Single Instance (#102)

Author: Mateusz-Nejman

Pixed/App.axaml.cs

@@ -3,15 +3,22 @@
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.Markup.Xaml;
+using Avalonia.Threading;
 using Microsoft.Extensions.DependencyInjection;
+using Newtonsoft.Json;
 using Pixed.DependencyInjection;
+using Pixed.Utils;
 using Pixed.Windows;
+using System;
+using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Pixed;
 
 public partial class App : Application
 {
+    private Mutex _mutex;
     internal static IPixedServiceProvider ServiceProvider { get; private set; }
     public override void Initialize()
     {
@@ -32,6 +39,11 @@ public async override void OnFrameworkInitializationCompleted()
 
     private async Task InitializeMainWindow(IClassicDesktopStyleApplicationLifetime desktop, Window splash)
     {
+        if (!HandleNewInstance(Dispatcher.UIThread, desktop))
+        {
+            splash.Close();
+            return;
+        }
         await Task.Delay(1500);
         BindingPlugins.DataValidators.RemoveAt(0);
 
@@ -47,4 +59,54 @@ private async Task InitializeMainWindow(IClassicDesktopStyleApplicationLifetime
         await Task.Delay(100);
         splash.Close();
     }
+
+    private bool HandleNewInstance(Dispatcher? dispatcher, IClassicDesktopStyleApplicationLifetime desktop)
+    {
+        _mutex = new(true, "pixed_mutex_name", out bool isOwned);
+        var handle = new EventWaitHandle(false, EventResetMode.AutoReset, "pixed_mutex_event_name");
+
+        GC.KeepAlive(_mutex);
+
+        if (dispatcher == null)
+            return true;
+
+        if (isOwned)
+        {
+            var thread = new Thread(
+                async () =>
+                {
+                    while (handle.WaitOne())
+                    {
+                        var pixed = await desktop.MainWindow.StorageProvider.GetPixedFolder();
+                        var filePath = Path.Combine(pixed.Path.AbsolutePath, "instance.lock");
+
+                        if (File.Exists(filePath))
+                        {
+                            string[] args = JsonConvert.DeserializeObject<string[]>(File.ReadAllText(filePath)) ?? [];
+
+                            if (args.Length > 0)
+                            {
+                                Subjects.NewInstanceHandled.OnNext(args);
+                            }
+                        }
+                    }
+                })
+            {
+                IsBackground = true
+            };
+
+            thread.Start();
+            return true;
+        }
+
+        Task.Run(async () =>
+        {
+            var pixed = await desktop.MainWindow.StorageProvider.GetPixedFolder();
+            File.WriteAllText(Path.Combine(pixed.Path.AbsolutePath, "instance.lock"), JsonConvert.SerializeObject(Environment.GetCommandLineArgs()));
+        });
+        handle.Set();
+
+        desktop.Shutdown();
+        return false;
+    }
 }

Pixed/IO/PixedProjectMethods.cs

@@ -3,6 +3,7 @@
 using Pixed.Utils;
 using Pixed.Windows;
 using System.IO;
+using System.Linq;
 using System.Threading.Tasks;
 
 namespace Pixed.IO;
@@ -103,7 +104,14 @@ public async Task Open(RecentFilesService recentFilesService)
 
     public void Open(string path)
     {
+        string[] formats = [".pixed", ".piskel", ".png"];
         FileInfo info = new(path);
+
+        if (!formats.Contains(info.Extension))
+        {
+            return;
+        }
+
         IPixedProjectSerializer serializer;
         Stream stream = File.OpenRead(path);
 

Pixed/Subjects.cs

@@ -14,6 +14,7 @@ internal static class Subjects
     public static Subject<bool> GridChanged { get; } = new Subject<bool>();
     public static Subject<BaseToolPair> ToolChanged { get; } = new Subject<BaseToolPair>();
     public static Subject<double> ZoomChanged { get; } = new Subject<double>();
+    public static Subject<string[]> NewInstanceHandled { get; } = new Subject<string[]>();
 
     public static Subject<BaseSelection> ClipboardCopy { get; } = new Subject<BaseSelection>();
     public static Subject<BaseSelection> ClipboardCut { get; } = new Subject<BaseSelection>();

Pixed/Utils/StorageProviderUtils.cs

@@ -0,0 +1,12 @@
+using Avalonia.Platform.Storage;
+using System.Threading.Tasks;
+
+namespace Pixed.Utils;
+internal static class StorageProviderUtils
+{
+    public async static Task<IStorageFolder?> GetPixedFolder(this IStorageProvider provider)
+    {
+        var documentsFolder = await provider.TryGetWellKnownFolderAsync(WellKnownFolder.Documents);
+        return await documentsFolder.CreateFolderAsync("Pixed");
+    }
+}

Pixed/Windows/MainWindow.axaml.cs

@@ -1,5 +1,6 @@
 using Avalonia.Controls;
 using Avalonia.Input;
+using Avalonia.Threading;
 using Pixed.Controls;
 using Pixed.Input;
 using Pixed.IO;
@@ -8,14 +9,16 @@
 using Pixed.Services;
 using Pixed.Services.Keyboard;
 using Pixed.Tools;
+using Pixed.Utils;
 using Pixed.ViewModels;
+using System;
 using System.IO;
 using System.Threading.Tasks;
 using System.Windows.Input;
 
 namespace Pixed.Windows;
 
-internal partial class MainWindow : PixedWindow<MainViewModel>
+internal partial class MainWindow : PixedWindow<MainViewModel>, IDisposable
 {
     private readonly ApplicationData _applicationData;
     private readonly PixedProjectMethods _pixedProjectMethods;
@@ -25,6 +28,9 @@ internal partial class MainWindow : PixedWindow<MainViewModel>
     private readonly RecentFilesService _recentFilesService;
     private readonly ToolSelector _toolSelector;
     private readonly MenuBuilder _menuBuilder;
+    private IDisposable _newInstanceHandled;
+    private bool _disposedValue;
+
     public static Window? Handle { get; private set; }
     public static ICommand? QuitCommand { get; private set; }
     public MainWindow(ApplicationData applicationData, PixedProjectMethods pixedProjectMethods, MenuBuilder builder, MenuItemRegistry menuItemRegistry,
@@ -39,6 +45,13 @@ public MainWindow(ApplicationData applicationData, PixedProjectMethods pixedProj
         _recentFilesService = recentFilesService;
         _toolSelector = toolSelector;
         _menuBuilder = builder;
+        _newInstanceHandled = Subjects.NewInstanceHandled.Subscribe(args =>
+        {
+            foreach (var arg in args)
+            {
+                Dispatcher.UIThread.Invoke(() => _pixedProjectMethods.Open(arg));
+            }
+        });
 
         InitializeWindow();
     }
@@ -72,6 +85,25 @@ protected override void OnInitialized()
         _menuBuilder.Build();
     }
 
+    protected virtual void Dispose(bool disposing)
+    {
+        if (!_disposedValue)
+        {
+            if (disposing)
+            {
+                _newInstanceHandled?.Dispose();
+            }
+
+            _disposedValue = true;
+        }
+    }
+
+    public void Dispose()
+    {
+        Dispose(disposing: true);
+        GC.SuppressFinalize(this);
+    }
+
     private void InitializeBeforeUI()
     {
         Handle = this;
@@ -145,9 +177,8 @@ private void Window_PointerReleased(object? sender, PointerReleasedEventArgs e)
 
     private async Task InitializeDataFolder()
     {
-        var documentsFolder = await StorageProvider.TryGetWellKnownFolderAsync(Avalonia.Platform.Storage.WellKnownFolder.Documents);
-        var pixedFolder = await documentsFolder.CreateFolderAsync("Pixed");
-        await documentsFolder.CreateFolderAsync("Pixed/Palettes");
+        var pixedFolder = await StorageProvider.GetPixedFolder();
+        await pixedFolder.CreateFolderAsync("Palettes");
         _applicationData.Initialize(pixedFolder);
     }