Rewrite wallpaper.el to use a cl-defstruct

* lisp/image/wallpaper.el
(wallpaper--default-commands): Delete variable.
(wallpaper-setter): New cl-defstruct.
(wallpaper--default-methods-create): New macro.
(wallpaper--default-setters):
(wallpaper--current-setter): New variables.
(wallpaper--find-setter): New defun to pick a wallpaper-setter.
(wallpaper--find-command, wallpaper--find-command-args):
Use 'wallpaper--find-setter'.
(wallpaper-command): Doc fix.

* test/lisp/image/wallpaper-tests.el
(wallpaper--find-command/return-string)
(wallpaper--find-command-args/return-list)
(wallpaper--image-file-regexp/return-string): New tests.

1 files changed, 11 insertions, 0 deletions

diff --git a/test/lisp/image/wallpaper-tests.el b/test/lisp/image/wallpaper-tests.el
index 8cd0fe2215e..80d512c9858 100644
--- a/test/lisp/image/wallpaper-tests.el
+++ b/test/lisp/image/wallpaper-tests.el
@@ -23,6 +23,17 @@
 (require 'ert-x)
 (require 'wallpaper)
 
+(ert-deftest wallpaper--find-command/return-string ()
+  (should (and (wallpaper--find-command)
+               (stringp (wallpaper--find-command)))))
+
+(ert-deftest wallpaper--find-command-args/return-list ()
+  (should (and (wallpaper--find-command-args)
+               (listp (wallpaper--find-command-args)))))
+
+(ert-deftest wallpaper--image-file-regexp/return-string ()
+  (should (stringp (wallpaper--image-file-regexp))))
+
 (ert-deftest wallpaper--get-default-file/empty-gives-nil ()
   (with-temp-buffer
     (should-not (wallpaper--get-default-file))))