Get data pointer in CListBox's MeasureItem()

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Hi,

I implement a list box which has items with variable height, to calculate height of item i need to obtain data attached with it in MeasureItem().

Here is part of code inserting item in list box

C++

INT idx = m_lstBox.AddString(strTxt);
m_lstBox.SetItemDataPtr(idx, pData);

Problem is that MeasureItem() function is called when the string is added, and at that time, data pointer is still not be set so i got bad pointer as result of GetItemDataPtr inside MeasureItem().

How can I set data pointer before MeasureItem call?

Quy

Posted 7-Jul-11 15:29pm

quyps

Updated 7-Jul-11 15:30pm

v2

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2 solutions

Solution 1

Are you sure you don't want to finish adding all the items, then perform an UpdateData so that the list item actually gets created first before you try to measure it?
I'm not 100% this would work as I haven't been in MFC for the last 6 months, but this did ring a bell.

Posted 7-Jul-11 16:02pm

fjdiewornncalwe

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quyps 8-Jul-11 0:01am

thanks Marcus! I have had a same thought. But there is another issue: how to know in MeasureItem() that it is called from AddItem() or UpdateData.

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Roger Allen · Accepted Answer · 2011-07-08T02:30:00

Solution 2

You can lock the window before adding items to it so that it will not redraw until your addition of items is complete:

m_lstBox.LockWindowUpdate();
int idx = m_lstBox.AddString(strTxt);
m_lstBox.SetItemDataPtr(idx, pData);
m_lstBox.UnlockWindowUpdate();

Posted 8-Jul-11 2:30am

Roger Allen

Comments

fjdiewornncalwe 8-Jul-11 10:23am

Excellent solution. I forgot about that.

quyps 11-Jul-11 22:06pm

I totally agree with Marcus. 5*!