Default to preventing multiple instances

Allow multiple instances if overridden with command line parameter
Allow starting minimised to tray with command line parameter

ntfysh_client/MainForm.cs

@@ -13,17 +13,43 @@ namespace ntfysh_client
     public partial class MainForm : Form
     {
         private readonly NotificationListener _notificationListener;
+        private bool _startInTray;
         private bool _trueExit;
 
-        public MainForm(NotificationListener notificationListener)
+        public MainForm(NotificationListener notificationListener, bool startInTray = false)
         {
             _notificationListener = notificationListener;
+            _startInTray = startInTray;
             _notificationListener.OnNotificationReceive += OnNotificationReceive;
             _notificationListener.OnConnectionMultiAttemptFailure += OnConnectionMultiAttemptFailure;
             _notificationListener.OnConnectionCredentialsFailure += OnConnectionCredentialsFailure;
             
             InitializeComponent();
         }
+        
+        private void MainForm_Load(object sender, EventArgs e) => LoadTopics();
+        
+        protected override void SetVisibleCore(bool value)
+        {
+            if (_startInTray)
+            {
+                _startInTray = false;
+                
+                /*
+                 * TODO This little workaround prevents the window from appearing with a flash, but the taskbar icon appears for a moment.
+                 *
+                 * TODO This is because we must call SetVisibleCore(true) for the initial load events in the MainForm to fire, which is what triggers the listener
+                 */
+                Opacity = 0;
+                base.SetVisibleCore(true);
+                base.SetVisibleCore(false);
+                Opacity = 1;
+                
+                return;
+            }
+            
+            base.SetVisibleCore(value);
+        }
 
         private void OnNotificationReceive(object sender, NotificationReceiveEventArgs e)
         {
@@ -42,8 +68,6 @@ namespace ntfysh_client
             MessageBox.Show($"Connecting to topic ID '{topic.TopicId}' on server '{topic.ServerUrl}' failed because {reason}.\n\nThis topic ID will be ignored and you will not receive notifications for it until you correct the credentials.", "Connection Authentication Failure", MessageBoxButtons.OK, MessageBoxIcon.Error);
         }
 
-        private void MainForm_Load(object sender, EventArgs e) => LoadTopics();
-
         private void subscribeNewTopic_Click(object sender, EventArgs e)
         {
             using SubscribeDialog dialog = new SubscribeDialog(notificationTopics);

ntfysh_client/MainForm.resx

@@ -67,7 +67,7 @@
   <data name="showControlWindowToolStripMenuItem.Image" type="System.Drawing.Bitmap, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
     <value>
         iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABGdBTUEAALGPC/xhBQAAACBjSFJNAAB6
-        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA6+AAAOvgHqQrHAAAAAiklE
+        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA69AAAOvQFH+5CtAAAAiklE
         QVQ4T8WPQQqAIBBFvUOrXIhu3dcZOkqtu5R1ia4SdRDrxyyGGKmBIOGBDL6nmk9WCGE9yUpW0q9Ads7V
         GuCQ/kHAe79joAEO6dcLFmttpQEO6c+Bvpm2oZ0zwB4zVQBiF8cIsMdMDPCb+G2vA/wgP/z6C6WAhBgo
         fUFCDGi4BxIGShLpvy5jDoPes/0oNG3VAAAAAElFTkSuQmCC
@@ -76,7 +76,7 @@
   <data name="exitToolStripMenuItem.Image" type="System.Drawing.Bitmap, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
     <value>
         iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABGdBTUEAALGPC/xhBQAAACBjSFJNAAB6
-        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA6+AAAOvgHqQrHAAAAAgUlE
+        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA69AAAOvQFH+5CtAAAAgUlE
         QVQ4T2OgGjjOLq4AZeIFWNWBBI9yib06zC3uABXCCkDyIHVYDTnMI2pzhEvs5VFucSeoEAo4wiNii08e
         DHAZQshwFICumCTNMADyK1gTl2gJiCYUNlgBSDPQ1v8gGipEPKDIBRSFAa6oIsoQQvGM1xCqpESsglgA
         seroBRgYAOoOWBJbfVcRAAAAAElFTkSuQmCC
@@ -267,7 +267,7 @@
   <data name="exitToolStripMenuItem1.Image" type="System.Drawing.Bitmap, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
     <value>
         iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABGdBTUEAALGPC/xhBQAAACBjSFJNAAB6
-        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA6+AAAOvgHqQrHAAAAAgUlE
+        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA69AAAOvQFH+5CtAAAAgUlE
         QVQ4T2OgGjjOLq4AZeIFWNWBBI9yib06zC3uABXCCkDyIHVYDTnMI2pzhEvs5VFucSeoEAo4wiNii08e
         DHAZQshwFICumCTNMADyK1gTl2gJiCYUNlgBSDPQ1v8gGipEPKDIBRSFAa6oIsoQQvGM1xCqpESsglgA
         seroBRgYAOoOWBJbfVcRAAAAAElFTkSuQmCC
@@ -276,7 +276,7 @@
   <data name="ntfyshWebsiteToolStripMenuItem.Image" type="System.Drawing.Bitmap, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
     <value>
         iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABGdBTUEAALGPC/xhBQAAACBjSFJNAAB6
-        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA6+AAAOvgHqQrHAAAABDElE
+        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA69AAAOvQFH+5CtAAABDElE
         QVQ4T91RO3bCQAzUy3uhChdJnTVlCj5FcMsZsF1jmy4XycPrzl6fBLgEXMFp4srRiF0wcaBP5j0VI2m0
         4zH9EwSq8gPP7ELPNFxtpxrbn9vVPkSsykOkqvHi2QxsWwAevhQTzG8eCb1yD7Glv2I5MlM+sLX0GqEq
         6+jVPFl6QZz7lOgdJVnzuMq/sEepbsGln2YnR3AAm0IcIE71geJsTO9mcOWAOa3zicxxxGWApXMGabaH
@@ -287,7 +287,7 @@
   <data name="aboutToolStripMenuItem.Image" type="System.Drawing.Bitmap, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
     <value>
         iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABGdBTUEAALGPC/xhBQAAACBjSFJNAAB6
-        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA6+AAAOvgHqQrHAAAAAwUlE
+        JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAACXBIWXMAAA69AAAOvQFH+5CtAAAAwUlE
         QVQ4T2OgClBUVHwAxP9JxA+g2sEG/JeTk5MkBYP0QLVTwQAFBYXHIAFSMEgPVDvYBfulpKSEScEgPVDt
         dDIA6OTNQHX/YXysBjAxMcUxMjKuBrGB9DIgPxqmARhwOUBD3sD4WA0QERGRBHLvCwoKygLpm6KiohIw
         DVBNz5HY2L0AtHkOEE8F4okgvoyMjDSSJsIGsLOzuwKFfnBycppJS0vLAJ39BUQTbQA6RnYBMkY3YAVI

ntfysh_client/Program.cs

@@ -1,25 +1,46 @@
 using System;
-using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
 using System.Linq;
-using System.Threading.Tasks;
+using System.Reflection;
 using System.Windows.Forms;
 
 namespace ntfysh_client
 {
     static class Program
     {
-        private static readonly NotificationListener NotificationListener = new NotificationListener();
+        private static readonly NotificationListener NotificationListener = new();
         
         /// <summary>
         /// The main entry point for the application.
         /// </summary>
         [STAThread]
-        static void Main()
+        private static void Main(string[] args)
         {
+            args = args.Select(a => a.ToLower()).ToArray();
+
+            if (args.Contains("-h") || args.Contains("--help"))
+            {
+                MessageBox.Show("Help:\n    -h\n    --help\n\nStart in tray:\n    -t\n    --start-in-tray\n\nAllow multiple instances:\n    -m\n    --allow-multiple-instances", "Help Menu", MessageBoxButtons.OK, MessageBoxIcon.Information);
+                return;
+            }
+
+            bool startInTray = args.Contains("-t") || args.Contains("--start-in-tray");
+            bool allowMultipleInstances = args.Contains("-m") || args.Contains("--allow-multiple-instances");
+
+            if (Process.GetProcessesByName(Path.GetFileNameWithoutExtension(Assembly.GetEntryAssembly()!.Location)).Length > 1)
+            {
+                if (!allowMultipleInstances)
+                {
+                    MessageBox.Show("Another instance is already running.\n\nUse -m or --allow-multiple-instances if you wish to start a second duplicate instance.\n\nThis instance will now close.", "Multiple Instances", MessageBoxButtons.OK, MessageBoxIcon.Warning);
+                    return;
+                }
+            }
+            
             Application.SetHighDpiMode(HighDpiMode.SystemAware);
             Application.EnableVisualStyles();
             Application.SetCompatibleTextRenderingDefault(false);
-            Application.Run(new MainForm(NotificationListener));
+            Application.Run(new MainForm(NotificationListener, startInTray));
         }
     }
 }