storm moss
I'm trying to get the cast bar to adjust the space between the dynamic groups in my weak aura.
https://wago.io/PKdBCJ3mU
So basically: SetRegionWidth(mainbar - (dynamic groups1 + dynamic groups2)) 
But since the dynamic groups are sometimes wider and sometimes narrower... here's my question:
Is it possible to query the width or number of active auras from another group?
mild vale
with some creativity, almost anything is possible
but you're well outside the supported feature set of WA
storm moss
Too bad, I thought someone had an idea 
celest notch
If it's a dynamic group with a custom grow code, then you can get the total width of it from in there. either because you set it via code in some way, or simply because you have access to all aura_env.childenvs in there and can add all their width (and the spacing) up.
and since your grow code runs whenever the dynamic group changes, you can send a fake event, carrying the total width, that your progress bar reacts to with a custom trigger and change the width accordingly.
If it's a default dynamic group then you can still get its "width" via accessing its sortedChildren table and summing that all up, but then the problem is executing your width change at the right time.