Drag text between edit controls

* How to use the CDragEdit ?

To use a drag edit control in an existing dialog box

To use a drag edit control in toolbar

For example, you want to use two drag edit controls in the CTestDragEDitDlg. You need to add some codes in your xxxDlg.h and xxxDlg.cpp as below:

////////////////////// //TestDragEditDlg.h ////////////////////// #include
"CDragEdit.h" //include it in your xxxDlg.h

class CTestDragEditDlg : public CDialog
{
	...
	// Dialog Data
	//{{AFX_DATA(CTestDragEditDlg)
	enum { IDD = IDD_DRAGEDIT };
	CDragEdit m_edit2; //declare a CDragEdit variable 
	CDragEdit m_edit1; //for each edit control
	//}}AFX_DATA
	...
}

//////////////////////
//TestDragEditDlg.cpp
//////////////////////
void CTestDragEditDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CTestDragEditDlg)
	DDX_Control(pDX, IDC_EDIT2, m_edit2); //subclass the standard edit
	DDX_Control(pDX, IDC_EDIT1, m_edit1); //control as a CDragEdit
	//}}AFX_DATA_MAP
}

BOOL CTestDragEditDlg::OnInitDialog() 
{
	...
	    //You need to initiate CDragEdit first 
	m_edit1.Init();
	    m_edit2.Init();
	...
}

How the CDragEdit works ?

As I mentioned, the drag-drop of CDragEdit is implemented via OLE drag-and-drop. So, I implemented a CDEDropTarget, which is based on COleDropTarget, and a CDEDataSource, which is based on COleDataSource. The CDEDropTaregt serves the CDragEdit as a data comsumer and the CCDEDataSource serves the CDragEdit as a data producer. Drag-drop data transfers usually begin when the user press the left button of mouse. So, in CDragEdit, simply handle the WM_LBUTTONDOWN messagem, coping selected string into a CDEDataSource object using CacheGlobalData(), and call CDEDataSource::DoDragDrop() to tranfer string to a drop target.

In CDragEdit::Init(), I register this window as a drop target by calling CDEDropTarget::Register(). Once a CDragEdit is registered with OLE to be a drop target, it becomes eligible to receive OnDropEnter(), OnDropOver(), OnDropLeave(), and OnDrop() notifications from OLE. In OnDrop(), the CDragEdit will retrieve data with CF_TEXT format from COleDataObject and place at the dropped point.

For more information, please refer to the comment of source code.