Add opt-in ELK layout support for mermaid diagrams#22
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Adds `mermaid_elk` config option (default false). When enabled, loads
@mermaid-js/layout-elk@0.2.1 from CDN and registers it before mermaid
initializes, enabling %%{init: {"layout": "elk"}}%% in diagrams.
Owner
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Thanks @fuzzybear3, this is the shape of opt-in I was hoping for. Default off, mirrors the bottom_padding placeholder pattern, fails gracefully inside the boot try/catch. Merging. One thing for later (not blocking): if ELK fails to load we could show a one-time inline note in the preview header so the user knows it fell back to dagre. Open a separate issue if you want to track that. |
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Summary
Adds a
mermaid_elkconfig option (defaultfalse). When enabled, the browser preview loads@mermaid-js/layout-elk@0.2.1from jsDelivr and registers it before mermaid initializes, allowing diagrams to use:Why
ELK produces noticeably cleaner layouts for medium/large flowcharts and class diagrams than mermaid's default dagre layout. It's opt-in because it adds ~800 KB on top of what the preview already fetches from CDN, and most diagrams don't need it.
Changes
lua/markdown_preview/init.lua: newmermaid_elkconfig (defaultfalse); substitutes a__MERMAID_ELK__placeholder when writingindex.html, mirroring the existing__BOTTOM_PADDING__pattern.assets/index.html: adds adata-mermaid-elkattribute on<html>; inboot(), conditionally dynamic-imports the ELK layout module and callsmermaid.registerLayoutLoaders(...)before the firstsync().Test plan
mermaid_elk = false(default), preview behaves exactly as before — no extra network request on boot.mermaid_elk = true, a diagram containing%%{init: {"layout": "elk"}}%%renders with the ELK layout.try/catchlogs the error and shows an inline error message rather than a blank preview.