More selective wiki link refontification

We only need to refontify wiki links in a region when
the range already contains text with a wiki link face
or if the wiki link regexp matches text in the region.
Otherwise, we can be sure there are no wiki links in
the region and can skip refontifying wiki links
(which is expensive in an after-change hook).

markdown-mode.el

@@ -5297,10 +5297,19 @@ given range."
                ;; and ends at safe places.
                (multiple-value-bind (new-from new-to)
                    (markdown-extend-changed-region from to)
-                 ;; Unfontify existing fontification (start from scratch)
-                 (markdown-unfontify-region-wiki-links new-from new-to)
-                 ;; Now do the fontification.
-                 (markdown-fontify-region-wiki-links new-from new-to)))))
+                 (goto-char new-from)
+                 ;; Only refontify when the range contains text with a
+                 ;; wiki link face or if the wiki link regexp matches.
+                 (when (or (markdown-range-property-any
+                            new-from new-to 'font-lock-face
+                            (list markdown-link-face
+                                  markdown-missing-link-face))
+                           (re-search-forward
+                            markdown-regex-wiki-link new-to t))
+                   ;; Unfontify existing fontification (start from scratch)
+                   (markdown-unfontify-region-wiki-links new-from new-to)
+                   ;; Now do the fontification.
+                   (markdown-fontify-region-wiki-links new-from new-to))))))
        (and (not modified)
             (buffer-modified-p)
             (set-buffer-modified-p nil)))))