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

[Pierre Neidhardt]

The patch does not seem to do it.  Unless load order matters?

The redifinition of `ansi-color-apply-face-function` works however, plus it comes at the bonus of making Eshell an order of magnitude faster!

I haven't tested estensively yet, but it seems to be a much better default.

On Mon, Jan 1, 2018 at 3:07 AM, Noam Postavsky <npostavs@users.sourceforge.net> wrote:

Pierre Neidhardt <ambrevar@gmail.com> 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.