A kind of a single instance mode

only first launched instance creates system tray icon and does not quit

Author: wl2776

src/App.axaml.cs

@@ -169,9 +169,9 @@ public static void SetTheme(string theme, string themeOverridesFile)
             }
         }
 
-        public static void SetupTrayIcon(bool enable)
+        public void SetupTrayIcon(bool enable)
         {
-            if (enable)
+            if (enable && Native.OS.EnsureSingleInstance())
             {
                 var icons = new TrayIcons {
                     new TrayIcon {
@@ -186,6 +186,7 @@ public static void SetupTrayIcon(bool enable)
                 };
                 icons[0].Clicked += (_, _) => ToggleWindow();
                 TrayIcon.SetIcons(Current, icons);
+                _createdSystemTrayIcon = true;
             }
         }
 
@@ -591,5 +592,6 @@ private void ShowSelfUpdateResult(object data)
         private ResourceDictionary _activeLocale = null;
         private ResourceDictionary _themeOverrides = null;
         private ResourceDictionary _fontsOverrides = null;
+        private bool _createdSystemTrayIcon = false;
     }
 }

src/Native/Linux.cs

@@ -11,6 +11,7 @@ namespace SourceGit.Native
     [SupportedOSPlatform("linux")]
     internal class Linux : OS.IBackend
     {
+        private FileStream _fs = null;
         public void SetupApp(AppBuilder builder)
         {
             builder.With(new X11PlatformOptions() { EnableIme = true });
@@ -97,6 +98,26 @@ public void OpenWithDefaultEditor(string file)
             }
         }
 
+        public bool EnsureSingleInstance()
+        {
+            var pidfile = Path.Combine(Path.GetTempPath(), "sourcegit.pid");
+            var pid = Process.GetCurrentProcess().Id.ToString();
+            Console.WriteLine("pid " + pid);
+
+            try
+            {
+                _fs = File.OpenWrite(pidfile);
+                _fs.Lock(0, 1000);
+                new StreamWriter(_fs).Write(pid);
+                return true;
+            }
+            catch (IOException)
+            {
+                Console.WriteLine("another SourceGit is running");
+                return false;
+            }
+        }
+        
         private string FindExecutable(string filename)
         {
             var pathVariable = Environment.GetEnvironmentVariable("PATH") ?? string.Empty;

src/Native/MacOS.cs

@@ -86,5 +86,7 @@ public void OpenWithDefaultEditor(string file)
         {
             Process.Start("open", $"\"{file}\"");
         }
+
+        public bool EnsureSingleInstance() { return true; }
     }
 }

src/Native/OS.cs

@@ -23,6 +23,8 @@ public interface IBackend
             void OpenInFileManager(string path, bool select);
             void OpenBrowser(string url);
             void OpenWithDefaultEditor(string file);
+
+            bool EnsureSingleInstance();
         }
 
         public static string DataDir {
@@ -217,6 +219,11 @@ private static void UpdateGitVersion()
         [GeneratedRegex(@"^git version[\s\w]*(\d+)\.(\d+)[\.\-](\d+).*$")]
         private static partial Regex REG_GIT_VERSION();
 
+        public static bool EnsureSingleInstance()
+        {
+            return _backend.EnsureSingleInstance();
+        }
+
         private static IBackend _backend = null;
         private static string _gitExecutable = string.Empty;
     }

src/Native/Windows.cs

@@ -14,6 +14,8 @@ namespace SourceGit.Native
     [SupportedOSPlatform("windows")]
     internal class Windows : OS.IBackend
     {
+        private FileStream _fs = null;
+        
         [StructLayout(LayoutKind.Sequential)]
         internal struct RTL_OSVERSIONINFOEX
         {
@@ -393,5 +395,25 @@ private string FindVSSolutionFile(DirectoryInfo dir, int leftDepth)
 
             return null;
         }
+
+        public bool EnsureSingleInstance()
+        {
+            var pidfile = Path.Combine(Path.GetTempPath(), "sourcegit.pid");
+            var pid = Process.GetCurrentProcess().Id.ToString();
+            Console.WriteLine("pid " + pid);
+
+            try
+            {
+                _fs = File.OpenWrite(pidfile);
+                _fs.Lock(0, 1000);
+                new StreamWriter(_fs).Write(pid);
+                return true;
+            }
+            catch (IOException)
+            {
+                Console.WriteLine("another SourceGit is running");
+                return false;
+            }
+        }
     }
 }