Исправление скрола логов

.semver.txt

@@ -1 +1 @@
-1.0.20
+1.0.22

src/MonsterMonitor/MonsterMonitor.csproj

@@ -6,10 +6,10 @@
     <LangVersion>7.3</LangVersion>
     <RootNamespace>MonsterMonitor</RootNamespace>
     <AssemblyName>devenv</AssemblyName>
-    <AssemblyVersion>1.0.20</AssemblyVersion>
+    <AssemblyVersion>1.0.22</AssemblyVersion>
-    <Version>1.0.20</Version>
+    <Version>1.0.22</Version>
-    <FileVersion>1.0.20</FileVersion>
+    <FileVersion>1.0.22</FileVersion>
-    <InformationalVersion>1.0.20</InformationalVersion>
+    <InformationalVersion>1.0.22</InformationalVersion>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Costura.Fody" Version="6.0.0">

src/MonsterMonitor/Program.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading;
 using System.Windows.Forms;
 using MonsterMonitor.UI;
 
@@ -6,9 +7,21 @@ namespace MonsterMonitor
 {
     internal static class Program
     {
+        private const string SingleInstanceMutexName = @"Global\MonsterMonitor_v2_SingleInstance";
+        private const string ActivateEventName = @"Global\MonsterMonitor_v2_Activate";
+
         [STAThread]
         private static void Main()
         {
+            var createdNew = false;
+            using (var mutex = new Mutex(true, SingleInstanceMutexName, out createdNew))
+            {
+                if (!createdNew)
+                {
+                    TrySignalExistingInstance();
+                    return;
+                }
+
             Application.ThreadException += (sender, args) =>
             {
                 MessageBox.Show(
@@ -29,7 +42,38 @@ namespace MonsterMonitor
 
             Application.EnableVisualStyles();
             Application.SetCompatibleTextRenderingDefault(false);
-            Application.Run(new MainForm());
+                using (var activateEvent = new EventWaitHandle(false, EventResetMode.AutoReset, ActivateEventName))
+                {
+                    var form = new MainForm();
+                    ThreadPool.RegisterWaitForSingleObject(
+                        activateEvent,
+                        (state, timedOut) =>
+                        {
+                            var mainForm = state as MainForm;
+                            mainForm?.RestoreAndActivateFromExternalSignal();
+                        },
+                        form,
+                        Timeout.Infinite,
+                        false);
+
+                    Application.Run(form);
+                }
+            }
+        }
+
+        private static void TrySignalExistingInstance()
+        {
+            try
+            {
+                using (var activateEvent = EventWaitHandle.OpenExisting(ActivateEventName))
+                {
+                    activateEvent.Set();
+                }
+            }
+            catch
+            {
+                // Если не удалось отправить сигнал, просто завершаем второй инстанс.
+            }
         }
     }
 }

src/MonsterMonitor/UI/MainForm.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Drawing;
+using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using System.Windows.Forms;
 using MonsterMonitor.Models;
@@ -9,6 +10,9 @@ namespace MonsterMonitor.UI
 {
     public sealed class MainForm : Form
     {
+        private const int EmGetFirstVisibleLine = 0x00CE;
+        private const int EmLineScroll = 0x00B6;
+
         private readonly RichTextBox _console = new RichTextBox();
         private readonly Button _btnSettings = new Button();
         private readonly Button _btnExit = new Button();
@@ -135,6 +139,33 @@ namespace MonsterMonitor.UI
             Activate();
         }
 
+        public void RestoreAndActivateFromExternalSignal()
+        {
+            if (InvokeRequired)
+            {
+                BeginInvoke(new Action(RestoreAndActivateFromExternalSignal));
+                return;
+            }
+
+            _log.Info("Получен сигнал активации от второго инстанса.");
+
+            if (!Visible)
+            {
+                Show();
+            }
+
+            if (WindowState == FormWindowState.Minimized)
+            {
+                WindowState = FormWindowState.Normal;
+            }
+
+            // Небольшой трюк для надежного вывода окна на передний план.
+            TopMost = true;
+            Activate();
+            TopMost = false;
+            Focus();
+        }
+
         private void ExitApplication()
         {
             _allowClose = true;
@@ -165,14 +196,49 @@ namespace MonsterMonitor.UI
                 return;
             }
 
+            var wasNearBottom = IsConsoleNearBottom();
+            var firstVisibleLineBeforeAppend = GetFirstVisibleLine(_console);
+
             _console.SelectionStart = _console.TextLength;
             _console.SelectionLength = 0;
             _console.SelectionColor = GetColor(entry.Level);
             _console.AppendText($"[{entry.Timestamp:HH:mm:ss}] [{entry.Level}] {entry.Message}{Environment.NewLine}");
             _console.SelectionColor = _console.ForeColor;
-            _console.ScrollToCaret();
+
+            if (wasNearBottom)
+            {
+                _console.ScrollToCaret();
+                return;
+            }
+
+            var firstVisibleLineAfterAppend = GetFirstVisibleLine(_console);
+            var linesToRestore = firstVisibleLineBeforeAppend - firstVisibleLineAfterAppend;
+            if (linesToRestore != 0)
+            {
+                SendMessage(_console.Handle, EmLineScroll, IntPtr.Zero, (IntPtr)linesToRestore);
+            }
         }
 
+        private bool IsConsoleNearBottom()
+        {
+            if (_console.TextLength == 0)
+            {
+                return true;
+            }
+
+            var bottomLeftPoint = new Point(1, Math.Max(0, _console.ClientSize.Height - 1));
+            var lastVisibleCharIndex = _console.GetCharIndexFromPosition(bottomLeftPoint);
+            return lastVisibleCharIndex >= _console.TextLength - 2;
+        }
+
+        private static int GetFirstVisibleLine(RichTextBox richTextBox)
+        {
+            return SendMessage(richTextBox.Handle, EmGetFirstVisibleLine, IntPtr.Zero, IntPtr.Zero).ToInt32();
+        }
+
+        [DllImport("user32.dll", CharSet = CharSet.Auto)]
+        private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
+
         private void ConfigureUpdateTimer()
         {
             _updateTimer.Interval = (int)TimeSpan.FromHours(1).TotalMilliseconds;