For https://alexdremov.me/exploring-swiftui-layout-protocol-creating-custom-layout/

example.swift

ColumnsLayout(columnsNumber: 2) {
    VStack {
        Text("That's one view")
        Image(systemName: "tortoise.fill")
    }
    .padding()
    .border(.red)
    Text("That's the second view ")
        .padding()
        .border(.red)
    Text("That's the third view with long lines that are warped automatically")
        .fixedSize(horizontal: false, vertical: true)
        .padding()
        .border(.red)
}
.border(.blue)
.padding()

helpers.swift

/**
 Get array of heights for every row.
 Just get max height on every row
 */
private func getRowHeights(subviews: Subviews, subviewProposal: ProposedViewSize) -> [CGFloat] {
    var subviewProposalNoHLimit = subviewProposal
    subviewProposalNoHLimit.height = .infinity
    
    var rowHeights = [CGFloat]()
    var index = 0
    while index < subviews.count {
        var rowMax: CGFloat = 0
        for _ in 0..<columnsNumber where index < subviews.count {
            let size = subviews[index].sizeThatFits(subviewProposalNoHLimit)
            rowMax = max(rowMax, size.height)
            index += 1
        }
        rowHeights.append(rowMax)
    }
    return rowHeights
}

/**
 Calculates proposal for subview — one cell in table
 */
func getSubviewProposal(subviewsCount: Int, from globalProposal: ProposedViewSize) -> ProposedViewSize {
    let rowHeight = max(ceil(Double(subviewsCount / columnsNumber)), 1)
    return ProposedViewSize(
        width: (globalProposal.width ?? 0)
                        / CGFloat(columnsNumber),
        height: (globalProposal.height ?? 0) / rowHeight
    )
}

placeSubviews.swift

public func placeSubviews(
    in bounds: CGRect,
    proposal: ProposedViewSize,
    subviews: Subviews,
    cache: inout ()
) {
    var subviewProposal = getSubviewProposal(
        subviewsCount: subviews.count,
        from: proposal
    )
    let colRealWidth = subviewProposal.width ?? 0
    let rowHeights = getRowHeights(subviews: subviews, subviewProposal: subviewProposal)
    
    var curPos: CGFloat = bounds.minX
    var curHeight: CGFloat = bounds.minY
    
    var rowIndex = 0
    for (index, subview) in subviews.enumerated() {
        subviewProposal.height = rowHeights[rowIndex]
        let size = subview.dimensions(in: subviewProposal)
        
        subview.place(
            at: CGPoint(x: curPos, y: curHeight),
            anchor: .topLeading,
            proposal: subviewProposal
        )
        
        if index % columnsNumber == columnsNumber - 1 {
            curPos = bounds.minX
            curHeight += rowHeights[rowIndex]
            rowIndex += 1
        } else {
        	curPos += colRealWidth
        }
    }
}

sizeThatFits.swift

public func sizeThatFits(
        proposal: ProposedViewSize,
        subviews: Subviews,
        cache: inout ()
    ) -> CGSize {
    
        let subviewProposal = getSubviewProposal(
            subviewsCount: subviews.count,
            from: proposal
        )
        
        let rowHeights = getRowHeights(
        	subviews: subviews,
            globalProposal: proposal
        )
        
        let resultWidth = proposal.width ?? 
        		((subviewProposal.width ?? 0) * CGFloat(columnsNumber))
        return CGSize(
            width: resultWidth,
            height: rowHeights.reduce(0, +)
        )
    }