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Multi-line entries in ListBoxes & ComboBoxes

I have combo boxes and list boxes that I fill with entries from a database. Some of these entries are very long. I have code that adjusts the width of the combobox droplist or list box extent to that of the longest line in it. Sometimes these are very wide and look kind of ackward. I was wondering if there was a way to have the text wrap to the next line in long strings. The highlighted entry then would have to be more than one line for these entries. Is this possible to do and if so, how?

migel

Hi! You can use Ownerdraw LisBox and ComboBox.
Just derive your own class from the MFC CListBox(CComboBox) and override OnMeasureItem and OnDrawItem methods.

OnMeasureItem method is very important for your task. In this method you must define height of the each item in the list(combo).
for example :// in Rc file list must be defined with LBS_OWNERDRAWVARIABLE style

OnMeasureItem(int nIDCtl, LPMEASUREITEMSTRUCT lpMeasureItemStruct)
{
CFont * pFont = GetFont();
CFont* pOldFont = 0;
CString str;
CDC* pDC = GetDC();
pOldFont = pDC->SelectObject(pFont);
GetText(lpMeasureItemStruct->itemID, str);
RECT rc = {0, 0, lpMeasureItemStruct->itemWidth, 0};
pDC->DrawText(str, str.GetLength(), &rc, DT_CALCRECT|DT_LEFT|DT_WORDBREAK);
lpMeasureItemStruct->itemHeight = rc.bottom;
pDC->SelectObject(pOldFont);
ReleaseDC(pDC);
}

// draw item
OnDrawItem( int nIDCtl, LPDRAWITEMSTRUCT lpDrawItemStruct )
{
CFont * pFont = GetFont();
CFont* pOldFont = 0;
CDC dc;
dc.Attach(lpDrawItemStruct->hDC);
CString str;
pOldFont = dc.SelectObject(pFont);
GetText(lpDrawItemStruct->itemID, str);
// select proper font and background colors according item state
// i can provide full code to do this
dc.DrawText(str, str.GetLength(), &lpDrawItemStruct->rcItem, DT_LEFT|DT_WORDBREAK);
lpMeasureItemStruct->itemHeight = rc.bottom;
dc.SelectObject(pOldFont);
dc.Detach();
}

joeslow

ASKER

Thank you for your help. I've played with the code a little and had to make a few minor changes that I think work (See // ***)
I don't know how to set the selected item to highlighted though. If you could help me with that, I would greatly appreciate it.

void CMultiLineListBox::DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct)
{
CFont * pFont = GetFont();
CFont* pOldFont = 0;
CDC dc;
dc.Attach(lpDrawItemStruct->hDC);
CString str;
pOldFont = dc.SelectObject(pFont);
GetText(lpDrawItemStruct->itemID, str);
// select proper font and background colors according item state
// i can provide full code to do this
dc.DrawText(str, str.GetLength(), &lpDrawItemStruct->rcItem, DT_LEFT|DT_WORDBREAK);
// **** lpDrawItemStruct->itemHeight = rc.bottom;
dc.SelectObject(pOldFont);
dc.Detach();
}

void CMultiLineListBox::MeasureItem(LPMEASUREITEMSTRUCT lpMeasureItemStruct)
{
CFont * pFont = GetFont();
CFont* pOldFont = 0;
CString str;
CDC* pDC = GetDC();
pOldFont = pDC->SelectObject(pFont);
GetText(lpMeasureItemStruct->itemID, str);
//**** RECT rc = {0, 0, lpMeasureItemStruct->itemWidth, 0};
RECT rc;
GetWindowRect(&rc);
rc.left = 0;
rc.top = 0;
rc.bottom = 0;
pDC->DrawText(str, str.GetLength(), &rc, DT_CALCRECT|DT_LEFT|DT_WORDBREAK);
lpMeasureItemStruct->itemHeight = rc.bottom;
pDC->SelectObject(pOldFont);
ReleaseDC(pDC);
}

migel

to reflect state of the item(selected, focused...) you must check itemState of the DRAWITEMSTRUCT:
for example:

COLORREF crOldColor;
if (lpDrawItemStruct->itemState & ODS_SELECTED)
      {
      CBrush bkgnd(::GetSysColor(COLOR_HIGHLIGHT));
      dc.FillRect(&rect, &bkgnd);
      crOldColor = dc.SetTextColor(::GetSysColor(COLOR_HIGHLIGHTTEXT));
      }
else
{
      CBrush bkgnd(::GetSysColor(COLOR_WINDOW));
      dc.FillRect(&lpDrawItemStruct->rcItem, &bkgnd);
      crOldColor = dc.SetTextColor(::GetSysColor(COLOR_WINDOWTEXT));
}
//..Draw Text
// ... select old colors
      dc.SetTextColor(crOldColor);

      if (lpDrawItemStruct->itemState & ODS_FOCUS)
            dc.DrawFocusRect(&lpDrawItemStruct->rcItem);

joeslow

ASKER

Now it seems to work pretty good. The only issue I have left is that when I call AddString("Some long string") during InitDialog it seems to add them fine. When I call the same function later, like on a button click, it adds only one line of the long string. I checked the rect calculated in MeasureItem's DrawText and it comes back with a height of only one line. What could be the problem?

ASKER CERTIFIED SOLUTION

migel

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joeslow

ASKER

Migel,

Thank you for your help. It works great. The following is the code I ended up with. Do you see anything wrong with it? Also, what would be the differences (if any) for a ComboBox (instead of a ListBox)?

void CMLListBox::DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct)
{
CFont * pFont = GetFont();
CFont* pOldFont = 0;
CDC dc;
dc.Attach(lpDrawItemStruct->hDC);
CString str;
pOldFont = dc.SelectObject(pFont);
GetText(lpDrawItemStruct->itemID, str);

int bkOldMode;
COLORREF crOldColor;
if (lpDrawItemStruct->itemState & ODS_SELECTED)
{
CBrush bkgnd(::GetSysColor(COLOR_HIGHLIGHT));
dc.FillRect(&lpDrawItemStruct->rcItem, &bkgnd);
crOldColor = dc.SetTextColor(::GetSysColor(COLOR_HIGHLIGHTTEXT));
bkOldMode = dc.SetBkMode(TRANSPARENT);
}
else
{
CBrush bkgnd(::GetSysColor(COLOR_WINDOW));
dc.FillRect(&lpDrawItemStruct->rcItem, &bkgnd);
crOldColor = dc.SetTextColor(::GetSysColor(COLOR_WINDOWTEXT));
}
//..Draw Text
dc.DrawText(str, str.GetLength(), &lpDrawItemStruct->rcItem, DT_LEFT|DT_WORDBREAK);

if (lpDrawItemStruct->itemState & ODS_FOCUS)
{
dc.DrawFocusRect(&lpDrawItemStruct->rcItem);
}

// ... select old colors
dc.SetTextColor(crOldColor);
dc.SelectObject(pOldFont);
dc.SetBkMode(bkOldMode);
dc.Detach();
}

void CMLListBox::MeasureItem(LPMEASUREITEMSTRUCT lpMeasureItemStruct)
{
CFont * pFont = GetFont();
CFont* pOldFont = 0;
CString str;
CDC* pDC = GetDC();
pOldFont = pDC->SelectObject(pFont);
GetText(lpMeasureItemStruct->itemID, str);

RECT rc;
::memset(&rc, 0, sizeof(RECT));
GetClientRect(&rc);

pDC->DrawText(str, str.GetLength(), &rc, DT_CALCRECT|DT_LEFT|DT_WORDBREAK);
lpMeasureItemStruct->itemHeight = rc.bottom;
pDC->SelectObject(pOldFont);
ReleaseDC(pDC);
}

talltk

Hi,

I'm an amateur reading this solution. I don't know where to ask this but, here it goes:

What class is GetText function in? I keep getting compiler errors when I call GetText(). I added the OnMeasureItem and OnDrawItem in my Dialog class with a member variable m_combobox.

If I try to replace GetText with m_combobox.GetLBText(), I also get errors. Please help.

Multi-line entries in ListBoxes &amp; ComboBoxes

Multi-line entries in ListBoxes & ComboBoxes