# `ExWapp.QR.Renderer`
[🔗](https://github.com/elchemista/ex_wapp/blob/v0.1.5/lib/ex_wapp/qr/renderer.ex#L1)

Contract for rendering a WhatsApp pairing payload with a host-owned QR library.

`ExWapp.pair/1` returns the raw payload; applications can render it using any
library or send it to a browser renderer. ExWapp has no QR package dependency.

To use the manual `ExWapp.Live` runner, supply `qr_renderer: MyApp.QRRenderer`
or set `config :ex_wapp, :qr_renderer, MyApp.QRRenderer`. Its `:qr_options`
option is passed unchanged to `render/2`. The renderer returns SVG, PNG, or
other file contents as binary/iodata; the runner writes them to `:qr_path`.
Choose a path extension matching the format returned by the renderer.

For example, if your application chooses the `qr_code` package:

    defmodule MyApp.QRRenderer do
      @behaviour ExWapp.QR.Renderer

      @impl true
      def render(payload, opts) do
        payload
        |> QRCode.create(Keyword.get(opts, :error_correction, :high))
        |> QRCode.render(Keyword.get(opts, :format, :svg))
      end
    end

Return `{:error, reason}` when rendering fails. The runner returns that error
and releases its QR subscription rather than waiting for an invisible code.

# `render`

```elixir
@callback render(payload :: String.t(), opts :: keyword()) ::
  {:ok, iodata()} | {:error, term()}
```

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*Consult [api-reference.md](api-reference.md) for complete listing*