Code highlighting

[piranha]

It would be nice to be able to highlight code on server-side instead of doing that on client-side (right now I'm thinking about HTML and not Latex output). I see two possibilities here:

• get blocks of code from the resulting HTML (by parsing it), highlight them and inject back,
• provide (optional) highlighting function to blackfriday which will be called during rendering parts of the code.

I believe that latter is better option both API- and performance-wise. Do you have any thoughts/opinion about this?

[phrozen]

I think there should be a branch for the next version of blackfriday that 1) supports weekly, and 2) follow the steps of Sundown (evolved from original Upskirt) -> https://github.com/tanoku/sundown

Sundown actually broke the way most markdown processors work exactly to achieve what this issue is all about. It is now what powers Github's syntax highlighting is pretty efficient and allows for multiple outputs by pipelining the rendering. Blackfriday is amazing, but it would be more awesome if it stays current with Sundown/Redcarpet (Ruby interface to the Sundown library by Github).

[cespare]

I hacked up Blackfriday to do syntax highlighting by introducing a callback for processing Github-style code blocks. You can see my changes over on my fork. My method is pretty hacky and I'm not happy with it as a general solution, so I'm not going to open a pull request for it.

Ideally, I think you'd be able to take the existing HTML renderer and selectively override certain functions. This is the way that Redcarpet does it and it works really well.

(By the way, you can see how I hooked up pygmentize to my fork of blackfriday over here).

[yonderblue]

👍 for a future server side highlight :)

[dmitshur]

The github_flavored_markdown renderer already does server-side highlighting for Go, diff file format and potentially other languages:

It uses these Go packages for performing server-side highlighting:

• https://github.com/sourcegraph/syntaxhighlight
• https://github.com/shurcooL/highlight_go
• https://github.com/shurcooL/highlight_diff

I think it's out of scope for blackfriday itself to be importing those packages. However, another higher-level package can import blackfriday and aforementioned highlighter packages and perform markdown rendering with code server-side highlighting.

[yonderblue]

I see the complete html page example here https://godoc.org/github.com/shurcooL/github_flavored_markdown#example-Markdown--CompleteHtmlPage but doesn't that rely on non existing .../github-flavored-markdown.css file?

[dmitshur]

Yes, a .css with a highlighting scheme is needed. GitHub API provides a Markdown rendering endpoint, but it also seems to expect you to bring .css yourself.

Edit in 2017: The CSS for GitHub-Flavored Markdown highlighting is now available at https://github.com/primer/primer-css/tree/master/modules/primer-markdown.

[egorsmkv]

@alecthomas created a nice library https://github.com/alecthomas/chroma

It remains only to make the integration.

[depado]

As shown in #396 I finally came up with this : https://github.com/Depado/bfchroma
(Hope that helps)