How to make your application a dropfile target in WTL

• Download demo project - 18.4 Kb

Introduction

By dropfile target I mean the application that can process file names dropped into it.

To modify your application to become a dropfile target all you have to do is to create your window with the extended window style WS_EX_ACCEPTFILES and handle WM_DROPFILES message.

Another way is to create a window and then call the following API function:

DragAcceptFiles(HWND hWnd, BOOL bAccept)

that turns the WS_EX_ACCEPTFILES style on or off based on the value of the bAccept parameter.

The obvious solution would be to create a class to encapsulate the above mentioned logic. So I present a class CDropFileTarget that does just that.

Using the code

It's very easy to use CDropFileTarget class. Just follow the following steps:

1. Add CDropFileTarget to the inheritance chain:

   class CMainDlg : public CDialogImpl<CMainDlg>,
           public CUpdateUI<CMainDlg>,
           public CMessageFilter, 
           public CIdleHandler,
           public CDropFileTarget<CMainDlg>

2. Add CHAIN_MSG_MAP statement to the message map of your class:

   BEGIN_MSG_MAP(CMainDlg)
       MESSAGE_HANDLER(WM_INITDIALOG, OnInitDialog)
       COMMAND_ID_HANDLER(ID_APP_ABOUT, OnAppAbout)
       COMMAND_ID_HANDLER(IDOK, OnOK)
       COMMAND_ID_HANDLER(IDCANCEL, OnCancel)
       CHAIN_MSG_MAP(CDropFileTarget<CMainDlg>)
   END_MSG_MAP()

3. In OnInitDialog() function register your class as a dropfile target

   LRESULT OnInitDialog(UINT /*uMsg*/, WPARAM /*wParam*/, 
     LPARAM /*lParam*/, BOOL& /*bHandled*/)
   {
       ...
       RegisterDropTarget();
       ...
   }
   

4. Add the following public function to process the dropped file

   void ProcessFile(LPCTSTR lpszPath)
   {
       // Add your logic
   }

That's it.

Conclusion

This class is very simple and may not meet all your requirements, but if you only need to allow your window to accept dropped files and process them then this class is for you.

Disclaimer

THIS SOFTWARE AND THE ACCOMPANYING FILES ARE DISTRIBUTED "AS IS" AND WITHOUT ANY WARRANTIES WHETHER EXPRESSED OR IMPLIED. NO RESPONSIBILITIES FOR POSSIBLE DAMAGES CAN BE TAKEN. THE USER MUST ASSUME THE ENTIRE RISK OF USING THIS SOFTWARE.