Handle system theme change

Author: t1m0thyj

src/AppContext.cs

@@ -78,6 +78,15 @@ private void InitializeTrayIcon()
             Localization.NotifyIfTestMode();
         }
 
+        public static void HandleThemeChange()
+        {
+            Application.SetColorMode(SystemColorMode.System);
+            foreach (Form form in Application.OpenForms)
+            {
+                form.Invalidate();
+            }
+        }
+
         public static void ShowPopup(string message, string title = null)
         {
             notifyIcon.BalloonTipTitle = title ?? "WinDynamicDesktop";

src/HiddenForm.cs

@@ -15,6 +15,7 @@ internal class HiddenForm : Form
         private const int ENDSESSION_CLOSEAPP = 0x1;
         private const int WM_QUERYENDSESSION = 0x11;
         private const int WM_ENDSESSION = 0x16;
+        private const int WM_SETTINGCHANGE = 0x1A;
         private const int WM_POWERBROADCAST = 0x0218;
         private const int PBT_POWERSETTINGCHANGE = 0x8013;
 
@@ -62,6 +63,12 @@ protected override void WndProc(ref Message m)
                     }
                     m.Result = IntPtr.Zero;
                     break;
+                case WM_SETTINGCHANGE:
+                    if (Marshal.PtrToStringUni(m.LParam) == "ImmersiveColorSet")
+                    {
+                        AppContext.HandleThemeChange();
+                    }
+                    break;
                 case WM_POWERBROADCAST:
                     if (m.WParam.ToInt32() == PBT_POWERSETTINGCHANGE && PowerSetting.IsExitingStandby(m.LParam))
                     {