New function `locate-user-emacs-file'.

* subr.el (locate-user-emacs-file): New function.
  (user-emacs-directory): Mention it in docstring.

* completion.el (save-completions-file-name):
* filesets.el (filesets-menu-cache-file):
* image-dired.el (image-dired-dir, image-dired-db-file)
  (image-dired-temp-image-file, image-dired-gallery-dir)
  (image-dired-temp-rotate-image-file):
* savehist.el (savehist-file):
* server.el (server-auth-dir):
* startup.el (auto-save-list-file-prefix):
* thumbs.el (thumbs-thumbsdir):
* tutorial.el (tutorial--saved-dir):
* play/gamegrid.el (gamegrid-user-score-file-directory): Use it.

* url.el (url-configuration-directory): Use `locate-user-emacs-file'.

* NEWS: New function `locate-user-emacs-file'.

15 files changed, 63 insertions, 38 deletions

diff --git a/etc/ChangeLog b/etc/ChangeLog
index 2a1ef635321..4afa26a5141 100644
--- a/etc/ChangeLog
+++ b/etc/ChangeLog
@@ -1,3 +1,7 @@
+2008-10-24  Juanma Barranquero  <lekktu@gmail.com>
+
+        * NEWS: New function `locate-user-emacs-file'.
+
 2008-10-18  Ulrich Mueller  <ulm@gentoo.org>
 
         * MACHINES: Add section for SuperH.
diff --git a/etc/NEWS b/etc/NEWS
index d50b9cc4029..70fc968440e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1636,6 +1636,10 @@ the match data.
 `serial-process-configure' provide a Lisp interface to the new serial
 port support (see Emacs changes, above).
 
+*** `locate-user-emacs-file' helps packages to select the appropriate
+place to save user-specific files.  It defaults to `user-emacs-directory'
+unless the file already exists at $HOME.
+
 ** Miscellaneous new variables
 
 +++
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index c0f03a63d2c..c115c29d93b 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,20 @@
+2008-10-24  Juanma Barranquero  <lekktu@gmail.com>
+
+        * subr.el (locate-user-emacs-file): New function.
+        (user-emacs-directory): Mention it in docstring.
+
+        * completion.el (save-completions-file-name):
+        * filesets.el (filesets-menu-cache-file):
+        * image-dired.el (image-dired-dir, image-dired-db-file)
+        (image-dired-temp-image-file, image-dired-gallery-dir)
+        (image-dired-temp-rotate-image-file):
+        * savehist.el (savehist-file):
+        * server.el (server-auth-dir):
+        * startup.el (auto-save-list-file-prefix):
+        * thumbs.el (thumbs-thumbsdir):
+        * tutorial.el (tutorial--saved-dir):
+        * play/gamegrid.el (gamegrid-user-score-file-directory): Use it.
+
 2008-10-23  Juanma Barranquero  <lekktu@gmail.com>
 
         * edmacro.el (edmacro-eight-bits, edmacro-mode): Fix docstring typos.
diff --git a/lisp/completion.el b/lisp/completion.el
index 6a5c06a62b6..2f925dd2066 100644
--- a/lisp/completion.el
+++ b/lisp/completion.el
@@ -296,13 +296,7 @@ See also `save-completions-retention-time'."
   :group 'completion)
 
 (defcustom save-completions-file-name
-  (let ((olddef (convert-standard-filename "~/.completions")))
-    (cond
-     ((file-readable-p olddef) olddef)
-     ((file-directory-p user-emacs-directory)
-      (convert-standard-filename
-       (expand-file-name "completions" user-emacs-directory)))
-     (t olddef)))
+  (locate-user-emacs-file "completions" ".completions")
   "The filename to save completions to."
   :type 'file
   :group 'completion)
diff --git a/lisp/filesets.el b/lisp/filesets.el
index 5620d167bdd..6bd6d304175 100644
--- a/lisp/filesets.el
+++ b/lisp/filesets.el
@@ -354,9 +354,7 @@ See `add-submenu' for documentation."
 ;;  :group 'filesets)
 
 (defcustom filesets-menu-cache-file
-  (if (featurep 'xemacs)
-      "~/.xemacs/filesets-cache.el"
-    (concat user-emacs-directory "filesets-cache.el"))
+  (locate-user-emacs-file "filesets-cache.el")
   "File to be used for saving the filesets menu between sessions.
 Set this to \"\", to disable caching of menus.
 Don't forget to check out `filesets-menu-ensure-use-cached'."
diff --git a/lisp/image-dired.el b/lisp/image-dired.el
index 7b0a55de226..f9f1a334e76 100644
--- a/lisp/image-dired.el
+++ b/lisp/image-dired.el
@@ -164,7 +164,7 @@
   :prefix "image-dired-"
   :group 'multimedia)
 
-(defcustom image-dired-dir (concat user-emacs-directory "image-dired/")
+(defcustom image-dired-dir (locate-user-emacs-file "image-dired/")
   "Directory where thumbnail images are stored."
   :type 'string
   :group 'image-dired)
@@ -186,19 +186,19 @@ that allows sharing of thumbnails across different programs."
   :group 'image-dired)
 
 (defcustom image-dired-db-file
-  (concat user-emacs-directory "image-dired/.image-dired_db")
+  (locate-user-emacs-file "image-dired/.image-dired_db")
   "Database file where file names and their associated tags are stored."
   :type 'string
   :group 'image-dired)
 
 (defcustom image-dired-temp-image-file
-  (concat user-emacs-directory "image-dired/.image-dired_temp")
+  (locate-user-emacs-file "image-dired/.image-dired_temp")
   "Name of temporary image file used by various commands."
   :type 'string
   :group 'image-dired)
 
 (defcustom image-dired-gallery-dir
-  (concat user-emacs-directory "image-dired/.image-dired_gallery")
+  (locate-user-emacs-file "image-dired/.image-dired_gallery")
   "Directory to store generated gallery html pages.
 This path needs to be \"shared\" to the public so that it can access
 the index.html page that image-dired creates."
@@ -343,7 +343,7 @@ original image file name and %t which is replaced by
   :group 'image-dired)
 
 (defcustom image-dired-temp-rotate-image-file
-  (concat user-emacs-directory "image-dired/.image-dired_rotate_temp")
+  (locate-user-emacs-file "image-dired/.image-dired_rotate_temp")
   "Temporary file for rotate operations."
   :type 'string
   :group 'image-dired)
diff --git a/lisp/play/gamegrid.el b/lisp/play/gamegrid.el
index 36362f2d49b..824e55043ec 100644
--- a/lisp/play/gamegrid.el
+++ b/lisp/play/gamegrid.el
@@ -65,7 +65,7 @@
   "Number of high scores to keep")
 
 (defvar gamegrid-user-score-file-directory
-  (concat user-emacs-directory "games")
+  (locate-user-emacs-file "games/")
   "A directory for game scores which can't be shared.
 If Emacs was built without support for shared game scores, then this
 directory will be used.")
diff --git a/lisp/savehist.el b/lisp/savehist.el
index e3150565d56..55a724452db 100644
--- a/lisp/savehist.el
+++ b/lisp/savehist.el
@@ -96,15 +96,7 @@ minibuffer histories, such as `compile-command' or `kill-ring'."
   :group 'savehist)
 
 (defcustom savehist-file
-  (cond
-   ;; Backward compatibility with previous versions of savehist.
-   ((file-exists-p "~/.emacs-history") "~/.emacs-history")
-   ((and (not (featurep 'xemacs)) (file-directory-p user-emacs-directory))
-    (concat user-emacs-directory "history"))
-   ((and (featurep 'xemacs) (file-directory-p "~/.xemacs/"))
-    "~/.xemacs/history")
-   ;; For users without `~/.emacs.d/' or `~/.xemacs/'.
-   (t (convert-standard-filename "~/.emacs-history")))
+  (locate-user-emacs-file "history" ".emacs-history")
   "*File name where minibuffer history is saved to and loaded from.
 The minibuffer history is a series of Lisp expressions loaded
 automatically when `savehist-mode' is turned on.  See `savehist-mode'
diff --git a/lisp/server.el b/lisp/server.el
index 8dfa6d19732..b69965f94a6 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -111,7 +111,7 @@ If set, the server accepts remote connections; otherwise it is local."
   :version "22.1")
 (put 'server-host 'risky-local-variable t)
 
-(defcustom server-auth-dir (concat user-emacs-directory "server/")
+(defcustom server-auth-dir (locate-user-emacs-file "server/")
   "Directory for server authentication files."
   :group 'server
   :type 'directory
diff --git a/lisp/startup.el b/lisp/startup.el
index 6185cd5975a..84c7341597d 100644
--- a/lisp/startup.el
+++ b/lisp/startup.el
@@ -350,9 +350,9 @@ init file is read, in case it sets `mail-host-address'."
 (defcustom auto-save-list-file-prefix
   (cond ((eq system-type 'ms-dos)
          ;; MS-DOS cannot have initial dot, and allows only 8.3 names
-         (concat user-emacs-directory "auto-save.list/_s"))
+         (locate-user-emacs-file "auto-save.list/_s"))
         (t
-         (concat user-emacs-directory "auto-save-list/.saves-")))
+         (locate-user-emacs-file "auto-save-list/.saves-")))
   "Prefix for generating `auto-save-list-file-name'.
 This is used after reading your `.emacs' file to initialize
 `auto-save-list-file-name', by appending Emacs's pid and the system name,
diff --git a/lisp/subr.el b/lisp/subr.el
index 40311c4e1f4..5a1f4d42ee2 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2156,7 +2156,24 @@ On other systems, this variable is normally always nil.")
     "~/.emacs.d/")
   "Directory beneath which additional per-user Emacs-specific files are placed.
 Various programs in Emacs store information in this directory.
-Note that this should end with a directory separator.")
+Note that this should end with a directory separator.
+See also `locate-user-emacs-file'.")
+
+(defun locate-user-emacs-file (new-name &optional old-name)
+  "Return an absolute per-user Emacs-specific file name.
+If OLD-NAME is non-nil and ~/OLD-NAME exists, return ~/OLD-NAME.
+Else return NEW-NAME in `user-emacs-directory', creating the
+directory if it does not exist."
+  (convert-standard-filename
+   (let* ((home (concat "~" (or init-file-user "")))
+          (at-home (and old-name (expand-file-name old-name home))))
+     (if (and at-home (file-readable-p at-home))
+         at-home
+       (unless (or purify-flag ;; don't create dir while dumping
+                   (file-accessible-directory-p
+                    (directory-file-name user-emacs-directory)))
+         (make-directory user-emacs-directory t)) ;; don't catch errors
+       (expand-file-name new-name user-emacs-directory)))))
 
 
 ;;;; Misc. useful functions.
diff --git a/lisp/thumbs.el b/lisp/thumbs.el
index bb62d4cf6a4..2c4642a4470 100644
--- a/lisp/thumbs.el
+++ b/lisp/thumbs.el
@@ -65,7 +65,7 @@
   :version "22.1"
   :group 'multimedia)
 
-(defcustom thumbs-thumbsdir (concat user-emacs-directory "thumbs")
+(defcustom thumbs-thumbsdir (locate-user-emacs-file "thumbs")
   "*Directory to store thumbnails."
   :type 'directory
   :group 'thumbs)
diff --git a/lisp/tutorial.el b/lisp/tutorial.el
index 93438076b92..456fe5f401e 100644
--- a/lisp/tutorial.el
+++ b/lisp/tutorial.el
@@ -625,7 +625,7 @@ with some explanatory links."
 
 (defun tutorial--saved-dir ()
   "Directory to which tutorials are saved."
-  (expand-file-name "tutorial" user-emacs-directory))
+  (locate-user-emacs-file "tutorial/"))
 
 (defun tutorial--saved-file ()
   "File name in which to save tutorials."
diff --git a/lisp/url/ChangeLog b/lisp/url/ChangeLog
index 7e7ead4dfdb..b27b7255e4d 100644
--- a/lisp/url/ChangeLog
+++ b/lisp/url/ChangeLog
@@ -1,3 +1,7 @@
+2008-10-24  Juanma Barranquero  <lekktu@gmail.com>
+
+        * url.el (url-configuration-directory): Use `locate-user-emacs-file'.
+
 2008-10-20  İsmail Dönmez  <ismail@namtrac.org>  (tiny change)
 
         * url-auth.el (url-basic-auth): Encode password string.
@@ -769,8 +773,7 @@
 
 2005-06-14  Juanma Barranquero  <lekktu@gmail.com>
 
-        * url-history.el (url-completion-function): Follow error
-        conventions.
+        * url-history.el (url-completion-function): Follow error conventions.
 
 2005-06-13  Stefan Monnier  <monnier@iro.umontreal.ca>
 
diff --git a/lisp/url/url.el b/lisp/url/url.el
index ac7e47d9cc0..c066e39c004 100644
--- a/lisp/url/url.el
+++ b/lisp/url/url.el
@@ -45,12 +45,8 @@
 (require 'url-util)
 
 
-;; FIXME convert-standard-filename?
 (defcustom url-configuration-directory
-  (if (and (file-directory-p user-emacs-directory)
-           (not (file-directory-p "~/.url")))
-      (expand-file-name "url" user-emacs-directory)
-    "~/.url")
+  (locate-user-emacs-file ".url/" "url/")
   "Directory used by the URL package for cookies, history, etc."
   :type 'directory
   :group 'url)