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An Enhanced CCheckComboBox

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10 Dec 2002 1  
Hybrid control simulating a combo box with checkboxes on a dropdown tree

Sample Image - CheckCmb.gif

Introduction

I wanted a control with both the functionality of a combo and of a tree with checkboxes. Such a control would act like a combo showing a dropdown and also allowing checking and fast checking items.

By the time I finished coding, I saw Magnus Egelberg's "CCheckComboBox" class, but I realize that my control has several advantages which anyway would have required the class to be completely rewritten.

My implementation (of a check list dropdown) is different from other implementations I seen, using a child, and not a popup window. Also for a better generality, I use a tree, letting user see the checked items, by showing them in an edit box with a tool tip. I simulated a combo box by using an owner draw button, thus not directly deriving it from CWnd or CComboBox. I think this approach has several advantages.

To integrate these classes in a new project, you would have to:

  1. Add the files "Check*" to your project
  2. On your form, add a button with owner draw style and map it to a control
  3. Change the name of the mapped control to "CCheckComboBox"

To add an item, you have to specify a caption, an ID and a level. The root has the level 0 (ROOT_LEVEL). All other nodes must be added with levels greater than 0 (ROOT_LEVEL), in the order in which they appear in the full-expanded tree. At any time, you can use the function "GetCheckedIDs" to get a string with all checked item's IDs on the highest level of the tree. It is also possible to get the checked IDs using the function "GetCheck".

// ADD tree items:
m_choCountries.AddString("North America");
    m_choCountries.AddString("USA",    5, ROOT_LEVEL + 2);
    m_choCountries.AddString("Canada", 6, ROOT_LEVEL + 2);
    m_choCountries.AddString("Europe");
    m_choCountries.AddString("UK",     7, ROOT_LEVEL + 2);

// CHECK all items
m_choCountries.CheckAll(TRUE);

// UNCHECK the item with ID = 6
m_choCountries.SetCheck(6, FALSE);

// GET all checked items
CString strCheckedItems = m_choCountries.GetCheckedIDs();

Any suggestions to improve this set of classes are welcome.

History

  • 6th June, 2002 - I let CTreeView alone interpret user keys, and introduced the OnGetDlgCode function for the combo.
  • 11th December, 2002 - In this update, I fixed 2 bugs and added a functionality.

License

This article has no explicit license attached to it, but may contain usage terms in the article text or the download files themselves. If in doubt, please contact the author via the discussion board below.

A list of licenses authors might use can be found here.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here