CMFCPropertyGrid: How to catch dropdown event of combobox property

user_5479979 0
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I have CMFCPropertyGrid control to which I have added a Combobox property with CMFCPropertyGridProperty::AddOption():

    foreach(auto i, list)
    {
        str.Format(_T("<%s> %s"), i.first, i.second);
        pProp->AddOption(str);
    }

Now I need to do some code when the user drops down the list in this CMFCPropertyGrid.

I would use CBN_DROPDOWN if it were a combobox control in dialog window (it has ID). But how can I do that in case of CMFCPropertyGrid?

mfc combobox visual-studio c++
2 Answers

For a combobox-style CMFCPropertyGridProperty, the framework calls the OnClickButton member when the user clicks the down-arrow button near the top-right of the control (which causes the dropdown list to appear).

So, create a class for your control (derived from CMFCPropertyGridProperty) and override the OnClickButton member to add the code you want to run. Here's an outline of what you could do:

class MyComboControl : public CMFCPropertyGridProperty
{
    public:
        // Constructor: add some options ...
        MyComboControl(void) : CMFCPropertyGridProperty(L"Choice:", _variant_t(L""), L"Description Text") {
            AllowEdit(FALSE);
            for (int i = 0; i < 3; ++i) {
                CString text;
                text.Format(L"Option #%d", i);
                AddOption(text.GetString());
                if (i == 0) SetValue(text.GetString());
            }
        }
        // Override to handle the dropdown activation ...
        void OnClickButton(CPoint pt) override {
            //... Add any pre-drop code here.
            CMFCPropertyGridProperty::OnClickButton(pt); // Call base class
            //... Add any post-drop code here
        }
};
user_108710730

MFC will notify the parent window for property changes throught AFX_WM_PROPERTY_CHANGED

Sent to the owner of the property grid control (CMFCPropertyGridCtrl) when the user changes the value of the selected property.

BEGIN_MESSAGE_MAP(CMyDialog, CDialogEx)
    ON_REGISTERED_MESSAGE(AFX_WM_PROPERTY_CHANGED, OnPropertyChanged)
END_MESSAGE_MAP()

afx_msg LRESULT CMyDialog::OnPropertyChanged(WPARAM wparam, LPARAM lparam)
{
    if (!lparam)
        return 0;
    auto prop = reinterpret_cast<CMFCPropertyGridProperty*>(lparam);
    if (prop != m_pProp) 
    {
        auto str_variant = prop->GetValue();
        CString str;
        if(str_variant.vt == VT_BSTR)
            str = CString(str_variant.bstrVal);
    }
    return 0;
}

If you have multiple control with the grid control, you want to declare pProp as a class member m_pProp so its value can be tested.

user_46036700
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