Listview control question.

To make an application faster and more responsive, I switched a list view
control to virtual. I'm not doing custom drawing, just owner data. Everything
works great except that I'm having trouble preserving one behavior of the
program. In the handler for a particular message which tells the dialog to
update the list data, I have logic which tries to select the last item and
bring it into view:

// WTL syntax:

numItems = Compute();
lastItem = numItems - 1;

m_list.SetItemCount(numItems);
m_list.SetItemState(lastItem, LVIS_FOCUSED | LVIS_SELECTED,
LVIS_FOCUSED | LVIS_SELECTED);
m_list.EnsureVisible(lastItem, TRUE);

Trouble is, the item is not selected and does not scroll into view. What's
more, the control seems to remember the previous selection. For instance
suppose that item 3 was previously selected (manually, by the user) and the
above tries to select the last item, say 23. The control will not scroll down
to show item 23. Moreover, if the user tries to move the cursor down, then
suddenly item 4 will be selected and focused.

Is there some trick to make this work with a virtual list view control? Maybe
it's sensitive as to when in the painting cycle these calls are made?

r_z_aret
Wed Oct 29 14:46:18 CST 2003

On 28 Oct 2003 14:18:23 -0800, kaz@ashi.footprints.net (Kaz Kylheku)
wrote:

>To make an application faster and more responsive, I switched a list view
>control to virtual. I'm not doing custom drawing, just owner data. Everything
>works great except that I'm having trouble preserving one behavior of the
>program. In the handler for a particular message which tells the dialog to
>update the list data, I have logic which tries to select the last item and
>bring it into view:
>
> // WTL syntax:
>
> numItems = Compute();
> lastItem = numItems - 1;
>
> m_list.SetItemCount(numItems);
> m_list.SetItemState(lastItem, LVIS_FOCUSED | LVIS_SELECTED,
> LVIS_FOCUSED | LVIS_SELECTED);
> m_list.EnsureVisible(lastItem, TRUE);
>
>Trouble is, the item is not selected and does not scroll into view. What's
>more, the control seems to remember the previous selection. For instance
>suppose that item 3 was previously selected (manually, by the user) and the
>above tries to select the last item, say 23. The control will not scroll down
>to show item 23. Moreover, if the user tries to move the cursor down, then
>suddenly item 4 will be selected and focused.
>
>Is there some trick to make this work with a virtual list view control? Maybe
>it's sensitive as to when in the painting cycle these calls are made?

I've never tried making a list view virtual. But I suspect folks who
have might want you to clarify whether the code worked before you made
the list view virtual.

The following is my code for non-virtual list views. I don't know
whether it will work with virtual list views. If nothing else, the
references in the comments might help.

BOOL centerSelection( int nChoice ) const // Centers
{ return ListView_EnsureVisible( m_hWnd, nChoice, FALSE );
} // 9 Oct 03 (4.0.0.28)


// ----------------------------------------------------------
// centerChoice
// Call centerSelection, then select specified line
BOOL ClsPFListView::centerChoice( int nChoice ) const
{
nChoice = max( 0, nChoice );
nChoice = min( nChoice, (GetNCount() -1) ); //lint !e666 side
effect & second arg
if (centerSelection( nChoice ))
{
#if 0
Click();
#else
// 9 Oct 03 (4.0.0.28)
#if 1
// See KnowledgeBase article Q131284
ListView_SetItemState( GetHwnd(), nChoice, (LVIS_SELECTED |
LVIS_FOCUSED), 0x000F );
#else
// Also, thread called "ListViews" in
powersoft.public.watcom_c_c++.general
// around 3 March 2003
// Also, 24 Jul 1999 contribution from Phaedrus to thread
called
// "How To Select Item in ListView?" in
comp.os.ms-windows.programmer.tools.mfc
ListView_SetItemState( GetHwnd(), nChoice, LVIS_SELECTED |
LVIS_FOCUSED, LVIS_SELECTED | LVIS_FOCUSED );
#endif
ASSERT( ListView_GetItemState( GetHwnd(), nChoice,
LVIS_SELECTED ) > 0 );
ASSERT( ListView_GetItemState( GetHwnd(), nChoice,
LVIS_FOCUSED ) > 0 );
VERIFY( ListView_Update( GetHwnd(), nChoice ) );
#endif
return TRUE;
}
else
return FALSE;
} // centerChoice


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Robert E. Zaret
PenFact, Inc.
500 Harrison Ave., Suite 3R
Boston, MA 02118
www.penfact.com