Make it easier to customize wallpaper command

* lisp/image/wallpaper.el
(wallpaper--default-commands): New defvar.
(wallpaper--find-command): Use above new defvar.
(wallpaper--find-command-arguments): New defun.
(wallpaper-command): Rename from 'wallpaper-commands' and change
type to string.  Use 'wallpaper--find-command' to set it.
(wallpaper-command-args): New defcustom.  Use
'wallpaper--find-command-arguments' to set it.
(wallpaper--set-wallpaper-command): New defun.  Use as :set property
for 'wallpaper-command'.
(wallpaper-set): Use above new defcustoms to set the wallpaper.
Suggested by Eli Zaretskii <eliz@gnu.org>.

diff --git a/etc/NEWS b/etc/NEWS
index 7505a37c06dc51d17e2abc06223d68f5b36094e2..5276a49d5cd6de1b03e8968c5e493312d46bcd3e 100644 (file)
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1997,7 +1997,8 @@ desktop background.
 On GNU/Linux and other Unix-like systems, it uses an external command
 (such as "swaybg", "gm", "display" or "xloadimage").  A suitable
 command should be detected automatically in most cases, but can also
-be customized manually with the new user option `wallpaper-commands'.
+be customized manually with the new user options 'wallpaper-command'
+and 'wallpaper-command-args' if needed.
 
 On Haiku, it uses the new function `haiku-set-wallpaper', which does
 not rely on any external command.

diff --git a/lisp/image/wallpaper.el b/lisp/image/wallpaper.el
index 172164fdf914a85b5cc94148c55e7bd78bc8eb06..e25ce448c1071b2ec03fcc4173957622bc27df32 100644 (file)
--- a/lisp/image/wallpaper.el
+++ b/lisp/image/wallpaper.el
@@ -35,14 +35,18 @@
 ;; right, as there is no lack of platforms, window managers, desktop
 ;; environments and tools.  However, it should be detected
 ;; automatically in most cases.  If it doesn't work in your
-;; environment, customize the user option `wallpaper-commands'.
+;; environment, customize the user options `wallpaper-command' and
+;; `wallpaper-command-args'.
 
 ;;; Code:
 
 (eval-when-compile (require 'subr-x))
 (require 'xdg)
 
-(defcustom wallpaper-commands
+\f
+;;; Finding the wallpaper command
+
+(defvar wallpaper--default-commands
   '(
     ;; Sway (Wayland)
     ("swaybg" "-o" "*" "-i" "%f" "-m" "fill")
@@ -60,9 +64,11 @@
     ("xloadimage" "-onroot" "-fullscreen" "%f")
     ("xsetbg" " %f")
     )
-  "List of executables and arguments for setting the wallpaper.
-This is used by `wallpaper-set', which will test the commands
-in the order they appear.
+  "Executable used for setting the wallpaper.
+This is used by `wallpaper--find-command' to automatically set
+`wallpaper-command', and by `wallpaper--find-command-args' to set
+`wallpaper-command-args'.  The commands will be tested in the
+order in which they appear.
 
 Every item in the list has the following form:
 
@@ -71,29 +77,8 @@ Every item in the list has the following form:
 COMMAND is the name of the executable (a string) and ARG1 .. ARGN
 is its command line arguments (also strings).
 
-In each of the command line arguments, \"%f\" will be replaced
-with the full file name, \"%h\" with the height of the selected
-frame's display (as returned by `display-pixel-height'), and
-\"%w\" with the width of the selected frame's display (as
-returned by `display-pixel-width').
-
-Note: If you find that you need to use a command that is not in
-this list to set the wallpaper in your environment, we would love
-to hear about it!  Please send an email to bug-gnu-emacs@gnu.org
-and tell us the command (and all options) that worked for you.
-You can also use \\[report-emacs-bug]."
-  :type '(repeat (repeat string))
-  :group 'image
-  :version "29.1")
-
-(defvar wallpaper-debug nil
-  "If non-nil, display debug messages.")
-
-(defun wallpaper-debug (&rest args)
-  (when wallpaper-debug
-    (apply #'message
-           (concat "wallpaper-debug: " (car args))
-           (cdr args))))
+In each of the command line arguments, \"%f\", \"%h\" and \"%w\"
+will be replaced as described in `wallpaper-command-args'.")
 
 (cl-defmethod wallpaper--check-command ((_type (eql 'gsettings)))
   (member "GNOME" (xdg-current-desktop)))
@@ -112,12 +97,77 @@ You can also use \\[report-emacs-bug]."
   t)
 
 (defun wallpaper--find-command ()
-  "Return a valid command for this system."
+  "Return a valid command to set the wallpaper in this environment."
   (catch 'found
-    (dolist (cmd wallpaper-commands)
+    (dolist (cmd wallpaper--default-commands)
       (if (and (wallpaper--check-command (intern (car cmd)))
                (executable-find (car cmd)))
-          (throw 'found cmd)))))
+          (throw 'found (car cmd))))))
+
+(defvar wallpaper-command) ; silence byte-compiler
+(defun wallpaper--find-command-arguments ()
+  "Return command line arguments matching `wallpaper-command'."
+  (cdr (assoc wallpaper-command wallpaper--default-commands)))
+
+\f
+;;; Customizable variables
+
+(defvar wallpaper-command-args) ; silence byte-compiler
+(defun wallpaper--set-wallpaper-command (sym val)
+  "Set `wallpaper-command', and update `wallpaper-command-args'."
+  ;; Note: `command-args' is used by `wallpaper--find-command-arguments'.
+  (prog1 (set-default sym val)
+    (set-default 'wallpaper-command-args
+                 (wallpaper--find-command-arguments))))
+
+(defcustom wallpaper-command (wallpaper--find-command)
+  "Executable used for setting the wallpaper.
+A suitable command for your environment should be detected
+automatically, so there is usually no need to customize this.
+However, if you do need to change this, you might also want to
+customize `wallpaper-command-args' to match.
+
+Note: If you find that you need to use a command in your
+environment that is not automatically detected, we would love to
+hear about it!  Please send an email to bug-gnu-emacs@gnu.org and
+tell us the command (and all options) that worked for you.  You
+can also use \\[report-emacs-bug]."
+  :type '(choice string
+                 (const :tag "Not set" nil))
+  :set #'wallpaper--set-wallpaper-command
+  :group 'image
+  :version "29.1")
+
+(defcustom wallpaper-command-args (wallpaper--find-command-arguments)
+  "Command line arguments for `wallpaper-command'.
+A suitable command for your environment should be detected
+automatically, so there is usually no need to customize this.
+However, if you do need to change this, you might also want to
+customize `wallpaper-command' to match.
+
+In each of the command line arguments, \"%f\" will be replaced
+with the full file name, \"%h\" with the height of the selected
+frame's display (as returned by `display-pixel-height'), and
+\"%w\" with the width of the selected frame's display (as
+returned by `display-pixel-width')."
+  :type '(repeat string)
+  :group 'image
+  :version "29.1")
+
+\f
+;;; Utility functions
+
+(defvar wallpaper-debug nil
+  "If non-nil, display debug messages.")
+
+(defun wallpaper-debug (&rest args)
+  (when wallpaper-debug
+    (apply #'message
+           (concat "wallpaper-debug: " (car args))
+           (cdr args))))
+
+\f
+;;; wallpaper-set
 
 (defvar wallpaper-default-width 1080
   "Default width used by `wallpaper-set'.
@@ -129,13 +179,13 @@ See also `wallpaper-default-height'.")
 This is only used when it can't be detected automatically.
 See also `wallpaper-default-width'.")
 
-(declare-function haiku-set-wallpaper "term/haiku-win.el")
-
 (defun wallpaper--get-height-or-width (desc fun default)
   (if (display-graphic-p)
       (funcall fun)
     (read-number (format "Wallpaper %s in pixels: " desc) default)))
 
+(declare-function haiku-set-wallpaper "term/haiku-win.el")
+
 (defun wallpaper-set (file)
   "Set the desktop background to FILE in a graphical environment.
 
@@ -161,8 +211,7 @@ On Haiku, no external command is needed, so the value of
   (cond ((featurep 'haiku)
          (haiku-set-wallpaper file))
         (t
-         (let* ((command (wallpaper--find-command))
-                (fmt-spec `((?f . ,(expand-file-name file))
+         (let* ((fmt-spec `((?f . ,(expand-file-name file))
                             (?h . ,(wallpaper--get-height-or-width
                                     "height"
                                     #'display-pixel-height
@@ -173,14 +222,15 @@ On Haiku, no external command is needed, so the value of
                                     wallpaper-default-width))))
                 (bufname (format " *wallpaper-%s*" (random)))
                 (process
-                 (and command
+                 (and wallpaper-command
                       (apply #'start-process "set-wallpaper" bufname
-                             (car command)
+                             wallpaper-command
                              (mapcar (lambda (arg) (format-spec arg fmt-spec))
-                                     (cdr command))))))
-           (unless command
-             (error "Can't find a suitable command for setting the wallpaper"))
-           (wallpaper-debug "Using command %s" (car command))
+                                     wallpaper-command-args)))))
+           (unless wallpaper-command
+             (error "Couldn't find a suitable command for setting the wallpaper"))
+           (wallpaper-debug "Using command %S %S" wallpaper-command
+                            wallpaper-command-args)
            (setf (process-sentinel process)
                  (lambda (process status)
                    (unwind-protect