# `ExRatatui.Layout`
[🔗](https://github.com/mcass19/ex_ratatui/blob/v0.7.1/lib/ex_ratatui/layout.ex#L1)

Layout system for splitting areas into sub-regions.

Uses ratatui's constraint-based layout engine to divide a `Rect` into
multiple sub-regions along a direction.

## Constraints

  * `{:percentage, n}` - percentage of the total space
  * `{:length, n}` - exact number of cells
  * `{:min, n}` - minimum number of cells
  * `{:max, n}` - maximum number of cells
  * `{:ratio, numerator, denominator}` - fractional ratio

## Example

    area = %Rect{x: 0, y: 0, width: 80, height: 24}

    [header, body, footer] = Layout.split(area, :vertical, [
      {:length, 3},
      {:min, 0},
      {:length, 1}
    ])

    [sidebar, main] = Layout.split(body, :horizontal, [
      {:percentage, 30},
      {:percentage, 70}
    ])

# `constraint`

```elixir
@type constraint() ::
  {:percentage, non_neg_integer()}
  | {:length, non_neg_integer()}
  | {:min, non_neg_integer()}
  | {:max, non_neg_integer()}
  | {:ratio, non_neg_integer(), non_neg_integer()}
```

# `direction`

```elixir
@type direction() :: :horizontal | :vertical
```

# `split`

```elixir
@spec split(ExRatatui.Layout.Rect.t(), direction(), [constraint()]) ::
  [ExRatatui.Layout.Rect.t()] | {:error, term()}
```

Splits a `Rect` into sub-regions based on direction and constraints.

Returns a list of `%Rect{}` structs or `{:error, reason}` on failure.

## Examples

    iex> alias ExRatatui.Layout
    iex> alias ExRatatui.Layout.Rect
    iex> area = %Rect{x: 0, y: 0, width: 80, height: 24}
    iex> [top, bottom] = Layout.split(area, :vertical, [{:percentage, 50}, {:percentage, 50}])
    iex> top
    %Rect{x: 0, y: 0, width: 80, height: 12}
    iex> bottom
    %Rect{x: 0, y: 12, width: 80, height: 12}

    iex> alias ExRatatui.Layout
    iex> alias ExRatatui.Layout.Rect
    iex> area = %Rect{x: 0, y: 0, width: 100, height: 1}
    iex> [left, right] = Layout.split(area, :horizontal, [{:length, 20}, {:min, 0}])
    iex> left
    %Rect{x: 0, y: 0, width: 20, height: 1}
    iex> right
    %Rect{x: 20, y: 0, width: 80, height: 1}

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