app: move pinging loop to daemon thread

app/Daemon.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Threading;
+
+namespace ParsecVDisplay
+{
+    internal static class Daemon
+    {
+        static Thread EventThread;
+        static CancellationTokenSource Cancellation;
+
+        public static void Start()
+        {
+            Cancellation = new CancellationTokenSource();
+            var token = Cancellation.Token;
+
+            EventThread = new Thread(() => EventLoop(token));
+            EventThread.IsBackground = false;
+            EventThread.Priority = ThreadPriority.Highest;
+
+            EventThread.Start();
+        }
+
+        public static void Stop()
+        {
+            Cancellation?.Cancel();
+            EventThread?.Join();
+        }
+
+        static void EventLoop(CancellationToken cancellation)
+        {
+            while (true)
+            {
+                if (cancellation.IsCancellationRequested)
+                    break;
+
+                ParsecVDD.Ping();
+
+                Thread.Sleep(100);
+            }
+        }
+    }
+}

app/ParsecVDisplay.csproj

@@ -89,6 +89,7 @@
       <DependentUpon>DisplayItem.xaml</DependentUpon>
     </Compile>
     <Compile Include="Config.cs" />
+    <Compile Include="Daemon.cs" />
     <Compile Include="Device.cs" />
     <Compile Include="Display.cs" />
     <Compile Include="Helper.cs" />

app/Program.cs

@@ -45,7 +45,11 @@ namespace ParsecVDisplay
                 if (InitDriver())
                 {
                     Helper.StayAwake(false);
+                    Daemon.Start();
+
                     Application.Run(new Tray());
+
+                    Daemon.Stop();
                     ParsecVDD.Uninit();
                 }
             }

app/Tray.cs

@@ -16,7 +16,6 @@ namespace ParsecVDisplay
         static System.Windows.Controls.ContextMenu Menu;
 
         Thread AppThread;
-        System.Windows.Forms.Timer VddTimer;
 
         ToolStripMenuItem MI_RunOnStartup;
         ToolStripMenuItem MI_RestoreDisplays;
@@ -46,11 +45,6 @@ namespace ParsecVDisplay
             AppThread.SetApartmentState(ApartmentState.STA);
             AppThread.Start();
 
-            VddTimer = new System.Windows.Forms.Timer();
-            VddTimer.Interval = 50;
-            VddTimer.Tick += VddTimer_Tick;
-            VddTimer.Start();
-
             var appName = Program.AppName;
             var appIcon = Icon.ExtractAssociatedIcon(Application.ExecutablePath);
 
@@ -281,9 +275,6 @@ namespace ParsecVDisplay
                     Config.DisplayCount = displays.Count;
             }
 
-            VddTimer.Tick -= VddTimer_Tick;
-            VddTimer.Stop();
-
             App.Current?.Dispatcher.Invoke(App.Current.Shutdown);
             AppThread.Join();
 
@@ -295,7 +286,6 @@ namespace ParsecVDisplay
         {
             if (disposing)
             {
-                VddTimer.Dispose();
                 TrayIcon.Dispose();
             }