VB.Net/Windows System/WndProc

Overrides WndProc(ByRef m As System.Windows.Forms.Message)

<source lang="vbnet"> Imports System Imports System.Runtime.InteropServices Imports System.Drawing Imports System.ruponentModel Imports System.Windows.Forms

Public Class MainClass

   Shared Sub Main(ByVal args As String())
       Dim myform As Form = New Form1()
       Application.Run(myform)
   End Sub

End Class

Public Class Form1

   Public Structure Rect
       Public left As Integer
       Public top As Integer
       Public right As Integer
       Public bottom As Integer
   End Structure
   Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
       Const WM_SIZING As Long = &H214
       Const WMSZ_LEFT As Integer = 1
       Const WMSZ_RIGHT As Integer = 2
       Const WMSZ_TOP As Integer = 3
       Const WMSZ_TOPLEFT As Integer = 4
       Const WMSZ_TOPRIGHT As Integer = 5
       Const WMSZ_BOTTOM As Integer = 6
       Const WMSZ_BOTTOMLEFT As Integer = 7
       Const WMSZ_BOTTOMRIGHT As Integer = 8
       Static fixed_aspect_ratio As Double = 0
       Dim new_aspect_ratio As Double
       If m.Msg = WM_SIZING And m.HWnd.Equals(Me.Handle) Then
           Dim r As Rect
           r = DirectCast( _
           Marshal.PtrToStructure(m.LParam, GetType(Rect)), _
           Rect)
           Dim width As Double = r.right - r.left
           Dim height As Double = r.bottom - r.top
           new_aspect_ratio = height / width
           If fixed_aspect_ratio = 0 Then
               fixed_aspect_ratio = new_aspect_ratio
           End If
           If fixed_aspect_ratio <> new_aspect_ratio Then
               If m.WParam.ToInt32 = WMSZ_TOPLEFT Or _
               m.WParam.ToInt32 = WMSZ_TOPRIGHT Or _
               m.WParam.ToInt32 = WMSZ_BOTTOMLEFT Or _
               m.WParam.ToInt32 = WMSZ_BOTTOMRIGHT _
               Then
                   If new_aspect_ratio > fixed_aspect_ratio Then
                       width = height / fixed_aspect_ratio
                   Else
                       height = width * fixed_aspect_ratio
                   End If
               ElseIf m.WParam.ToInt32 = WMSZ_LEFT Or _
               m.WParam.ToInt32 = WMSZ_RIGHT _
               Then
                   height = width * fixed_aspect_ratio
               ElseIf m.WParam.ToInt32 = WMSZ_TOP Or _
               m.WParam.ToInt32 = WMSZ_BOTTOM _
               Then
                   width = height / fixed_aspect_ratio
               End If
               If m.WParam.ToInt32 = WMSZ_TOP Or _
               m.WParam.ToInt32 = WMSZ_TOPLEFT Or _
               m.WParam.ToInt32 = WMSZ_TOPRIGHT _
               Then
                   r.top = r.bottom - CInt(height)
               Else
                   r.bottom = r.top + CInt(height)
               End If
               If m.WParam.ToInt32 = WMSZ_LEFT Or _
               m.WParam.ToInt32 = WMSZ_TOPLEFT Or _
               m.WParam.ToInt32 = WMSZ_BOTTOMLEFT _
               Then
                   r.left = r.right - CInt(width)
               Else
                   r.right = r.left + CInt(width)
               End If
               Marshal.StructureToPtr(r, m.LParam, True)
           End If
       End If
       MyBase.WndProc(m)
   End Sub

End Class <Global.Microsoft.VisualBasic.rupilerServices.DesignerGenerated()> _ Partial Public Class Form1

   Inherits System.Windows.Forms.Form
   "Form overrides dispose to clean up the component list.
   <System.Diagnostics.DebuggerNonUserCode()> _
   Protected Overrides Sub Dispose(ByVal disposing As Boolean)
       If disposing AndAlso components IsNot Nothing Then
           components.Dispose()
       End If
       MyBase.Dispose(disposing)
   End Sub
   "Required by the Windows Form Designer
   Private components As System.ruponentModel.IContainer
   "NOTE: The following procedure is required by the Windows Form Designer
   "It can be modified using the Windows Form Designer.  
   "Do not modify it using the code editor.
   <System.Diagnostics.DebuggerStepThrough()> _
   Private Sub InitializeComponent()
       Me.SuspendLayout()
       "
       "Form1
       "
       Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
       Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
       Me.ClientSize = New System.Drawing.Size(292, 273)
       Me.Name = "Form1"
       Me.Text = "FixedAspectRatio"
       Me.ResumeLayout(False)
   End Sub

End Class

      </source>