Save and restore buffer-display-time

* desktop.el (desktop-locals-to-save): Add `buffer-display-time'
(desktop-read): Set `desktop-file-modtime' before loading the desktop file
(desktop-create-buffer): Adjust `buffer-display-time' for the downtime

1 files changed, 15 insertions, 1 deletions

diff --git a/lisp/desktop.el b/lisp/desktop.el
index df4ff551c2d..9fb8393e76c 100644
--- a/lisp/desktop.el
+++ b/lisp/desktop.el
@@ -367,6 +367,7 @@ these won't be deleted."
     column-number-mode
     size-indication-mode
     buffer-file-coding-system
+    buffer-display-time
     indent-tabs-mode
     tab-width
     indicate-buffer-boundaries
@@ -1233,8 +1234,8 @@ Using it may cause conflicts.  Use it anyway? " owner)))))
                   (memq 'desktop-auto-save-set-timer window-configuration-change-hook))
             (desktop-auto-save-disable)
             ;; Evaluate desktop buffer and remember when it was modified.
-            (load (desktop-full-file-name) t t t)
             (setq desktop-file-modtime (nth 5 (file-attributes (desktop-full-file-name))))
+            (load (desktop-full-file-name) t t t)
             ;; If it wasn't already, mark it as in-use, to bother other
             ;; desktop instances.
             (unless (eq (emacs-pid) owner)
@@ -1536,6 +1537,19 @@ and try to load that."
               ;; An entry of the form `symbol'.
               (make-local-variable this)
               (makunbound this)))
+          ;; adjust `buffer-display-time' for the downtime. e.g.,
+          ;; * if `buffer-display-time' was 8:00
+          ;; * and emacs stopped at `desktop-file-modtime' == 11:00
+          ;; * and we are loading the desktop file at (current-time) 12:30,
+          ;; -> then we restore `buffer-display-time' as 9:30,
+          ;; for the sake of `clean-buffer-list': preserving the invariant
+          ;; "how much time the user spent in Emacs without looking at this buffer".
+          (setq buffer-display-time
+                (if buffer-display-time
+                    (time-add buffer-display-time
+                              (time-subtract (current-time)
+                                             desktop-file-modtime))
+                  (current-time)))
           (unless (< desktop-file-version 208) ; Don't misinterpret any old custom args
             (dolist (record compacted-vars)
               (let*