How to draw a border inside a view

Paul Hudson    @twostraws    December 1st 2022

Updated for Xcode 14.2

SwiftUI gives us both stroke() and strokeBorder() modifiers for drawing borders around shapes, and they have subtly different behavior:

• The strokeBorder() modifier insets the view by half your border width then applies the stroke, meaning that the entire border is drawn inside the view.
• The stroke() modifier draws a border centered on the view’s edge, meaning that half the border is inside the view and half outside.

Important: Both of these modifiers only apply to shapes – you can use stroke() and strokeBorder() with Circle, Rectangle, Capsule, and so on, but not with Text, Image or other non-shape views. If you want to draw a border around non-shape views, you should use the border() modifier instead – see “How to draw a border around a view”.

If you want to see strokeBorder() in action, try this:

Circle()
    .strokeBorder(.blue, lineWidth: 50)
    .frame(width: 200, height: 200)
    .padding()

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Because that uses strokeBorder(), the 50-point blue stroke will be drawn entirely inside the circle.

If you aren’t quite sure of the difference from stroke(), try changing your code to this:

Circle()
    .stroke(.blue, lineWidth: 50)
    .frame(width: 200, height: 200)
    .padding()

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Now you’ll see the circle looks bigger because the stroke is drawn half inside and half outside the circle.

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