Question

I have a WH_CALLWNDPROC hook code which handles WM_INITDIALOG message to get information about message boxes. I could get “Message”, “Title”, “Buttons” but I couldnt get “icon” information. I’m trying to use a function like below:

long getIcon(HWND hwnd) { // handle of messagebox dialog
    HWND hlbl = GetDlgItem(hwnd,20);

    wcout << "LABEL HWND: " << hlbl << endl;

    if (hlbl != NULL) { 
         LRESULT r =  SendMessage(hlbl,WM_GETICON,0,0);
         return (long)r; 
    }

    return 0; 
}

function always returns 0. I have checked by MS Spy++ and I saw that icon handle is 0.
What is the correct way to get icon?

Answer 1

The icon that is displayed on the message box dialog is implemented using a STATIC control with SS_ICON style. You can obtain the icon handle by sending that control the STM_GETICON message.

In the code in your question, the variable named hlbl is actually the window handle of the STATIC control that contains the icon. I’d name it hIconWnd. With that name change, the code to obtain the icon would look like this:

HICON getIcon(HWND hwnd) { // handle of messagebox dialog
    HWND hIconWnd = GetDlgItem(hwnd, 20);
    if (hIconWnd != NULL) { 
         return (HICON)SendMessage(hIconWnd, STM_GETICON, 0, 0); 
    }
    return NULL; 
}