[PATCH] avoid hard-coded assumptions in image scaling

["James N. V. Cash" <james.nvc@gmail.com>]

In image-compute-scaling-factor in images.el, it currently hard-codes
the assumption that the average character width is 10 pixels. Since
`frame-char-width` gives this information though, it seems like it's less
error-prone to use that function instead of assuming.

---
 lisp/image.el | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/lisp/image.el b/lisp/image.el
index 610d020aab..8a9cfec841 100644
--- a/lisp/image.el
+++ b/lisp/image.el
@@ -561,12 +561,11 @@ image-compute-scaling-factor
    ((numberp scaling) scaling)
    ((eq scaling 'auto)
     (let ((width (/ (float (window-width nil t)) (window-width))))
-      ;; If we assume that a typical character is 10 pixels in width,
-      ;; then we should scale all images according to how wide they
-      ;; are.  But don't scale images down.
-      (if (< width 10)
+      ;; We should scale all images according to how wide they are.
+      ;; But don't scale images down.
+      (if (< width (frame-char-width))
           1
-        (/ (float width) 10))))
+        (/ (float width) (frame-char-width)))))
    (t
     (error "Invalid scaling factor %s" scaling))))

--
2.25.1