Binaryworld - Prevent an iconized window from being restored ... [ VB -> Forms & Controls ]

When the user clicks on an iconized (minimized) form in the taskbar, Windows sends that form a WM_QUERYOPEN message, and inspects the value returned to the operating system. If this value is zero, the operation is canceled.

Using subclassing you can therefore determine when a form is about to be restored, and you can also refuse to restore it by returning 0. Here is a code snippet that does the trick:

Click here to copy the following block

' REQUIRES THE MSGHOOK.DLL COMPONENT
'
' you can omit the following constant definition,
' because it is contained in the MsgHook type library
Const WM_QUERYOPEN = &H13

Dim WithEvents FormHook As MsgHook

Private Sub Form_Load()
  ' start form subclassing
  Set FormHook = New MsgHook
  FormHook.StartSubclass hWnd
End Sub

Private Sub FormHook_AfterMessage(ByVal uMsg As Long, ByVal wParam As Long, _
  ByVal lParam As Long, retValue As Long)
  If uMsg = WM_QUERYOPEN Then
    ' The iconized form is being restored.
    ' ...
    ' Uncomment the next line to prevent the window from being restored.
    ' retValue = False
  End If
End Sub