How to load string of array in to combobox faster in MFC?

Question

I have an array of 1000 strings how to load them in to combo box faster like kind of dumping in to rather than iterating it? And to copy the combo box data to some 10 other combo box?

Answer 1

I'm not aware of any way to load multiple strings atomically, but there are a couple of things that you can do to make the process more efficient:

• Call CComboBox::InitStorage before adding items to pre-allocate memory
• Use InsertString instead of AddString to prevent triggering a sort on each addition (assuming the CBS_SORT style is enabled)

Answer 2

I will consider using a pick list instead of a combo box for performance.

A general rule of thumb to improve performance when inserting many item in a UI list is to call before the insertion and setting it back to true after.

Here's the correct syntax

#define NB_ITEM 1000
#define ITEM_LENGTH 10

void CMFCComboDlg::InitMyCombo()
{
    CString _strData;
    m_cbMyCombo.SetRedraw( FALSE );

    m_cbMyCombo.Clear();

    m_cbMyCombo.InitStorage(NB_ITEM, ITEM_LENGTH); 

    for( int i = 0; i < NB_ITEM; i++ )
    {
     _strData.Format( L"Test %ld", i );
     m_cbMyCombo.InsertString( i, _strData );
    }

    m_cbMyCombo.SetCurSel(0);

    m_cbMyCombo.SetRedraw( TRUE );
}

EDIT: Improve the solution to include smacl suggestion

Answer 3

If you have 1,000 strings repeated in 10 comboboxes, you may want to consider using an owner drawn combobox, which draws the strings on the fly based on indices into your array, rather than storing them in the combobox at all. Way faster, way more memory efficient. Check out the DrawItem method and DRAWITEMSTRUCT structure in the on-line help. Basically, you would do something like using InitStorage and InsertString (as mentioned by NuSonic) to create your 1000 blank items in your combobx, and override DrawItem to extract and draw the required string, based on index, as it needs to be drawn.

Answer 4

Possibly faster than CComboBox with DrawItem would be an owner data CListCtrl. This would also serve your goal of duplicating a subset of the items into other lists, since a common data source could be used.

I suggest this because a 1000-item CComboBox isn't going to be very usable.