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LayoutEngine Class

Provides the base class for implementing layout engines.

Namespace:  System.Windows.Forms.Layout
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

'Declaration
Public MustInherit Class LayoutEngine
'Usage
Dim instance As LayoutEngine

Use the LayoutEngine class when you want to create custom layout behavior at run time. Derive your own class from the LayoutEngine class and override the Layout method to define your custom layout behavior.

The following code example demonstrates the use of the LayoutEngine class to implement custom layout behavior.

Imports System
Imports System.Collections.Generic
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Imports System.Windows.Forms.Layout

' This class demonstrates a simple custom layout panel. 
' It overrides the LayoutEngine property of the Panel 
' control to provide a custom layout engine.  
Public Class DemoFlowPanel
    Inherits Panel

    Private layoutEng As DemoFlowLayout

    Public Sub New()
    End Sub 

    Public Overrides ReadOnly Property LayoutEngine() As LayoutEngine
        Get 
            If layoutEng Is Nothing Then
                layoutEng = New DemoFlowLayout()
            End If 

            Return layoutEng
        End Get 
    End Property 
End Class 

' This class demonstrates a simple custom layout engine. 
Public Class DemoFlowLayout
   Inherits LayoutEngine

    Public Overrides Function Layout( _
    ByVal container As Object, _
    ByVal layoutEventArgs As LayoutEventArgs) As Boolean 

        Dim parent As Control = container

        ' Use DisplayRectangle so that parent.Padding is honored. 
        Dim parentDisplayRectangle As Rectangle = parent.DisplayRectangle
        Dim nextControlLocation As Point = parentDisplayRectangle.Location

        Dim c As Control
        For Each c In parent.Controls

            ' Only apply layout to visible controls. 
            If c.Visible <> True Then 
                Continue For 
            End If 

            ' Respect the margin of the control: 
            ' shift over the left and the top.
            nextControlLocation.Offset(c.Margin.Left, c.Margin.Top)

            ' Set the location of the control.
            c.Location = nextControlLocation

            ' Set the autosized controls to their  
            ' autosized heights. 
            If c.AutoSize Then
                c.Size = c.GetPreferredSize(parentDisplayRectangle.Size)
            End If 

            ' Move X back to the display rectangle origin.
            nextControlLocation.X = parentDisplayRectangle.X

            ' Increment Y by the height of the control  
            ' and the bottom margin.
            nextControlLocation.Y += c.Height + c.Margin.Bottom
        Next c

        ' Optional: Return whether or not the container's  
        ' parent should perform layout as a result of this  
        ' layout. Some layout engines return the value of  
        ' the container's AutoSize property. 
        Return False 

    End Function 
End Class

System.Object
  System.Windows.Forms.Layout.LayoutEngine

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0
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