Stop that Flickering!

Do your applications flicker whilst you update your controls? Find out how to stop it happening with one little-known API call, in this handy copy-and-paste code snippet.

To run, simply copy the below code into a module, then call the LockWindow method, passing the handle (.hWnd property) of the object you want to lock, such as your form or a particular control.

To unlock, simply run the UnlockWindow method.

This code works by calling the LockWindowUpdate API call of User32.dll, which simply 'locks' a form - effectively displaying just the image of it, until an unlock is performed.

Usage

LockWindow(Form1.hWnd)

'Do updating here

UnloadWindow

Code

Declare Function LockWindowUpdate Lib "user32" _
    (ByVal hWnd As Long) As Long

Public Sub LockWindow(hWnd As Long)
    LockWindowUpdate hWnd
End Sub

Public Sub UnlockWindow()
    LockWindowUpdate 0
End Sub