I have a buffer with terminal escape codes in it and I want them to be colored:
I was able to do this with (ansi-color-apply-on-region (point-min) (point-max)):
However, my file is really big and that command is really slow. Is there any mode that colors terminal escape codes with font lock? I imagine that would be much faster.
NOTE: What I am looking at is a log file, not a shell buffer, so solutions involving M-x shell output are irrelevant to me.
If you set up your shell buffer to convert the escape codes to color automatically, it works much faster. I have the following config:
(add-to-list 'comint-output-filter-functions 'ansi-color-process-output)
(ansi-color-for-comint-mode-on)
With this set, when I run a shell in emacs (i.e., M-x shell), the output is colored automatically each time it is produced. That means you only wait an undetectable short period for emacs to color each line of output, rather than waiting for the entire buffer to be colored like you're experiencing.
find-file and it “just works.”
Commented
Jul 18, 2018 at 19:23
cat in M-x shell provides color output even without your ELisp snippet. However, I think that trick is irrelevant to solving this question the “right” way, because it runs into the same problem I posed in my question, i.e. cat results in coloring an entire enormous file. I also don’t want to view the file in shell-mode, I want to view it in fundamental-mode.
Commented
Jul 18, 2018 at 19:56
I was able to do this with
(ansi-color-apply-on-region (point-min) (point-max)):However, my file is really big and that command is really slow.
That function uses overlays by default, which will quickly become very slow when you have many of them. Try
(let ((ansi-color-apply-face-function
(lambda (beg end face)
(when face
(put-text-property beg end 'face face)))))
(ansi-color-apply-on-region (point-min) (point-max)))
See also
font-lock-faceproperties so that font-lock will show the colours is precisely whatansi-color-applyis doing.ansi-color-apply? In the question it looks like the entire buffer is converted at once, which is time consuming for large buffers. Normally, font-lock rules are only applied to the visible part of a buffer which makes them much faster.ansi-color-applydeletes the ansi escape code characters from the text and adds text properties in their place. I didn't think that was a task for which font-lock was suitable, but you'll know much better than I do.invisibletext property without altering the actual text. In addition, ANSI sequences stretching over multiple lines may be problematic, since font-lock only highlights one or a few lines at a time.ansi-color-applyandansi-color-apply-on-regiondo things very differently! The former putsfont-lock-facetext properties on the string, while the latter creates overlays and placesfaceproperties on those.