Prevent a window from repainting

Author:

Steve McMahon(steve@vbaccelerator.com)

Keywords:

API,GDI,Graphics,Windows Controls

Updated:

01/08/98

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This tip show show to prevent an area of a window from repainting. When you have a lot of items to add to a control, such as a ListBox or ListView, this can considerably speed up the process. On my system, it speeds up adding 10,000 items to a List Box by over 30%.

Create a new project, and add a ListBox, a Command Button and a CheckBox to the form. Change the caption of the CheckBox to '&Lock Update' and change the caption of the Command Button to '&Load...'. Then paste the following code into the form:

Private Declare Function LockWindowUpdate Lib "user32" (ByVal hwndLock As Long) As Long
Private Declare Function timeGetTime Lib "winmm.dll" () As Long

Private Sub Command1_Click()
Dim i As Long
Dim lTIme As Long

    lTIme = timeGetTime()
   
    If (Check1.Value = Checked) Then
        LockWindowUpdate List1.hWnd
    End If
   
    List1.Clear
    For i = 1 To 10000
        List1.AddItem "Test " & i
    Next i
   
    If (Check1.Value = Checked) Then
        LockWindowUpdate 0
        List1.Refresh
    End If
   
    MsgBox "Time: " & timeGetTime - lTIme
   
End Sub

Related Tips and Articles:

• Force an area of a Window to Repaint