grain.social/grain-ios

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import SwiftUI

/// Lays children out left to right, wrapping to a new row when one won't fit
/// — the shape a row of chips wants. Every row is as tall as its tallest child.
struct FlowLayout: Layout {
    var spacing: CGFloat = 8

    func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache _: inout ()) -> CGSize {
        let width = proposal.width ?? .infinity
        return place(in: width, subviews: subviews).size
    }

    func placeSubviews(in bounds: CGRect, proposal _: ProposedViewSize, subviews: Subviews, cache _: inout ()) {
        let layout = place(in: bounds.width, subviews: subviews)
        for (index, origin) in layout.origins.enumerated() {
            subviews[index].place(
                at: CGPoint(x: bounds.minX + origin.x, y: bounds.minY + origin.y),
                proposal: .unspecified
            )
        }
    }

    private func place(in width: CGFloat, subviews: Subviews) -> (size: CGSize, origins: [CGPoint]) {
        var origins: [CGPoint] = []
        var x: CGFloat = 0
        var y: CGFloat = 0
        var rowHeight: CGFloat = 0
        var widest: CGFloat = 0

        for subview in subviews {
            let size = subview.sizeThatFits(.unspecified)
            if x > 0, x + size.width > width {
                x = 0
                y += rowHeight + spacing
                rowHeight = 0
            }
            origins.append(CGPoint(x: x, y: y))
            x += size.width + spacing
            rowHeight = max(rowHeight, size.height)
            widest = max(widest, x - spacing)
        }
        return (CGSize(width: widest, height: y + rowHeight), origins)
    }
}