The problem isn't exactly the same (my mouse can enter the emacs window with no problems, but /does/ fail upon clicking into it), but it seems similar enough to give it a go.
> Can you clarify whether the patch has been applied to stretch?
It took a little bit of learning, but I don't think that patch is present in stretch yet. (I used `apt-get source libgtk-3-dev` after pointing apt to the source repositories.) I can follow up with the GTK maintainers as to how to get that patch on my system and/or compile GTK from source (or better yet,
Thanks, and nice find!
-Sean