Overcome OS Imposed Windows Form Minimum Size Limit

Question

In an application I am developing, I need to be able to make a windows form smaller than the minimum height limit imposed by the operating system (36 px in Vista). I have t

Answer 1

I wish I could give more than +1 to Zach for that, it's great and saved my bacon. For future readers, here's the VB translation of Zach's code:

Imports System.Runtime.InteropServices
Imports System.Windows.Forms
Imports System.Drawing

Public Class MyForm

    ' Ghastly hack to allow the form to be narrower than the widows-imposed limit (about 132 in WIndows 7)
    ' Thanks to http://stackoverflow.com/questions/992352/overcome-os-imposed-windows-form-minimum-size-limit

    Private Const WM_WINDOWPOSCHANGING As Integer = &H46
    Private Const WM_GETMINMAXINFO As Integer = &H24
    Protected Overrides Sub WndProc(ByRef m As Message)
        If m.Msg = WM_WINDOWPOSCHANGING Then
            Dim windowPos As WindowPos = CType(m.GetLParam(GetType(WindowPos)), WindowPos)

            ' Make changes to windowPos

            ' Then marshal the changes back to the message
            Marshal.StructureToPtr(windowPos, m.LParam, True)
        End If

        MyBase.WndProc(m)

        ' Make changes to WM_GETMINMAXINFO after it has been handled by the underlying
        ' WndProc, so we only need to repopulate the minimum size constraints
        If m.Msg = WM_GETMINMAXINFO Then
            Dim minMaxInfo As MINMAXINFO = DirectCast(m.GetLParam(GetType(MINMAXINFO)), MINMAXINFO)
            minMaxInfo.ptMinTrackSize.X = Me.MinimumSize.Width
            minMaxInfo.ptMinTrackSize.Y = Me.MinimumSize.Height
            Marshal.StructureToPtr(minMaxInfo, m.LParam, True)
        End If
    End Sub

    Private Structure WindowPos
        Public hwnd As IntPtr
        Public hwndInsertAfter As IntPtr
        Public x As Integer
        Public y As Integer
        Public width As Integer
        Public height As Integer
        Public flags As UInteger
    End Structure
     _
    Private Structure MINMAXINFO
        Dim ptReserved As Point
        Dim ptMaxSize As Point
        Dim ptMaxPosition As Point
        Dim ptMinTrackSize As Point
        Dim ptMaxTrackSize As Point
    End Structure

    .... rest of the form

End Class