Vertical size of owner draw combo box bigger than that of non owner draw combo box

Question

I have a dialog containing two combo boxes, one owner draw and one non owner draw.

This is how they are defined in the .rc file:

COMBOBOX        IDC_COMBO2,149,49,77,73,
                CBS_DROPDOWNLIST | CBS_OWNERDRAWFIXED | CBS_SORT | VS_VSCROLL
COMBOBOX        IDC_COMBO3,237,49,48,30,
                CBS_DROPDOWNLIST CBS_SORT | WS_VSCROLL

They have exactly the same height in the .rc file, but the owner draw one (the one on the left side) is slightly higher that the non owner drawn one:

.

You need to specify the CBS_NOINTEGRALHEIGHT combo box style, ideally for both. The difference in height might be due to a standard combo box using different defaults from an owner draw one. That's speculation, though. — IInspectable
@IInspectable CBS_NOINTEGRALHEIGHT is unrelated, I tried but it doesn't change anything. I suppose this is only for the drop down listbox . — Jabberwocky

xMRi xMRi · Accepted Answer · 2017-10-11T11:03:56

First the given height in the resource is the height of the combo box in the dropped down state.

This behavior is by design. The size of the combobox item height is I believe determined by the font height of the font assigned to the control. With an owner-draw combobox the system has no idea so it sends you a WM_MEASUREITEM initialized with the default size of the combobox (probably depending on the system font rather than the gui font).

So you need to handle WM_MEASUREITEM in the parent dialog...

Something like this might help (code not validated against a compiler):

void CMyDlg::OnMeasureItem(int nIDCtl, LPMEASUREITEMSTRUCT lpMeasureItemStruct)
{
  CClientDC dc(this);
  CFont* pFont = GetFont();
  CFont* pFontPrev = NULL;

  if (pFont != NULL)
    pFontPrev = dc.SelectObject(pFont);

  int iborder = ::GetSystemMetrics(SM_CYBORDER);
  CSize sz = dc.GetTextExtent(_T("0"));
  lpMeasureItemStruct->itemHeight = sz.cy + 2*iborder;

  if (pFont != NULL)
    dc.SelectObject(pFontPrev);

  __super::OnMeasureItem(nIDCtl, lpMeasureItemStruct);
}

Vertical size of owner draw combo box bigger than that of non owner draw combo box

2 Answers