Add Idle for updating the UI asynchronously

.gitignore

@@ -11,4 +11,5 @@ DerivedData/
 .Ulysses-Group.plist
 /.docc-build
 /io.github.AparokshaUI.Generation.json
-/.vscode
+/io.github.AparokshaUI.swiftlint.json
+/.vscode

Sources/Adwaita/Model/Data Flow/Idle.swift

@@ -0,0 +1,110 @@
+//
+//  Idle.swift
+//  Adwaita
+//
+//  Created by david-swift on 02.05.24.
+//
+
+import CAdw
+
+/// Add a task to GLib's idle.
+public struct Idle {
+
+    /// The idle handler.
+    static let handler = IdleHandler()
+
+    /// Run a function whenever there are no higher priority events pending to the default main loop.
+    /// - Parameters:
+    ///     - priority: The task's priority, default priority by default.
+    ///     - closure: The closure to run.
+    @discardableResult
+    public init(
+        priority: Priority = .defaultIdle,
+        closure: @escaping () -> Void
+    ) {
+        Self.handler.add({ closure(); return false }, priority: .init(priority.rawValue))
+    }
+
+    /// Repeat a function with a certain delay.
+    /// - Parameters:
+    ///     - delay: The delay between the repetitions.
+    ///     - priority: The task's priority, default priority by default.
+    ///     - closure: The closure to run. Return if you want to exit the loop.
+    @discardableResult
+    public init(
+        delay: Duration,
+        priority: Priority = .defaultIdle,
+        closure: @escaping () -> Bool
+    ) {
+        Self.handler.add(closure, priority: .init(priority.rawValue), delay: delay)
+    }
+
+    /// The priority of an idle task.
+    public enum Priority: Int {
+
+        /// A very low priority background task.
+        case low = 300
+        /// A high priority event source.
+        case high = -100
+        /// A default priority event source.
+        case `default` = 0
+        /// A high priority idle function.
+        case highIdle = 100
+        /// A default priority idle function.
+        case defaultIdle = 200
+
+    }
+
+    /// An idle handler.
+    class IdleHandler {
+
+        /// Add a function to be called whenever there are no higher priority events pending to the default main loop.
+        /// - Parameter closure: The function.
+        func add(_ closure: @escaping () -> Bool, priority: Int32, delay: Duration? = nil) {
+            let context = UnsafeMutableRawPointer(Unmanaged.passRetained(ClosureContainer(closure: closure)).toOpaque())
+            let secondsToMilliseconds: Int64 = 1_000
+            let attosecondsToMilliseconds: Int64 = 1_000_000_000_000_000
+            if let delay {
+                let milliseconds = delay.components.seconds * secondsToMilliseconds
+                + (delay.components.attoseconds / attosecondsToMilliseconds)
+                // swiftlint:disable prefer_self_in_static_references
+                g_timeout_add_full(priority, .init(milliseconds), { IdleHandler.run(pointer: $0) }, context, nil)
+                // swiftlint:enable prefer_self_in_static_references
+            } else {
+                // swiftlint:disable prefer_self_in_static_references
+                g_idle_add_full(priority, { IdleHandler.run(pointer: $0) }, context, nil)
+                // swiftlint:enable prefer_self_in_static_references
+            }
+        }
+
+        /// Execute the function.
+        /// - Parameter pointer: The closure wrapper's pointer.
+        static func run(pointer: gpointer?) -> Int32 {
+            if let pointer {
+                let container = Unmanaged<ClosureContainer>.fromOpaque(pointer).takeUnretainedValue()
+                let result = container.closure()
+                if !result {
+                    Unmanaged<ClosureContainer>.fromOpaque(pointer).release()
+                }
+                return result.cBool
+            }
+            return G_SOURCE_REMOVE
+        }
+
+    }
+
+    /// A reference type holding a closure.
+    class ClosureContainer {
+
+        /// The closure.
+        var closure: () -> Bool
+
+        /// Initialize an object.
+        /// - Parameter closure: The closure.
+        init(closure: @escaping () -> Bool) {
+            self.closure = closure
+        }
+
+    }
+
+}

Sources/Adwaita/Window/Window.swift

@@ -110,7 +110,7 @@ public struct Window: WindowScene {
             updateAppShortcuts(app: app)
         }
         for signal in signals where signal.update {
-            Task {
+            Idle {
                 app.showWindow(signal.id.uuidString)
             }
         }

Tests/IdleDemo.swift

@@ -0,0 +1,50 @@
+//
+//  IdleDemo.swift
+//  Adwaita
+//
+//  Created by david-swift on 05.05.24.
+//
+
+// swiftlint:disable missing_docs
+
+import Adwaita
+
+struct IdleDemo: View {
+
+    @State private var progress = 0.0
+    @State private var activeProcess = false
+    let max = 500.0
+    let delayFactor = 5.0
+    let maxWidth = 300
+
+    var view: Body {
+        ProgressBar(value: progress, total: max)
+            .vexpand()
+            .valign(.center)
+            .frame(maxWidth: maxWidth)
+        Button("Play") {
+            Task {
+                Idle {
+                    activeProcess = true
+                    progress = 0
+                }
+                Idle(delay: .seconds(delayFactor / max)) {
+                    progress += 1
+                    let done = progress == max
+                    if done {
+                        activeProcess = false
+                    }
+                    return !done
+                }
+            }
+        }
+        .padding()
+        .style("pill")
+        .hexpand()
+        .halign(.center)
+        .insensitive(activeProcess)
+    }
+
+}
+
+// swiftlint:enable missing_docs

Tests/Page.swift

@@ -29,6 +29,7 @@ enum Page: String, Identifiable, CaseIterable, Codable {
     case flowBox
     case navigationView
     case picture
+    case idle
 
     var id: Self {
         self
@@ -94,6 +95,8 @@ enum Page: String, Identifiable, CaseIterable, Codable {
             return "A page-based navigation container"
         case .picture:
             return "Display an image"
+        case .idle:
+            return "Update UI from an asynchronous context"
         }
     }
 
@@ -135,6 +138,8 @@ enum Page: String, Identifiable, CaseIterable, Codable {
             NavigationViewDemo(app: app)
         case .picture:
             PictureDemo(url: pictureURL, app: app, window: window)
+        case .idle:
+            IdleDemo()
         }
     }
     // swiftlint:enable cyclomatic_complexity