Subject: Re: bug#48674: Frames and minibuffer bug

From: Alan Mackenzie <[email-masked]>
Date: Fri, 28 May 2021 20:14:41 +0000

Hello, Martin.

On Fri, May 28, 2021 at 17:15:37 +0000, Alan Mackenzie wrote:
> On Fri, May 28, 2021 at 10:26:32 +0200, martin rudalics wrote:

[ .... ]

> > But why precisely does Fselect_window fail here?

> Sorry, my last night's reply wasn't very clear.  That Fselect_window in
> do_switch_frame will fail when a later Fselect_window (or more precisely,
> Fset_frame_selected_window) in move_minibuffers_onto_frame selects a
> different window for that frame.  That happens when with-selected-frame
> selects a different frame, moving the minibuffers onto that other frame.

> I have another idea for solving this problem.  Suppose when we switch
> from F1 to F2, and F1's selected window is the mini-window, we allow F1
> to remain in the MW.  The minibuffer stack gets moved to F2.  Some sort
> of commands or Lisp runs in F2, then we return to F1.  Should any
> minibuffer come back to F1, we allow the MW to remain selected.
> Otherwise we select a different window in F1.

> I think this would work better that what I proposed last night.  I'll try
> and formulate a patch for this this evening.

I think the following patch, along the above lines, solves the bug
completely.  Could you review it for me, please?

diff --git a/src/minibuf.c b/src/minibuf.c
index cffb7fe787..c97a672ad6 100644
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -192,10 +192,10 @@ move_minibuffers_onto_frame (struct frame *of, bool for_deletion)
   struct frame *f = XFRAME (selected_frame);
 
   minibuf_window = f->minibuffer_window;
-  if (!(minibuf_level
-	&& (for_deletion || minibuf_follows_frame () || FRAME_INITIAL_P (of))))
+  if (!(for_deletion || minibuf_follows_frame () || FRAME_INITIAL_P (of)))
     return;
-  if (FRAME_LIVE_P (f)
+  if (minibuf_level
+      && FRAME_LIVE_P (f)
       && !EQ (f->minibuffer_window, of->minibuffer_window)
       && WINDOW_LIVE_P (f->minibuffer_window) /* F not a tootip frame */
       && WINDOW_LIVE_P (of->minibuffer_window))
@@ -203,15 +203,12 @@ move_minibuffers_onto_frame (struct frame *of, bool for_deletion)
       zip_minibuffer_stacks (f->minibuffer_window, of->minibuffer_window);
       if (for_deletion && XFRAME (MB_frame) != of)
 	MB_frame = selected_frame;
-      if (!for_deletion
-	  && MINI_WINDOW_P (XWINDOW (FRAME_SELECTED_WINDOW (of))))
-	{
-	  Lisp_Object old_frame;
-	  XSETFRAME (old_frame, of);
-	  Fset_frame_selected_window (old_frame,
-				      Fframe_first_window (old_frame), Qnil);
-	}
     }
+  /* If the new frame's selected window is the mini-window, select
+     some other window if we don't have an active minibuffer there.  */
+  if (MINI_WINDOW_P (XWINDOW (FRAME_SELECTED_WINDOW (f)))
+      && !live_minibuffer_p (XWINDOW (FRAME_SELECTED_WINDOW (f))->contents))
+    Fselect_window (Fframe_first_window (selected_frame), Qnil);
 }
 
 DEFUN ("active-minibuffer-window", Factive_minibuffer_window,

-- 
Alan Mackenzie (Nuremberg, Germany).