# llimphi-widget-fitted-box

Scales a subtree to the available slot.

The analogue of Flutter's `FittedBox`: the caller passes the content's **natural
size** and a **fit policy**, and the widget applies an affine `transform` to the
subtree so it fits the real slot (measured through the compositor's
`LayoutBuilder` seam). The subtree ends up **centred** and, except under
`BoxFit::Fill`, **preserves its aspect ratio**.

Why it does not come for free: `taffy` sizes containers, but the content (text,
image, custom painter) does not scale with its container — it is only positioned
inside it. `FittedBox` applies a VISUAL scale over the whole subtree, so a
`paint_with` canvas or a large piece of text fits into a tiny cell without the
caller re-measuring anything.

The widget's parent has `clip(true)` so no pixel escapes the slot (it only
matters when the content's aspect does NOT match the slot under `BoxFit::None`,
and never with `Contain`/`Fill`).

## API

```ignore
use llimphi_widget_fitted_box::{fitted_box, BoxFit};
// An 800×600 image that must fit any slot, preserving aspect
// (shown whole, possibly with bands).
fitted_box((800.0, 600.0), BoxFit::Contain, || my_image_view())
```

## Pure functions

`compute_fit` returns `(sx, sy, dx, dy)` for a given `(slot, inner, fit)` and is
testable without a runtime. Useful to validate the algorithm, and for cases where
the caller already has its own transform to compose with.

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Part of **llimphi** — see [llimphi](../../README.md).