Subject: Re: bug#29854: 25.3; Eshell buffer editing gets slower as colored output grows

From: Noam Postavsky <[email-masked]>
Date: Sun, 31 Dec 2017 21:07:55 -0500

Pierre Neidhardt <[email-masked]> writes:

> The recipe with Evil is as follows:
>
> - Start Emacs.
>
> - `M-x eshell'.
>
> - Insert lots of colored text. On Linux, you can call `dmesg -L=always' a few times.
>
> - Go to normal state and press `x' wherever you can delete a character.
>
> It should be possible to reproduce without Evil, I just could not figure
> out a slow operation to replace the last step in the recipe.
>
> According to the Evil maintainer, the issue comes from markers left
> behind.

So does this fix it?

--- i/lisp/ansi-color.el
+++ w/lisp/ansi-color.el
@@ -417,3 +417,7 @@ ansi-color-apply-on-region
 		 start-marker end-marker (ansi-color--find-face codes))
-	(setq ansi-color-context-region (if codes (list codes)))))))
+	(setq ansi-color-context-region (if codes (list codes)))))
+    ;; Clean up our temporary markers.
+    (unless (eq start-marker (cadr ansi-color-context-region))
+      (set-marker start-marker nil))
+    (set-marker end-marker nil)))

Also, I wonder if doing this would help also?

    (setq
     ansi-color-apply-face-function
     (lambda (beg end face)
       (when face
         (put-text-property beg end 'face face))))

That should make Emacs use text properties instead of overlays for the
colored text.