Is there a way to interrupt a callback?

[mkouhia]

Hi,
I am writing a Dear PyGui interface to perform a long-running calculation process and examine its outputs. I would like to provide some way to interrupt the process without having to exit GUI. However, as the callbacks are processed from the queue one by one, one callback cannot be employed to send messages to another.

Is there a way I could send an interrupt signal to a callback? Or would I have to implement my own thread management somehow? How would you go about it?

import time

import dearpygui.dearpygui as dpg

dpg.create_context()
dpg.create_viewport(title='Custom Title', width=600, height=300)

def run(sender, app_data, user_data):
    dpg.configure_item("cancel_btn", show=True)
    dpg.set_value("progress", 0.0)

    for i in range(user_data):
        dpg.set_value("progress", i/user_data)
        dpg.configure_item("pbar", overlay=f"{i}/{user_data}")

        # Here would be a call to function, whose individual runtime could be a couple
        # of seconds, in total some hundreds to thousands of loops.
        time.sleep(0.5)

    dpg.set_value("progress", 1.0)
    dpg.configure_item("pbar", overlay="Ready!")
    dpg.configure_item("cancel_btn", show=False)

def cancel_run(sender, app_data):
    # This is not run until the first callback ends
    print("Hello")
    ...

with dpg.value_registry():
    dpg.add_float_value(tag="progress", default_value=0.0)

with dpg.window(label="Example Window", width=400):
    dpg.add_progress_bar(tag="pbar", source="progress", width=-1)
    with dpg.group(horizontal=True):
        dpg.add_button(label="Start", callback=run, user_data=10)
        dpg.add_button(label="Cancel", tag="cancel_btn", show=False, callback=cancel_run)

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

[hoffstadt]

Hmm. At the moment, we do not provide a standard way to handle this, so its on the user in the current version. However, I do see this as an easy add on our part to help. I will part this as an improvement we can add soon!

[mkouhia]

Ok, thank you for the response and consideration!

[plucian]

Hi guys, is there a solution now to this problem ? I added a counter in the callback and every 500 frames I could check for other events, on other frameworks I would issue a root.update() and that would allow for an interrupt if needed.. Here I could not find something similar..

[puglet5]

Hi! I suppose you could run the callback in a separate thread with a killswitch and have a button to set it.

In the loop you would have:

if killswitch.is_set():
   # stop calculation

You will have to wait one whole iteration before it stops though, which if you say

could be a couple of seconds

doesn't seem too bad.