master 32b7aaa9f1 2/4: Add new library wallpaper.el

[Stefan Kangas]

branch: master
commit 32b7aaa9f1e1fa12ea1db92594a872503f0de498
Author: Stefan Kangas <stefankangas@gmail.com>
Commit: Stefan Kangas <stefankangas@gmail.com>

    Add new library wallpaper.el
    
    * lisp/image/wallpaper.el: New file.
---
 etc/NEWS                |   6 ++
 lisp/image/wallpaper.el | 146 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 152 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index 5416aa8066..db3fcf19e5 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1989,6 +1989,12 @@ and is bound to "s p" in Image mode.
 *** Users can now add special image conversion functions.
 This is done via 'image-converter-add-handler'.
 
+---
+*** New library wallpaper.el.
+This library contains the command `wallpaper-set', which uses an
+external command to set the desktop background.  The new user option
+`wallpaper-commands' controls which command is being used.
+
 ** Image-Dired
 
 +++
diff --git a/lisp/image/wallpaper.el b/lisp/image/wallpaper.el
new file mode 100644
index 0000000000..d997cb48d7
--- /dev/null
+++ b/lisp/image/wallpaper.el
@@ -0,0 +1,146 @@
+;;; wallpaper.el --- Set wallpaper using external command  -*- 
lexical-binding: t; -*-
+
+;; Copyright (C) 2022 Free Software Foundation, Inc.
+
+;; Author: Stefan Kangas <stefankangas@gmail.com>
+;; Keywords: images
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This library provides the command `wallpaper-set', which uses an
+;; external command to set the desktop background.  This is obviously
+;; a bit tricky to get right, as there is no lack of platforms, window
+;; managers, desktop environments and tools.
+;;
+;; If this doesn't work in your environment, customize the user option
+;; `wallpaper-commands'.
+
+;;; Code:
+
+(defcustom wallpaper-commands
+  '(
+    ;; Sway (Wayland)
+    ("swaybg" "-o" "*" "-i" "%f" "-m" "fill")
+    ;; Gnome
+    ("gsettings" "set" "org.gnome.desktop.background" "picture-uri" 
"file://%f")
+    ;; Other / General X
+    ("gm" "display" "-size" "%wx%h" "-window" "root" "%f")
+    ("display" "-resize" "%wx%h" "-window" "root" "%f")
+    ("feh" "--bg-max" "%f")
+    ("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.
+
+Every item in the list has the following form:
+
+  (COMMAND ARG1 .. ARGN)
+
+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))))
+
+(cl-defmethod wallpaper--check-command ((_type (eql 'gsettings)))
+  (equal (getenv "XDG_CURRENT_DESKTOP") "GNOME"))
+
+(cl-defmethod wallpaper--check-command ((_type (eql 'swaybg)))
+  (and (getenv "WAYLAND_DISPLAY")
+       (getenv "SWAYSOCK")))
+
+(cl-defmethod wallpaper--check-command (_type)
+  t)
+
+(defun wallpaper--find-command ()
+  "Return a valid command for this system."
+  (catch 'found
+    (dolist (cmd wallpaper-commands)
+      (if (and (wallpaper--check-command (intern (car cmd)))
+               (executable-find (car cmd)))
+          (throw 'found cmd)))))
+
+(defun wallpaper-set (file)
+  "Set the desktop background to FILE in a graphical environment."
+  (interactive (list (and
+                      (display-graphic-p)
+                      (read-file-name "Set desktop background to: "
+                                      default-directory nil t nil
+                                      (lambda (fn)
+                                        (or (file-directory-p fn)
+                                            (string-match 
(image-file-name-regexp) fn)))))))
+  (when (file-directory-p file)
+    (error "Can't set wallpaper to a directory: %s" file))
+  (unless (file-exists-p file)
+    (error "No such file: %s" file))
+  (unless (file-readable-p file)
+    (error "File is not readable: %s" file))
+  (when (display-graphic-p)
+    (let* ((command (wallpaper--find-command))
+           (fmt-spec `((?f . ,(expand-file-name file))
+                       (?h . ,(display-pixel-height))
+                       (?w . ,(display-pixel-width))))
+           (bufname (format " *wallpaper-%s*" (random)))
+           (process
+            (and command
+                 (apply #'start-process "set-wallpaper" bufname
+                        (car 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))
+      (setf (process-sentinel process)
+            (lambda (process status)
+              (unwind-protect
+                  (unless (and (eq (process-status process) 'exit)
+                               (zerop (process-exit-status process)))
+                    (message "command %S %s: %S" (string-join (process-command 
process) " ")
+                             (string-replace "\n" "" status)
+                             (with-current-buffer (process-buffer process)
+                               (string-clean-whitespace (buffer-string)))))
+                (ignore-errors
+                  (kill-buffer (process-buffer process))))))
+      process)))
+
+(provide 'wallpaper)
+
+;;; wallpaper.el ends here