bug#57207: 29.0.50; Fontification is slow after e7b5912b23 (Improvements to long lines handling)

[Lars Ingebrigtsen]

Gregory Heytings <gregory@heytings.org> writes:

> I cannot reproduce that here: after evalling the recipe, typing "bar"
> and then doing M-< bar works as expected.

Here's a full test case.

emacs -Q and then:

(progn
  (pop-to-buffer "foo.txt")
  (flyspell-mode)
  (insert "\n\n"
          (propertize (make-string 20000 ?x) 'display "foo")
          "\n\nbar\nzot\n")
  (goto-char (point-min)))
 
Then type `d'.  Everything after "foo" disappears.