Implement basics of WinUIBackend under new layout system (RNG ex works)

Coming along well so far. The biggest hiccups have been setting the
minimum sizes of windows (not solved yet) and getting the 'natural size'
of UI elements before they're rendered (kinda solved with a hacky
workaround).

Author: stackotter

Examples/Sources/RandomNumberGeneratorExample/RandomNumberGeneratorApp.swift

@@ -75,6 +75,6 @@ struct RandomNumberGeneratorApp: App {
             }
         }
         .defaultSize(width: 500, height: 0)
-        .windowResizability(.contentSize)
+        .windowResizability(.contentMinSize)
     }
 }

Package.resolved

@@ -74,7 +74,7 @@ extension App {
 
     private static func extractSwiftBundlerMetadata() -> AppMetadata? {
         guard let executable = Bundle.main.executableURL else {
-            print("No executable url")
+            print("warning: No executable url")
             return nil
         }
 
@@ -86,7 +86,6 @@ extension App {
         // Check if executable has Swift Bundler metadata magic bytes.
         let bytes = Array(data)
         guard bytes.suffix(8) == Array("SBUNMETA".utf8) else {
-            print("no magic bytes")
             return nil
         }
 

Sources/SwiftCrossUI/App.swift

@@ -141,7 +141,7 @@ public protocol AppBackend {
 
     /// Runs an action in the app's main thread if required to perform UI updates
     /// by the backend. Predominantly used by ``Publisher`` to publish changes to a thread
-    /// compatible with dispatching UI updates.
+    /// compatible with dispatching UI updates. Can be synchronous or asynchronous (for now).
     func runInMainThread(action: @escaping () -> Void)
 
     /// Computes the root environment for an app (e.g. by checking the system's current
@@ -384,7 +384,10 @@ public protocol AppBackend {
     /// - Parameter progressFraction: If `nil`, then the bar should show an indeterminate
     ///   animation if possible.
     func updateProgressBar(
-        _ widget: Widget, progressFraction: Double?, environment: EnvironmentValues)
+        _ widget: Widget,
+        progressFraction: Double?,
+        environment: EnvironmentValues
+    )
 
     /// Creates a popover menu (the sort you often see when right clicking on
     /// apps). The menu won't be visible until you call
@@ -502,7 +505,7 @@ extension AppBackend {
         todo()
     }
 
-    public func setColor(ofColorableRectangle widget: Widget) {
+    public func setColor(ofColorableRectangle widget: Widget, to color: Color) {
         todo()
     }
 
@@ -696,7 +699,7 @@ extension AppBackend {
     public func createProgressBar() -> Widget {
         todo()
     }
-    func updateProgressBar(
+    public func updateProgressBar(
         _ widget: Widget,
         progressFraction: Double?,
         environment: EnvironmentValues
@@ -734,14 +737,14 @@ extension AppBackend {
     ) {
         todo()
     }
-    func showAlert(
+    public func showAlert(
         _ alert: Alert,
         window: Window?,
         responseHandler handleResponse: @escaping (Int) -> Void
     ) {
         todo()
     }
-    func dismissAlert(_ alert: Alert, window: Window?) {
+    public func dismissAlert(_ alert: Alert, window: Window?) {
         todo()
     }
 

Sources/SwiftCrossUI/Backend/AppBackend.swift

@@ -1,4 +1,3 @@
-import CoreFoundation
 import Dispatch
 import Foundation
 
@@ -15,7 +14,7 @@ public class Publisher {
 
     /// The time at which the last update merging event occurred in
     /// `observeOnMainThreadAvoidingStarvation`.
-    private var lastUpdateMergeTime: CFAbsoluteTime = 0
+    private var lastUpdateMergeTime: TimeInterval = 0
     /// The amount of time taken per state update, exponentially averaged over time.
     private var exponentiallySmoothedUpdateLength: Double = 0
 
@@ -106,7 +105,7 @@ public class Publisher {
                 // It's a bit of a hack but we just reuse the serial update handling queue
                 // for synchronisation since updating this variable isn't super time sensitive
                 // as long as it happens within the next update or two.
-                let mergeTime = CFAbsoluteTimeGetCurrent()
+                let mergeTime = ProcessInfo.processInfo.systemUptime
                 serialUpdateHandlingQueue.async {
                     self.lastUpdateMergeTime = mergeTime
                 }
@@ -127,9 +126,9 @@ public class Publisher {
 
                     // Run the closure and while we're at it measure how long it takes
                     // so that we can use it when throttling if updates start backing up.
-                    let start = CFAbsoluteTimeGetCurrent()
+                    let start = ProcessInfo.processInfo.systemUptime
                     closure()
-                    let elapsed = CFAbsoluteTimeGetCurrent() - start
+                    let elapsed = ProcessInfo.processInfo.systemUptime - start
 
                     // I chose exponential smoothing because it's simple to compute, doesn't
                     // require storing a window of previous values, and quickly converges to
@@ -139,7 +138,7 @@ public class Publisher {
                         elapsed / 2 + self.exponentiallySmoothedUpdateLength / 2
                 }
 
-                if CFAbsoluteTimeGetCurrent() - self.lastUpdateMergeTime < 1 {
+                if ProcessInfo.processInfo.systemUptime - self.lastUpdateMergeTime < 1 {
                     // The factor of 1.5 was determined empirically. This algorithm is
                     // open for improvements since it's purely here to reduce the risk
                     // of UI freezes.