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  "identifier" : "/documentation/SwiftUI/NSHostingController/sizingOptions",
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  "title" : "sizingOptions"
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# sizingOptions

The options for how the hosting controller’s view creates and updates
constraints based on the size of its SwiftUI content.

```
@MainActor @preconcurrency var sizingOptions: NSHostingSizingOptions { get set }
```

## Discussion

NSHostingController can create minimum, maximum, and ideal (content
size) constraints that are derived from its SwiftUI view content. These
constraints are only created when Auto Layout constraints are otherwise
being used in the containing window.

If the NSHostingController is set as the `contentViewController` of an
`NSWindow`, it will also update the window’s `contentMinSize` and
`contentMaxSize` based on the minimum and maximum size of its SwiftUI
content.

`sizingOptions` defaults to `.standardBounds` (which includes
`minSize`, `intrinsicContentSize`, and `maxSize`), but can be set to an
explicit value to control this behavior. For instance, setting a value
of `.minSize` will only create the constraints necessary to maintain the
minimum size of the SwiftUI content, or setting a value of `[]` will
create no constraints at all.

If a use case can make assumptions about the size of the
`NSHostingController` relative to its displayed content, such as the
always being displayed in a fixed frame, setting this to a value with
fewer options can improve performance as it reduces the amount of layout
measurements that need to be performed. If an `NSHostingController` has
a `frame` that is smaller or larger than that required to display its
SwiftUI content, the content will be centered within that frame.

---

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