PPT97: Sample VB Code to Control Window Redraw

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Overview of LockWindowUpdate() API Function

To use the LockWindowUpdate function, you must have a handle (HWND) to the window you want to lock. The sample code uses the FindWindow() API function to obtain a handle to the main application window:

   hwnd = FindWindow("PP97FrameClass", 0&)
				

If FindWindow() is successful, the variable hwnd (a long) holds a handle to the main application window. Now that you have a handle you can use the LockWindowUpdate() function to prevent that window from redrawing:

   LockWindowUpdate (hwnd)
				

To unlock the window you must call LockWindowUpdate() with NULL (0&) as the parameter.

   LockWindowUpdate (0&)
				

It is very important to add this statement. If your code locks a window and then fails to unlock it, the window stays locked even after your macro ends.

The Lock Window Version of the SetSmallCaps Macro

' API declarations for LockWindowUpdate() and FindWindow().
   Declare Function LockWindowUpdate Lib "user32" _
      (ByVal hwndLock As Long) As Long
   Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
      (ByVal lpClassName As String, ByVal lpWindowName As Long) As Long

   Sub SetSmallCaps()

      ' Used to trap errors.
      On Error Resume Next
      Err.Clear

      ' Dimension variables.
      Dim oTextRange As TextRange
      Dim oWordRange As TextRange
      Dim lNewFontSize As Long
      Dim i As Long
      Dim hwnd As Long

      ' Get a handle to the main application window.
      hwnd = FindWindow("PP97FrameClass", 0&)

      ' Lock the main applicationwindow. 
      ' Prevents PowerPoint from redrawing the main window.
      LockWindowUpdate (hwnd)

      ' Get reference to the selected text.
      Set oTextRange = ActiveWindow.Selection.TextRange

      ' Check if error occurred getting text selection.
      If Err.Number <> 0 Then

         MsgBox "Cannot apply Small Caps to selection. Please select " _
            & "some text and run the macro again.", vbExclamation, _
            "Invalid Selection"

         ' Stop the macro.
         End
      End If

      ' Loop through the words in the selection.
      For i = 1 To oTextRange.Paragraphs.Words.Count

         ' Get a reference to the first word in the selection.
         Set oWordRange = oTextRange.Paragraphs.Words(i, 1)

         'With oWordRange.Paragraphs.Characters(1, 1)
         With oWordRange.Characters(1, 1)

            ' Set the first letter to be upper case.
            .ChangeCase ppCaseUpper

            ' Calculate the new font size.
            lNewFontSize = ((.Font.Size) / 1.3)

         End With

         ' Change the remaining characters to the new font size.
         With oWordRange
            .Characters(2, (oWordRange.Length)).Font.Size = lNewFontSize
            .Characters(2, (oWordRange.Length)).ChangeCase ppCaseUpper
         End With

      Next i

      ' Unlocks the main application window. Whenever you use the
      ' LockWindowUpdate API to lock a window, you must call
      ' LockWindowUpdate again (with a Null parameter 0&) to allow the
      ' window to redraw.
      LockWindowUpdate (0&)

   End Sub