How to be notified when the active collection changes

Question

I tried this

subscribe_to = (bpy.types.ViewLayer, "active_layer_collection")
bpy.msgbus.subscribe_rna(
    key=subscribe_to,
    owner=bpy,
    args=(None,),
    notify=update,
)

I also tried these:

subscribe_to = (bpy.types.Context, "collection")
subscribe_to = (bpy.context, "collection")
subscribe_to = (bpy.context.view_layer, "active_layer_collection")
...

And more, they don't work.

How to be notified when the active collection changes?

Another question: when context.selected_objects changes, get notified.

subscribe_to = (bpy.types.LayerObjects, 'selected')
subscribe_to = (bpy.context, 'selected_objects')
...

It doesn't work either.

msgbus unfortunately often doesn't work. You can use the Application Handler instead, and on every change check if what you're interested in has changed. I show this technique (though not using app handler) here: Driver based on shading types/ change boolean when switching shading types — Markus von Broady, Oct 04 '22 at 15:06
Thanks SpaceOutliner.draw_handler_add(update, (), 'WINDOW', 'POST_PIXEL') This works. — Kayon, Oct 05 '22 at 04:40
You can post your own answer to the question for future visitors having a similar problem. — Markus von Broady, Oct 05 '22 at 08:38

score 2 · Answer 1 · answered Oct 05 '22 at 12:36

2

Finally, I solved the problem in this way.

Thanks for the method provided by Markus von Broady.

import bpy
from bpy.types import SpaceOutliner
def update():
    if bpy.context.area.type != "OUTLINER":
        return
# update bpy.context.collection
# update bpy.context.selected_object
# ...


def register():
    SpaceOutliner.my_handler = SpaceOutliner.draw_handler_add(update, (), 'WINDOW', 'POST_PIXEL')
def unregister():
    SpaceOutliner.draw_handler_remove(SpaceOutliner.my_handler, 'WINDOW')

answered Oct 05 '22 at 12:36

Kayon

61
3

It looks like this method is very computationally intensive, because it doesn't check if the collection was changed since the last function call (and the function is called on each mouse cursor draw for example, so quite a lot). Maybe you just didn't show it in your answer, but just in case, you could add on line 3 last_col = None, and then inside update() somewhere early if bpy.context.collection == last_col: return, and below that last_col = bpy.context.collection. – Markus von Broady Oct 05 '22 at 13:54

How to be notified when the active collection changes

1 Answers1