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Using the Clipboard, Part I : Transferring Simple Text

, 6 May 2002
In this first article of a four-part series on learning everything you ever wanted to know about programming the Windows Clipboard, you'll discover the basic steps of using the Clipboard API to transfer simple (ANSI) text to and from the Clipboard.
// SimpleTextTransferDlg.cpp : implementation file
//

#include "stdafx.h"
#include "SimpleTextTransfer.h"
#include "SimpleTextTransferDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#endif


// CAboutDlg dialog used for App About

class CAboutDlg : public CDialog
{
public:
	CAboutDlg();

// Dialog Data
	enum { IDD = IDD_ABOUTBOX };

	protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support

// Implementation
protected:
	DECLARE_MESSAGE_MAP()
public:
  afx_msg void OnBnClickedOk();
};

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
}

void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
  ON_BN_CLICKED(IDOK, OnBnClickedOk)
END_MESSAGE_MAP()


// CSimpleTextTransferDlg dialog



CSimpleTextTransferDlg::CSimpleTextTransferDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CSimpleTextTransferDlg::IDD, pParent)
{
	m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void CSimpleTextTransferDlg::DoDataExchange(CDataExchange* pDX)
{
  CDialog::DoDataExchange(pDX);
  DDX_Control(pDX, ID_EDTTOCLIPBOARD, m_edtToClipboard);
  DDX_Control(pDX, ID_EDTFROMCLIPBOARD, m_edtFromClipboard);
}

BEGIN_MESSAGE_MAP(CSimpleTextTransferDlg, CDialog)
	ON_WM_SYSCOMMAND()
	ON_WM_PAINT()
	ON_WM_QUERYDRAGICON()
	//}}AFX_MSG_MAP
	ON_BN_CLICKED(ID_BTNCOPY, OnBnClickedBtncopy)
	ON_BN_CLICKED(ID_BTNCUT, OnBnClickedBtncut)
	ON_BN_CLICKED(ID_BTNPASTE, OnBnClickedBtnpaste)
  ON_BN_CLICKED(IDC_BUTTON1, OnBnClickedButton1)
END_MESSAGE_MAP()


// CSimpleTextTransferDlg message handlers

BOOL CSimpleTextTransferDlg::OnInitDialog()
{
	CDialog::OnInitDialog();

	// Add "About..." menu item to system menu.

	// IDM_ABOUTBOX must be in the system command range.
	ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
	ASSERT(IDM_ABOUTBOX < 0xF000);

	CMenu* pSysMenu = GetSystemMenu(FALSE);
	if (pSysMenu != NULL)
	{
		CString strAboutMenu;
		strAboutMenu.LoadString(IDS_ABOUTBOX);
		if (!strAboutMenu.IsEmpty())
		{
			pSysMenu->AppendMenu(MF_SEPARATOR);
			pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
		}
	}

	// Set the icon for this dialog.  The framework does this automatically
	//  when the application's main window is not a dialog
	SetIcon(m_hIcon, TRUE);			// Set big icon
	SetIcon(m_hIcon, FALSE);		// Set small icon

	m_edtToClipboard.SetWindowText("Sample data to copy to Clipboard");
	
	return TRUE;  // return TRUE  unless you set the focus to a control
}

void CSimpleTextTransferDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
	if ((nID & 0xFFF0) == IDM_ABOUTBOX)
	{
		CAboutDlg dlgAbout;
		dlgAbout.DoModal();
	}
	else
	{
		CDialog::OnSysCommand(nID, lParam);
	}
}

// If you add a minimize button to your dialog, you will need the code below
//  to draw the icon.  For MFC applications using the document/view model,
//  this is automatically done for you by the framework.

void CSimpleTextTransferDlg::OnPaint() 
{
	if (IsIconic())
	{
		CPaintDC dc(this); // device context for painting

		SendMessage(WM_ICONERASEBKGND, reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// Draw the icon
		dc.DrawIcon(x, y, m_hIcon);
	}
	else
	{
		CDialog::OnPaint();
	}
}

// The system calls this function to obtain the cursor to display while the user drags
//  the minimized window.
HCURSOR CSimpleTextTransferDlg::OnQueryDragIcon()
{
	return static_cast<HCURSOR>(m_hIcon);
}

void CSimpleTextTransferDlg::OnBnClickedBtncopy()
{
	if (UpdateData())
  {
    CString strData;
    m_edtToClipboard.GetWindowText(strData);

    // test to see if we can open the clipboard first before
    // wasting any cycles with the memory allocation
	  if (OpenClipboard())
	  {
      // Empty the Clipboard. This also has the effect
      // of allowing Windows to free the memory associated
      // with any data that is in the Clipboard
		  EmptyClipboard();

      // Ok. We have the Clipboard locked and it's empty. 
      // Now let's allocate the global memory for our data.

      // Here I'm simply using the GlobalAlloc function to 
      // allocate a block of data equal to the text in the
      // "to clipboard" edit control plus one character for the
      // terminating null character required when sending
      // ANSI text to the Clipboard.
		  HGLOBAL hClipboardData;
		  hClipboardData = GlobalAlloc(GMEM_DDESHARE, 
		                               strData.GetLength()+1);

		  // Calling GlobalLock returns to me a pointer to the 
		  // data associated with the handle returned from GlobalAlloc
		  char * pchData;
		  pchData = (char*)GlobalLock(hClipboardData);
		  
		  // At this point, all I need to do is use the standard 
		  // C/C++ strcpy function to copy the data from the local 
		  // variable to the global memory.
		  strcpy(pchData, LPCSTR(strData));
		  
		  // Once done, I unlock the memory - remember you don't call
		  // GlobalFree because Windows will free the memory 
		  // automatically when EmptyClipboard is next called.
		  GlobalUnlock(hClipboardData);
		  
		  // Now, set the Clipboard data by specifying that 
		  // ANSI text is being used and passing the handle to
		  // the global memory.
		  SetClipboardData(CF_TEXT,hClipboardData);
		  
		  // Finally, when finished I simply close the Clipboard
		  // which has the effect of unlocking it so that other
		  // applications can examine or modify its contents.
		  CloseClipboard();
	  }
  }
}

void CSimpleTextTransferDlg::OnBnClickedBtncut()
{
	OnBnClickedBtncopy();
	m_edtToClipboard.SetWindowText("");
}

void CSimpleTextTransferDlg::OnBnClickedBtnpaste()
{
 // Test to see if we can open the clipboard first.
 if (OpenClipboard()) 
 {
  if (::IsClipboardFormatAvailable(CF_TEXT)
  || ::IsClipboardFormatAvailable(CF_OEMTEXT))
  {
    // Retrieve the Clipboard data (specifying that 
    // we want ANSI text (via the CF_TEXT value).
    HANDLE hClipboardData = GetClipboardData(CF_TEXT);

    // Call GlobalLock so that to retrieve a pointer
    // to the data associated with the handle returned
    // from GetClipboardData.
    char *pchData = (char*)GlobalLock(hClipboardData);

    // Set a local CString variable to the data
    // and then update the dialog with the Clipboard data
    CString strFromClipboard = pchData;
    m_edtFromClipboard.SetWindowText(strFromClipboard);

    // Unlock the global memory.
    GlobalUnlock(hClipboardData);
  }
  else
  { 
    AfxMessageBox("There is no text (ANSI) data on the Clipboard.");
  }

  // Finally, when finished I simply close the Clipboard
  // which has the effect of unlocking it so that other
  // applications can examine or modify its contents.
  CloseClipboard();
 }
}

void CAboutDlg::OnBnClickedOk()
{
  CWaitCursor wait;

  CString strUrl = "http://www.thecodechannel.com/redirect.asp?u=/&s=vcnb";
  if (32 >= (int)ShellExecute(NULL, "open", strUrl, NULL, NULL, SW_SHOWNORMAL))
  {
    AfxMessageBox("::ShellExecute failed to open this link!");
  }
}

void CSimpleTextTransferDlg::OnBnClickedButton1()
{
  CAboutDlg().DoModal();
}

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About the Author

Tom Archer
Software Developer (Senior) Microsoft
United States United States
I'm a Senior Programming Writer in the Microsoft Windows Server organization where my focus is WMI, BITS, WinRM, and SMI-S.

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