Subclassing controls

Hi all - I just wanted to ask a question regarding subclassing multiple controls in the one dialog.

For instance If I have a dialog with three edit controls, all of which must only take integers between 0 and 255 - the only way I think I can achieve this is to subclass the controls (which is no problem). However, what is the ettiquette with regards to this? If each of the three controls are identical, is it OK to use the same WNDPROC to subclass the controls, or should they be seperate (in effect replicating the code)?

Thanks all.

Speaking of subclassing controls - i have subclassed an edit control to make sure that the user only enters unsigned integers no greater or less than 255 or 0. But the code looks really ugly. Any suggestions for improving this, or perhaps I have overlooked a much simpler way of achieving this. ;)

Code:

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LRESULT CALLBACK CApp::EditRedProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
        BOOL fError;
        UINT value;
        LRESULT lresult;
        HWND hParent = GetParent(hwnd);

        if (msg == WM_CHAR)
        {
                // We have to allow the backspace character through!
                if ((char)wParam == '\b')
                        return CallWindowProc(OldRedEditProc, hwnd, msg, wParam, lParam);

                // Make sure we have an actual digit
                if (!isdigit((char)wParam))
                        return 0;
                else
                {
                        lresult = CallWindowProc(OldRedEditProc, hwnd, msg, wParam, lParam);

                        value = GetDlgItemInt(hParent, IDC_REDEDIT, &fError, FALSE);
                        if (value > 255 || value < 0 || fError == FALSE)
                        {
                                // Clean out the edit control
                                SendMessage(hwnd, WM_SETTEXT, 0, (LPARAM)TEXT(""));
                        }
                        return lresult;
                }
        }
        else
                return CallWindowProc(OldRedEditProc, hwnd, msg, wParam, lParam);
}

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Quote:

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Originally Posted by filler_bunny

three edit controls, all of which must only take integers between 0 and 255 - the only way I think I can achieve this is to subclass the controls.

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You don't have to subclass them to achieve this. Instead you can give them the ES_NUMBER style, send an EM_SETLIMITTEXT message to limit the maximum number of characters the edit can contain to three and handle EN_CHANGE notifications (as parent WM_COMMAND messages) to ensure the 0-255 range is not exceeded.

Having said that, if you still prefer to subclass the controls then a single subclass procedure is perfectly fine. To satisfy your curiosity you may wish to compare the returned WNDPROC values from SetWindowLongPtr when you subclass windows with the same window class name.

Excellent - thank you very much. :)