# `DocShell.Presentation.Backlink`
[🔗](https://github.com/futhr/doc_shell/blob/v2.0.0/lib/doc_shell/presentation/backlink.ex#L1)

A document that links to another, for rendering "referenced by" panels.

Backlinks are the reverse of the links inside a document: given a page, which
other pages point at it. They are what lets a reader landing on a low-level
module page find the guide that explains when to use it.

DocShell does not compute backlinks. Resolving a link in a document to the
entry it refers to needs a routing scheme and a naming convention, and both
belong to the host. What DocShell provides is the shape those relationships
take on the wire, so that a graph-backed producer and a renderer agree
without a private contract between them.

The `backlinks` key is optional in `t:DocShell.Presentation.Source.presentation/0`
precisely because most producers have nothing to put there. When present it
maps an entry id to the entries referencing it, and
`DocShell.Presentation.GraphProjector.validate/1` checks the shape.

Only enough is carried to render a link — id, title, path. A renderer wanting
more looks the referencing entry up in the navigation index.

# `t`

```elixir
@type t() :: %DocShell.Presentation.Backlink{
  id: String.t(),
  path: String.t(),
  title: String.t()
}
```

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