Fix Anchors in PermonitorV2 mode applications.

src/System.Windows.Forms/src/System/Windows/Forms/ContainerControl.cs

@@ -48,6 +48,11 @@ public class ContainerControl : ScrollableControl, IContainerControl
         /// </summary>
         private bool _isScaledByDpiChangedEvent;
 
+        /// <summary>
+        ///  Indicates scaling, due to DPI changed event, of the container control is in progress.
+        /// </summary>
+        internal bool _dpiScalingInProgress;
+
         private BitVector32 _state;
 
         /// <summary>
@@ -1441,6 +1446,8 @@ internal void ScaleContainerForDpi(int deviceDpiNew, int deviceDpiOld, Rectangle
             SuspendAllLayout(this);
             try
             {
+                _dpiScalingInProgress = true;
+
                 if (LocalAppContextSwitches.ScaleTopLevelFormMinMaxSizeForDpi)
                 {
                     // The suggested rectangle comes from Windows, and it does not match with our calculations for scaling controls by AutoscaleFactor.
@@ -1491,6 +1498,9 @@ internal void ScaleContainerForDpi(int deviceDpiNew, int deviceDpiOld, Rectangle
                 // We want to perform layout for dpi-changed high Dpi improvements - setting the second parameter to 'true'
                 ResumeAllLayout(this, true);
                 _isScaledByDpiChangedEvent = false;
+
+                // Scaling and ResumeLayout, due to DPI changed event, should be finished by now for this container.
+                _dpiScalingInProgress = false;
             }
         }
 

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

@@ -1713,10 +1713,10 @@ internal bool IsTopMdiWindowClosing
         }
 
         /// <summary>
-        ///  returns bool indicating whether the control is currently being scaled.
+        ///  Returns bool indicating whether the control is currently being scaled.
         ///  This property is set in ScaleControl method to allow method being called to condition code that should not run for scaling.
         /// </summary>
-        internal bool IsCurrentlyBeingScaled
+        internal bool ScalingInProgress
         {
             get => GetExtendedState(ExtendedStates.CurrentlyBeingScaled);
             private set => SetExtendedState(ExtendedStates.CurrentlyBeingScaled, value);
@@ -10450,7 +10450,7 @@ internal void ScaleControl(SizeF includedFactor, SizeF excludedFactor, Control r
         {
             try
             {
-                IsCurrentlyBeingScaled = true;
+                ScalingInProgress = true;
 
                 BoundsSpecified includedSpecified = BoundsSpecified.None;
                 BoundsSpecified excludedSpecified = BoundsSpecified.None;
@@ -10489,7 +10489,7 @@ internal void ScaleControl(SizeF includedFactor, SizeF excludedFactor, Control r
             }
             finally
             {
-                IsCurrentlyBeingScaled = false;
+                ScalingInProgress = false;
             }
         }
 
@@ -10589,9 +10589,6 @@ protected virtual void ScaleControl(SizeF factor, BoundsSpecified specified)
             scaledSize = LayoutUtils.UnionSizes(scaledSize, minSize);
 
             if (DpiHelper.IsScalingRequirementMet
-                // In the v2 layout, anchors are updated/computed after the controls bounds changed
-                // and, thus, don't need scaling.
-                && !DefaultLayout.UseAnchorLayoutV2(this)
                 && ParentInternal is { } parent
                 && (parent.LayoutEngine == DefaultLayout.Instance))
             {

src/System.Windows.Forms/src/System/Windows/Forms/Layout/DefaultLayout.cs

@@ -896,6 +896,12 @@ internal static void UpdateAnchorInfoV2(Control control)
                 return;
             }
 
+            // Anchors are already scaled for the new DPI.
+            if (DpiScalingInProgress(control, parent))
+            {
+                return;
+            }
+
             AnchorInfo anchorInfo = GetAnchorInfo(control);
             if (anchorInfo is null)
             {
@@ -913,6 +919,28 @@ internal static void UpdateAnchorInfoV2(Control control)
 
             anchorInfo.Right = displayRect.Width - (x + elementBounds.Width);
             anchorInfo.Bottom = displayRect.Height - (y + elementBounds.Height);
+
+            // Walk through parent hierarchy and check if scaling due to DPI change is in progress.
+            static bool DpiScalingInProgress(Control control, Control parent)
+            {
+                if (control.ScalingInProgress
+                    || (control is ContainerControl container && container._dpiScalingInProgress))
+                {
+                    return true;
+                }
+
+                while (parent is not null)
+                {
+                    if (parent is ContainerControl parentContainer && parentContainer._dpiScalingInProgress)
+                    {
+                        return true;
+                    }
+
+                    parent = parent.Parent;
+                }
+
+                return false;
+            }
         }
 
         public static AnchorStyles GetAnchor(IArrangedElement element) => CommonProperties.xGetAnchor(element);

src/System.Windows.Forms/src/System/Windows/Forms/MonthCalendar.cs

@@ -1756,7 +1756,7 @@ protected override void SetBoundsCore(int x, int y, int width, int height, Bound
 
             // Second argument to GetPreferredWidth and GetPreferredHeight is a boolean specifying if we should update the number of rows/columns.
             // We only want to update the number of rows/columns if we are not currently being scaled.
-            bool updateRowsAndColumns = !DpiHelper.IsScalingRequirementMet || !IsCurrentlyBeingScaled;
+            bool updateRowsAndColumns = !DpiHelper.IsScalingRequirementMet || !ScalingInProgress;
 
             if (width != oldBounds.Width)
             {