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@excalidraw/utils is a browser bundle -- it references devicePixelRatio, location, matchMedia etc. as bare globals the way inline <script> code would, not as window.foo. Only copying window/document/navigator onto Node's global left everything else undefined, so the very first bare reference threw a ReferenceError as soon as the module loaded. Copy jsdom's entire window onto global instead, enable pretendToBeVisual so jsdom actually populates devicePixelRatio/requestAnimationFrame, and stub matchMedia since jsdom doesn't implement it at all.
45 lines
2.3 KiB
Markdown
45 lines
2.3 KiB
Markdown
# whiteboard-render
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Local sidecar for whiteboard frame mode -- see `server.js`'s own header
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comment for the full "why Node, why not a headless browser" reasoning.
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Not an independently deployed service: it runs as a second process
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inside the main server's container (`../Dockerfile` installs Node,
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`../start.sh` launches this in the background before `exec`-ing
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uvicorn), reachable only at `127.0.0.1:3001` from the Python process in
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that same container.
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**Not runtime-tested against a real `npm install` during development**
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-- this environment had no Node.js/npm available, only the npm registry
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API (used to verify the dependency versions/licenses in `package.json`
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actually exist and resolve). The code is written carefully against each
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library's documented API (`@excalidraw/utils`'s `exportToSvg`,
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`@resvg/resvg-js`'s `Resvg` class), but `docker compose build`+actually
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running it is the first time this has executed end to end -- and the
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first real run did in fact crash: `@excalidraw/utils`'s bundle touches
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bare browser globals (`devicePixelRatio`, `location`, `matchMedia`, ...)
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the same way inline `<script>` code in a real page would, not as
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`window.foo` -- jsdom only puts those *on* `dom.window`, so only
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copying `window`/`document`/`navigator` onto Node's `global` (the
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original version of this file) left everything else undefined. Fixed
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by copying jsdom's entire `window` onto `global` plus a `matchMedia`
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stub (jsdom doesn't implement it at all). If another crash like this
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shows up, it's almost certainly the same shape -- another bare global
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the bundle expects that this file hasn't stubbed yet. One other gap
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worth knowing about going in: jsdom's `<canvas>` has no real 2D
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rendering context (no `node-canvas` installed), so if Excalidraw's text
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measurement path depends on `canvas.getContext('2d').measureText(...)`
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rather than pure SVG/font-metrics math, that could be a next thing to
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watch for -- not something confirmed broken, just not yet exercised.
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## Local development (if you have Node 20.19+/22.13+ installed)
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```sh
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cd render-service
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npm install
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npm start # listens on 127.0.0.1:3001
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curl -X POST http://127.0.0.1:3001/render \
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-H "Content-Type: application/json" \
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-d '{"elements": [], "width": 800}' \
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-o /tmp/test.png # an empty scene -- just checks the service comes up and returns a valid PNG
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```
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