MFC Combo-Box Control is not showing the full list of items when I click the drop-down menu

Question

I'm coding an app in MSVS 2008, which has a ComboBox control which I initialize thru the code as below:

static char*                    OptionString[4] = {"Opt1",
                                                   "Opt2",
                                                   "Opt3",
                                                   "Opt4"};


BOOL CMyAppDlg::OnInitDialog()
{
    CDialog::OnInitDialog();

 // Set the icon for this dialog.  The framework does this automatically
 //  when the application's main window is not a dialog
 SetIcon(m_hIcon, TRUE);   // Set big icon
 SetIcon(m_hIcon, FALSE);  // Set small icon

    // TODO: Add extra initialization here

    m_Option.AddString(OptionString[0]);
    m_Option.AddString(OptionString[1]);
    m_Option.AddString(OptionString[2]);
    m_Option.AddString(OptionString[3]);
    m_Option.SetCurSel(0);

    return TRUE;  // return TRUE  unless you set the focus to a control
}

In the above code, m_Option is the Control variable for the ComboBox Control.

Now, when I build the app and click the down-arrow, the drop-down box shows the first option ONLY(since I've selected that thru my code). But, if i press down-arrow key on keyboard, it cycles thru the options in the order I've inserted, but never does it show more than 1 option in the box. So, In case an user wants to select option3, he has to cycle through options 1 and 2 !! Though once I select any option using the keyboard, the appropriate event handlers are fired, I'm miffed by this behaviour , as is understandable.

I'm listing the properties of the combo-box control as well - only the properties that are true(rest are set to false):

1. Type - Dropdown
2. Vertical Scrollbar
3. Visible Tabstop

This has bugged me for weeks now. Can anyone pls enlighten me ?

Answer 1

In the dialog layout designer, while designing the dialog, click the "down arrow" on the combobox. You can then drag down on the bottom of the combobox's outline to increase its height.

Answer 2

We can programmatically modify dropdown height as:

CRect rctCmbCountry, rctDropDownCountry;
m_Cmb_Country.GetClientRect(&rctCmbCountry); 
m_Cmb_Country.GetDroppedControlRect(&rctDropDownCountry); 
itemHeight = m_Cmb_UI_Country.GetItemHeight(-1); 
m_Cmb_UI_Country.GetParent()->ScreenToClient(&rctDropDownCountry); 
rctDropDownCountry.bottom = rctDropDownCountry.top + rctCmbCountry.Height() + itemHeight * iNoOfITemToShowInComboDropDown; 
m_Cmb_UI_Country.MoveWindow(&rctDropDownCountry);

reference: http://codetechnic.blogspot.com/2012/04/vc-mfc-how-to-set-combobox-dropdown.html#:~:text=1)%20Designer%20%2D%20through%20the%20designer,you%20it's%20anything%20but%20intuitive.