TaskBar is aware of resizes.

Author: Toemsel

.vs/TaskbarHook/v15/.suo

@@ -32,5 +32,5 @@
 // Sie können alle Werte angeben oder Standardwerte für die Build- und Revisionsnummern verwenden,
 // indem Sie "*" wie unten gezeigt eingeben:
 // [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("1.0.0.0")]
-[assembly: AssemblyFileVersion("1.0.0.0")]
+[assembly: AssemblyVersion("1.1.0.0")]
+[assembly: AssemblyFileVersion("1.1.0.0")]

TaskbarHook/Properties/AssemblyInfo.cs

@@ -21,12 +21,16 @@ public static class TaskBarFactory
         /// <exception cref="PlatformNotSupportedException">No TaskBar could be obtained.</exception>
         public static Taskbar GetTaskbar()
         {
+            if (Taskbar.Instance != null)
+                return Taskbar.Instance;
+
             IntPtr taskbarHandle = TaskBarHandle;
 
             if (taskbarHandle == IntPtr.Zero)
                 throw new PlatformNotSupportedException($"The TaskBar cound't be obtained.");
 
-            return new Taskbar(taskbarHandle);
+            Taskbar.CreateAndInitialize(taskbarHandle);
+            return GetTaskbar();
         }
     }
 }

TaskbarHook/TaskBarFactory.cs

@@ -4,24 +4,30 @@
 
 namespace TaskbarHook
 {
-    public class Taskbar
+    public class Taskbar : IDisposable
     {
-        public Taskbar(IntPtr handle)
-        {
-            Handle = handle;
+        private static WinEventDelegate eventDelegate = new WinEventDelegate(TaskBarResizeEvent);
 
-            Initialize();
-        }
+        private Taskbar() { }
 
-        private void Initialize()
+        internal static void CreateAndInitialize(IntPtr handle)
         {
-            Rectangle = User32.GetWindowRectangle(Handle);
+            Instance = new Taskbar();
+            Instance.Handle = handle;
+            Instance.Rectangle = User32.GetWindowRectangle(Instance.Handle);
+            Instance.ResizeHandle = User32.RegisterWindowSizeChangeEvent(Instance.Handle, eventDelegate);
         }
 
+        internal static Taskbar Instance { get; private set; }
+
         public IntPtr Handle { get; private set; }
 
+        private IntPtr ResizeHandle { get; set; }
+
         public Rectangle Rectangle { get; private set; }
 
+        public Action SizeChanged { get; set; }
+
         public async Task<TaskbarElement> AddToTaskbar() => await AddToTaskbar(Process.GetCurrentProcess());
 
         public async Task<TaskbarElement> AddToTaskbar(Process process)
@@ -34,5 +40,9 @@ public async Task<TaskbarElement> AddToTaskbar(Process process)
 
             return taskbarElement;
         }
+
+        private static void TaskBarResizeEvent(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime) => Instance?.SizeChanged();
+
+        public void Dispose() => User32.UnRegisterWindowSizeChangeEvent(ResizeHandle);
     }
 }

TaskbarHook/Taskbar.cs

@@ -52,6 +52,7 @@
     <Compile Include="Rectangle.cs" />
     <Compile Include="Taskbar.cs" />
     <Compile Include="User32.cs" />
+    <Compile Include="WinEventDelegate.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
 </Project>

TaskbarHook/TaskbarHook.csproj

@@ -5,6 +5,10 @@ namespace TaskbarHook
 {
     internal static class User32
     {
+        private const uint EVENT_SYSTEM_MOVESIZESTART = 0x000A;
+        private const uint EVENT_SYSTEM_MOVESIZEEND = 0x000B;
+        private const uint WINEVENT_OUTOFCONTEXT = 0;
+
         #region DLLImports
         [DllImport("user32.dll", SetLastError = true)]
         private static extern IntPtr GetWindow(IntPtr hWnd, uint uCmd);
@@ -26,6 +30,15 @@ internal static class User32
 
         [DllImport("user32.dll", EntryPoint = "ShowWindow", SetLastError = true)]
         private static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
+
+        [DllImport("user32.dll")]
+        private static extern IntPtr SetWinEventHook(uint eventMin, uint eventMax, IntPtr hmodWinEventProc, WinEventDelegate lpfnWinEventProc, uint idProcess, uint idThread, uint dwFlags);
+
+        [DllImport("user32.dll")]
+        private static extern bool UnhookWinEvent(IntPtr hWinEventHook);
+
+        [DllImport("user32.dll", SetLastError = true)]
+        private static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint processId);
         #endregion
 
         internal static bool SetWindowPosition(IntPtr handle, int x, int y) => SetWindowPos(handle, 0, x, y, 0, 0, 0x0001) != IntPtr.Zero;
@@ -38,6 +51,16 @@ internal static class User32
 
         internal static bool SetVisibilityState(IntPtr handle, int state) => ShowWindow(handle, state);
 
+        internal static IntPtr RegisterWindowSizeChangeEvent(IntPtr handle, WinEventDelegate delegateCallback)
+        {
+            uint process, thread = 0;
+            thread = GetWindowThreadProcessId(handle, out process);
+
+            return SetWinEventHook(EVENT_SYSTEM_MOVESIZESTART, EVENT_SYSTEM_MOVESIZEEND, IntPtr.Zero, delegateCallback, process, thread, WINEVENT_OUTOFCONTEXT);
+        }
+
+        internal static bool UnRegisterWindowSizeChangeEvent(IntPtr hoockHandle) => UnhookWinEvent(hoockHandle);
+
         internal static IntPtr GetWindowParent(IntPtr handle) => GetParent(handle);
 
         internal static IntPtr GetWindow(string className) => GetWindow(IntPtr.Zero, className);

TaskbarHook/User32.cs

@@ -0,0 +1,6 @@
+using System;
+
+namespace TaskbarHook
+{
+    internal delegate void WinEventDelegate(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime);
+}