Adding GUI project.

src/GUI/App.axaml

@@ -0,0 +1,15 @@
+<Application xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             x:Class="GUI.App"
+             xmlns:local="using:GUI"
+             RequestedThemeVariant="Default">
+             <!-- "Default" ThemeVariant follows system theme variant. "Dark" or "Light" are other available options. -->
+
+    <Application.DataTemplates>
+        <local:ViewLocator/>
+    </Application.DataTemplates>
+  
+    <Application.Styles>
+        <FluentTheme />
+    </Application.Styles>
+</Application>

src/GUI/App.axaml.cs

@@ -0,0 +1,31 @@
+using Avalonia;
+using Avalonia.Controls.ApplicationLifetimes;
+using Avalonia.Data.Core;
+using Avalonia.Data.Core.Plugins;
+using System.Linq;
+using Avalonia.Markup.Xaml;
+using GUI.ViewModels;
+using GUI.Views;
+
+namespace GUI;
+
+public partial class App : Application
+{
+    public override void Initialize()
+    {
+        AvaloniaXamlLoader.Load(this);
+    }
+
+    public override void OnFrameworkInitializationCompleted()
+    {
+        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
+        {
+            desktop.MainWindow = new MainWindow
+            {
+                DataContext = new MainWindowViewModel(),
+            };
+        }
+
+        base.OnFrameworkInitializationCompleted();
+    }
+}

src/GUI/GUI.csproj

@@ -0,0 +1,31 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <OutputType>WinExe</OutputType>
+        <TargetFramework>net10.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <ApplicationManifest>app.manifest</ApplicationManifest>
+        <AvaloniaUseCompiledBindingsByDefault>true</AvaloniaUseCompiledBindingsByDefault>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <Folder Include="Models\"/>
+        <AvaloniaResource Include="Assets\**"/>
+    </ItemGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Avalonia" Version="12.0.0"/>
+        <PackageReference Include="Avalonia.Desktop" Version="12.0.0"/>
+        <PackageReference Include="Avalonia.Themes.Fluent" Version="12.0.0"/>
+        <PackageReference Include="Avalonia.Fonts.Inter" Version="12.0.0"/>
+        <PackageReference Include="AvaloniaUI.DiagnosticsSupport" Version="2.2.0">
+            <IncludeAssets Condition="'$(Configuration)' != 'Debug'">None</IncludeAssets>
+            <PrivateAssets Condition="'$(Configuration)' != 'Debug'">All</PrivateAssets>
+        </PackageReference>
+        <PackageReference Include="CommunityToolkit.Mvvm" Version="8.4.1"/>
+        <PackageReference Include="Tmds.DBus.Protocol" Version="0.93.0" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <ProjectReference Include="..\Core\Core.csproj" />
+    </ItemGroup>
+</Project>

src/GUI/Program.cs

@@ -0,0 +1,24 @@
+using Avalonia;
+using System;
+
+namespace GUI;
+
+sealed class Program
+{
+    // Initialization code. Don't use any Avalonia, third-party APIs or any
+    // SynchronizationContext-reliant code before AppMain is called: things aren't initialized
+    // yet and stuff might break.
+    [STAThread]
+    public static void Main(string[] args) => BuildAvaloniaApp()
+        .StartWithClassicDesktopLifetime(args);
+
+    // Avalonia configuration, don't remove; also used by visual designer.
+    public static AppBuilder BuildAvaloniaApp()
+        => AppBuilder.Configure<App>()
+            .UsePlatformDetect()
+#if DEBUG
+            .WithDeveloperTools()
+#endif
+            .WithInterFont()
+            .LogToTrace();
+}

src/GUI/ViewLocator.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using Avalonia.Controls;
+using Avalonia.Controls.Templates;
+using GUI.ViewModels;
+
+namespace GUI;
+
+/// <summary>
+/// Given a view model, returns the corresponding view if possible.
+/// </summary>
+[RequiresUnreferencedCode(
+    "Default implementation of ViewLocator involves reflection which may be trimmed away.",
+    Url = "https://docs.avaloniaui.net/docs/concepts/view-locator")]
+public class ViewLocator : IDataTemplate
+{
+    public Control? Build(object? param)
+    {
+        if (param is null)
+            return null;
+
+        var name = param.GetType().FullName!.Replace("ViewModel", "View", StringComparison.Ordinal);
+        var type = Type.GetType(name);
+
+        if (type != null)
+        {
+            return (Control)Activator.CreateInstance(type)!;
+        }
+
+        return new TextBlock { Text = "Not Found: " + name };
+    }
+
+    public bool Match(object? data)
+    {
+        return data is ViewModelBase;
+    }
+}

src/GUI/ViewModels/MainWindowViewModel.cs

@@ -0,0 +1,6 @@
+namespace GUI.ViewModels;
+
+public partial class MainWindowViewModel : ViewModelBase
+{
+    public string Greeting { get; } = "Welcome to Avalonia!";
+}

src/GUI/ViewModels/ViewModelBase.cs

@@ -0,0 +1,7 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace GUI.ViewModels;
+
+public abstract class ViewModelBase : ObservableObject
+{
+}

src/GUI/Views/MainWindow.axaml

@@ -0,0 +1,20 @@
+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:vm="using:GUI.ViewModels"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
+        x:Class="GUI.Views.MainWindow"
+        x:DataType="vm:MainWindowViewModel"
+        Icon="/Assets/avalonia-logo.ico"
+        Title="GUI">
+
+    <Design.DataContext>
+        <!-- This only sets the DataContext for the previewer in an IDE,
+             to set the actual DataContext for runtime, set the DataContext property in code (look at App.axaml.cs) -->
+        <vm:MainWindowViewModel/>
+    </Design.DataContext>
+
+    <TextBlock Text="{Binding Greeting}" HorizontalAlignment="Center" VerticalAlignment="Center"/>
+
+</Window>

src/GUI/Views/MainWindow.axaml.cs

@@ -0,0 +1,11 @@
+using Avalonia.Controls;
+
+namespace GUI.Views;
+
+public partial class MainWindow : Window
+{
+    public MainWindow()
+    {
+        InitializeComponent();
+    }
+}

src/GUI/app.manifest

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
+  <!-- This manifest is used on Windows only.
+       Don't remove it as it might cause problems with window transparency and embedded controls.
+       For more details visit https://learn.microsoft.com/en-us/windows/win32/sbscs/application-manifests -->
+  <assemblyIdentity version="1.0.0.0" name="GUI.Desktop"/>
+
+  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
+    <application>
+      <!-- A list of the Windows versions that this application has been tested on
+           and is designed to work with. Uncomment the appropriate elements
+           and Windows will automatically select the most compatible environment. -->
+
+      <!-- Windows 10 -->
+      <supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}" />
+    </application>
+  </compatibility>
+</assembly>

src/Resonance.sln

@@ -6,6 +6,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Core.Tests", "Core.Tests\Co
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AtlFieldExtractor", "AtlFieldExtractor\AtlFieldExtractor.csproj", "{17699013-3F4A-408F-84CE-FD4178B1699D}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "GUI", "GUI\GUI.csproj", "{9AB83303-0D46-4557-A62D-3753A0BE2103}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -52,6 +54,18 @@ Global
 		{17699013-3F4A-408F-84CE-FD4178B1699D}.Release|x64.Build.0 = Release|Any CPU
 		{17699013-3F4A-408F-84CE-FD4178B1699D}.Release|x86.ActiveCfg = Release|Any CPU
 		{17699013-3F4A-408F-84CE-FD4178B1699D}.Release|x86.Build.0 = Release|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Debug|x64.Build.0 = Debug|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Debug|x86.Build.0 = Debug|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Release|Any CPU.Build.0 = Release|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Release|x64.ActiveCfg = Release|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Release|x64.Build.0 = Release|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Release|x86.ActiveCfg = Release|Any CPU
+		{9AB83303-0D46-4557-A62D-3753A0BE2103}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE