Add support for environment properties

Sources/Model/Data Flow/Environment.swift

@@ -0,0 +1,49 @@
+//
+//  Environment.swift
+//  Meta
+//
+//  Created by david-swift on 23.10.24.
+//
+
+/// A property wrapper for properties in a view that should be stored throughout view updates.
+@propertyWrapper
+public struct Environment<Value>: EnvironmentProtocol {
+
+    /// Access the environment value.
+    public var wrappedValue: Value? {
+        content.value as? Value
+    }
+    /// The value's identifier.
+    var id: String
+    /// The content.
+    let content = EnvironmentContent()
+
+    // swiftlint:disable function_default_parameter_at_end
+    /// Initialize a property representing an environment value in the view.
+    /// - Parameters:
+    ///     - wrappedValue: The wrapped value.
+    ///     - id: The environment value's identifier.
+    public init(wrappedValue: Value? = nil, _ id: String) {
+        self.id = id
+    }
+    // swiftlint:enable function_default_parameter_at_end
+
+}
+
+/// An environment property's content.
+class EnvironmentContent {
+
+    /// The value.
+    var value: Any?
+
+}
+
+/// The environment property protocol.
+protocol EnvironmentProtocol {
+
+    /// The content.
+    var content: EnvironmentContent { get }
+    /// The identifier.
+    var id: String { get }
+
+}

Sources/Model/User Interface/View/View.swift

@@ -32,7 +32,7 @@ extension View {
 
     /// The view's content.
     public var viewContent: Body {
-        [StateWrapper(content: { view }, state: getState())]
+        [StateWrapper(content: { view }, state: getState(), environment: getEnvironmentVariables())]
     }
 
     /// Get the state from the properties.
@@ -47,4 +47,16 @@ extension View {
         return state
     }
 
+    /// Get the environment properties.
+    /// - Returns: The environment properties.
+    func getEnvironmentVariables() -> [String: any EnvironmentProtocol] {
+        var environment: [String: any EnvironmentProtocol] = [:]
+        for property in Mirror(reflecting: self).children {
+            if let label = property.label, let value = property.value as? any EnvironmentProtocol {
+                environment[label] = value
+            }
+        }
+        return environment
+    }
+
 }

Sources/View/DataWrapper.swift

@@ -0,0 +1,67 @@
+//
+//  StateWrapper.swift
+//  Meta
+//
+//  Created by david-swift on 09.06.24.
+//
+
+/// Assign values to the environment.
+///
+/// Access the environment in views (``View``) via `@Environment`.
+struct DataWrapper: ConvenienceWidget {
+
+    /// The content.
+    var content: Body
+    /// The identifier for the new environment value.
+    var label: String
+    /// The environment value.
+    var data: Any
+
+    /// Get a view storage.
+    /// - Parameters:
+    ///     - data: Modify views before being updated.
+    ///     - type: The view render data type.
+    /// - Returns: The view storage.
+    func container<Data>(
+        data: WidgetData,
+        type: Data.Type
+    ) -> ViewStorage where Data: ViewRenderData {
+        content.storage(data: data.modify { $0.fields[label] = self.data }, type: type)
+    }
+
+    /// Update a view storage.
+    /// - Parameters:
+    ///     - storage: The view storage.
+    ///     - data: Modify views before being updated.
+    ///     - updateProperties: Whether to update properties.
+    ///     - type: The view render data type.
+    /// - Returns: The view storage.
+    func update<Data>(
+        _ storage: ViewStorage,
+        data: WidgetData,
+        updateProperties: Bool,
+        type: Data.Type
+    ) where Data: ViewRenderData {
+        content
+            .updateStorage(
+                storage,
+                data: data.modify { $0.fields[label] = self.data },
+                updateProperties: updateProperties,
+                type: type
+            )
+    }
+
+}
+
+extension AnyView {
+
+    /// Assign a value to an environment label.
+    /// - Parameters:
+    ///     - label: The environment label.
+    ///     - data: The value.
+    /// - Returns: The view.
+    public func environment(_ label: String, data: Any) -> AnyView {
+        DataWrapper(content: [self], label: label, data: data)
+    }
+
+}

Sources/View/StateWrapper.swift

@@ -12,6 +12,8 @@ struct StateWrapper: ConvenienceWidget {
     var content: () -> Body
     /// The state information (from properties with the `State` wrapper).
     var state: [String: StateProtocol] = [:]
+    /// The environment properties.
+    var environment: [String: any EnvironmentProtocol] = [:]
 
     /// Initialize a `StateWrapper`.
     /// - Parameter content: The view content.
@@ -23,9 +25,15 @@ struct StateWrapper: ConvenienceWidget {
     /// - Parameters:
     ///   - content: The view content.
     ///   - state: The state information.
-    init(content: @escaping () -> Body, state: [String: StateProtocol]) {
+    ///   - environment: The environment properties.
+    init(
+        content: @escaping () -> Body,
+        state: [String: StateProtocol],
+        environment: [String: any EnvironmentProtocol]
+    ) {
         self.content = content
         self.state = state
+        self.environment = environment
     }
 
     /// Update a view storage.
@@ -51,6 +59,7 @@ struct StateWrapper: ConvenienceWidget {
                 property.value.content.update = false
             }
         }
+        assignEnvironment(data: data)
         guard let storage = storage.content[.mainContent]?.first else {
             return
         }
@@ -66,6 +75,7 @@ struct StateWrapper: ConvenienceWidget {
         data: WidgetData,
         type: Data.Type
     ) -> ViewStorage where Data: ViewRenderData {
+        assignEnvironment(data: data)
         let content = content().storage(data: data, type: type)
         let storage = ViewStorage(content.pointer, content: [.mainContent: [content]])
         storage.state = state
@@ -75,4 +85,12 @@ struct StateWrapper: ConvenienceWidget {
         return storage
     }
 
+    /// Assign an environment value to the environment property.
+    /// - Parameter data: The widget data.
+    func assignEnvironment(data: WidgetData) {
+        for property in environment {
+            property.value.content.value = data.fields[property.value.id]
+        }
+    }
+
 }

Tests/DemoApp/DemoApp.swift

@@ -23,6 +23,7 @@ struct DemoApp: App {
     var scene: Scene {
         Backend1.Window("main", spawn: 1) {
             DemoView(app: app)
+                .environment("test", data: 5)
         }
     }
 
@@ -31,6 +32,8 @@ struct DemoApp: App {
 struct DemoView: View {
 
     @State private var model = TestModel()
+    @Environment("test")
+    private var test: Int?
     var app: any AppStorage
     let condition = false
 
@@ -46,6 +49,7 @@ struct DemoView: View {
                     app.addSceneElement("main")
                 }
             }
+            .onAppear { print(test ?? 0) }
         }
         TestView()
         testContent