How to make a form ALWAYS ON TOP!

[TT(n)]

    Const HWND_NOTOPMOST As Int32 = -2
    Const HWND_TOPMOST As Int32 = -1
    Const HWND_TOP As Int32 = 0
    Const HWND_BOTTOM As Int32 = 1
    Const SWP_NOSIZE As Int32 = 1
    Private Structure RECT
        Public rLeft, rTop, rRight, rBottom As Int32
    End Structure
    Private Declare Function apiGetTopWindow Lib "user32" Alias "GetTopWindow" (ByVal hWnd As Int32) As Int32
    Private Declare Function apiGetWindowRect Lib "user32" Alias "GetWindowRect" (ByVal hWnd As Int32, ByRef lpRect As RECT) As Boolean
    Private Declare Function apiSetWindowPos Lib "user32" Alias "SetWindowPos" (ByVal hWnd As Int32, ByVal hWndInsertAfter As Int32, ByVal X As Int32, ByVal Y As Int32, ByVal cx As Int32, ByVal cy As Int32, ByVal wFlags As Int32) As Boolean
    Private Declare Function apiLockWindowUpdate Lib "user32" Alias "LockWindowUpdate" (ByVal hWndLock As Int32) As Int32
    Private t As New Threading.Thread(AddressOf KeepOnTop)
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        t.Start() '''''''''''''''''''''''''''''Start thread to keep top most status
    End Sub
    Private Sub Form1_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
        t.Abort() ''''''''''''''''''''''''''''''''Abort keeping the window topmost
    End Sub
    Private Sub KeepOnTop()
        Dim hwnd As Int32, r As New RECT
        Do
            hwnd = Me.Handle.ToInt32
            apiLockWindowUpdate(0)'''''''''''''''''''''''''''Unlock any previous calls
            apiLockWindowUpdate(hwnd) ''''''''''''''''''''Lock the desktop from updating for a moment, so that tooltips dont get stranded
            If apiGetTopWindow(HWND_TOP) <> hwnd Then ''''If the topmost window is not the specified window
                apiGetWindowRect(hwnd, r) ''''''''''''''''Get rectangular dimensions of the specified window
                apiSetWindowPos(hwnd, HWND_TOPMOST, r.rLeft, r.rTop, 0, 0, SWP_NOSIZE) 'Set the specified window as the topmost
                apiLockWindowUpdate(0) '''''''''''''''''''''''Unlock desktop so that it can update itself visually
            End If
            System.Threading.Thread.Sleep(1) '''''''''''''Sleep for the shortest period possible
        Loop
    End Sub

[Cutha]

No workie in 2005, generates a cross-thread error.

[Cutha]

This takes care of the cross threading issue, using Delegates. Is this the best way to do this in this example? Aside from using the SetWindowPos API to set the form on top

Public Class Form1

    Public Declare Function apiFindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Integer
    Public Declare Function apiGetTopWindow Lib "user32" Alias "GetTopWindow" (ByVal hwnd As Integer) As Integer
    Public Declare Function apiGetDesktopWindow Lib "user32" Alias "GetDesktopWindow" () As Integer
    Dim rTopMost As New System.Threading.Thread(AddressOf ReturnTopMost) 'Declare thread for returning topmost

    Delegate Function HandleDelegate() As Int32
    Public hndl As HandleDelegate

    Delegate Sub setTopMostDelegate()
    Public setTopMost As setTopMostDelegate

    Delegate Sub setRefreshDelegate()
    Public setRefresh As setRefreshDelegate

    Delegate Function getTextDelegate() As String
    Public getText As getTextDelegate

    Public Sub setTopMostSub()
        Me.TopMost = True
    End Sub

    Public Sub setRefreshSub()
        Me.Refresh()
    End Sub

    Public Function getHandleFunc() As Int32
        Return Me.Handle.ToInt32
    End Function

    Public Function getTextSub() As String
        Return Me.Text.ToString
    End Function

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        hndl = New HandleDelegate(AddressOf getHandleFunc)
        setTopMost = New setTopMostDelegate(AddressOf setTopMostSub)
        setRefresh = New setRefreshDelegate(AddressOf setRefreshSub)
        getText = New getTextDelegate(AddressOf getTextSub)

        rTopMost.Start() 'Start Return Top Most thread.
    End Sub

    Private Sub Form1_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
        rTopMost.Abort() 'Abort TopMost thread if the main form is closed 
    End Sub

    Public Sub ReturnTopMost()

        Dim iHndl As Int32

        iHndl = Me.Invoke(hndl)

        Try
            Do
                System.Threading.Thread.Sleep(1) 'Sleep for a short period
                If apiGetTopWindow(apiGetDesktopWindow) <> iHndl Then
                    Me.Invoke(setTopMost)
                    Me.Invoke(setRefresh)
                End If
                apiFindWindow(vbNullString, Me.Invoke(getText))  'This throws an error if the main window has been terminated.
            Loop
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try

    End Sub

End Class

[TT(n)]

Thanks, it looks pretty good!
I think SetWindowPos, would be better for use with external forms.
A bit more more work perhaps.

[TT(n)]

OOoops, Cutha you must of looked at the example after I edited it.

The refresh should be in the loop every time. Sorry.
Check to make sure it does not consume cycles in an idle state.
For example Sleep(0), uses a bunch.


Change the ReturnTopMost sub:

   Public Sub ReturnTopMost()

        Dim iHndl As Int32

        iHndl = Me.Invoke(hndl)

        Try
            Do
                System.Threading.Thread.Sleep(1) 'Sleep for a short period
                If apiGetTopWindow(apiGetDesktopWindow) <> iHndl Then
                    Me.Invoke(setTopMost)
                End If
                    Me.Invoke(setRefresh)
                apiFindWindow(vbNullString, Me.Invoke(getText))  'This throws an error if the main window has been terminated.
            Loop
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try

    End Sub

[jhammer]

You did it right by using Invoke.

I just have a non-relevant comment that I couldn't stop myself from writing: Don't use On Error GoTo. This is VB6 syntax. Never use GoTo and Labels. Use exceptions instead (Try...Catch)