canvas

Overview ¶

Package canvas draws a chart into a browser canvas.

It is the browser half of v0.5, and it is in the core module because it needs nothing to be there: a `<canvas>` element's 2D context is reached through `syscall/js`, which is the standard library, so figure in a browser links exactly what figure on a server links.

//go:build js && wasm

el := js.Global().Get("document").Call("getElementById", "chart")
live, err := p.Live(canvas.Element(el))
defer live.Close()
live.Draw()
canvas.Bind(el, live)   // wire pointer, wheel and drag

Only on js/wasm ¶

Every symbol in this package is behind `js && wasm`, so on any other platform the package is empty. That is deliberate: a stub that compiled everywhere and failed at run time would let a chart reach production before finding out there is no canvas on a Linux server.

Not WebGPU ¶

CONCEPT.md's roadmap put browser rendering behind the gg backend, on WebGPU with a canvas fallback. gg has no js support at the version this backend was written against — no `syscall/js` anywhere in it — so there is no WebGPU path to take and no canvas fallback to fall back to. figure therefore draws on the 2D context itself, exactly as it emits its own PDF for the same kind of reason. See docs/adr/0017-browser-backend.md.