Line breaks

tevelee · Dec 19, 2024 · c8e85a7 · c8e85a7
1 parent c563b27
commit c8e85a7
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Showing 4 changed files with 59 additions and 5 deletions.
diff --git a/Sources/Flow/Internal/Layout.swift b/Sources/Flow/Internal/Layout.swift
@@ -172,6 +172,7 @@ struct FlowLayout: Sendable {
         let breakpoints: [Int] = lineBreaker.wrapItemsToLines(
             sizes: sizes.map(\.breadth),
             spacings: spacings,
+            lineBreaks: cache.subviewsCache.enumerated().filter(\.element.shouldStartInNewLine).map(\.offset),
             in: proposedSize.replacingUnspecifiedDimensions(by: .infinity).value(on: axis)
         )
 
@@ -181,7 +182,7 @@ struct FlowLayout: Sendable {
             for index in start ..< end {
                 let subview = subviews[index]
                 let size = sizes[index]
-                let spacing = index == start ? 0 : spacings[index] // Reset spacing for the first item in each line
+                let spacing = index == start || cache.subviewsCache[index - 1].isLineBreak ? 0 : spacings[index] // Reset spacing for the first item in each line
                 line.append((subview, cache.subviewsCache[index]), size: size, spacing: spacing)
             }
             lines.append(line)

diff --git a/Sources/Flow/Internal/LineBreaking.swift b/Sources/Flow/Internal/LineBreaking.swift
@@ -3,7 +3,7 @@ import CoreFoundation
 @usableFromInline
 protocol LineBreaking {
     @inlinable
-    func wrapItemsToLines(sizes: [CGFloat], spacings: [CGFloat], in availableSpace: CGFloat) -> [Int]
+    func wrapItemsToLines(sizes: [CGFloat], spacings: [CGFloat], lineBreaks: [Int], in availableSpace: CGFloat) -> [Int]
 }
 
 @usableFromInline
@@ -12,13 +12,13 @@ struct FlowLineBreaker: LineBreaking {
     init() {}
 
     @inlinable
-    func wrapItemsToLines(sizes: [CGFloat], spacings: [CGFloat], in availableSpace: CGFloat) -> [Int] {
+    func wrapItemsToLines(sizes: [CGFloat], spacings: [CGFloat], lineBreaks: [Int], in availableSpace: CGFloat) -> [Int] {
         var breakpoints: [Int] = []
         var currentLineSize: CGFloat = 0
 
         for (index, size) in sizes.enumerated() {
             let requiredSpace = spacings[index] + size
-            if currentLineSize + requiredSpace > availableSpace {
+            if currentLineSize + requiredSpace > availableSpace || lineBreaks.contains(index) {
                 breakpoints.append(index)
                 currentLineSize = size
             } else {
@@ -40,8 +40,31 @@ struct KnuthPlassLineBreaker: LineBreaking {
     @inlinable
     init() {}
 
+    @inlinable
+    func wrapItemsToLines(sizes: [CGFloat], spacings: [CGFloat], lineBreaks: [Int], in availableSpace: CGFloat) -> [Int] {
+        if lineBreaks.isEmpty {
+            return wrapItemsToLines(sizes: sizes, spacings: spacings, in: availableSpace)
+        }
+        var result: [Int] = []
+        var start: Int = 0
+        for lineBreak in lineBreaks + [sizes.endIndex] {
+            let partial = wrapItemsToLines(
+                sizes: Array(sizes[start..<lineBreak]),
+                spacings: Array(spacings[start..<lineBreak]),
+                in: availableSpace
+            )
+            result.append(contentsOf: partial.map { $0 + start }.dropLast())
+            start = lineBreak
+        }
+        result.append(sizes.endIndex)
+        return result
+    }
+
     @inlinable
     func wrapItemsToLines(sizes: [CGFloat], spacings: [CGFloat], in availableSpace: CGFloat) -> [Int] {
+        if sizes.isEmpty {
+            return []
+        }
         let count = sizes.count
         var costs: [CGFloat] = Array(repeating: .infinity, count: count + 1)
         var breaks: [Int?] = Array(repeating: nil, count: count + 1)
@@ -68,7 +91,7 @@ struct KnuthPlassLineBreaker: LineBreaking {
         }
 
         if breaks.compactMap({ $0 }).isEmpty {
-            return Array(0 ... sizes.endIndex)
+            return [0, sizes.endIndex]
         }
 
         var breakpoints: [Int] = []

diff --git a/Sources/Flow/Internal/Protocols.swift b/Sources/Flow/Internal/Protocols.swift
@@ -12,6 +12,7 @@ protocol Subview {
     func sizeThatFits(_ proposal: ProposedViewSize) -> CGSize
     func dimensions(_ proposal: ProposedViewSize) -> any Dimensions
     func place(at position: CGPoint, anchor: UnitPoint, proposal: ProposedViewSize)
+    subscript<K: LayoutValueKey>(key: K.Type) -> K.Value { get }
 }
 
 extension LayoutSubview: Subview {

diff --git a/Sources/Flow/Support.swift b/Sources/Flow/Support.swift
@@ -37,6 +37,8 @@ public struct FlowLayoutCache {
         var min: Size
         var ideal: Size
         var max: Size
+        var shouldStartInNewLine: Bool
+        var isLineBreak: Bool
 
         @usableFromInline
         init(_ subview: some Subview, axis: Axis) {
@@ -45,6 +47,8 @@ public struct FlowLayoutCache {
             min = subview.dimensions(.zero).size(on: axis)
             ideal = subview.dimensions(.unspecified).size(on: axis)
             max = subview.dimensions(.infinity).size(on: axis)
+            shouldStartInNewLine = subview[ShouldStartInNewLine.self]
+            isLineBreak = subview[ShouldStartInNewLine.self]
         }
     }
 
@@ -58,3 +62,28 @@ public struct FlowLayoutCache {
         }
     }
 }
+
+public struct LineBreak: View {
+    public var body: some View {
+        Color.clear
+            .frame(width: 0, height: 0)
+            .layoutValue(key: IsLineBreak.self, value: true)
+            .startInNewLine()
+    }
+
+    public init() {}
+}
+
+struct ShouldStartInNewLine: LayoutValueKey {
+    static let defaultValue = false
+}
+
+struct IsLineBreak: LayoutValueKey {
+    static let defaultValue = false
+}
+
+extension View {
+    public func startInNewLine() -> some View {
+        layoutValue(key: ShouldStartInNewLine.self, value: true)
+    }
+}