Fix horizontal scrolling of images with C-f

* lisp/image-mode.el (image-forward-hscroll): Calculate the
window-width more accurately, as the number of full columns that
fits in the window's text-area.  (Bug#65187)

diff --git a/lisp/image-mode.el b/lisp/image-mode.el
index 1820defa195d1c7968b9237e66f54ed7d7355d25..336d89dd52db4f5e78f4e210ac164d6cd935eb2c 100644 (file)
--- a/lisp/image-mode.el
+++ b/lisp/image-mode.el
@@ -248,8 +248,9 @@ Stop if the right edge of the image is reached."
         (image-set-window-hscroll (max 0 (+ (window-hscroll) n))))
        (t
         (let* ((image (image-get-display-property))
-               (edges (window-inside-edges))
-               (win-width (- (nth 2 edges) (nth 0 edges)))
+               (edges (window-edges nil t nil t))
+               (win-width (- (/ (nth 2 edges) (frame-char-width))
+                              (/ (nth 0 edges) (frame-char-width))))
                (img-width (ceiling (car (image-display-size image)))))
           (image-set-window-hscroll (min (max 0 (- img-width win-width))
                                          (+ n (window-hscroll))))))))