Fix minibuffer window related docs and strings (Bug#28978)

* src/frame.c (Vdefault_minibuffer_frame): Fix doc-string.
* src/window.c (Fminibuffer_selected_window): Fix doc-string.
* doc/lispref/frames.texi (Buffer Parameters): Rewrite
description of `minibuffer' parameter.
* doc/lispref/minibuf.texi (Minibuffer Windows): Reorder
entries and partly rewrite section.
(Minibuffer Misc): Clarify description of
`minibuffer-selected-window'.
* etc/NEWS: Mention new semantics of 'minibuffer' frame
parameter.

1 files changed, 5 insertions, 10 deletions

diff --git a/src/frame.c b/src/frame.c
index ab801eec9c7..fe1709e6ede 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -5895,16 +5895,11 @@ or call the function `tool-bar-mode'.  */);
 #endif
 
   DEFVAR_KBOARD ("default-minibuffer-frame", Vdefault_minibuffer_frame,
-                 doc: /* Minibufferless frames use this frame's minibuffer.
-Emacs cannot create minibufferless frames unless this is set to an
-appropriate surrogate.
-
-Emacs consults this variable only when creating minibufferless
-frames; once the frame is created, it sticks with its assigned
-minibuffer, no matter what this variable is set to.  This means that
-this variable doesn't necessarily say anything meaningful about the
-current set of frames, or where the minibuffer is currently being
-displayed.
+                 doc: /* Minibuffer-less frames by default use this frame's minibuffer.
+Emacs consults this variable only when creating a minibuffer-less frame
+and no explicit minibuffer window has been specified for that frame via
+the `minibuffer' frame parameter.  Once such a frame has been created,
+setting this variable does not change that frame's previous association.
 
 This variable is local to the current terminal and cannot be buffer-local.  */);