The TBTextTarget class

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The TBTextTarget class
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Doing it the OLE way... an interface class to derive from

If you are a MFC purist and only want to have CObject derived classes in your project, than consider the pure MFC drop target.

You find the sample project in step3generic or you may download only the TBTextTarget class

A generic IDropTarget COM class for dropped texts

I promised you "a better way" and I fulfill this promise now - at least half of it because its for the drop target, the IDropSouce and IDataObject parts are missing, but the MFC support for the begin of dragging out of CListCtrl is quite good (perhaps someone else can take this as an excersice and I'll puplish her/his work as an addendum of this article :)

The OLE doc’s say: "If you want your (window) class to be drop-enabled, implement a IDropTarget interface." Nice - eh' what did it say? In plain English I’d say: your drop-enabled class needs a couple of functions which do the right things. The bundle of these functions make out "the interface" and because some interfaces are "at the top" of others you have - a kind of class hierarchy!

Due to the fact that we are talking about text dragging the private data format described in the other articles of this series is just omitted, but might easily . Implement the drag sources as common interface (CF_TEXT, see "Data is going abroad..." for the drop part do the following (and compare with the pure MFC stuff!)

1. Create your CWnd-based class (CYourClass, e.g. your dialog) as usual.
2. include the files TBTextTarget.h and TBTextTarget.cpp in your project.
3. Go to the class definition of CYourClass and derive it from TBTextTarget too: e.g. the line
       class CDropDialog : public CDialog
   will become
       class CDropDialog : public CDialog, TBTextTarget
4. Don’t forget to #include "TBTextTarget.h"
5. Don't forget to make a call to AfxOleInit() in your application’s InitInstance function before creating any windows or document templates.
6. At a point where this window is created (for example: OnInitDialog is great), tell Windows that you are drag&drop-enabled:
   

        BOOL CDropDialog::OnInitDialog()
        {
            CDialog::OnInitDialog();
            ::RegisterDragDrop(GetSafeHwnd(), this);
            // the other stuff follows ....
        }

7. Add this function to CYourClass (it’s pure virtual in TBTextTarget because it depents on YOU what you do with YOUR data):
   

            void ProcessData(CString Data)

   This function will be called when a text was dragged into your window. Do with it what ever you like (or need). For example:
   

        CDropDialog::ProcessData(CString Data)
        {
            CString t1(Data), t2;
            int idx =     t1.Find('\n');
        
            while (idx     !=-1)
            {
                t2 = t1.Left(idx);
                t1 = t1.Mid(idx+1);
                InsertRow(t2);
                idx = t1.Find('\n');
            }
        }
        

8. Ready!