Support dired-movement-style in dired-next-dirline and dired-prev-dirline

* lisp/dired.el (dired-movement-style): Mention dired-next-dirline
and dired-prev-dirline in the docstring (bug#67303).
(dired-next-line): Refactor most code to dired--move-to-next-line.
(dired--move-to-next-line): New function with code from dired-next-line.
(dired--trivial-next-dirline): Rename from dired-next-dirline.
(dired-next-dirline): New function body that uses dired-movement-style,
dired--move-to-next-line and dired--trivial-next-dirline.
(dired-prev-dirline): Mention dired-movement-style in the docstring.

etc/NEWS

@@ -490,10 +490,11 @@ that shows as diffs replacements in the marked files in Dired.
 
 ---
 *** New user option 'dired-movement-style'.
-When non-nil, make 'dired-next-line' and 'dired-previous-line' skip
-empty lines.  It also controls how to move point when encountering a
-boundary (e.g., if every line is visible, invoking 'dired-next-line'
-at the last line will move to the first line).  The default is nil.
+When non-nil, make 'dired-next-line', 'dired-previous-line',
+'dired-next-dirline', 'dired-prev-dirline' skip empty lines.
+It also controls how to move point when encountering a boundary
+(e.g., if every line is visible, invoking 'dired-next-line' at
+the last line will move to the first line).  The default is nil.
 
 ** Ediff
 

lisp/dired.el

@@ -499,7 +499,8 @@ to nil: a pipe using `zcat' or `gunzip -c' will be used."
 
 (defcustom dired-movement-style nil
   "Non-nil means point skips empty lines when moving in Dired buffers.
-This affects only `dired-next-line' and `dired-previous-line'.
+This affects only `dired-next-line', `dired-previous-line',
+`dired-next-dirline', `dired-prev-dirline'.
 
 Possible non-nil values:
  * `cycle':   when moving from the last/first visible line, cycle back
@@ -2705,6 +2706,10 @@ Whether to skip empty lines and how to move from last line
 is controlled by `dired-movement-style'."
   (interactive "^p" dired-mode)
   (if dired-movement-style
+      (dired--move-to-next-line arg #'dired--trivial-next-line)
+    (dired--trivial-next-line arg)))
+
+(defun dired--move-to-next-line (arg jumpfun)
   (let ((old-position (progn
                         ;; It's always true that we should move
                         ;; to the filename when possible.
@@ -2716,7 +2721,7 @@ is controlled by `dired-movement-style'."
                        -1)))            ; means Up.
     ;; Line by line in case we forget to skip empty lines.
     (while (not (zerop arg))
-          (dired--trivial-next-line moving-down)
+      (funcall jumpfun moving-down)
       (when (= old-position (point))
         ;; Now point is at beginning/end of movable area,
         ;; but it still wants to move farther.
@@ -2726,22 +2731,15 @@ is controlled by `dired-movement-style'."
                            (point-min)
                          (point-max)))
           ;; `bounded': go back to the last non-empty line.
-              (while (string-match-p "\\`[[:blank:]]*\\'"
-                                     (buffer-substring-no-properties
-                                      (line-beginning-position)
-                                      (line-end-position)))
-                (dired--trivial-next-line (- moving-down)))
+          (while (dired-between-files)
+            (funcall jumpfun (- moving-down)))
           ;; Encountered a boundary, so let's stop movement.
           (setq arg moving-down)))
-          (when (not (string-match-p "\\`[[:blank:]]*\\'"
-                                     (buffer-substring-no-properties
-                                      (line-beginning-position)
-                                      (line-end-position))))
+      (unless (dired-between-files)
         ;; Has moved to a non-empty line.  This movement does
         ;; make sense.
         (cl-decf arg moving-down))
-          (setq old-position (point))))
-    (dired--trivial-next-line arg)))
+      (setq old-position (point)))))
 
 (defun dired-previous-line (arg)
   "Move up ARG lines, then position at filename.
@@ -2753,9 +2751,8 @@ is controlled by `dired-movement-style'."
   (interactive "^p" dired-mode)
   (dired-next-line (- (or arg 1))))
 
-(defun dired-next-dirline (arg &optional opoint)
+(defun dired--trivial-next-dirline (arg &optional opoint)
   "Goto ARGth next directory file line."
-  (interactive "p" dired-mode)
   (or opoint (setq opoint (point)))
   (if (if (> arg 0)
 	  (re-search-forward dired-re-dir nil t arg)
@@ -2763,10 +2760,24 @@ is controlled by `dired-movement-style'."
 	(re-search-backward dired-re-dir nil t (- arg)))
       (dired-move-to-filename)		; user may type `i' or `f'
     (goto-char opoint)
-    (error "No more subdirectories")))
+    (unless dired-movement-style
+      (error "No more subdirectories"))))
+
+(defun dired-next-dirline (arg &optional _opoint)
+  "Goto ARGth next directory file line.
+
+Whether to skip empty lines and how to move from last line
+is controlled by `dired-movement-style'."
+  (interactive "p" dired-mode)
+  (if dired-movement-style
+      (dired--move-to-next-line arg #'dired--trivial-next-dirline)
+    (dired--trivial-next-dirline arg)))
 
 (defun dired-prev-dirline (arg)
-  "Goto ARGth previous directory file line."
+  "Goto ARGth previous directory file line.
+
+Whether to skip empty lines and how to move from last line
+is controlled by `dired-movement-style'."
   (interactive "p" dired-mode)
   (dired-next-dirline (- arg)))