1/// A scrolling row of windows. Opening one never shrinks the others.
2public struct Strip {
3    public private(set) var columns: [StripColumn] = []
4    public private(set) var focused = 0
5
6    public mutating func insert(_ id: WindowID) {
7        guard !contains(id) else { return }
8        let column = StripColumn(windows: [id], width: defaultWidth)
9        let index = columns.isEmpty ? 0 : focused + 1
10        columns.insert(column, at: index)
11        focused = index
12    }
13
14    public mutating func cycleWidth() {
15        let width = columns[focused].width
16        let next = presets.first { $0 > width } ?? presets[0]
17        columns[focused].width = next
18    }
19
20    /// The scroll offset that keeps the focused column fully on screen.
21    public func offset(viewport: Double) -> Double {
22        let left = columns.prefix(focused).reduce(0) { $0 + $1.width }
23        return min(left, max(0, total - viewport))
24    }
25}