Fixed the issue of the secondary screen's taskbar becoming transparent after restarting in mixed DPI multi-screen setups.

Author: lingyongji

.gitignore

@@ -0,0 +1,10 @@
+################################################################################
+# 此 .gitignore 文件已由 Microsoft(R) Visual Studio 自动创建。
+################################################################################
+
+/.dotnet_cli/.dotnet
+/.vs
+/bin/Debug/net8.0-windows
+/LiteMonitor.Updater/obj
+/obj
+/bin/Debug

src/System/Program.cs

@@ -84,6 +84,7 @@ static void Main()
             try
             {
                 // ★★★ 3. 启动应用 ★★★
+                Application.SetHighDpiMode(HighDpiMode.PerMonitorV2);
                 ApplicationConfiguration.Initialize();
                 Application.Run(new MainForm());
             }
@@ -148,4 +149,4 @@ static void LogCrash(Exception? ex, string source)
             }
         }
     }
-}
+}

src/UI/Helpers/TaskbarWinHelper.cs

@@ -215,7 +215,7 @@ private IntPtr FindSecondaryTaskbar(Screen screen)
                 if (screen.Bounds.Contains(r.Location) || screen.Bounds.IntersectsWith(r))
                     return hWnd;
             }
-            return FindWindow("Shell_TrayWnd", null);
+            return IntPtr.Zero;
         }
 
         public Rectangle GetTaskbarRect(IntPtr hTaskbar, string targetDevice)
@@ -264,7 +264,7 @@ public Rectangle GetTaskbarRect(IntPtr hTaskbar, string targetDevice)
 
                             if (!isVertical)
                             {
-                                int dpi = GetTaskbarDpi();
+                                int dpi = GetTaskbarDpi(hTaskbar);
                                 int standardHeight = (int)Math.Round(48.0 * dpi / 96.0);
 
                                 if (rectPhys.Height > (standardHeight * 0.8))
@@ -312,16 +312,21 @@ public static bool IsCenterAligned()
             catch { return false; }
         }
 
-        public static int GetTaskbarDpi()
+        public static int GetTaskbarDpi(IntPtr hWnd)
         {
-            IntPtr taskbar = FindWindow("Shell_TrayWnd", null);
-            if (taskbar != IntPtr.Zero)
+            if (hWnd != IntPtr.Zero)
             {
-                try { return (int)GetDpiForWindow(taskbar); } catch { }
+                try { return (int)GetDpiForWindow(hWnd); } catch { }
             }
             return 96;
         }
 
+        public static int GetTaskbarDpi()
+        {
+            IntPtr taskbar = FindWindow("Shell_TrayWnd", null);
+            return GetTaskbarDpi(taskbar);
+        }
+
         public static int GetWidgetsWidth()
         {
             int dpi = GetTaskbarDpi();

src/UI/TaskbarForm.cs

@@ -57,12 +57,11 @@ public TaskbarForm(Settings cfg, UIController ui, MainForm mainForm)
             TopMost = false;
             DoubleBuffered = true;
 
-            ReloadLayout();
-
             _bizHelper.CheckTheme(true);
             _bizHelper.FindHandles();
 
             _bizHelper.AttachToTaskbar();
+            ReloadLayout();
             _winHelper.ApplyLayeredStyle(_bizHelper.TransparentKey, _cfg.TaskbarClickThrough);
 
             _timer.Interval = Math.Max(_cfg.RefreshMs, 60);
@@ -79,7 +78,10 @@ public void ReloadLayout()
         {
             _layout = new HorizontalLayout(ThemeManager.Current, 300, LayoutMode.Taskbar, _cfg);
             _lastLayoutSignature = ""; // 重置签名，强制重算
-            _winHelper.ApplyLayeredStyle(_bizHelper.TransparentKey, _cfg.TaskbarClickThrough);
+            if (IsHandleCreated)
+            {
+                _winHelper.ApplyLayeredStyle(_bizHelper.TransparentKey, _cfg.TaskbarClickThrough);
+            }
             _bizHelper.CheckTheme(true);
 
             // 更新悬浮窗模式 (支持热切换)