////////////////////////////////////////////////////////////////// MSDN Magazine -- October 2004// If this code works, it was written by Paul DiLascia.// If not, I don't know who wrote it.// Compiles with Visual Studio .NET 2003 on Windows XP. Tab size=3.//// Implementation of generic inter-app drag-drop manager//#pragma once#include <afxTempl.h>// registered messages sent by drag-drop managerconst UINT WM_DD_DRAGENTER = RegisterWindowMessage(_T("WM_DD_DRAGENTER"));const UINT WM_DD_PREDRAGMOVE  = RegisterWindowMessage(_T("WM_DD_PREDRAGMOVE"));const UINT WM_DD_DRAGOVER  = RegisterWindowMessage(_T("WM_DD_DRAGOVER"));
const UINT WM_DD_DRAGDROP  = RegisterWindowMessage(_T("WM_DD_DRAGDROP"));const UINT WM_DD_DRAGABORT = RegisterWindowMessage(_T("WM_DD_DRAGABORT"));

// return values for WM_DD_DRAGOVER
enum
{
	DD_DROPEFFECT_NONE = 0,
	DD_DROPEFFECT_MOVE,
	DD_DROPEFFECT_COPY,
	DD_DROPEFFECT_LINK
};// bit flags used for window type in window map
enum
{
    DDW_NONE   = 0x00,
    DDW_SOURCE = 0x01,   // window is drag-drop source
    DDW_TARGET = 0x02,   // window is drag-drop target
};// Used to create drag-drop window map. Map is an array of these structs,// each entry specifies a child window ID and whether the window is a source,// target, or both.struct DRAGDROPWND {	UINT id;				// window ID	UINT type;				// DDW_ flags above};// Abstract drag-drop data knows how to draw itself.//class CDragDropData {public:	CDragDropData() { }	virtual ~CDragDropData() { }	virtual CImageList* CreateDragImage(CWnd* pWnd, CRect& rc);	// derived classes must implement these:	virtual CSize OnGetDragSize(CDC& dc) = 0;	virtual void  OnDrawData(CDC& dc, CRect& rc, COLORREF& crMask) = 0;	virtual void* OnGetData() = 0;protected:	CBitmap			m_bitmap; // bitmap used for drawing};//////////////////// Concrete class for drag-drop text data.//class CDragDropText : public CDragDropData {protected:	enum { MAXWIDTH=64 };	CString m_text;public:    CDragDropText(LPCTSTR text) : m_text(text) { }	~CDragDropText() { }	virtual CSize OnGetDragSize(CDC& dc);	virtual void  OnDrawData(CDC& dc, CRect& rc, COLORREF& crMask);	virtual void* OnGetData() { return (void*)(LPCTSTR)m_text; }};//////////////////// Drag-drop structure passed as LPARAM in WM_DD_ messages.//struct DRAGDROPINFO {	HWND hwndSource;		// source window	HWND hwndTarget;		// target window
	BOOL bLeftDrag;			// left or right button drag	CDragDropData* pData;	// data to drag/drop	POINT pt;				// current point (cursor) in client coords							// of whatever window is identified by WPARAM};//////////////////// Inter-app drag-drop manager. To use this, instantiate one instance in your// main window class and call Install from your OnCreate or OnInitDialog// method. You must also override your main window's PreTranslateMessage to// call CDragDropMgr::PreTranslateMessage.//typedef CMap<HWND, HWND, UINT, UINT&> HWNDMAP;class CDragDropMgr {public:	CDragDropMgr();	virtual ~CDragDropMgr();	// Call this to initialize. 2nd arg is array of DRAGDROPWND's, one for	// each source/target child window.	BOOL Install(CWnd *pMainWnd, DRAGDROPWND* pWnds);	BOOL Install(CWnd *pMainWnd, HWND hwnd, int type = DDW_SOURCE | DDW_TARGET);
	// You must call this from your main window's PreTranslateMessage.	UINT ProcessMessage(const MSG* pMsg, BOOL bAllowNcDrag = FALSE);	// Call these to add/remove source/target windows dynamically.	void AddWindow(HWND hwnd, int type);	void RemoveWindow(HWND hwnd);

	void DragShowNolock(BOOL bShow);
	inline BOOL IsDragging() { return m_iState>=LDRAGGING; }
    protected:	enum { NONE=0, CAPTURED, LDRAGGING, RDRAGGING }; // internal states	// static stuff 	CWnd*			m_pMainWnd;				 // main window	HWNDMAP			m_mapHwnd;				 // map of source/target windows	// dyanmic stuff used during dragging	DRAGDROPINFO	m_ddi;					 // data during drag/drop	UINT			m_iState;				 // current state: CAPTURED/DRAGGING	HWND			m_hwndTracking;	    	 // window w/mouse capture	CPoint			m_ptOrg;				 // original point start of drag	CImageList*		m_pDragImage;			 // imagelist for dragging	HCURSOR			m_hCursorSave;			 // save cursor
	HINSTANCE		m_hInstOle32;
protected:	// mouse input handlers: can override if you derive	virtual BOOL OnButtonDown(const MSG& msg);	virtual BOOL OnButtonUp(const MSG& msg);
	virtual BOOL OnMouseMove(const MSG& msg);	// internal helper functions	void SetState(UINT iState);	    inline BOOL IsCaptured() { return m_iState>=CAPTURED; }    inline BOOL IsSourceWnd(HWND hwnd) { return (GetWindowType(hwnd) & DDW_SOURCE); }     inline BOOL IsTargetWnd(HWND hwnd) { return (GetWindowType(hwnd) & DDW_TARGET); }	UINT GetWindowType(HWND hwnd);

	UINT SendDragMessage(UINT nMessage);	};