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Tree ComboBox Control

, 16 Oct 2014 CPOL
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Tree ComboBox Control

TreeCComboBoxControl/treecombobox.gif

Introduction

Recently, I needed a tree control inside a combobox, and during my search on Google I found something, but it was a little more complicated than I required. I started to draft one myself, and am sharing the result with you.

Using the Code

Everything is based on CTreeComboBox, which is derived from the standard CComboBox. Here I have a CComboTreeCtrl variable member and methods characteristic to a tree control. In CTreeComboBox::PreSubclassWindow, I create and initialize m_Tree and stretch on the combobox dropdown list.

void CTreeComboBox::PreSubclassWindow() 
{
    // TODO: Add your specialized code here and/or call the base class

    CComboBox::PreSubclassWindow();

    CRect rect(0, 0, 0, 0);
    DWORD dwStyle =  WS_POPUP | WS_BORDER | TVS_DISABLEDRAGDROP | 
    TVS_HASLINES | TVS_LINESATROOT | TVS_HASBUTTONS | TVS_FULLROWSELECT | 
    TVS_CHECKBOXES;
    m_Tree.CreateEx(0, WC_TREEVIEW, NULL, dwStyle, rect, GetParent(), 0, NULL);
    m_Tree.Init(this);

    GetClientRect(rect);
    SetDroppedWidth(rect.Width());
    SetDroppedHeight(m_droppedHeight);

    dwStyle = 0x03 & GetStyle();
    ASSERT(dwStyle == CBS_DROPDOWNLIST);
}

At first click, or arrow key down, the tree window will open.

void CTreeComboBox::OnLButtonDown(UINT nFlags, CPoint point) 
{
    // TODO: Add your message handler code here and/or call default

    m_bTree = ! m_bTree;
    if(m_bTree)DisplayTree();

//    CComboBox::OnLButtonDown(nFlags, point);
}

and:

BOOL CTreeComboBox::PreTranslateMessage(MSG* pMsg) 
{
    // TODO: Add your specialized code here and/or call the base class

    if(pMsg->message == WM_KEYDOWN && pMsg->wParam == VK_DOWN)
    {
        DisplayTree();
        return TRUE;
    }

    return CComboBox::PreTranslateMessage(pMsg);
}

But the tree window should close at second click, escape key, Enter key, or lost focus. I tried a few ways but I failed, so my solution was to send to the parent (CTreeComboBox) a message to close.

LRESULT CTreeComboBox::OnCloseControl(WPARAM wParam, LPARAM lParam)
{
    TreeCtrlDone();
    m_Tree.ShowWindow(SW_HIDE);
    m_bTree = FALSE;

    return 1;
}

ComboBox must setup with CBS_DROPDOWNLIST or else you'll be ASSERTed Smile | :)

In order to use this control, you need #include "TreeComboBox.h" and further handle combobox like it is a tree control (you can see how in the sample project).

Enjoy it!

History

  • 26 April, 2011: Initial version.
  • 20 February, 2012: Added CTreeCtrl and GetTreeCtrl() methods to the CTreeComboBox class, so now it has full access to the tree control.
  • 10 May, 2013: Updated the control archive.
  • 16 Oct., 2014: The drop down is dropped by screen position (down or up); The drop down can not be closed by Alt+F4.
  • 14 Nov. 2014: I updated the code in order to be used on newer versions of Visual Studio (VS2008 for instance).
  • 18 Nov. 2014: I added posibility that combobox could be dropped down through F4. I added CComboTreeCtrlExt class in order to be customized tree control of combobox without mess up CComboTreeCtrl class.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Flaviu2

Romania Romania
No Biography provided

Comments and Discussions

 
GeneralMy vote of 5 Pinmemberhuwuling3-May-12 6:10 
GeneralRe: My vote of 5 PinmemberFlaviu211-May-12 3:11 

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