Add support for mermaid diagrams to the forum

meta
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Mermaid seems to allow for many different kinds of figures (some info and examples here: About Mermaid | Mermaid), and it would be great to have the ability to quickly create diagrams in posts. The following discourse component appears to support this:

Might this possibly be worth setting up for the rust forum site?

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I kind of hate mermaid, but much less than everything else I've tried, and it's supported pretty much everywhere now. I guess this is agreement? :person_shrugging:

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Who is responsible for the site, and what is the process for trying out something new like this?

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Bumping this thread - does anyone know what the process / governance related to making site changes is?

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Perhaps @moderators can help here.

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Or perhaps not? :frowning:

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The site is powered by Discourse. I would recommend you submit this feature request to them as the moderators on this site (presumably) aren't the correct people to ask to add this given that (if I recall correctly) this forum is hosted for us by the folks at Discourse.

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The link at the top of this thread is to the official Discourse component for Mermaid.

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Here's some Discourse info on the feature.

It doesn't work with fontawesome (whatever that is).

Under Discourse pricing it is not listed as optional.

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Oops, I completely missed that omnibox. My apologies...

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Given that there really hasn't been any discussion about whether we should add mermaid or not, I'd like to raise my concerns of adding this as a feature, mainly for two reasons:

  • I feel like URLO/Discourse is already quite slow to load and interact with on mobile. Adding 30MB of JS for a feature that I believe won't be used really that often isn't going to help.

  • You can just link your mermaid diagram from the online mermaid editor and embed it as markdown. Here an example I created for one of my projects:

    It is literally as easy as linking to a playground.

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Linking to the mermaid-editor does look like a decent solution. The only concern I see is about how long these diagrams will be available, and if there's a chance that the service will change in the future in a way that prevents them from being accessed.

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And for reference in case the online editor is ever removed, the underlying diagram is stored in the URL as base 64 encoded deflated JSON. The following code is a bad implementation of URL to JSON string conversion:

use anyhow::Context as _;
use base64::engine::general_purpose::URL_SAFE;
use base64::Engine;
use flate2::Decompress;

const MAX_DECOMPRESSED_SIZE: usize = 2 * 65536;

fn main() -> anyhow::Result<()> {
    let url = "https://mermaid.live/edit#pako:eNp1k9uK2zAQhl9l0FULsZftmVwUGmcPtKS71O1SsENRpPFaxJaMDlsWO-_ecXwopKkvjDTzjWb-GallwkhkS1ZU5rcoufWw-p5roM-F3aPlTQlGNxbrrOBuWfDIoX1CC3ca7smqHG5PcGGNzhL6wWezG52rzAb9a8fFPjSxK0crajks-pAo-thdxrAxQfsumbKVUsKFxKcLJ_nl9i8NPf4-hh-6PgZAcuJ7FUPaKA2h6UAY7bnSVPUAJVEUrbMXD6YKNb78p_6Jphp2fQ3SiD3FJpN9DLjK_qtnXly37SgkUN_gk6yVPhxOEu4_uEmuqEyQkFTB-TnPTXbXoH64_zrub7OURqAEws8tSY3gS5Z67rEIVYqejKfNndVTX6B7HfdKNApq2s1Z4g0RFulEWB0FdnB7lnsbwzrUzUi5DtZnsXc0CSoGrqINVxV0cM0WrEZbcyXp4rV9UM58iTXmbElLiQUPlc_ZYnDNV7N3t0OOmfpGR6NFO4Ritc9ZT1CPD5SGB2_SZy3Y0tuAC2ZNeCwZdbpytAuNJJVrxWkO9YSgVN7YzfAqjo_j8Ac9Xgak";

    let stripped = url
        .strip_prefix("https://mermaid.live/edit#pako:")
        .context("Removing URL prefix")?;
    let decoded = URL_SAFE
        .decode(stripped)
        .context("While decoding base64 lump")?;

    let mut decompressor = Decompress::new(true);
    let mut output = Vec::with_capacity(MAX_DECOMPRESSED_SIZE);
    decompressor.decompress_vec(&decoded, &mut output, flate2::FlushDecompress::Finish)?;

    let output = String::from_utf8_lossy(&output);
    println!("{output}");

    Ok(())
}
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