UnitPoint
A normalized 2D point in a view’s coordinate space.
Declaration
@frozen struct UnitPointOverview
Use a unit point to represent a location in a view without having to know the view’s rendered size. The point stores a value in each dimension that indicates the fraction of the view’s size in that dimension — measured from the view’s origin — where the point appears. For example, you can create a unit point that represents the center of any view by using the value 0.5 for each dimension:
let unitPoint = UnitPoint(x: 0.5, y: 0.5)To project the unit point into the rendered view’s coordinate space, multiply each component of the unit point with the corresponding component of the view’s size:
let projectedPoint = CGPoint(
x: unitPoint.x * size.width,
y: unitPoint.y * size.height
)You can perform this calculation yourself if you happen to know a view’s size, or if you want to use the unit point for some custom purpose, but SwiftUI typically does this for you to carry out operations that you request, like when you:
Transform a shape using a shape modifier. For example, to rotate a shape with rotation(_:anchor:), you indicate an anchor point that you want to rotate the shape around.
Override the alignment of the view in a Grid cell using the gridCellAnchor(_:) view modifier. The grid aligns the projection of a unit point onto the view with the projection of the same unit point onto the cell.
Create a gradient that has a center, or start and stop points, relative to the shape that you are styling. See the gradient methods in ShapeStyle.
You can create custom unit points with explicit values, like the example above, or you can use one of the built-in unit points that SwiftUI provides, like zero, center, or topTrailing. The built-in values correspond to the alignment positions of the similarly named, built-in Alignment types.
Layout direction
When a person configures their device to use a left-to-right language like English, the system places the view’s origin in its top-left corner, with positive x toward the right and positive y toward the bottom of the view. In a right-to-left environment, the origin moves to the upper-right corner, and the positive x direction changes to be toward the left. You don’t typically need to do anything to handle this change, because SwiftUI applies the change to all aspects of the system. For example, see the discussion about layout direction in HorizontalAlignment.
It’s important to test your app for the different locales that you distribute your app in. For more information about the localization process, see Localization.