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How to disable ComboBox automatic scrolling?

Posted on 2000-03-26
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Last Modified: 2013-11-20
I have class MyComboBox. When I select an item from a ListBox, ComboBox is scrolled automatically that selected item is the first on ListBox. How could I disable it?
I tried to do it in OnDropDown, OnLButtonDown in OnClouseUp. Always without success!
I would like to control scrolling by my code!

Thanks all!
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Question by:si124
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yarond earned 400 total points
ID: 2660165
Well, it's not very elegant, but it will work.
The combobox scrolls the drop-down listbox to the selected item. So what you can do is on the OnDropDown use SetCurSel(-1) which will clear the selection.
However, if you want the selected item to remain selected when you close the drop-down without selecting a different one, before using SetCurSel(-1) use GetCurSel() and keep the return value, and then on OnCloseUp check if GetCurSel()==CB_ERR, and if so (no new item was selected) use SetCurSel(m_PrevSelection).
It will also work properly on the first run because CB_ERR==-1 so if nothing was selected no harm is done. Although it would be much nice to search for this condition on the OnDropDown and not count on it...
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Author Comment

by:si124
ID: 2661688
Thank you very much for your help.
I managed to control scrolling by myself.

I would like to leave selected text in EditBox on DropDown. In this case EditBox is empty (unusal).
Is it possible to fix it?

Thanks!
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Expert Comment

by:yarond
ID: 2663534
I found a totally different solution, which is IMHO much better, and answers all your requirements (that I know of).
In the OnDropDown, assuming you have a CComboBox control named m_Combo, use either:
::PostMessage(m_Combo.m_hWnd,CB_SETTOPINDEX,0,0);
or:
m_Combo.PostMessage(CB_SETTOPINDEX,0,0);
If you use PostMessage and not SendMessage it gets processed only after the dropdown operation is finished, and so it scrolls to the top position.
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Author Comment

by:si124
ID: 2663810
I used this option before!!!
I send my own WM_USER+1 message and in it I scroll down ListBox to right position.
I can't use SetTopIndex because I have header control on the top of ListBox, so I have to leave it on the top!
Your last solution was OK, except the problem of empty EditBox!
Is there any other possibility to solve my problem!

Thanks!



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Author Comment

by:si124
ID: 2663812
I have to repair myself. I meant Post WM_USER+1 message!
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Expert Comment

by:yarond
ID: 2663881
One rather ugly option would be to put a different editbox on top of the combobox's editbox, and in OnDropDown, copying the selected item to it, making it visible, and only then clearing the selection.
But I don't exactly understand how does the header control prevent you from using SetTopIndex. Where exactly is the header control placed, and what happens to it when you use SetTopIndex?
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Author Comment

by:si124
ID: 2663990
My header control is child window of ListBox. When I use SetTopIndex, windows is scrolled so header control disappears from the view.
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Expert Comment

by:yarond
ID: 2664683
I can't think of a better solution for you right now. I'll withdraw my answer so someone else might be able to help you.
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Author Comment

by:si124
ID: 2665147
In any case thank you very very much for your help!!!!!
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