bug#33498: 26.1; Unable to delete minibuffer-only+child frames

[martin rudalics <rudalics@gmx.at>]

 > Are you talking about a different feature here ? Because, this is what I
 > understand `keep-ratio' is supposed to be doing.

'keep-ratio' simply correlates the sizes of a child and its parent
frame.  If you make a parent frame half its size, 'keep-ratio' makes
its child frames half their size as well.  What I mean is the usual
expanding/shrinking of the minibuffer window you can observe on a
normal minibuffer equipped frame.  For example, via (message"\n\n").

 > So, you are saying it's supposed to be like that ?

Yes.

 > Them, I don't see a
 > reason, why Emacs should disallow deleting the minibuffer-frame as a
 > child-frame in this case.

For internal reasons each live frame must have a minibuffer window.
This is hardcoded in a couple of internal routines and if you remove
that restriction (it's the "Attempt to delete a surrogate minibuffer
frame" in frame.c) Emacs will crash soon after that.  Note that a
child frame minibuffer is handled like a normal minibuffer-only frame
in this regard.

martin