Subject: Re: bug#55070: 28.1; desktop-load doesn't work in -nw (non-gui) emacs

From: Juri Linkov <[email-masked]>
Date: Tue, 26 Apr 2022 10:58:28 +0300

> OK, thanks for the details.  They tell me that what you see is the
> intended behavior: desktop.el doesn't restore frames and windows on
> text-mode terminals.  This is because restoring frames and windows in
> a -nw session is problematic, especially if the desktop was saved from
> a GUI session.

Interesting, I see this is disabled explicitly by display-graphic-p in:

  (defun desktop-restoring-frameset-p ()
    "True if calling `desktop-restore-frameset' will actually restore it."
    (and desktop-restore-frames desktop-saved-frameset (display-graphic-p) t))

When I tried to remove display-graphic-p, then it's problematic indeed
and fails with:

  frameset-move-onscreen(#<frame F1 0x5645998d8be0> t)
  frameset--restore-frame(((minibuffer . t) (tty-type . "xterm-256color") ...
  frameset-restore([frameset 1 ...
  desktop-restore-frameset()
  desktop-read(nil (4))
  funcall-interactively(desktop-read nil (4))
  command-execute(desktop-read record)

So the problem is in frameset-move-onscreen.  A little debugging
revealed that it fails on the nil frame-parameter 'left',
so a small patch could fix it, then restoring frames
in a -nw session works fine:

diff --git a/lisp/frameset.el b/lisp/frameset.el
index 05884eed3a..32966376d8 100644
--- a/lisp/frameset.el
+++ b/lisp/frameset.el
@@ -883,8 +883,8 @@ frameset-move-onscreen
   (pcase-let* ((`(,left ,top ,width ,height) (cdadr (frame-monitor-attributes frame)))
 	       (right (+ left width -1))
 	       (bottom (+ top height -1))
-	       (fr-left (frameset-compute-pos (frame-parameter frame 'left) left right))
-	       (fr-top (frameset-compute-pos (frame-parameter frame 'top) top bottom))
+	       (fr-left (frameset-compute-pos (or (frame-parameter frame 'left) 0) left right))
+	       (fr-top (frameset-compute-pos (or (frame-parameter frame 'top) 0) top bottom))
 	       (ch-width (frame-char-width frame))
 	       (ch-height (frame-char-height frame))
 	       (fr-width (max (frame-pixel-width frame) (* ch-width (frame-width frame))))