Add ZStack

Co-authored-by: projhect <[email protected]>

Sources/SwiftTUI/View/Views/Stacks/ZStack.swift

@@ -0,0 +1,108 @@
+import Foundation
+
+public struct ZStack<Content: View>: View, Primitive, LayoutRoot {
+    public let content: Content
+    let alignment: Alignment
+
+    public init(alignment: Alignment = .topLeading, @ViewBuilder _ content: () -> Content) {
+        self.content = content()
+        self.alignment = alignment
+    }
+
+    init(content: Content, alignment: Alignment = .center) {
+        self.content = content
+        self.alignment = alignment
+    }
+
+    static var size: Int? { 1 }
+
+    func loadData(node: Node) {
+        for i in 0 ..< node.children[0].size {
+            (node.control as! ZStackControl).addSubview(node.children[0].control(at: i), at: i)
+        }
+    }
+
+    func buildNode(_ node: Node) {
+        node.addNode(at: 0, Node(nodeBuilder: content.nodeBuilder))
+        node.control = ZStackControl(alignment: alignment)
+    }
+
+    func updateNode(_ node: Node) {
+        node.nodeBuilder = self
+        node.children[0].update(using: content.nodeBuilder)
+        let control = node.control as! ZStackControl
+        control.alignment = alignment
+    }
+
+    func insertControl(at index: Int, node: Node) {
+        (node.control as! ZStackControl).addSubview(node.children[0].control(at: index), at: index)
+    }
+
+    func removeControl(at index: Int, node: Node) {
+        (node.control as! ZStackControl).removeSubview(at: index)
+    }
+
+}
+
+private class ZStackControl: Control {
+    var alignment: Alignment
+
+    init(alignment: Alignment) {
+        self.alignment = alignment
+    }
+
+    // MARK: - Layout
+    override func size(proposedSize: Size) -> Size {
+        var size: Size = .zero
+        for control in children {
+            let childSize = control.size(proposedSize: Size(width: proposedSize.width, height: proposedSize.height))
+            size.height = max(size.height, childSize.height)
+            size.width = max(size.width, childSize.width)
+        }
+        return size
+    }
+
+    override func layout(size: Size) {
+        super.layout(size: size)
+        for control in children {
+            let childSize = control.size(proposedSize: Size(width: size.width, height: size.height))
+            control.layout(size: childSize)
+        }
+        for control in children {
+            switch alignment.horizontalAlignment {
+            case .leading: control.layer.frame.position.column = 0
+            case .center: control.layer.frame.position.column = (size.width - control.layer.frame.size.width) / 2
+            case .trailing: control.layer.frame.position.column = size.width - control.layer.frame.size.width
+            }
+            switch alignment.verticalAlignment {
+            case .top: control.layer.frame.position.line = 0
+            case .center: control.layer.frame.position.line = (size.height - control.layer.frame.size.height) / 2
+            case .bottom: control.layer.frame.position.line = size.height - control.layer.frame.size.height
+            }
+        }
+    }
+
+    // MARK: - Selection
+    override func selectableElement(below index: Int) -> Control? {
+        var index = index + 1
+        while index < children.count {
+            if let element = children[index].firstSelectableElement {
+                return element
+            }
+            index += 1
+        }
+        return super.selectableElement(below: index)
+    }
+
+    override func selectableElement(above index: Int) -> Control? {
+        var index = index - 1
+        while index >= 0 {
+            if let element = children[index].firstSelectableElement {
+                return element
+            }
+            index -= 1
+        }
+        return super.selectableElement(above: index)
+    }
+
+}