Subclassing Question *Resolved*

[Illspirit]

Hi,

I havent used subclassing much before, but I'm trying to stop picturebox control from being painted (long story, dont think its relevent to the Q).

I've subclassed the picturebox and when i receive a WM_PAINT message, can i just disguard it? I want all the other messages to work as normal. Ive tried this...

Public Function WindProc(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    
    If Not wMsg = WM_PAINT Then
        WindProc = CallWindowProc(WndProcOld&, hwnd&, wMsg&, wParam&, lParam&)
    End If
    Debug.Print wMsg, Now
    
End Function

...but the debug window gets printed with loads of '15's over and over and over, which doesnt seem right. I'm a bit clueless here, can anyone point me in the right direction?

Thanks,
Illspirit

[Illspirit]

*bump*

[plenderj]

Can you post all of your code related to the subclassing ?

[MerrionComputin]

WM_PAINT is a special kind of message in that it is posted to a window whenever that window's message queue is empty and the window has been marked as needing repainting.

Simply ignoring the message will have no effect because once you return from your subclassing function the queue will be empty and the window will still be marked as requiring painting, so another WM_PAINT message will be posted and so on ad infinitum.

To mark the window as no longer needing painting you must call the ValidateRect API e.g.:

Declare Function ValidateRectByLong Lib "user32" Alias "ValidateRect" (ByVal hwnd As Long,Byval lpRect As Long) As Long
 
'...
Public Function WindProc(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    
    If Not wMsg = WM_PAINT Then
        WindProc = CallWindowProc(WndProcOld&, hwnd&, wMsg&, wParam&, lParam&)
    Else
       Call ValidateRect(hwnd,0)
    End If
        
End Function

[plenderj]

Originally posted by MerrionComputin
WM_PAINT is a special kind of message in that it is posted to a window whenever that window's message queue is empty and the window has been marked as needing repainting.

Simply ignoring the message will have no effect because once you return from your subclassing function the queue will be empty and the window will still be marked as requiring painting, so another WM_PAINT message will be posted and so on ad infinitum.

To mark the window as no longer needing painting you must call the ValidateRect API e.g.:

Declare Function ValidateRectByLong Lib "user32" Alias "ValidateRect" (ByVal hwnd As Long,Byval lpRect As Long) As Long
 
'...
Public Function WindProc(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    
    If Not wMsg = WM_PAINT Then
        WindProc = CallWindowProc(WndProcOld&, hwnd&, wMsg&, wParam&, lParam&)
    Else
       Call ValidateRect(hwnd,0)
    End If
        
End Function

What a coincidence. I just about to say that with the exact same code.

[Illspirit]

great stuff! thanks alot