Extend DarkMode opt-out option for multiple descendant scenarios.

src/System.Windows.Forms/System/Windows/Forms/Control.cs

@@ -298,6 +298,11 @@ public unsafe partial class Control :
 
     internal byte LayoutSuspendCount { get; private set; }
 
+    // Flag for the youngest control in the descendant-inheritance hierarchy as the
+    // ultimate truth if the control - by having set the ControlStyles. -
+    // indicates to participate in automatic dark mode theming or not.
+    internal bool? _darkModeRequestState;
+
     /// <summary>
     ///  Initializes a new instance of the <see cref="Control"/> class.
     /// </summary>
@@ -7379,7 +7384,7 @@ protected virtual void OnHandleCreated(EventArgs e)
 
 #pragma warning disable WFO5001 // Type is for evaluation purposes only and is subject to change or removal in future updates.
             if (Application.IsDarkModeEnabled
-                && GetStyle(ControlStyles.ApplyThemingImplicitly)
+                && _darkModeRequestState is true
                 && !RecreatingHandle)
             {
                 _ = PInvoke.SetWindowTheme(
@@ -9344,7 +9349,7 @@ internal virtual void RecreateHandleCore()
             // ensure that the theming is applied to all child controls as well.
 #pragma warning disable WFO5001
             if (Application.IsDarkModeEnabled
-                && GetStyle(ControlStyles.ApplyThemingImplicitly))
+                && _darkModeRequestState is true)
             {
                 _ = PInvoke.SetWindowTheme(
                     hwnd: HWND,
@@ -10325,12 +10330,27 @@ private protected void SetExtendedState(ExtendedStates flag, bool value)
     ///  NOTE: This is control style, not the Win32 style of the hWnd.
     /// </summary>
     [EditorBrowsable(EditorBrowsableState.Advanced)]
+#pragma warning disable WFO5001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
     protected void SetStyle(ControlStyles flag, bool value)
     {
         // WARNING: if we ever add argument checking to "flag", we will need
         // to move private styles like Layered to State.
         _controlStyle = value ? _controlStyle | flag : _controlStyle & ~flag;
+
+        // We need to special-treat ApplyThemingImplicitly, as it is not a real style,which we
+        // would hand down to Win32. It's important, that we capture what an inherited control
+        // wanted in terms of getting the respective dark mode theme applied automatically.
+        // Since the inherited control sets or clears this style implicitly in CreateParams
+        // (Which always runs _before_ its constructor code runs), and since base controls can
+        // reset those settings - the source of truth ultimately is the value which gets set
+        // for the first time a control sets or clears this style explicitly in CreateParams.
+        if ((flag & ControlStyles.ApplyThemingImplicitly) == ControlStyles.ApplyThemingImplicitly
+            && !_darkModeRequestState.HasValue)
+        {
+            _darkModeRequestState = value;
+        }
     }
+#pragma warning restore WFO5001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
 
     internal virtual void SetToolTip(ToolTip toolTip)
     {
@@ -10391,7 +10411,8 @@ protected virtual void SetVisibleCore(bool value)
                 {
                     // We shouldn't mess with the color mode if users haven't specifically set it.
                     // https://github.com/dotnet/winforms/issues/12014
-                    if (value && Application.ColorModeSet)
+                    // And we shouldn't prepare dark mode, if the form opted out.
+                    if (value && Application.ColorModeSet && _darkModeRequestState is true)
                     {
                         PrepareDarkMode(HWND, Application.IsDarkModeEnabled);
                     }

src/System.Windows.Forms/System/Windows/Forms/Controls/Buttons/Button.cs

@@ -168,7 +168,7 @@ private protected override bool OwnerDraw
                 && Image is null
 
                 // ...the user wants to opt out of implicit DarkMode rendering.
-                && GetStyle(ControlStyles.ApplyThemingImplicitly)
+                && _darkModeRequestState is true
 
                 // And all of this only counts for FlatStyle.Standard. For the
                 // rest, we're using specific renderers anyway, which check

src/System.Windows.Forms/System/Windows/Forms/Controls/ListView/ListView.cs

@@ -4673,7 +4673,7 @@ protected override void OnHandleCreated(EventArgs e)
     private void ApplyDarkModeOnDemand()
     {
         if (Application.IsDarkModeEnabled
-            && GetStyle(ControlStyles.ApplyThemingImplicitly))
+            && _darkModeRequestState is true)
         {
             // Enable double buffering when in dark mode to reduce flicker.
             uint exMask = PInvoke.LVS_EX_ONECLICKACTIVATE | PInvoke.LVS_EX_TWOCLICKACTIVATE |

src/System.Windows.Forms/System/Windows/Forms/Controls/TextBox/TextBoxBase.cs

@@ -290,7 +290,7 @@ public override Color BackColor
 
                     // If we're ReadOnly and in DarkMode, we are using a different background color.
                     ? Application.IsDarkModeEnabled
-                        && GetStyle(ControlStyles.ApplyThemingImplicitly)
+                        && _darkModeRequestState is true
                             ? SystemColors.ControlDarkDark
                             : SystemColors.Control
                     : SystemColors.Window;
@@ -955,7 +955,7 @@ private void EnsureReadonlyBackgroundColor(bool value)
     {
         // If we have no specifically defined back color, we set the back color in case we're in dark mode.
         if (Application.IsDarkModeEnabled
-            && GetStyle(ControlStyles.ApplyThemingImplicitly))
+            && _darkModeRequestState is true)
         {
             base.BackColor = value ? SystemColors.ControlLight : SystemColors.Window;
             Invalidate();