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52 lines
2.2 KiB
Markdown
52 lines
2.2 KiB
Markdown
# Go + WASM Render Plugin Example
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This example shows how to build a frontend render plugin whose heavy lifting
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runs inside a WebAssembly module compiled from Go. The plugin loads the WASM
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binary in the browser, asks Go to post-process the fetched file content, and
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then renders the result inside the file viewer.
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## Files
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- `manifest.json` — plugin metadata consumed by the Gitea backend
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- `render.js` — the ES module entry point that initializes the Go runtime and
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renders files handled by the plugin
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- `wasm/` — contains the Go source that compiles to `plugin.wasm`
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- `wasm_exec.js` — the Go runtime shim required by all Go-generated WASM
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binaries (copied verbatim from the Go distribution)
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- `build.sh` — helper script that builds `plugin.wasm` and produces a zip
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archive ready for upload
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## Build & Install
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1. Build the WASM binary and zip archive:
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```bash
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cd contrib/render-plugins/example-wasm
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./build.sh
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```
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The script requires Go 1.21+ on your PATH. It stores the compiled WASM and
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an installable `example-go-wasm.zip` under `dist/`.
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2. In the Gitea web UI, visit `Site Administration → Render Plugins`, upload
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`dist/example-go-wasm.zip`, and enable the plugin.
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3. Open any file whose name ends with `.wasmnote`; the viewer will show the
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processed output from the Go code running inside WebAssembly.
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## How It Works
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- `wasm/main.go` exposes a single `wasmProcessFile` function to JavaScript. It
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uppercases each line, prefixes it with the line number, and runs entirely
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inside WebAssembly compiled from Go.
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- `render.js` injects the Go runtime (`wasm_exec.js`), instantiates the compiled
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module, and caches the exported `wasmProcessFile` function.
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- During initialization the frontend passes the sniffed MIME type and the first
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1 KiB of file data to the plugin (`options.mimeType`/`options.headChunk`),
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allowing renderers to make decisions without issuing extra network requests.
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- During rendering the plugin downloads the target file, passes the contents to
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Go, and displays the transformed text with minimal styling.
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Feel free to modify the Go source or the JS wrapper to experiment with richer
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interfaces between JavaScript and WebAssembly.
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