event):
                    # please not be confused: "operator" here references to
                    # SverchPresetAddOperator instance, and "self" references to
                    # SvPreset instance.  
                    ntree = context.space_data.node_tree
                    id_tree = ntree.name
                    ng = bpy.data.node_groups[id_tree]

                    if ng:
                        # Deselect everything, so as a result only imported nodes
                        # will be selected
                        operator.first_mouse_x = event.mouse_x
                        operator.first_mouse_y = event.mouse_y
                        bpy.ops.node.select_all(action='DESELECT')
                        import_tree(ng, self.path)
                        context.window_manager.modal_handler_add(operator)
                        return {'RUNNING_MODAL'}
                    else:
                        operator.report({'WARNING'}, "No active nodetree")
                        return {'CANCELLED'}


                    # bpy.ops.node.translate_attach(NODE_OT_insert_offset={"value":(77.3197, 37.8496, 0)})
                    return {'FINISHED'}