Visual Studio MFC change text in Edit Control while typing/dynamically

Question

Hello,

I am trying to set up a MFC C++ App in Visual Studio 2019 such that if the user turns on a 'Letters to Numbers' mode via a radio button, the letters in their text change AS THEY TYPE to numbers.

void Onsomebtnclick()
{
//convert CString to String of m_inputString
//do some string manipulation
//convert back to CString
//SetDlgItemText(txtInputBox, result)
}

Currently, for testing I can see how it would work for a button on click, it would do the logic, and just SetDlgItemText of the result. But that would be after they have typed, not WHILE they are typing.

Answer 1

Hi daktaklakpak-2506

Maybe you could use OnEnChangeEdit event to modify your string, and then use DoDataExchange method to update your edit control, which is like:

void CMFCApplication1Dlg::DoDataExchange(CDataExchange* pDX)  
{  
    CDialogEx::DoDataExchange(pDX);  
    DDX_Control(pDX, IDC_EDIT1, m_editctrl);  
    if (str) {  
        DDX_Text(pDX, IDC_EDIT1, str);  
    }     
}  

void CMFCApplication1Dlg::OnEnChangeEdit1()  
{  
    // TODO:  If this is a RICHEDIT control, the control will not  
    // send this notification unless you override the CDialogEx::OnInitDialog()  
    // function and call CRichEditCtrl().SetEventMask()  
    // with the ENM_CHANGE flag ORed into the mask.  

    // TODO:  Add your control notification handler code here  

    GetDlgItemText(IDC_EDIT1,str);  

    if (str) {  
        CString r = str.Right(1);  

        if (r == 'I' || r == 'i')  
            str.Replace(r, _T("1"));  
        else if (r == 'E' || r == 'e')  
            str.Replace(r, _T("3"));  
        else if (r == 'O' || r == 'o')  
            str.Replace(r, _T("0"));  

        UpdateData(false);  
        len = m_editctrl.GetWindowTextLengthW();    
        m_editctrl.SetSel(len, len,false);    //Move the cursor to the end of the text  
        m_editctrl.SetFocus();  
    }  
}  

Hope it could help you.

Best Regards,
Dylan

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Answer 2

One approach would be to derive your own class from CEdit. In your derived class override PreTranslateMessage to inspect WM_CHAR messages and replace characters based on your defined rules.

Add a flag that can be checked in your PreTranslateMessage override to turn replacement on or off. Set or clear the flag in the dialog's handlers for the radio button BN_CLICKED notifications.

Answer 3

@Dylan Zhu-MSFT
Hello Dylan, I just got something similar to work where the text is changing correctly, but I am a newbie and didn't understand until I read your code that I need to set a Control variable to do the SetSel and SetFocus methods. Your answer was super helpful and got me going. Thanks!

P.S. I'm guessing I can set multiple variables (of either type VALUE or CONTROL) to any widget in my DLG?