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Add Mermaid diagram rendering for markdown pages #415

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Add Mermaid diagram rendering for markdown pages #415

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2eaf715
Add Mermaid.js diagram rendering support
mprokopov Apr 3, 2026
74f616c
Fix mermaid detection for Rouge plaintext fallback
mprokopov Apr 3, 2026
7717cb0
Move mermaid setup to application.js via importmap
mprokopov Apr 3, 2026
85ef58f
Add mermaid rendering screenshot for PR
mprokopov Apr 3, 2026
e956396
Address code review feedback
mprokopov Apr 3, 2026
0d4fd8b
Merge branch 'basecamp:main' into main
mprokopov Jun 1, 2026
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19 changes: 19 additions & 0 deletions app/javascript/application.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,4 +3,23 @@ import "@hotwired/turbo-rails"
import "actions"
import "controllers"
import "house"
import mermaid from "mermaid"

const MERMAID_KEYWORDS = /^(flowchart|graph|sequenceDiagram|classDiagram|stateDiagram|erDiagram|gantt|pie|gitGraph|mindmap|timeline|sankey|xychart|block)\b/

mermaid.initialize({ startOnLoad: false, theme: window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "default" })

document.addEventListener("turbo:load", () => {
const targets = [...document.querySelectorAll("code.language-mermaid, pre.highlight.plaintext > code")]
.filter(el => el.classList.contains("language-mermaid") || MERMAID_KEYWORDS.test(el.textContent.trim()))
if (!targets.length) return
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targets.forEach(el => {
const div = document.createElement("div")
div.className = "mermaid"
div.textContent = el.textContent
el.closest("pre").replaceWith(div)
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})
mermaid.run()
Comment on lines +18 to +26
})

1 change: 1 addition & 0 deletions config/importmap.rb
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Expand Up @@ -8,6 +8,7 @@
pin "house", to: "house.min.js"

pin_all_from "app/javascript/actions", under: "actions"
pin "mermaid", to: "https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs"
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pin_all_from "app/javascript/controllers", under: "controllers"
pin_all_from "app/javascript/helpers", under: "helpers"
pin_all_from "app/javascript/lib", under: "lib"
Binary file added mermaid-screenshot.png
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