fix interactive eww issue

Author: Danny McClanahan

markdown-mode.el

@@ -5868,8 +5868,13 @@ buffer. Inverse of `markdown-live-preview-buffer'.")
         (get-buffer "*eww*"))
     (error "eww is not present or not loaded on this version of emacs")))
 
-(defun markdown-get-lines-between-points (beg end)
-  (cl-count ?\n (buffer-substring-no-properties beg end)))
+(defun markdown-visual-lines-between-points (beg end)
+  (save-excursion
+    (goto-char beg)
+    (cl-loop with count = 0
+             while (and (< (point) end) (line-move-visual 1 t))
+             do (cl-incf count)
+             finally return count)))
 
 (defun markdown-live-preview-window-serialize (buf)
   "Get window point and scroll data for all windows displaying BUF if BUF is
@@ -5881,13 +5886,18 @@ non-nil."
          (let* ((pt (window-point win))
                 (pt-or-sym (cond ((= pt (point-min)) 'min)
                                  ((= pt (point-max)) 'max)
-                                 (t pt))))
-           (list win pt-or-sym
-                 ;; should use visual lines, not physical lines, but eww fits
-                 ;; line widths so there are no differences
-                 (markdown-get-lines-between-points (window-start win) pt))))
+                                 (t pt)))
+                (diff (markdown-visual-lines-between-points
+                       (window-start win) pt)))
+           (list win pt-or-sym diff)))
        (get-buffer-window-list buf)))))
 
+(defun markdown-get-point-back-lines (pt num-lines)
+  (save-excursion
+    (goto-char pt)
+    (line-move-visual (- num-lines) t)
+    (point)))
+
 (defun markdown-live-preview-window-deserialize (window-posns)
   "Apply window point and scroll data from WINDOW-POSNS, given by
 `markdown-live-preview-window-serialize'."
@@ -5900,12 +5910,8 @@ non-nil."
               (min (list (point-min) 0))
               (max (list (point-max) start))
               (t (list pt-or-sym start)))
-          (let ((start-pt
-                 (save-excursion
-                   (goto-char actual-pt)
-                   (forward-line (- actual-diff))
-                   (point))))
-            (set-window-start win start-pt))
+          (set-window-start
+           win (markdown-get-point-back-lines actual-pt actual-diff))
           (set-window-point win actual-pt))))))
 
 (defun markdown-live-preview-export ()

tests/markdown-test.el

@@ -3739,7 +3739,7 @@ Detail: https://github.com/jrblevin/markdown-mode/issues/79"
 
 (defmacro markdown-temp-eww (&rest body)
   `(progn
-     ,@(if (featurep 'eww) body
+     ,@(if (require 'eww nil t) body
          `((ad-enable-advice #'markdown-live-preview-window-eww
                              'around 'markdown-create-fake-eww)
            (ad-activate #'markdown-live-preview-window-eww)
@@ -3802,28 +3802,31 @@ Detail: https://github.com/jrblevin/markdown-mode/issues/79"
        ;; test that still starts at point-min
        (with-selected-window (get-buffer-window markdown-live-preview-buffer)
          (should (= (window-point) 1))
-         (goto-char (point-max))
-         (setq final-pt (point)
-               final-win-st-diff (markdown-get-lines-between-points
-                                  (window-start) final-pt)))
+         (should (= (markdown-visual-lines-between-points
+                     (window-start) (window-point))
+                    0))
+         (set-window-point (selected-window) (point-max))
+         (setq final-pt (window-point)
+               final-win-st-diff (markdown-visual-lines-between-points
+                                  (window-start) (window-point))))
        (goto-char (point-min))
        (insert "this is ")
        (markdown-live-preview-export)
-       ;; test that still starts at point-max, with correct line difference
        (with-selected-window (get-buffer-window markdown-live-preview-buffer)
          (should (= (window-point) (+ final-pt (length "this is "))))
-         (should (= (markdown-get-lines-between-points
+         (should (= (markdown-visual-lines-between-points
                      (window-start) (window-point))
                     final-win-st-diff))
+         ;; test that still starts at point-max, with correct line difference
          (goto-char (floor (/ (float (- (point-max) (point-min))) 2)))
          (setq final-pt (point)
-               final-win-st-diff (markdown-get-lines-between-points
+               final-win-st-diff (markdown-visual-lines-between-points
                                   (window-start) final-pt)))
        (markdown-live-preview-export)
        ;; test that still starts at same point, with correct line difference
        (with-selected-window (get-buffer-window markdown-live-preview-buffer)
          (should (= (window-point) final-pt))
-         (should (= (markdown-get-lines-between-points
+         (should (= (markdown-visual-lines-between-points
                      (window-start) (window-point))
                     final-win-st-diff)))))))