# ViewDimensions A view’s size and alignment guides in its own coordinate space. ``` struct ViewDimensions ``` ## Overview This structure contains the size and alignment guides of a view. You receive an instance of this structure to use in a variety of layout calculations, like when you: - Define a default value for a custom alignment guide; see [`defaultValue(in:)`](/documentation/SwiftUI/AlignmentID/defaultValue(in:)). - Modify an alignment guide on a view; see [`alignmentGuide(_:computeValue:)`](/documentation/SwiftUI/View/alignmentGuide(_:computeValue:)). - Ask for the dimensions of a subview of a custom view layout; see [`dimensions(in:)`](/documentation/SwiftUI/LayoutSubview/dimensions(in:)). ### Custom alignment guides You receive an instance of this structure as the `context` parameter to the [`defaultValue(in:)`](/documentation/SwiftUI/AlignmentID/defaultValue(in:)) method that you implement to produce the default offset for an alignment guide, or as the first argument to the closure you provide to the [`alignmentGuide(_:computeValue:)`](/documentation/SwiftUI/View/alignmentGuide(_:computeValue:)) view modifier to override the default calculation for an alignment guide. In both cases you can use the instance, if helpful, to calculate the offset for the guide. For example, you could compute a default offset for a custom [`VerticalAlignment`](/documentation/SwiftUI/VerticalAlignment) as a fraction of the view’s [`height`](/documentation/SwiftUI/ViewDimensions/height): ``` private struct FirstThirdAlignment: AlignmentID { static func defaultValue(in context: ViewDimensions) -> CGFloat { context.height / 3 } } extension VerticalAlignment { static let firstThird = VerticalAlignment(FirstThirdAlignment.self) } ``` As another example, you could use the view dimensions instance to look up the offset of an existing guide and modify it: ``` struct ViewDimensionsOffset: View { var body: some View { VStack(alignment: .leading) { Text("Default") Text("Indented") .alignmentGuide(.leading) { context in context[.leading] - 10 } } } } ``` The example above indents the second text view because the subtraction moves the second text view’s leading guide in the negative x direction, which is to the left in the view’s coordinate space. As a result, SwiftUI moves the second text view to the right, relative to the first text view, to keep their leading guides aligned:  ### Layout direction The discussion above describes a left-to-right language environment, but you don’t change your guide calculation to operate in a right-to-left environment. SwiftUI moves the view’s origin from the left to the right side of the view and inverts the positive x direction. As a result, the existing calculation produces the same effect, but in the opposite direction. You can see this if you use the [`environment(_:_:)`](/documentation/SwiftUI/View/environment(_:_:)) modifier to set the [`layoutDirection`](/documentation/SwiftUI/EnvironmentValues/layoutDirection) property for the view that you defined above: ``` ViewDimensionsOffset() .environment(\.layoutDirection, .rightToLeft) ``` With no change in your guide, this produces the desired effect — it indents the second text view’s right side, relative to the first text view’s right side. The leading edge is now on the right, and the direction of the offset is reversed:  ## Topics ### Getting dimensions [`height`](/documentation/SwiftUI/ViewDimensions/height) The view’s height. [`width`](/documentation/SwiftUI/ViewDimensions/width) The view’s width. ### Accessing guide values [`subscript ( _ :)`](/documentation/SwiftUI/ViewDimensions/subscript(_:)) Gets the value of the given horizontal guide. [`subscript ( explicit :)`](/documentation/SwiftUI/ViewDimensions/subscript(explicit:)) Gets the explicit value of the given horizontal alignment guide. ## Relationships ### Conforms To [`Equatable`](/documentation/Swift/Equatable) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)