If they don't get focus when they pop-up, and not get focus via mouse and if they also
don't have decorations, what is considered as full functionality of "normal" frames?
That sounds to me a bit like a popup window. Do you give them focus by switching
with keyboard, like moving focus to "other window"?
"The concern is how to control
aspects like appearance, placement, focusing and stacking order of some
specific Emacs frames, without affecting the remaining frames."
As you yourself point out, certain WMs does allow you to create rules per windows. On some
managers one can set rule based on window title bar, window class or class name,
xid, role etc. I don't know if title bar property can be used if titlebar exist but is hidden.
Maybe a separate class name could be used for that kind of windows so one can set
appropriate hints for that frame. Or maybe you are already doing that? Just an idea,
I haven't looked at your patch to be honest.
I cloned code today from git and compilations is crashing on me, when dumping lisp code:
(without your patch applied):
Loading /home/arthur/emacs/lisp/international/characters.el (source)...
Wrong type argument: char-table-p, nil
make: *** [Makefile:752: bootstrap-emacs] Error 255
make: Leaving directory '/home/arthur/emacs/src'
make: *** [Makefile:409: src] Error 2
Will be interesting to test it once I manage to compile Emacs.