Parent could not be deduced

[gsal]

Beginner, here:

Trying to pass an object (doc) to a call back function (new_figure_callback), that is supposed to contain some UUID of interest (doc.win), but somehow, I cannot use it within the call back function.

Hints, please.

Below, please find minimal test program and error message.

Test programs:

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import os
import sys
import dearpygui.dearpygui as dpg

class Figure():
    """A figure with one or more plots."""
    def __init__(self):
        self.plots = []         # list of plots
        self.win = None         # presumably to store the document window UUID ?

class Document():
    """A document of one or more figures."""
    def __init__(self):
        self.figures = []       # list of figures
        self.win = None         # presumably to store the document window UUID ?

#
# = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
#

def new_figure_callback(sender, app_data, doc):
    n = len(doc.figures)
    doc.figures.append(Figure())
    doc.figures[n].win = dpg.add_group(parent=doc.win)

def new_doc_callback():
    doc = Document()
    doc.win = dpg.window(label="New doc", width=800, height=600)
    dpg.add_button(label="New Figure", callback=new_figure_callback, user_data=doc, parent=doc.win)

#
# = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
#

dpg.create_context()
dpg.create_viewport(title='Test', width=1000, height=800)

with dpg.viewport_menu_bar():
    with dpg.menu(label="File"):
        dpg.add_menu_item(label="New Document", callback=new_doc_callback)

dpg.setup_dearpygui()
dpg.show_viewport()
dpg.start_dearpygui()
dpg.destroy_context()

sys.exit(0)

Error message:

Exception:
Error:     [1011]
Command:   add_*
Item:      24
Label:     New Figure
Item Type: mvAppItemType::mvButton
Message:   Parent could not be deduced.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\salazag\programs\pyprojects\g\test-passing-doc.py", line 32, in new_doc_callback
    dpg.add_button(label="New Figure", callback=new_figure_callback, user_data=doc, parent=doc.win)
  File "C:\Users\salazag\programs\dear\lib\site-packages\dearpygui\dearpygui.py", line 2982, in add_button
    return internal_dpg.add_button(label=label, user_data=user_data, use_internal_label=use_internal_label, tag=tag, width=width, height=height, indent=indent, parent=parent, before=before, payload_type=payload_type, callback=callback, drag_callback=drag_callback, drop_callback=drop_callback, show=show, enabled=enabled, pos=pos, filter_key=filter_key, tracked=tracked, track_offset=track_offset, small=small, arrow=arrow, direction=direction, **kwargs)
SystemError: <built-in function add_button> returned a result with an exception set

[vyrjana]

The problem is that you are calling dpg.window() instead of dpg.add_window(). If you check the type of the value returned by each of those functions, then you would see that the former returns something like <contextlib._GeneratorContextManager object at 0x7f5cda637910> whereas the latter returns an integer (i.e. the ID that you are looking for).

So you could just switch over to dpg.add_window(). If you absolutely wanted to use dpg.window(), then you could do something like:

def new_doc_callback():
    doc = Document()
    with dpg.window(label="New doc", width=800, height=600) as window:
        doc.win = window
        dpg.add_button(label="New Figure", callback=new_figure_callback, user_data=doc, parent=doc.win)

Note that the official documentation for the two functions states that dpg.window() yields and dpg.add_window() returns, respectively, a Union[int, str]. It is easy to miss that at first glance, but it is a crucial distinction to make.

[gsal]

Aaahhh, ok; thanks for pointing that out...I will be looking for that, too, then, as I learn and consult the API.

Thanks for the prompt reply.