Retain window size across sessions

src/Nerdbank.Zcash.App/Nerdbank.Zcash.App/App.axaml.cs

@@ -117,6 +117,24 @@ public override void OnFrameworkInitializationCompleted()
 			}
 
 			this.ViewModel.TopLevel = TopLevel.GetTopLevel(desktop.MainWindow);
+
+			// Remember the size of the window.
+			if (desktop.MainWindow.CanResize && this.settings is not null)
+			{
+				if (this.settings?.WindowSize is Size size)
+				{
+					desktop.MainWindow.Width = size.Width;
+					desktop.MainWindow.Height = size.Height;
+				}
+
+				desktop.MainWindow.Resized += (s, e) =>
+				{
+					if (this.settings is not null)
+					{
+						this.settings.WindowSize = new(desktop.MainWindow.Width, desktop.MainWindow.Height);
+					}
+				};
+			}
 		}
 		else if (this.ApplicationLifetime is ISingleViewApplicationLifetime singleViewPlatform)
 		{

src/Nerdbank.Zcash.App/Nerdbank.Zcash.App/AppSettings.cs

@@ -4,6 +4,7 @@
 using System.ComponentModel;
 using System.Text.Json;
 using System.Text.Json.Serialization;
+using Avalonia;
 using Nerdbank.Cryptocurrencies;
 
 namespace Nerdbank.Zcash.App;
@@ -84,6 +85,18 @@ public string? LastUsedAccountName
 		set => this.RaiseAndSetIfChanged(ref this.lastUsedAccountName, value);
 	}
 
+	[JsonIgnore]
+	public Size? WindowSize
+	{
+		get => this.WindowWidth is double w && this.WindowHeight is double h ? new(w, h) : null;
+		set
+		{
+			this.WindowWidth = value?.Width;
+			this.WindowHeight = value?.Height;
+			this.RaisePropertyChanged();
+		}
+	}
+
 	/// <summary>
 	/// Gets or sets a value indicating whether exchange rates will be automatically downloaded.
 	/// </summary>
@@ -112,6 +125,12 @@ public bool IsDirty
 		set => this.RaiseAndSetIfChanged(ref this.isDirty, value);
 	}
 
+	[JsonInclude]
+	internal double? WindowWidth { get; set; }
+
+	[JsonInclude]
+	internal double? WindowHeight { get; set; }
+
 	public static AppSettings Load(Stream stream) => JsonSerializer.Deserialize(stream, JsonSourceGenerationContext.Default.AppSettings)!;
 
 	public Task SaveAsync(Stream stream, CancellationToken cancellationToken) => JsonSerializer.SerializeAsync(stream, this, JsonSourceGenerationContext.Default.AppSettings, cancellationToken);