LOCAL oForm As TForm
oForm = CREATEOBJECT("TForm")
oForm.Visible=.T.
READ EVENTS
* end of main
 
DEFINE CLASS TForm As Form
#DEFINE WM_DROPFILES 0x0233
#DEFINE GWL_WNDPROC -4
#DEFINE MAX_PATH 260
 
PROTECTED hWindow, hOrigProc
    hWindow=0
    hOrigProc=0
    Width=350
    Height=200
    MinButton=.F.
    MaxButton=.F.
    Caption=" Dropping files on the form"
    ShowWindow=2
    Autocenter=.T.
 
    ADD OBJECT ch As CheckBox WITH;
    Left=10, Top=10, Autosize=.T., BackStyle=0,;
    Caption="Accept dropped files", Value=0
 
    ADD OBJECT lst As ListBox WITH;
    Left=5, Top=40, Width=340, Height=130
 
    ADD OBJECT lbl As Label WITH;
    Left=10, Top=176, Autosize=.T., BackStyle=0,;
    Caption="Drag files from an Explorer window and drop on the listbox"
 
PROCEDURE Init
    THIS.declare
 
PROCEDURE Destroy
    THIS.ReleaseAccept
    CLEAR EVENTS
 
PROCEDURE ch.InteractiveChange
    IF THIS.Value = 1
        ThisForm.SetAccept
    ELSE
        ThisForm.ReleaseAccept
    ENDIF
 
PROCEDURE SetAccept
    THIS.hWindow = GetFocus()
    THIS.hOrigProc = GetWindowLong(THIS.hWindow, GWL_WNDPROC)
 
    IF VERSION(5) >= 900
        = BINDEVENT(THIS.hWindow, WM_DROPFILES,;
            THIS, "OnFilesDropped")
    ENDIF
    = DragAcceptFiles(THIS.hWindow, 1)
 
PROCEDURE ReleaseAccept
    = UNBINDEVENTS(THIS)
 
    IF THIS.hWindow <> 0
        = DragAcceptFiles(THIS.hWindow, 0)
        THIS.hWindow=0
    ENDIF
 
PROCEDURE OnFilesDropped(hWindow as Integer,;
    nMsgID as Integer, wParam as Integer, lParam as Integer)
* requires VFP9, otherwise ignored
* note that input parameters are predefined and should not be changed
* see WindowProc function for details
 
    LOCAL nReturn
    nReturn=0
 
    DO CASE
    CASE nMsgID=WM_DROPFILES
        THIS.ProcessDroppedFiles(wParam)
 
    OTHERWISE
    * pass control to the original window procedure
        nReturn = CallWindowProc(THIS.hOrigProc, THIS.hWindow,;
            m.nMsgID, m.wParam, m.lParam)
    ENDCASE
RETURN nReturn
 
PROTECTED PROCEDURE ProcessDroppedFiles(hDrop)
    LOCAL cPoint, nX, nY
    cPoint = REPLICATE(CHR(0),8)  && POINT buffer
    = DragQueryPoint(hDrop, @cPoint)
    nX = buf2dword(SUBSTR(cPoint,1,4))
    nY = buf2dword(SUBSTR(cPoint,5,4))
 
    * only if clicked inside the listbox
    WITH THIS.lst
        IF NOT (BETWEEN(nX, .Left, .Left+.Width-1);
            AND BETWEEN(nY, .Top, .Top+.Height-1))
            RETURN
            = DragFinish(hDrop)
        ENDIF
    ENDWITH
 
    THIS.lst.Clear
 
    LOCAL nFilecount, nIndex, cBuffer, nLength
    nFilecount = DragQueryFile(hDrop, 0xFFFFFFFF, Null, 0)
 
    FOR nIndex=0 TO nFilecount-1
        cBuffer = REPLICATE(CHR(0), MAX_PATH)
        nLength = DragQueryFile(hDrop, nIndex, @cBuffer, MAX_PATH)
        cBuffer = SUBSTR(cBuffer, 1, nLength)
        THIS.lst.AddItem(cBuffer)
    NEXT
 
    = DragFinish(hDrop)
 
PROTECTED PROCEDURE declare
    DECLARE INTEGER GetFocus IN user32
    DECLARE DragFinish IN shell32 INTEGER hDrop
 
    DECLARE DragAcceptFiles IN Shell32;
        INTEGER hWindow, INTEGER fAccept
 
    DECLARE INTEGER DragQueryFile IN shell32;
        INTEGER hDrop, INTEGER iFile,;
        STRING @lpszFile, INTEGER cch
 
    DECLARE INTEGER DragQueryPoint IN shell32;
        INTEGER hDrop, STRING @lppt
 
    DECLARE INTEGER CallWindowProc IN user32;
        INTEGER lpPrevWndFunc, INTEGER hWindow, LONG Msg,;
        INTEGER wParam, INTEGER lParam
 
    DECLARE INTEGER GetWindowLong IN user32;
        INTEGER hWindow, INTEGER nIndex
 
ENDDEFINE
 
FUNCTION buf2dword(lcBuffer)
RETURN Asc(SUBSTR(lcBuffer, 1,1)) + ;
    BitLShift(Asc(SUBSTR(lcBuffer, 2,1)),  8) +;
    BitLShift(Asc(SUBSTR(lcBuffer, 3,1)), 16) +;
    BitLShift(Asc(SUBSTR(lcBuffer, 4,1)), 24)