Add basic display list + String support (#146)

Sources/OpenSwiftUICore/Render/DisplayList/DisplayList+String.swift

@@ -0,0 +1,91 @@
+//
+//  DisplayList+String.swift
+//  OpenSwiftUICore
+//
+//  Audited for RELEASE_2024
+//  Status: WIP
+//  ID: 11125C146A81D1913BFBD53B89D010C6
+
+extension DisplayList.Item {
+    // TODO
+    var features: DisplayList.Features { [] }
+    var properties: DisplayList.Properties { [] }
+
+    fileprivate func print(into printer: inout SExpPrinter) {
+        printer.push("item")
+        if identity.value != .zero {
+            printer.print("#:identity \(identity.value)", newline: false)
+        }
+        printer.print("#:version \(version.value)", newline: false)
+        if features.contains(.required) {
+            printer.print("#:required true", newline: false)
+        }
+        if features.contains(.views) {
+            printer.print("#:views true", newline: false)
+        }
+        printer.print("(frame (\(position.x) \(position.y); \(size.width) \(size.height)))")
+        switch value {
+        case .empty:
+            break
+        case let .content(content):
+            printer.print("(content-seed \(content.seed.value))")
+            switch content.value {
+            case let .placeholder(id: identity):
+                printer.print("(placeholder \(identity))")
+            default:
+                // TOOD
+                break
+            }
+        default:
+            // TODO
+            break
+        }
+        printer.pop()
+    }
+
+    fileprivate func printMinimally(into printer: inout SExpPrinter) {
+        printer.push("I:\(identity.value)")
+        switch value {
+        case .empty:
+            break
+        case let .content(content):
+            switch content.value {
+            case let .placeholder(id: identity):
+                printer.print("@\(identity))")
+            default:
+                // TOOD
+                break
+            }
+        default:
+            // TODO
+            break
+        }
+        printer.pop()
+    }
+}
+
+
+extension DisplayList: CustomStringConvertible {
+    public var description: String {
+        var printer = SExpPrinter(tag: "display-list", singleLine: false)
+        for item in items {
+            item.print(into: &printer)
+        }
+        return printer.end()
+    }
+
+    package var minimalDescription: String {
+        var printer = SExpPrinter(tag: "DL", singleLine: true)
+        for item in items {
+            item.printMinimally(into: &printer)
+        }
+        return printer.end()
+    }
+}
+extension DisplayList.Item: CustomStringConvertible {
+    package var description: String {
+        var printer = SExpPrinter(tag: "display-list-item", singleLine: false)
+        print(into: &printer)
+        return printer.end()
+    }
+}

Sources/OpenSwiftUICore/Render/DisplayList.swift → Sources/OpenSwiftUICore/Render/DisplayList/DisplayList.swift

@@ -63,15 +63,29 @@ package struct DisplayList: Equatable {
     }
 
     package init(_ item: Item) {
-        fatalError("TODO")
+        switch item.value {
+        case .empty:
+            items = []
+            features = []
+            properties = []
+        default:
+            items = [item]
+            features = item.features
+            properties = item.properties
+        }
     }
 
+    // TO BE VERIFIED
     package init(_ items: [Item]) {
-        guard !items.isEmpty else {
-            self.init()
-            return
+        var features: Features = []
+        var properties: Properties = []
+        for item in items {
+            features.formUnion(item.features)
+            properties.formUnion(item.properties)
         }
-        fatalError("TODO")
+        self.items = items
+        self.features = features
+        self.properties = properties
     }
 
     package mutating func append(_ item: Item) {
@@ -264,7 +278,7 @@ extension DisplayList {
         package static let screencaptureProhibited = Properties(rawValue: 1 << 7)
     }
 
-    package struct Key : PreferenceKey {
+    package struct Key: PreferenceKey {
         package static let _includesRemovedValues: Bool = true
         package static let defaultValue = DisplayList()
         package static func reduce(value: inout DisplayList, nextValue: () -> DisplayList) {

Tests/OpenSwiftUICoreTests/Render/DisplayList/DisplayList+StringTests.swift

@@ -0,0 +1,65 @@
+//
+//  DisplayList+StringTests.swift
+//  OpenSwiftUICoreTests
+
+import OpenSwiftUICore
+import Testing
+
+struct DisplayList_StringTests {
+    @Test
+    func plain() {
+        let emptyList = DisplayList()
+        #expect(emptyList.description == "(display-list)")
+        #expect(emptyList.minimalDescription == "(DL)")
+    }
+
+    @Test
+    func emptyItem() {
+        let item = DisplayList.Item(.empty, frame: .zero, identity: .init(decodedValue: 1), version: .init(decodedValue: 0))
+        let d = item.description
+        print(d)
+
+        #expect(item.description == """
+        (display-list-item
+          (item #:identity 1 #:version 0
+            (frame (0.0 0.0; 0.0 0.0))))
+        """)
+
+        let list = DisplayList(item)
+        #expect(list.description == "(display-list)")
+        #expect(list.minimalDescription == "(DL)")
+
+        let list2 = DisplayList([item])
+        #expect(list2.description == """
+        (display-list
+          (item #:identity 1 #:version 0
+            (frame (0.0 0.0; 0.0 0.0))))
+        """)
+        #expect(list2.minimalDescription == "(DL(I:1))")
+    }
+
+    func placeholdItem() {
+        let item = DisplayList.Item(.content(.init(.placeholder(id: .init(decodedValue: 2)), seed: .init(decodedValue: 4))), frame: .zero, identity: .init(decodedValue: 1), version: .init(decodedValue: 0))
+        let expectedDescription = """
+        (display-list
+          (item #:identity 1 #:version 0 #:views true
+            (frame (0.0 0.0; 0.0 0.0))
+            (content-seed 4)
+            (placeholder #2)))
+        """
+
+        let expectedMinimalDescription = """
+        (DL(I:1 @#2))
+        """
+
+
+        let list = DisplayList(item)
+        #expect(list.description == expectedDescription)
+        #expect(list.minimalDescription == expectedMinimalDescription)
+
+        let list2 = DisplayList([item])
+        #expect(list2.description == expectedDescription)
+        #expect(list2.minimalDescription == expectedMinimalDescription)
+    }
+
+}

Tests/OpenSwiftUICoreTests/Render/DisplayList_StableIdentityTests.swift → Tests/OpenSwiftUICoreTests/Render/DisplayList/DisplayList_StableIdentityTests.swift

@@ -5,8 +5,6 @@
 import OpenSwiftUICore
 import Testing
 
-@_spi(Debug) import OpenGraphShims
-
 struct DisplayList_StableIdentityTests {
     @Test
     func formUnion() {