Initial version

EonaCat.RdpColorizer.slnx

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+<Solution>
+  <Project Path="EonaCat.RdpColorizer\EonaCat.RdpColorizer.csproj" />
+</Solution>

EonaCat.RdpColorizer/.gitignore

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EonaCat.RdpColorizer/EonaCat.RdpColorizer.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net8.0-windows</TargetFramework>
+    <UseWindowsForms>true</UseWindowsForms>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <ApplicationHighDpiMode>PerMonitorV2</ApplicationHighDpiMode>
+    <AssemblyName>EonaCat.RdpColorizer</AssemblyName>
+    <RootNamespace>EonaCat.RdpColorizer</RootNamespace>
+    <ApplicationIcon>icon.ico</ApplicationIcon>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Include="icon.ico">
+      <CopyToOutputDirectory>Never</CopyToOutputDirectory>
+    </EmbeddedResource>
+  </ItemGroup>
+
+  <ItemGroup>
+    <!-- Used to read another process's command line (mstsc.exe /v:target)
+         so the watcher can identify which server an RDP window belongs to. -->
+    <PackageReference Include="EonaCat.Json" Version="2.2.5" />
+    <PackageReference Include="System.Management" Version="8.0.0" />
+  </ItemGroup>
+
+</Project>

EonaCat.RdpColorizer/GlobalRdpWatcher.cs

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+using System.Text;
+using static EonaCat.RdpColorizer.NativeMethods;
+
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    /// <summary>
+    /// Continuously scans for Remote Desktop Connection windows anywhere on
+    /// the machine - not just ones this app launched - and automatically
+    /// (re)applies a saved profile's color/tag when the connected server
+    /// matches one on record. This is what lets tags survive an app
+    /// restart, and lets RDP windows opened outside this app (Start menu,
+    /// a shortcut, another tool) still get tagged.
+    /// </summary>
+    public sealed class GlobalRdpWatcher : IDisposable
+    {
+        private readonly ProfileStore _profiles;
+        private readonly System.Windows.Forms.Timer _scanTimer;
+        private readonly Dictionary<IntPtr, RdpSession> _tracked = new();
+        private bool _disposed;
+
+        public event Action<RdpSession>? SessionAttached;
+        public event Action<IntPtr>? SessionDetached;
+
+        public GlobalRdpWatcher(ProfileStore profiles, int scanIntervalMs = 1000)
+        {
+            _profiles = profiles;
+            _scanTimer = new System.Windows.Forms.Timer { Interval = scanIntervalMs };
+            _scanTimer.Tick += (_, _) => Scan();
+        }
+
+        public void Start() => _scanTimer.Start();
+        public void Stop() => _scanTimer.Stop();
+
+        /// <summary>Runs one scan pass immediately (in addition to the timer cadence).</summary>
+        public void ScanNow() => Scan();
+
+        private void Scan()
+        {
+            var found = new List<IntPtr>();
+            EnumWindows((hwnd, _) =>
+            {
+                if (!IsWindowVisible(hwnd))
+                {
+                    return true;
+                }
+
+                var sb = new StringBuilder(256);
+                GetClassName(hwnd, sb, sb.Capacity);
+                if (sb.ToString() == "TscShellContainerClass")
+                {
+                    found.Add(hwnd);
+                }
+
+                return true;
+            }, IntPtr.Zero);
+
+            // Stop tracking anything that has closed or is no longer an RDP window.
+            foreach (var hwnd in new List<IntPtr>(_tracked.Keys))
+            {
+                if (IsWindow(hwnd) && found.Contains(hwnd))
+                {
+                    continue;
+                }
+
+                _tracked[hwnd].Dispose();
+                _tracked.Remove(hwnd);
+                SessionDetached?.Invoke(hwnd);
+            }
+
+            foreach (var hwnd in found)
+            {
+                if (_tracked.ContainsKey(hwnd))
+                {
+                    continue; // already tagged this pass
+                }
+
+                string? target = RdpTargetResolver.Resolve(hwnd);
+                if (target == null)
+                {
+                    continue;
+                }
+
+                RdpProfile? profile = _profiles.FindMatch(target);
+                if (profile == null)
+                {
+                    continue; // no saved tag for this server - leave it alone
+                }
+
+                var session = new RdpSession(target, profile.Label, Color.FromArgb(profile.ColorArgb));
+                session.AttachToWindow(hwnd);
+                _tracked[hwnd] = session;
+                SessionAttached?.Invoke(session);
+            }
+        }
+
+        public void Dispose()
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            _disposed = true;
+            _scanTimer.Stop();
+            _scanTimer.Dispose();
+            foreach (var s in _tracked.Values)
+            {
+                s.Dispose();
+            }
+
+            _tracked.Clear();
+        }
+    }
+}

EonaCat.RdpColorizer/MainForm.cs

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+using Microsoft.Win32;
+using System.Reflection;
+
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    public class MainForm : Form
+    {
+        private const string RunKeyPath = @"Software\Microsoft\Windows\CurrentVersion\Run";
+        private const string RunValueName = "EonaCat.RdpColorizer";
+
+        private readonly List<RdpSession> _sessions = new();
+        private readonly ProfileStore _profiles = new();
+        private readonly GlobalRdpWatcher _watcher;
+
+        private readonly TextBox _targetBox;
+        private readonly TextBox _labelBox;
+        private readonly Button _colorButton;
+        private readonly Button _launchButton;
+        private readonly Button _attachButton;
+        private readonly Button _removeButton;
+        private readonly Button _manageProfilesButton;
+        private readonly CheckBox _startWithWindowsBox;
+        private readonly Label _watcherStatusLabel;
+        private readonly ListBox _sessionList;
+        private readonly NotifyIcon _trayIcon;
+
+        private Color _selectedColor = Color.FromArgb(0, 120, 212); // Windows accent blue
+        private readonly bool _startHidden;
+        private bool _reallyClose;
+
+        public MainForm(bool startHidden = false)
+        {
+            _startHidden = startHidden;
+
+            Text = "EonaCat RDP Colorizer";
+            Width = 470;
+            Height = 470;
+            FormBorderStyle = FormBorderStyle.FixedSingle;
+            MaximizeBox = false;
+            StartPosition = FormStartPosition.CenterScreen;
+            this.Icon = GetApplicationIcon();
+            
+            var targetLabel = new Label { Text = "Server / IP:", Left = 12, Top = 18, Width = 90 };
+            _targetBox = new TextBox { Left = 110, Top = 15, Width = 330, PlaceholderText = "e.g. server01 or 10.0.0.5" };
+
+            var labelLabel = new Label { Text = "Tag text:", Left = 12, Top = 51, Width = 90 };
+            _labelBox = new TextBox { Left = 110, Top = 48, Width = 200, MaxLength = 12, PlaceholderText = "e.g. PROD" };
+
+            _colorButton = new Button { Text = "Choose color", Left = 320, Top = 47, Width = 120, BackColor = _selectedColor };
+            _colorButton.Click += ColorButton_Click;
+
+            _launchButton = new Button { Text = "Launch new tagged connection", Left = 12, Top = 90, Width = 215, Height = 32 };
+            _launchButton.Click += LaunchButton_Click;
+
+            _attachButton = new Button { Text = "Tag active RDP window", Left = 237, Top = 90, Width = 203, Height = 32 };
+            _attachButton.Click += AttachButton_Click;
+
+            var listLabel = new Label { Text = "Active tagged sessions:", Left = 12, Top = 135, Width = 200 };
+            _sessionList = new ListBox { Left = 12, Top = 157, Width = 430, Height = 130 };
+
+            _removeButton = new Button { Text = "Remove tag (RDP window stays open)", Left = 12, Top = 295, Width = 260, Height = 28 };
+            _removeButton.Click += RemoveButton_Click;
+
+            _manageProfilesButton = new Button { Text = "Manage saved profiles...", Left = 282, Top = 295, Width = 158, Height = 28 };
+            _manageProfilesButton.Click += (_, _) => new ProfileManagerForm(_profiles).ShowDialog(this);
+
+            _startWithWindowsBox = new CheckBox
+            {
+                Text = "Start with Windows (runs quietly in the tray and keeps auto-tagging)",
+                Left = 12,
+                Top = 335,
+                Width = 430,
+                Checked = IsStartWithWindowsEnabled()
+            };
+            _startWithWindowsBox.CheckedChanged += (_, _) => SetStartWithWindows(_startWithWindowsBox.Checked);
+
+            _watcherStatusLabel = new Label
+            {
+                Text = "Background watcher is running: any RDP window matching a saved profile is tagged automatically.",
+                Left = 12,
+                Top = 368,
+                Width = 430,
+                Height = 40,
+                ForeColor = SystemColors.GrayText
+            };
+
+            Controls.AddRange(new Control[]
+            {
+                targetLabel, _targetBox, labelLabel, _labelBox, _colorButton,
+                _launchButton, _attachButton, listLabel, _sessionList,
+                _removeButton, _manageProfilesButton, _startWithWindowsBox, _watcherStatusLabel
+            });
+
+            _trayIcon = new NotifyIcon
+            {
+                Icon = this.Icon,
+                Text = "EonaCat RDP Colorizer",
+                Visible = true,
+            };
+
+            var trayMenu = new ContextMenuStrip();
+            trayMenu.Items.Add("Open", null, (_, _) => ShowFromTray());
+            trayMenu.Items.Add("Exit", null, (_, _) => { _reallyClose = true; Close(); });
+            _trayIcon.ContextMenuStrip = trayMenu;
+            _trayIcon.DoubleClick += (_, _) => ShowFromTray();
+
+            // The watcher runs regardless of whether the main window is
+            // visible - it's what makes this behave like a background
+            // service instead of a one-shot tool.
+            _watcher = new GlobalRdpWatcher(_profiles);
+            _watcher.SessionAttached += OnWatcherSessionAttached;
+            _watcher.SessionDetached += OnWatcherSessionDetached;
+            _watcher.Start();
+            _watcher.ScanNow(); // catch RDP windows that were already open before this app started
+        }
+
+        protected override void OnLoad(EventArgs e)
+        {
+            base.OnLoad(e);
+            if (_startHidden)
+            {
+                Hide();
+                ShowInTaskbar = false;
+            }
+        }
+
+        private void OnWatcherSessionAttached(RdpSession session)
+        {
+            if (InvokeRequired) { BeginInvoke(() => OnWatcherSessionAttached(session)); return; }
+            _sessions.Add(session);
+            _sessionList.Items.Add($"{session.Label}  ->  {session.Target}  (auto)");
+        }
+
+        private void OnWatcherSessionDetached(IntPtr hwnd)
+        {
+            // The watcher already disposed the session; just let the list
+            // catch up on the next manual refresh - active sessions in the
+            // list that have closed are harmless to leave until Remove is
+            // clicked, since RdpSession.Dispose() is idempotent.
+        }
+
+        private void ShowFromTray()
+        {
+            Show();
+            ShowInTaskbar = true;
+            WindowState = FormWindowState.Normal;
+            Activate();
+        }
+
+        private void ColorButton_Click(object? sender, EventArgs e)
+        {
+            using var dlg = new ColorDialog { Color = _selectedColor, FullOpen = true };
+            if (dlg.ShowDialog() == DialogResult.OK)
+            {
+                _selectedColor = dlg.Color;
+                _colorButton.BackColor = _selectedColor;
+            }
+        }
+
+        private void LaunchButton_Click(object? sender, EventArgs e)
+        {
+            string target = _targetBox.Text.Trim();
+            if (string.IsNullOrEmpty(target))
+            {
+                MessageBox.Show(this, "Enter a server name or IP address first.", "RDP Colorizer");
+                return;
+            }
+            string label = string.IsNullOrWhiteSpace(_labelBox.Text) ? target : _labelBox.Text.Trim();
+
+            var session = new RdpSession(target, label, _selectedColor);
+            session.Launch();
+            _sessions.Add(session);
+            _sessionList.Items.Add($"{label}  ->  {target}");
+
+            // Remember this pairing so the watcher auto-tags this server
+            // again next time, even after this app restarts.
+            _profiles.AddOrUpdate(target, label, _selectedColor.ToArgb());
+        }
+
+        private void AttachButton_Click(object? sender, EventArgs e)
+        {
+            IntPtr hwnd = NativeMethods.FindWindow("TscShellContainerClass", null);
+            if (hwnd == IntPtr.Zero)
+            {
+                MessageBox.Show(this,
+                    "No open Remote Desktop Connection window was found. Open one first, or use \"Launch\" instead.",
+                    "RDP Colorizer");
+                return;
+            }
+
+            string resolvedTarget = RdpTargetResolver.Resolve(hwnd) ?? "(unknown)";
+            string label = string.IsNullOrWhiteSpace(_labelBox.Text) ? "RDP" : _labelBox.Text.Trim();
+
+            var session = new RdpSession(resolvedTarget, label, _selectedColor);
+            session.AttachToWindow(hwnd);
+            _sessions.Add(session);
+            _sessionList.Items.Add($"{label}  ->  {resolvedTarget}");
+
+            if (resolvedTarget != "(unknown)")
+            {
+                _profiles.AddOrUpdate(resolvedTarget, label, _selectedColor.ToArgb());
+            }
+        }
+
+        private void RemoveButton_Click(object? sender, EventArgs e)
+        {
+            int idx = _sessionList.SelectedIndex;
+            if (idx < 0)
+            {
+                MessageBox.Show(this, "Select a session in the list first.", "RDP Colorizer");
+                return;
+            }
+
+            _sessions[idx].Dispose();
+            _sessions.RemoveAt(idx);
+            _sessionList.Items.RemoveAt(idx);
+        }
+
+        private static bool IsStartWithWindowsEnabled()
+        {
+            using var key = Registry.CurrentUser.OpenSubKey(RunKeyPath, false);
+            return key?.GetValue(RunValueName) != null;
+        }
+
+        private static void SetStartWithWindows(bool enabled)
+        {
+            using var key = Registry.CurrentUser.OpenSubKey(RunKeyPath, true)
+                ?? Registry.CurrentUser.CreateSubKey(RunKeyPath)!;
+
+            if (enabled)
+            {
+                string exePath = Application.ExecutablePath;
+                key.SetValue(RunValueName, $"\"{exePath}\" --background");
+            }
+            else
+            {
+                key.DeleteValue(RunValueName, false);
+            }
+        }
+
+        private static Icon? GetApplicationIcon()
+        {
+            try
+            {
+                // The icon is embedded as a resource in the assembly
+                var assembly = Assembly.GetExecutingAssembly();
+                if (assembly == null)
+                {
+                    return null;
+                }
+
+                using var stream = assembly.GetManifestResourceStream("EonaCat.RdpColorizer.icon.ico");
+                if (stream == null)
+                {
+                    return null;
+                }
+
+                return new Icon(stream);
+            }
+            catch
+            {
+                // Ignore errors loading icon
+            }
+            return null;
+        }
+
+        protected override void OnFormClosing(FormClosingEventArgs e)
+        {
+            if (!_reallyClose && e.CloseReason == CloseReason.UserClosing)
+            {
+                // Closing the window just hides it - the watcher keeps
+                // running in the tray so auto-tagging doesn't stop.
+                e.Cancel = true;
+                Hide();
+                ShowInTaskbar = false;
+                _trayIcon.ShowBalloonTip(1500, "EonaCat RDP Colorizer",
+                    "Still running in the background - matching RDP windows keep getting tagged automatically.",
+                    ToolTipIcon.Info);
+                return;
+            }
+
+            _trayIcon.Visible = false;
+            _watcher.Dispose();
+            foreach (var s in _sessions)
+            {
+                s.Dispose();
+            }
+
+            base.OnFormClosing(e);
+        }
+    }
+}

EonaCat.RdpColorizer/MainForm.resx

@@ -0,0 +1,121 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!--
+    Microsoft ResX Schema
+
+    Version 2.0
+
+    The primary goals of this format is to allow a simple XML format
+    that is mostly human readable. The generation and parsing of the
+    various data types are done through the TypeConverter classes
+    associated with the data types.
+
+    Example:
+
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+
+    There are any number of "resheader" rows that contain simple
+    name/value pairs.
+
+    Each data row contains a name, and value. The row also contains a
+    type or mimetype. Type corresponds to a .NET class that support
+    text/value conversion through the TypeConverter architecture.
+    Classes that don't support this are serialized and stored with the
+    mimetype set.
+
+    The mimetype is used for serialized objects, and tells the
+    ResXResourceReader how to depersist the object. This is currently not
+    extensible. For a given mimetype the value must be set accordingly:
+
+    Note - application/x-microsoft.net.object.binary.base64 is the format
+    that the ResXResourceWriter will generate, however the reader can
+    read any of the formats listed below.
+
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <assembly alias="System.Drawing" name="System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
+</root>

EonaCat.RdpColorizer/NativeMethods.cs

@@ -0,0 +1,77 @@
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    internal static class NativeMethods
+    {
+        // DWM window attributes (DWMWA_CAPTION_COLOR / DWMWA_TEXT_COLOR are
+        // only honored on Windows 11, build 22000 and later).
+        internal const int DWMWA_BORDER_COLOR = 34;
+        internal const int DWMWA_CAPTION_COLOR = 35;
+        internal const int DWMWA_TEXT_COLOR = 36;
+
+        [DllImport("dwmapi.dll", PreserveSig = true)]
+        internal static extern int DwmSetWindowAttribute(IntPtr hwnd, int dwAttribute, ref int pvAttribute, int cbAttribute);
+
+        [DllImport("user32.dll", CharSet = CharSet.Auto)]
+        internal static extern IntPtr FindWindow(string? lpClassName, string? lpWindowName);
+
+        [DllImport("user32.dll")]
+        internal static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);
+
+        [DllImport("user32.dll")]
+        internal static extern bool IsWindow(IntPtr hWnd);
+
+        [DllImport("user32.dll")]
+        internal static extern bool IsWindowVisible(IntPtr hWnd);
+
+        [DllImport("user32.dll")]
+        internal static extern bool IsIconic(IntPtr hWnd);
+
+        [DllImport("user32.dll", SetLastError = true)]
+        internal static extern int GetWindowLong(IntPtr hWnd, int nIndex);
+
+        [DllImport("user32.dll", SetLastError = true)]
+        internal static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
+
+        [DllImport("user32.dll")]
+        internal static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags);
+
+        [DllImport("user32.dll")]
+        internal static extern bool EnumWindows(EnumWindowsProc lpEnumFunc, IntPtr lParam);
+
+        [DllImport("user32.dll")]
+        internal static extern int GetWindowThreadProcessId(IntPtr hWnd, out int lpdwProcessId);
+
+        [DllImport("user32.dll", CharSet = CharSet.Auto)]
+        internal static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);
+
+        [DllImport("user32.dll", CharSet = CharSet.Auto)]
+        internal static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);
+
+        internal delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam);
+
+        internal const int GWL_EXSTYLE = -20;
+        internal const int WS_EX_LAYERED = 0x80000;
+        internal const int WS_EX_TRANSPARENT = 0x20;
+        internal const int WS_EX_TOOLWINDOW = 0x80;
+        internal const int WS_EX_NOACTIVATE = 0x8000000;
+
+        internal const uint SWP_NOACTIVATE = 0x0010;
+        internal const uint SWP_SHOWWINDOW = 0x0040;
+
+        internal static readonly IntPtr HWND_TOPMOST = new IntPtr(-1);
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct RECT
+        {
+            public int Left, Top, Right, Bottom;
+            public int Width => Right - Left;
+            public int Height => Bottom - Top;
+        }
+    }
+}

EonaCat.RdpColorizer/ProfileManagerForm.cs

@@ -0,0 +1,95 @@
+using System.Reflection;
+
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    /// <summary>Lets the user review and delete saved server -> tag/color profiles.</summary>
+    public sealed class ProfileManagerForm : Form
+    {
+        private readonly ProfileStore _store;
+        private readonly ListBox _list;
+
+        public ProfileManagerForm(ProfileStore store)
+        {
+            _store = store;
+            Text = "Saved profiles";
+            Width = 420;
+            Height = 340;
+            FormBorderStyle = FormBorderStyle.FixedDialog;
+            MaximizeBox = false;
+            MinimizeBox = false;
+            StartPosition = FormStartPosition.CenterParent;
+            this.Icon = GetApplicationIcon();
+
+            _list = new ListBox { Left = 12, Top = 12, Width = 380, Height = 230 };
+            RefreshList();
+
+            var removeButton = new Button { Text = "Remove selected", Left = 12, Top = 252, Width = 150, Height = 28 };
+            removeButton.Click += (_, _) =>
+            {
+                int idx = _list.SelectedIndex;
+                if (idx < 0)
+                {
+                    return;
+                }
+
+                _store.Remove(_store.Profiles[idx]);
+                RefreshList();
+            };
+
+            var closeButton = new Button { Text = "Close", Left = 242, Top = 252, Width = 150, Height = 28 };
+            closeButton.Click += (_, _) => Close();
+
+            var hint = new Label
+            {
+                Text = "These are the servers the background watcher will auto-tag on sight.",
+                Left = 12,
+                Top = 285,
+                Width = 380,
+                ForeColor = System.Drawing.SystemColors.GrayText
+            };
+
+            Controls.Add(_list);
+            Controls.Add(removeButton);
+            Controls.Add(closeButton);
+            Controls.Add(hint);
+        }
+
+        private void RefreshList()
+        {
+            _list.Items.Clear();
+            foreach (var p in _store.Profiles)
+            {
+                _list.Items.Add($"{p.Target}   [{p.Label}]");
+            }
+        }
+
+        private static Icon? GetApplicationIcon()
+        {
+            try
+            {
+                // The icon is embedded as a resource in the assembly
+                var assembly = Assembly.GetExecutingAssembly();
+                if (assembly == null)
+                {
+                    return null;
+                }
+
+                using var stream = assembly.GetManifestResourceStream("EonaCat.RdpColorizer.icon.ico");
+                if (stream == null)
+                {
+                    return null;
+                }
+
+                return new Icon(stream);
+            }
+            catch
+            {
+                // Ignore errors loading icon
+            }
+            return null;
+        }
+    }
+}

EonaCat.RdpColorizer/ProfileManagerForm.resx

@@ -0,0 +1,121 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!--
+    Microsoft ResX Schema
+
+    Version 2.0
+
+    The primary goals of this format is to allow a simple XML format
+    that is mostly human readable. The generation and parsing of the
+    various data types are done through the TypeConverter classes
+    associated with the data types.
+
+    Example:
+
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+
+    There are any number of "resheader" rows that contain simple
+    name/value pairs.
+
+    Each data row contains a name, and value. The row also contains a
+    type or mimetype. Type corresponds to a .NET class that support
+    text/value conversion through the TypeConverter architecture.
+    Classes that don't support this are serialized and stored with the
+    mimetype set.
+
+    The mimetype is used for serialized objects, and tells the
+    ResXResourceReader how to depersist the object. This is currently not
+    extensible. For a given mimetype the value must be set accordingly:
+
+    Note - application/x-microsoft.net.object.binary.base64 is the format
+    that the ResXResourceWriter will generate, however the reader can
+    read any of the formats listed below.
+
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <assembly alias="System.Drawing" name="System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
+</root>

EonaCat.RdpColorizer/ProfileStore.cs

@@ -0,0 +1,94 @@
+using EonaCat.Json;
+
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    public sealed class RdpProfile
+    {
+        public string Target { get; set; } = "";
+        public string Label { get; set; } = "";
+        public int ColorArgb { get; set; }
+    }
+
+    /// <summary>
+    /// Persists known server -> tag/color mappings to
+    /// %AppData%\EonaCat.RdpColorizer\profiles.json so they survive app
+    /// restarts and let the background watcher auto re-tag matching RDP
+    /// windows without the user having to re-launch or re-attach manually.
+    /// </summary>
+    public sealed class ProfileStore
+    {
+        private readonly string _path;
+        private readonly List<RdpProfile> _profiles = new();
+
+        public IReadOnlyList<RdpProfile> Profiles => _profiles;
+
+        public ProfileStore()
+        {
+            string dir = Path.Combine(
+                Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
+                "EonaCat.RdpColorizer");
+            Directory.CreateDirectory(dir);
+            _path = Path.Combine(dir, "profiles.json");
+            Load();
+        }
+
+        public void Load()
+        {
+            _profiles.Clear();
+            if (!File.Exists(_path))
+            {
+                return;
+            }
+
+            try
+            {
+                string json = File.ReadAllText(_path);
+                var loaded = JsonHelper.ToObject<List<RdpProfile>>(json);
+                if (loaded != null)
+                {
+                    _profiles.AddRange(loaded);
+                }
+            }
+            catch
+            {
+                // Corrupt or unreadable file - start fresh rather than crash.
+            }
+        }
+
+        public void Save()
+        {
+            string json = JsonHelper.ToJson(_profiles);
+            File.WriteAllText(_path, json);
+        }
+
+        /// <summary>Adds a new profile, or updates the label/color of an existing one for the same target.</summary>
+        public void AddOrUpdate(string target, string label, int colorArgb)
+        {
+            var existing = _profiles.FirstOrDefault(p => string.Equals(p.Target, target, StringComparison.OrdinalIgnoreCase));
+            if (existing != null)
+            {
+                existing.Label = label;
+                existing.ColorArgb = colorArgb;
+            }
+            else
+            {
+                _profiles.Add(new RdpProfile { Target = target, Label = label, ColorArgb = colorArgb });
+            }
+            Save();
+        }
+
+        public void Remove(RdpProfile profile)
+        {
+            _profiles.Remove(profile);
+            Save();
+        }
+
+        public RdpProfile? FindMatch(string target)
+        {
+            return _profiles.FirstOrDefault(p => string.Equals(p.Target, target, StringComparison.OrdinalIgnoreCase));
+        }
+    }
+}

EonaCat.RdpColorizer/Program.cs

@@ -0,0 +1,30 @@
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    internal static class Program
+    {
+        [STAThread]
+        private static void Main(string[] args)
+        {
+            // Prevent duplicate background watchers if the app is both set
+            // to start with Windows and launched manually.
+            using var mutex = new Mutex(true, "EonaCat.RdpColorizer.SingleInstance", out bool createdNew);
+            if (!createdNew)
+            {
+                MessageBox.Show(
+                    "EonaCat RDP Colorizer is already running - check the system tray.",
+                    "EonaCat RDP Colorizer");
+                return;
+            }
+
+            ApplicationConfiguration.Initialize();
+
+            bool startHidden = args.Contains("--background", StringComparer.OrdinalIgnoreCase);
+            Application.Run(new MainForm(startHidden));
+
+            GC.KeepAlive(mutex);
+        }
+    }
+}

EonaCat.RdpColorizer/RdpSession.cs

@@ -0,0 +1,200 @@
+using System.Diagnostics;
+using System.Text;
+using static EonaCat.RdpColorizer.NativeMethods;
+
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    /// <summary>
+    /// Represents one launched (or attached) Remote Desktop connection whose
+    /// title bar is colorized and labeled with an overlay tag. Polls the
+    /// target window's position so the tag follows it when moved or resized.
+    /// </summary>
+    public sealed class RdpSession : IDisposable
+    {
+        public string Target { get; }
+        public string Label { get; }
+        public Color TagColor { get; }
+
+        private Process? _process;
+        private IntPtr _rdpHwnd = IntPtr.Zero;
+        private readonly System.Windows.Forms.Timer _watchTimer;
+        private TagOverlayForm? _overlay;
+        private bool _disposed;
+
+        public RdpSession(string target, string label, Color tagColor)
+        {
+            Target = target;
+            Label = label;
+            TagColor = tagColor;
+
+            _watchTimer = new System.Windows.Forms.Timer { Interval = 150 };
+            _watchTimer.Tick += WatchTimer_Tick;
+        }
+
+        /// <summary>Launches mstsc.exe against the target and starts tracking it.</summary>
+        public void Launch()
+        {
+            var psi = new ProcessStartInfo
+            {
+                FileName = "mstsc.exe",
+                Arguments = $"/v:{Target}",
+                UseShellExecute = true
+            };
+            _process = Process.Start(psi);
+            _watchTimer.Start();
+        }
+
+        /// <summary>Attaches to an already-open mstsc window instead of launching a new one.</summary>
+        public void AttachToWindow(IntPtr hwnd)
+        {
+            _rdpHwnd = hwnd;
+            OnWindowFound();
+            _watchTimer.Start();
+        }
+
+        private void WatchTimer_Tick(object? sender, EventArgs e)
+        {
+            if (_rdpHwnd == IntPtr.Zero)
+            {
+                if (_process == null)
+                {
+                    return;
+                }
+
+                IntPtr hwnd = FindMstscWindowForProcess(_process.Id);
+                if (hwnd != IntPtr.Zero)
+                {
+                    _rdpHwnd = hwnd;
+                    OnWindowFound();
+                }
+                return;
+            }
+
+            if (!IsWindow(_rdpHwnd))
+            {
+                // The RDP window was closed; clean up and stop watching.
+                Dispose();
+                return;
+            }
+
+            RepositionOverlay();
+        }
+
+        private void OnWindowFound()
+        {
+            ApplyCaptionColor();
+            CreateOverlay();
+            RepositionOverlay();
+        }
+
+        private void ApplyCaptionColor()
+        {
+            // DWMWA_CAPTION_COLOR/TEXT_COLOR only take effect on Windows 11
+            // (build 22000+). On older builds these calls fail silently and
+            // the overlay tag remains the only visible identifier.
+            try
+            {
+                int colorRef = ToColorRef(TagColor);
+                DwmSetWindowAttribute(_rdpHwnd, DWMWA_CAPTION_COLOR, ref colorRef, sizeof(int));
+
+                double luminance = (0.299 * TagColor.R + 0.587 * TagColor.G + 0.114 * TagColor.B) / 255.0;
+                Color textColor = luminance > 0.6 ? Color.Black : Color.White;
+                int textColorRef = ToColorRef(textColor);
+                DwmSetWindowAttribute(_rdpHwnd, DWMWA_TEXT_COLOR, ref textColorRef, sizeof(int));
+            }
+            catch
+            {
+                // Ignore - unsupported OS version.
+            }
+        }
+
+        private static int ToColorRef(Color c) => c.R | (c.G << 8) | (c.B << 16); // COLORREF is 0x00BBGGRR
+
+        private void CreateOverlay()
+        {
+            _overlay = new TagOverlayForm(Label, TagColor);
+            _overlay.Show();
+
+            int exStyle = GetWindowLong(_overlay.Handle, GWL_EXSTYLE);
+            exStyle |= WS_EX_LAYERED | WS_EX_TOOLWINDOW | WS_EX_NOACTIVATE;
+            SetWindowLong(_overlay.Handle, GWL_EXSTYLE, exStyle);
+        }
+
+        private void RepositionOverlay()
+        {
+            if (_overlay == null || _overlay.IsDisposed)
+            {
+                return;
+            }
+
+            if (!GetWindowRect(_rdpHwnd, out RECT rect))
+            {
+                return;
+            }
+
+            // Hide the tag while the RDP window is minimized; there's no
+            // caption bar to sit on in that state.
+            if (IsIconic(_rdpHwnd))
+            {
+                if (_overlay.Visible)
+                {
+                    _overlay.Hide();
+                }
+
+                return;
+            }
+            if (!_overlay.Visible)
+            {
+                _overlay.Show();
+            }
+
+            // Sit the tag near the left of the caption bar, just right of
+            // the system icon.
+            int tagX = rect.Left + (rect.Right - rect.Left) / 2 + 46;
+            int tagY = rect.Top + 6;
+
+            SetWindowPos(_overlay.Handle, HWND_TOPMOST, tagX, tagY,
+                _overlay.Width, _overlay.Height, SWP_NOACTIVATE | SWP_SHOWWINDOW);
+        }
+
+        private static IntPtr FindMstscWindowForProcess(int processId)
+        {
+            IntPtr found = IntPtr.Zero;
+            EnumWindows((hwnd, _) =>
+            {
+                GetWindowThreadProcessId(hwnd, out int pid);
+                if (pid != processId || !IsWindowVisible(hwnd))
+                {
+                    return true;
+                }
+
+                var sb = new StringBuilder(256);
+                GetClassName(hwnd, sb, sb.Capacity);
+                if (sb.ToString() == "TscShellContainerClass")
+                {
+                    found = hwnd;
+                    return false; // stop enumeration
+                }
+                return true;
+            }, IntPtr.Zero);
+            return found;
+        }
+
+        public void Dispose()
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            _disposed = true;
+            _watchTimer.Stop();
+            _watchTimer.Dispose();
+            _overlay?.Close();
+            _overlay?.Dispose();
+        }
+    }
+}

EonaCat.RdpColorizer/RdpTargetResolver.cs

@@ -0,0 +1,90 @@
+using System.Management;
+using System.Text;
+using System.Text.RegularExpressions;
+using static EonaCat.RdpColorizer.NativeMethods;
+
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    /// <summary>
+    /// Figures out which server/IP an mstsc.exe window is actually connected
+    /// to, so the watcher can match it against saved profiles. Prefers the
+    /// process command line (exact, e.g. "10.0.0.5:3389") and falls back to
+    /// the window title (e.g. "SERVER01 - Remote Desktop Connection") when
+    /// the command line can't be read - which happens if mstsc.exe is
+    /// running elevated or under a different user account than this app.
+    /// </summary>
+    internal static class RdpTargetResolver
+    {
+        public static string? Resolve(nint hwnd)
+        {
+            GetWindowThreadProcessId(hwnd, out int pid);
+
+            return TryGetCommandLineTarget(pid) ?? TryGetTitleTarget(hwnd);
+        }
+
+        private static string? TryGetCommandLineTarget(int pid)
+        {
+            try
+            {
+                using var searcher = new ManagementObjectSearcher(
+                    $"SELECT CommandLine FROM Win32_Process WHERE ProcessId = {pid}");
+
+                foreach (ManagementObject mo in searcher.Get())
+                {
+                    string? cmdLine = mo["CommandLine"]?.ToString();
+                    if (string.IsNullOrEmpty(cmdLine))
+                    {
+                        continue;
+                    }
+
+                    Match match = Regex.Match(cmdLine, @"/v:([^\s""]+)", RegexOptions.IgnoreCase);
+                    if (match.Success)
+                    {
+                        return Normalize(match.Groups[1].Value);
+                    }
+                }
+            }
+            catch
+            {
+                // WMI query can fail for permission reasons (e.g. mstsc.exe
+                // running elevated); fall back to reading the window title.
+            }
+            return null;
+        }
+
+        private static string? TryGetTitleTarget(nint hwnd)
+        {
+            var sb = new StringBuilder(512);
+            GetWindowText(hwnd, sb, sb.Capacity);
+            string title = sb.ToString();
+
+            // Typical titles: "SERVER01 - Remote Desktop Connection" or,
+            // while still negotiating, just "Remote Desktop Connection".
+            Match match = Regex.Match(title, @"^(.*?)\s*-\s*Remote Desktop Connection", RegexOptions.IgnoreCase);
+            if (match.Success && !string.IsNullOrWhiteSpace(match.Groups[1].Value))
+            {
+                return Normalize(match.Groups[1].Value);
+            }
+
+            return null;
+        }
+
+        private static string Normalize(string target)
+        {
+            target = target.Trim();
+
+            // Drop a trailing ":port" (but leave bare IPv6 addresses alone -
+            // we only strip when there's exactly one colon, i.e. IPv4/hostname:port).
+            int colonCount = target.Split(':').Length - 1;
+            if (colonCount == 1)
+            {
+                int idx = target.IndexOf(':');
+                target = target[..idx];
+            }
+            return target;
+        }
+    }
+}

EonaCat.RdpColorizer/TagOverlayForm.cs

@@ -0,0 +1,74 @@
+using System.Reflection;
+
+namespace EonaCat.RdpColorizer
+{
+    // This file is part of the EonaCat project(s) which is released under the Apache License.
+    // See the LICENSE file or go to https://EonaCat.com/License for full license details.
+
+    /// <summary>
+    /// A tiny borderless, always-on-top badge showing a colored background
+    /// and label text. RdpSession positions this over an RDP window's
+    /// caption bar to act as a visual identifier (e.g. "PROD", "DEV-DB1").
+    /// </summary>
+    public sealed class TagOverlayForm : Form
+    {
+        public TagOverlayForm(string text, Color backColor)
+        {
+            FormBorderStyle = FormBorderStyle.None;
+            StartPosition = FormStartPosition.Manual;
+            ShowInTaskbar = false;
+            TopMost = true;
+            BackColor = backColor;
+            this.Icon = GetApplicationIcon();
+
+            // Pick readable text color based on the tag's brightness.
+            double luminance = (0.299 * backColor.R + 0.587 * backColor.G + 0.114 * backColor.B) / 255.0;
+            Color foreColor = luminance > 0.6 ? Color.Black : Color.White;
+
+            var label = new Label
+            {
+                Text = text,
+                AutoSize = false,
+                Dock = DockStyle.Fill,
+                TextAlign = ContentAlignment.MiddleCenter,
+                ForeColor = foreColor,
+                Font = new Font("Segoe UI", 8f, FontStyle.Bold)
+            };
+            Controls.Add(label);
+
+            using var g = CreateGraphics();
+            SizeF measured = g.MeasureString(text, label.Font);
+            Width = (int)measured.Width + 24;
+            Height = 20;
+        }
+
+        // Prevents the badge from stealing focus when shown.
+        protected override bool ShowWithoutActivation => true;
+
+        private static Icon? GetApplicationIcon()
+        {
+            try
+            {
+                // The icon is embedded as a resource in the assembly
+                var assembly = Assembly.GetExecutingAssembly();
+                if (assembly == null)
+                {
+                    return null;
+                }
+
+                using var stream = assembly.GetManifestResourceStream("EonaCat.RdpColorizer.icon.ico");
+                if (stream == null)
+                {
+                    return null;
+                }
+
+                return new Icon(stream);
+            }
+            catch
+            {
+                // Ignore errors loading icon
+            }
+            return null;
+        }
+    }
+}

EonaCat.RdpColorizer/TagOverlayForm.resx

@@ -0,0 +1,121 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!--
+    Microsoft ResX Schema
+
+    Version 2.0
+
+    The primary goals of this format is to allow a simple XML format
+    that is mostly human readable. The generation and parsing of the
+    various data types are done through the TypeConverter classes
+    associated with the data types.
+
+    Example:
+
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+
+    There are any number of "resheader" rows that contain simple
+    name/value pairs.
+
+    Each data row contains a name, and value. The row also contains a
+    type or mimetype. Type corresponds to a .NET class that support
+    text/value conversion through the TypeConverter architecture.
+    Classes that don't support this are serialized and stored with the
+    mimetype set.
+
+    The mimetype is used for serialized objects, and tells the
+    ResXResourceReader how to depersist the object. This is currently not
+    extensible. For a given mimetype the value must be set accordingly:
+
+    Note - application/x-microsoft.net.object.binary.base64 is the format
+    that the ResXResourceWriter will generate, however the reader can
+    read any of the formats listed below.
+
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <assembly alias="System.Drawing" name="System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
+</root>

LICENSE

@@ -1,73 +1,204 @@
-Apache License
+                                 
-Version 2.0, January 2004
+				Apache License
-http://www.apache.org/licenses/
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+                        https://EonaCat.com/license/
 
-TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 
+                   OF SOFTWARE BY EONACAT (JEROEN SAEY)
 
-1. Definitions.
+   1. Definitions.
 
-"License" shall mean the terms and conditions for use, reproduction, and distribution as defined by Sections 1 through 9 of this document.
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
 
-"Licensor" shall mean the copyright owner or entity authorized by the copyright owner that is granting the License.
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
 
-"Legal Entity" shall mean the union of the acting entity and all other entities that control, are controlled by, or are under common control with that entity. For the purposes of this definition, "control" means (i) the power, direct or indirect, to cause the direction or management of such entity, whether by contract or otherwise, or (ii) ownership of fifty percent (50%) or more of the outstanding shares, or (iii) beneficial ownership of such entity.
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
 
-"You" (or "Your") shall mean an individual or Legal Entity exercising permissions granted by this License.
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
 
-"Source" form shall mean the preferred form for making modifications, including but not limited to software source code, documentation source, and configuration files.
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
 
-"Object" form shall mean any form resulting from mechanical transformation or translation of a Source form, including but not limited to compiled object code, generated documentation, and conversions to other media types.
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
 
-"Work" shall mean the work of authorship, whether in Source or Object form, made available under the License, as indicated by a copyright notice that is included in or attached to the work (an example is provided in the Appendix below).
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
 
-"Derivative Works" shall mean any work, whether in Source or Object form, that is based on (or derived from) the Work and for which the editorial revisions, annotations, elaborations, or other modifications represent, as a whole, an original work of authorship. For the purposes of this License, Derivative Works shall not include works that remain separable from, or merely link (or bind by name) to the interfaces of, the Work and Derivative Works thereof.
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
 
-"Contribution" shall mean any work of authorship, including the original version of the Work and any modifications or additions to that Work or Derivative Works thereof, that is intentionally submitted to Licensor for inclusion in the Work by the copyright owner or by an individual or Legal Entity authorized to submit on behalf of the copyright owner. For the purposes of this definition, "submitted" means any form of electronic, verbal, or written communication sent to the Licensor or its representatives, including but not limited to communication on electronic mailing lists, source code control systems, and issue tracking systems that are managed by, or on behalf of, the Licensor for the purpose of discussing and improving the Work, but excluding communication that is conspicuously marked or otherwise designated in writing by the copyright owner as "Not a Contribution."
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
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+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
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+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
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+      designated in writing by the copyright owner as "Not a Contribution."
 
-"Contributor" shall mean Licensor and any individual or Legal Entity on behalf of whom a Contribution has been received by Licensor and subsequently incorporated within the Work.
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
 
-2. Grant of Copyright License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare Derivative Works of, publicly display, publicly perform, sublicense, and distribute the Work and such Derivative Works in Source or Object form.
+   2. Grant of Copyright License. Subject to the terms and conditions of
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+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
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-3. Grant of Patent License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the Work, where such license applies only to those patent claims licensable by such Contributor that are necessarily infringed by their Contribution(s) alone or by combination of their Contribution(s) with the Work to which such Contribution(s) was submitted. If You institute patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that the Work or a Contribution incorporated within the Work constitutes direct or contributory patent infringement, then any patent licenses granted to You under this License for that Work shall terminate as of the date such litigation is filed.
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+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
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+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
 
-4. Redistribution. You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium, with or without modifications, and in Source or Object form, provided that You meet the following conditions:
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+      meet the following conditions:
 
-     (a) You must give any other recipients of the Work or Derivative Works a copy of this License; and
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
 
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+      (d) If the Work includes a "NOTICE" text file as part of its
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+   limitations under the License.

README.md

@@ -1,3 +1,106 @@
-# EonaCat.RdpColorizer
+# EonaCat RDP Colorizer
 
-EonaCat RdpColorizer
+A Windows utility that colors the title bar of Remote Desktop windows and
+overlays a small colored tag (e.g. `PROD`, `DEV-DB1`) on the caption, so you
+can tell multiple RDP sessions apart at a glance. It runs in the background,
+remembers which color/tag belongs to which server, and automatically
+re-applies that tag any time a matching RDP window shows up - including
+after you restart the app, and for windows opened outside the app entirely.
+
+## A note on "running as a service"
+
+A true Windows Service (the kind registered with the Service Control
+Manager) runs in **Session 0**, which has been isolated from the
+interactive desktop since Windows Vista. A Session 0 process cannot see or
+draw on windows in your logon session at all - this is an OS-level
+security boundary, not something that can be coded around. So a real SCM
+service could never color or overlay another window's title bar.
+
+What actually achieves the goal - always running, no manual relaunching,
+automatic re-tagging - is a background app that starts at logon inside
+your own session. That's what this app now does:
+
+- It starts hidden in the **system tray** (no window, no taskbar entry)
+  when launched with `--background`, or normally shows its control panel
+  when opened by hand.
+- Closing the window just hides it to the tray; the watcher keeps running
+  until you choose **Exit** from the tray icon's menu.
+- Check **Start with Windows** in the app to have it launch automatically
+  at logon (writes a `HKCU\...\Run` entry pointing at the exe with
+  `--background` - no admin rights required).
+
+If your environment specifically requires an SCM-registered service (e.g.
+for a policy or monitoring reason), that service could still exist to
+supervise/restart this tray app, but it would not be able to perform the
+window coloring itself.
+
+## How the coloring and tagging work
+
+1. **Native caption color** - `DwmSetWindowAttribute` with
+   `DWMWA_CAPTION_COLOR` / `DWMWA_TEXT_COLOR`. Only honored on **Windows 11
+   (build 22000+)**; ignored on Windows 10.
+2. **Overlay tag label** - a small always-on-top badge window positioned
+   over the caption bar, showing your text on your chosen color. Works on
+   any Windows version and follows the RDP window as it moves, resizes, or
+   restores (hidden while minimized).
+
+## Auto re-attach by server / IP
+
+- Whenever you tag a connection (Launch or Attach), the target
+  (server name or IP) plus your chosen label/color is saved to
+  `%AppData%\EonaCat.RdpColorizer\profiles.json`.
+- A background watcher scans for RDP windows **system-wide** every second.
+  For each one it doesn't recognize yet, it resolves the actual connection
+  target - first by reading the `mstsc.exe` process's command line
+  (`/v:target`) via WMI, falling back to parsing the window title if that
+  fails (e.g. if `mstsc.exe` is running elevated or under a different
+  account than this app).
+- If the resolved target matches a saved profile, the tag/color is applied
+  automatically - no manual step needed, including for connections opened
+  straight from the Start menu or a saved `.rdp` file.
+- Use **Manage saved profiles...** to review or delete remembered
+  server → tag mappings.
+
+## Requirements
+
+- Windows 10 or 11
+- [.NET 8 SDK](https://dotnet.microsoft.com/download) to build
+
+## Build & run
+
+```powershell
+cd EonaCat.RdpColorizer
+dotnet build
+dotnet run
+```
+
+Or publish a standalone exe:
+
+```powershell
+dotnet publish -c Release -r win-x64 --self-contained false
+```
+
+## Using it
+
+1. Enter a server name/IP and a short tag, pick a color, then click
+   **Launch new tagged connection** (runs `mstsc.exe /v:target`) or
+   **Tag active RDP window** to attach to one already open.
+2. That server/tag/color is now remembered - close and reopen the app (or
+   just leave it running in the tray) and any future RDP window to that
+   same server gets tagged automatically.
+3. Tick **Start with Windows** so this happens without you having to open
+   the app at all.
+
+## Notes / limitations
+
+- Windows caption theming (`DWMWA_CAPTION_COLOR`) is Windows 11 only;
+  there is no public equivalent for Windows 10 - the overlay tag is your
+  cross-version fallback.
+- The overlay tag is a separate always-on-top window layered over the
+  caption, so it will show up as its own tiny entry in things like Alt+Tab
+  previews - expected behavior, not a bug.
+- Command-line resolution via WMI requires the watcher to have permission
+  to query the `mstsc.exe` process; if it's elevated or owned by another
+  user, the watcher falls back to matching on the window title instead
+  (which shows the resolved computer name rather than the raw IP you
+  typed - keep that in mind when naming profiles for IP-based targets).