Crash when using justification

[josipbernat]

When I want to wrap RadioCollection in HFlow and use justification I am getting following crash:

SwiftUICore/Layout.swift:1534: Fatal error: view origin is invalid: (nan, 0.0), UnitPoint(x: 0.0, y: 0.0), (inf, 20.5)

Am I doing something wrong or is this a bug in the library?

Btw. awesome work, keep going on!

[tevelee]

Thanks for the crash report! Do you have sample code to reproduce the issue?

I tried the following but didn't crash:

import Flow
import SwiftUI
import SwiftUIRadioButtons

@main
struct ExampleApp: App {
    var body: some Scene {
        WindowGroup {
            Bug()
        }
    }
}

struct Bug: View {
    @State private var selected: String? = nil

    var body: some View {
        HFlow(justification: .stretchItemsAndSpaces) {
            HRadioCollection(
                selectedData: $selected,
                data: ["a", "b", "c"]
            ) { value in
                Text(value)
            }
        }
    }
}

extension String: @retroactive Identifiable {
    public var id: String { self }
}

[josipbernat]

I really tried to reproduce this crash using sample code and extending it but I can't. It happens after doing drag & drop and even though I added this functionality to the sample app it still works properly. I checked and both apps are using the latest v2.5.0 release. Unfortunately the crash is still happening in the app.

But maybe this can help you:

The crash cause happens here:

    @usableFromInline
    func placeSubviews(
        in bounds: CGRect,
        proposal: ProposedViewSize,
        subviews: some Subviews,
        cache: inout FlowLayoutCache
    ) {
        guard !subviews.isEmpty else { return }

        var target = bounds.origin.size(on: axis)
        var reversedBreadth = self.reversedBreadth

        let lines = calculateLayout(in: proposal, of: subviews, cache: cache)    ---> This function returns `Size` that has `breadth: nan`, check the console output below.

        for line in lines {
            adjust(&target, for: line, on: .vertical, reversed: reversedDepth) { target in
                target.breadth = reversedBreadth ? bounds.maximumValue(on: axis) : bounds.minimumValue(on: axis)

                for item in line.item {
                    adjust(&target, for: item, on: .horizontal, reversed: reversedBreadth) { target in
                        alignAndPlace(item, in: line, at: target)
                    }
                }

                if alternatingReversedBreadth {
                    reversedBreadth.toggle()
                }
            }
        }
    }

Maybe this output can help you identify where the problem occurs?

(lldb) po line
▿ ItemWithSpacing<Array<ItemWithSpacing<(subview: Subview, cache: SubviewCache)>>>
  ▿ item : 3 elements
    ▿ 0 : ItemWithSpacing<(subview: Subview, cache: SubviewCache)>
      ▿ item : 2 elements
        ▿ subview : LayoutSubview
          ▿ proxy : LayoutProxy
            ▿ context : AnyRuleContext
              ▿ attribute : #442544
                - rawValue : 442544
            ▿ attributes : LayoutProxyAttributes
              ▿ _layoutComputer : #448392
                ▿ base : #448392
                  ▿ identifier : #448392
                    - rawValue : 448392
              ▿ _traitsList : #446824
                ▿ base : #446824
                  ▿ identifier : #446824
                    - rawValue : 446824
          - index : 0
          - containerLayoutDirection : SwiftUI.LayoutDirection.leftToRight
        ▿ cache : SubviewCache
          - priority : 0.0
          ▿ spacing : Spacing [
  (EdgeBelowText, top) : 0.0
  (EdgeAboveText, bottom) : 0.0
  (EdgeLeftText, right) : 0.0
]
            ▿ spacing : Spacing [
  (EdgeBelowText, top) : 0.0
  (EdgeAboveText, bottom) : 0.0
  (EdgeLeftText, right) : 0.0
]
              ▿ minima : 3 elements
                ▿ 0 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d48062e0).EdgeAboveText
                    - edge : SwiftUI.AbsoluteEdge.bottom
                  ▿ value : Value
                    - distance : 0.0
                ▿ 1 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d4806328).EdgeLeftText
                    - edge : SwiftUI.AbsoluteEdge.right
                  ▿ value : Value
                    - distance : 0.0
                ▿ 2 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d48062bc).EdgeBelowText
                    - edge : SwiftUI.AbsoluteEdge.top
                  ▿ value : Value
                    - distance : 0.0
            ▿ layoutDirection : Optional<LayoutDirection>
              - some : SwiftUI.LayoutDirection.leftToRight
          ▿ min : Size
            - breadth : 28.0
            - depth : 35.0
          ▿ ideal : Size
            - breadth : 104.5
            - depth : 36.5
          ▿ max : Size
            - breadth : inf
            - depth : 36.5
      ▿ size : Size
        - breadth : 104.5
        - depth : 36.5
      - leadingSpace : nan
    ▿ 1 : ItemWithSpacing<(subview: Subview, cache: SubviewCache)>
      ▿ item : 2 elements
        ▿ subview : LayoutSubview
          ▿ proxy : LayoutProxy
            ▿ context : AnyRuleContext
              ▿ attribute : #442544
                - rawValue : 442544
            ▿ attributes : LayoutProxyAttributes
              ▿ _layoutComputer : #452488
                ▿ base : #452488
                  ▿ identifier : #452488
                    - rawValue : 452488
              ▿ _traitsList : #450920
                ▿ base : #450920
                  ▿ identifier : #450920
                    - rawValue : 450920
          - index : 1
          - containerLayoutDirection : SwiftUI.LayoutDirection.leftToRight
        ▿ cache : SubviewCache
          - priority : 0.0
          ▿ spacing : Spacing [
  (EdgeBelowText, top) : 0.0
  (EdgeAboveText, bottom) : 0.0
  (EdgeLeftText, right) : 0.0
]
            ▿ spacing : Spacing [
  (EdgeBelowText, top) : 0.0
  (EdgeAboveText, bottom) : 0.0
  (EdgeLeftText, right) : 0.0
]
              ▿ minima : 3 elements
                ▿ 0 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d48062e0).EdgeAboveText
                    - edge : SwiftUI.AbsoluteEdge.bottom
                  ▿ value : Value
                    - distance : 0.0
                ▿ 1 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d4806328).EdgeLeftText
                    - edge : SwiftUI.AbsoluteEdge.right
                  ▿ value : Value
                    - distance : 0.0
                ▿ 2 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d48062bc).EdgeBelowText
                    - edge : SwiftUI.AbsoluteEdge.top
                  ▿ value : Value
                    - distance : 0.0
            ▿ layoutDirection : Optional<LayoutDirection>
              - some : SwiftUI.LayoutDirection.leftToRight
          ▿ min : Size
            - breadth : 28.0
            - depth : 35.0
          ▿ ideal : Size
            - breadth : 112.0
            - depth : 36.5
          ▿ max : Size
            - breadth : inf
            - depth : 36.5
      ▿ size : Size
        - breadth : 112.0
        - depth : 36.5
      - leadingSpace : inf
    ▿ 2 : ItemWithSpacing<(subview: Subview, cache: SubviewCache)>
      ▿ item : 2 elements
        ▿ subview : LayoutSubview
          ▿ proxy : LayoutProxy
            ▿ context : AnyRuleContext
              ▿ attribute : #442544
                - rawValue : 442544
            ▿ attributes : LayoutProxyAttributes
              ▿ _layoutComputer : #456584
                ▿ base : #456584
                  ▿ identifier : #456584
                    - rawValue : 456584
              ▿ _traitsList : #455016
                ▿ base : #455016
                  ▿ identifier : #455016
                    - rawValue : 455016
          - index : 2
          - containerLayoutDirection : SwiftUI.LayoutDirection.leftToRight
        ▿ cache : SubviewCache
          - priority : 0.0
          ▿ spacing : Spacing [
  (EdgeBelowText, top) : 0.0
  (EdgeAboveText, bottom) : 0.0
  (EdgeLeftText, right) : 0.0
]
            ▿ spacing : Spacing [
  (EdgeBelowText, top) : 0.0
  (EdgeAboveText, bottom) : 0.0
  (EdgeLeftText, right) : 0.0
]
              ▿ minima : 3 elements
                ▿ 0 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d4806328).EdgeLeftText
                    - edge : SwiftUI.AbsoluteEdge.right
                  ▿ value : Value
                    - distance : 0.0
                ▿ 1 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d48062e0).EdgeAboveText
                    - edge : SwiftUI.AbsoluteEdge.bottom
                  ▿ value : Value
                    - distance : 0.0
                ▿ 2 : 2 elements
                  ▿ key : Key
                    ▿ category : Optional<Category>
                      ▿ some : Category
                        - type : SwiftUI.Spacing.Category.(unknown context at $1d48062bc).EdgeBelowText
                    - edge : SwiftUI.AbsoluteEdge.top
                  ▿ value : Value
                    - distance : 0.0
            ▿ layoutDirection : Optional<LayoutDirection>
              - some : SwiftUI.LayoutDirection.leftToRight
          ▿ min : Size
            - breadth : 28.0
            - depth : 35.0
          ▿ ideal : Size
            - breadth : 109.0
            - depth : 36.5
          ▿ max : Size
            - breadth : inf
            - depth : 36.5
      ▿ size : Size
        - breadth : 109.0
        - depth : 36.5
      - leadingSpace : inf
  ▿ size : Size
    - breadth : nan     ----> Here it is!
    - depth : 36.5
  - leadingSpace : 0.0

Then when the execution reaches:

private func adjust<T>(
        _ target: inout Size,
        for item: ItemWithSpacing<T>,
        on axis: Axis,
        reversed: Bool,
        body: (inout Size) -> Void
    ) {
        let leadingSpace = item.leadingSpace
        let size = item.size[axis]
        target[axis] += reversed ? -leadingSpace-size : leadingSpace ----> It assignees `nan` here
        body(&target)
        target[axis] += reversed ? 0 : size
    }

And the crash finally happens here:

    private func alignAndPlace(
        _ item: Line.Element,
        in line: Lines.Element,
        at target: Size
    ) {
        var position = target
        let lineDepth = line.size.depth
        let size = Size(breadth: item.size.breadth, depth: lineDepth)
        let proposedSize = ProposedViewSize(size: size, axis: axis)
        let itemDepth = item.size.depth
        if itemDepth > 0 {
            let dimensions = item.item.subview.dimensions(proposedSize)
            let alignedPosition = alignmentOnDepth(dimensions)
            position.depth += (alignedPosition / itemDepth) * (lineDepth - itemDepth)
        }
        let point = CGPoint(size: position, axis: axis)
        item.item.subview.place(at: point, anchor: .topLeading, proposal: proposedSize) ---> here is the actual crash.
    }

I thin that the root cause is in the fact that

    public func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: LayoutSubviews, cache: inout FlowLayoutCache) {
        layout.placeSubviews(in: bounds, proposal: proposal, subviews: subviews, cache: &cache)
    }

bounds had width: 0

Printing description of bounds:
▿ (0.0, 0.0, 0.0, 36.5)
  ▿ origin : (0.0, 0.0)
    - x : 0.0
    - y : 0.0
  ▿ size : (0.0, 36.5)
    - width : 0.0
    - height : 36.5

I hope this helps!

[tevelee]

Thank you for the debug info! I'll take a look.