Mermaid.js default character limit is too low

[neon-dev]

Description

Mermaid.js has a default maxTextSize of 50000:
https://github.com/mermaid-js/mermaid/blob/dd0304387e85fc57a9ebb666f89ef788c012c2c5/packages/mermaid/src/schemas/config.schema.yaml#L95-L98

Can we increase

gitea/modules/setting/markup.go

Line 64 in a323a82

MermaidMaxSourceCharacters = rootCfg.Section("markup").Key("MERMAID_MAX_SOURCE_CHARACTERS").MustInt(5000)

to the same value?

Gitea Version

1.22.2

Can you reproduce the bug on the Gitea demo site?

Yes

Log Gist

No response

Screenshots

No response

Git Version

No response

Operating System

No response

How are you running Gitea?

Database

None

[yp05327]

But this is configurable.

[neon-dev]

Is there a reason to keep the default value different from what the creators of mermaid.js intended?

[yp05327]

I don't know why, but I found this: #16513 (comment)
Maybe 5000 is older than this default value.

[neon-dev]

Looks like there was no limit a few years ago: mermaid-js/mermaid@4ad354a
Maybe the config value in Gitea should become optional then?

[neon-dev]

I also checked out GitLab's original implementation of the character limit that was mentioned in your linked comment. It is just supposed to defer rendering of larger graphs so it doesn't slow down the initial page load. There is no hard limit that denies rendering them altogether like Gitea currently handles this. And from my limited testing on GitHub, they don't even seem to have any limit or it is not triggered easily.

In summary, Gitea's current implementation and default value try to solve one issue by creating an entirely new one: Not being able to render a graph.
I suggest evaluating at what threshold performance issues start to ocurr (should only happen with multiple graphs on a page) and deciding a new strategy to handle such cases. GitLab also revised their strategy with a later commit by tracking how many elements have been rendered in total on a page.

[wxiaoguang]

Can we increase ... to the same value?

Sure: Set MERMAID_MAX_SOURCE_CHARACTERS to 50000 #34152