Deeply nested controls do not resize properly when their parents are resized

Source: Microsoft Support

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A parent control is resized in an application with deeply-nested, docked controls.

The nested controls do not resize or dock properly.

In .NET applications, docked controls sometimes do not resize when their parents are resized if they are deeply nested.  This problem occurs on both 64-bit and on 32-bit platforms, but requires a deeper nesting level on 32-bit systems.


What happens is that when the top level control lays out, SetBoundsCore calls SetWindowPos to resize the child controls. Each child control receives a WM_WINDOWPOSCHANGED notification, which triggers a layout event, which calls SetBoundsCore, which calls SetWindowPos.  Each call to SetWindowPos goes into kernel mode and then back out to deliver the WM_WINDOWPOSCHANGED notification. Eventually the thread runs out of kernel stack space and SetWindowPos fails silently.

To work around this problem, override the nested container (often a Panel or GroupBox) control's OnSizeChanged event as shown below and use this custom implementation of the Panel or GroupBox instead of the default .Net Panel control.

Visual C#

1) Add a new class named MyPanel to the project

2) Use the following code in the MyPanel Class

public class MyPanel : Panel

{

    protected override void OnSizeChanged(EventArgs e)

    {

        if (this.Handle != null)

        {

            this.BeginInvoke((MethodInvoker)delegate

            {

                base.OnSizeChanged(e);

            });

        }

    }

}





3) Build the project and use the MyPanel component from the ToolBox

Visual Basic

1) Add a new class named MyPanel to the project

2) Use the following code in the MyPanel Class

 

Public Class MyPanel

    Inherits Panel

 

    Public Delegate Sub SizeChangedDelegate(ByVal e As EventArgs)

 

    Private Sub SizeChangedDelegateHandler(ByVal e As EventArgs)

        MyBase.OnSizeChanged(e)

    End Sub

 

    Protected Overrides Sub OnSizeChanged(ByVal e As EventArgs)

        If Me.Handle.ToInt32 > 0 Then

 

            Dim obj(0) As Object

            obj(0) = e

 

            Dim scd As New SizeChangedDelegate(AddressOf SizeChangedDelegateHandler)

            Me.BeginInvoke(scd, obj)

        End If

    End Sub

 

 

End Class

 



3) Build the project and use the MyPanel component from the ToolBox



Note
The asynchronous BeginInvoke call will introduce a small delay, so have only some of the nested Panels derive from MyPanel.

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