refactor<*>: rewrite all with AvaloniaUI

src/ViewModels/Popup.cs

@@ -0,0 +1,51 @@
+using Avalonia.Threading;
+using CommunityToolkit.Mvvm.ComponentModel;
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Threading.Tasks;
+
+namespace SourceGit.ViewModels {
+    public class Popup : ObservableValidator {
+        public string HostPageId {
+            get;
+            set;
+        }
+
+        public object View {
+            get;
+            set;
+        }
+
+        public bool InProgress {
+            get => _inProgress;
+            set => SetProperty(ref _inProgress, value);
+        }
+
+        public string ProgressDescription {
+            get => _progressDescription;
+            set => SetProperty(ref _progressDescription, value);
+        }
+
+        [UnconditionalSuppressMessage("AssemblyLoadTrimming", "IL2026:RequiresUnreferencedCode")]
+        public bool Check() {
+            if (HasErrors) return false;
+            ValidateAllProperties();
+            return !HasErrors;
+        }
+
+        public virtual Task<bool> Sure() {
+            return null;
+        }
+
+        protected void CallUIThread(Action action) {
+            Dispatcher.UIThread.Invoke(action);
+        }
+
+        protected void SetProgressDescription(string description) {
+            CallUIThread(() => ProgressDescription = description);
+        }
+
+        private bool _inProgress = false;
+        private string _progressDescription = string.Empty;
+    }
+}