# `Yog.Layout.Grid`
[🔗](https://github.com/code-shoily/yog_ex/blob/v1.0.0/lib/yog/layout/grid.ex#L1)

Grid layout algorithm for positioning graph nodes in Elixir.

Positions nodes deterministically on a 2D grid based on user-supplied rows or columns.
This layout is ideal for structured diagrams (e.g. architecture layouts, UMLs, C4 models)
where predictability, alignment, and pixel-exact placement are required rather than
organic force-directed aesthetics.

## Mathematical Model

Given a 2D grid origin $(O_x, O_y)$ and cell dimensions $(W_{	ext{cell}}, H_{	ext{cell}})$:

Each node positioned at grid coordinates $(	ext{row}, 	ext{col})$ is mapped to:
$$x = O_x + 	ext{col} cdot W_{	ext{cell}}$$
$$y = O_y + 	ext{row} cdot H_{	ext{cell}}$$

Empty cells can be specified using a placeholder (`nil` or `:_`), which leaves the slot empty
and aligns subsequent elements correctly.

## Complexities

* **Time Complexity:** $O(V)$ where $V$ is the number of nodes.
* **Space Complexity:** $O(V)$ auxiliary space.

# `layout`

```elixir
@spec layout(
  Yog.Graph.t() | Yog.DAG.t(),
  keyword()
) :: %{required(Yog.Graph.node_id()) => {float(), float()}}
```

Positions nodes on a grid using rows or columns.

## Options

  * `:rows` - List of lists of node IDs, representing rows of the grid.
  * `:columns` - List of lists of node IDs, representing columns of the grid.
  * `:cell` - A `{cell_width, cell_height}` tuple representing dimensions of each grid cell (default: `{1.0, 1.0}`).
  * `:cell_width` - Bypasses width from `:cell` if specified.
  * `:cell_height` - Bypasses height from `:cell` if specified.
  * `:origin` - A `{x_origin, y_origin}` tuple representing the top-left offset of the grid (default: `{0.0, 0.0}`).

## Examples

    iex> graph = Yog.undirected() |> Yog.add_nodes_from([:client, :api, :db])
    iex> pos = Yog.Layout.Grid.layout(graph, rows: [[:client], [:api], [:db]], cell: {100, 50})
    iex> pos[:client]
    {0.0, 0.0}
    iex> pos[:api]
    {0.0, 50.0}

---

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