Please do try to come up with a recipe.

Uncompress the attached file, and "emacs -Q x.txt"

Then, M-:, and insert this:

    (progn
      (setq scroll-conservatively 101)
      (font-lock-add-keywords nil '(((lambda (bound)) (1 'error prepend t))) t)
      (setq auto-hscroll-mode 'current-line)
      (setq truncate-lines t)
      (goto-char (point-max)))

Emacs will stop at line 19232 (point 3323065), but the file has 48263 lines.

As it turned out, this uses a rarely used configuration setting (auto-hscroll-mode set to current-line), so this issue is not a big deal I suppose.