Re: How to restore the layout?

[Juanma Barranquero]

This is basically the same patch as before, only slightly more
polished. It's surprisingly functional for its tiny size.

Changes:
- Window/frame config is still saved as a global variable, but not
from desktop-globals-to-save, which is a user option.
- Some frame parameters are not saved, mostly those that cannot be
read back or makes no sense to do so.
- Errors while restoring the config do not interrupt the restoring;
there's just a message afterwards.

There are many things still unimplemented, some of which should be
discussed before throwing code at it. From the top of my head:

1) When restoring frames, what to do with the existing ones? They can
be reused, or deleted. Reusing them will cause less "flicker".

2) What to do with frames with a buffer-predicate? Currently I'm
excluding that frame parameter. It could be saved if it is a symbol,
of course.

3) What about maximized / fullscreen frames? Currently they don't
restore too well. It would be possible, but the original
pre-(fullscreen|maximized) size will not be saved. It could be saved
by de-maximizing the frame before saving it and then maximizing it
back again, but if the user is just calling desktop-save in the middle
of a session, that will make the maximized frame flicker.

4) I'm not saving the `minibuffer' parameter, though I should. It's
trivial for t/nil/only, but what about minibuffer . <#window...>?
Should we try to save/restore that somehow?

5) Presumably, for Emacs on X I should make sure that each frame is
restored in the corresponding display. I'm not yet doing that (I don't
have a way to test it).

All in all, the patch is small and non-intrusive. Perhaps I could
install it (with desktop-save-windows defaulting to nil) so people
could experiment and say what works and what doesn't. That would be
particularly useful from people who use multi-frame setups (Stefan and
Drew come to mind).

Comments?

    J



=== modified file 'lisp/desktop.el'
--- lisp/desktop.el 2013-05-02 17:47:39 +0000
+++ lisp/desktop.el 2013-06-26 17:15:07 +0000
@@ -371,6 +371,12 @@
   :type '(repeat symbol)
   :group 'desktop)

+(defcustom desktop-save-windows t
+  "When non-nil, save window/frame configuration to desktop file."
+  :type 'boolean
+  :group 'desktop
+  :version "24.4")
+
 (defcustom desktop-file-name-format 'absolute
   "Format in which desktop file names should be saved.
 Possible values are:
@@ -556,6 +562,9 @@
   "Checksum of the last auto-saved contents of the desktop file.
 Used to avoid writing contents unchanged between auto-saves.")

+(defvar desktop--window-state nil
+  "Internal use only.")
+
 ;; ----------------------------------------------------------------------------
 ;; Desktop file conflict detection
 (defvar desktop-file-modtime nil
@@ -858,6 +867,37 @@


 ;; ----------------------------------------------------------------------------
+(defconst desktop--excluded-frame-parameters
+  '(minibuffer-predicate
+    minibuffer
+    buffer-list
+    buried-buffer-list
+    window-id
+    outer-window-id)
+  "Frame parameters not saved or restored.")
+
+(defun desktop--filter-frame-parms (frame)
+  "Return frame parameters of FRAME.
+Parameters in `desktop--excluded-frame-parameters' are excluded.
+Internal use only."
+  (let (params)
+    (dolist (param (frame-parameters frame))
+      (unless (memq param desktop--excluded-frame-parameters)
+ (push param params)))
+    params))
+
+(defun desktop--save-windows ()
+  "Save window/frame state, as a global variable.
+Intended to be called from `desktop-save'.
+Internal use only."
+  (setq desktop--window-state
+ (and desktop-save-windows
+     (mapcar (lambda (frame)
+       (cons (desktop--filter-frame-parms frame)
+     (window-state-get (frame-root-window frame) t)))
+     (frame-list))))
+  (desktop-outvar 'desktop--window-state))
+
 ;;;###autoload
 (defun desktop-save (dirname &optional release auto-save)
   "Save the desktop in a desktop file.
@@ -896,6 +936,9 @@
   (save-excursion (run-hooks 'desktop-save-hook))
   (goto-char (point-max))
   (insert "\n;; Global section:\n")
+  ;; Called here because we save the window/frame state as a global
+  ;; variable for compatibility with previous Emacsen.
+  (desktop--save-windows)
   (mapc (function desktop-outvar) desktop-globals-to-save)
   (when (memq 'kill-ring desktop-globals-to-save)
     (insert
@@ -954,6 +997,20 @@
 (defvar desktop-lazy-timer nil)

 ;; ----------------------------------------------------------------------------
+(defun desktop--restore-windows ()
+  "Restore window/frame configuration.
+Internal use only."
+  (when (and desktop-save-windows desktop--window-state)
+    (let ((current (frame-list))
+  (failure nil))
+      (dolist (state desktop--window-state)
+ (condition-case nil
+    (window-state-put (cdr state) (frame-root-window (make-frame (car state))))
+  (error (setq failure t))))
+      (if failure
+  (message "Error loading window configuration from desktop file")
+ (mapc #'delete-frame current)))))
+
 ;;;###autoload
 (defun desktop-read (&optional dirname)
   "Read and process the desktop file in directory DIRNAME.
@@ -1022,6 +1079,7 @@
     (switch-to-buffer (car (buffer-list)))
     (run-hooks 'desktop-delay-hook)
     (setq desktop-delay-hook nil)
+    (desktop--restore-windows)
     (run-hooks 'desktop-after-read-hook)
     (message "Desktop: %d buffer%s restored%s%s."
      desktop-buffer-ok-count

desktop.patch
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