' Allow dragging and dropping of files

$TYPECHECK ON

CONST WM_DROPFILES = &H233

TYPE TPOINT
    X AS LONG
    Y AS LONG
END TYPE

DIM Point AS TPOINT

DECLARE SUB DragAcceptFiles LIB "SHELL32" ALIAS "DragAcceptFiles" (hWnd AS LONG, Accept AS LONG)
DECLARE SUB DragFinish LIB "SHELL32" ALIAS "DragFinish" (hDrop AS LONG)
DECLARE FUNCTION DragQueryFile LIB "SHELL32" ALIAS "DragQueryFileA" _
                 (hDrop AS LONG, iFile AS LONG, lpszFile AS LONG, cch AS LONG) AS LONG
DECLARE FUNCTION DragQueryPoint LIB "SHELL32" ALIAS "DragQueryPoint" _
                 (hDrop AS LONG, lppt AS TPOINT) AS LONG

DECLARE SUB FormWndProc (Hwnd&, uMsg&, wParam&, lParam&)


DIM Form AS QForm
DIM Listbox as QLISTBOX
Listbox.parent = form
DIM S AS STRING
DIM I AS INTEGER, Count AS INTEGER, Length AS INTEGER

Form.Caption = "Drag and drop files"
Form.Center
DragAcceptFiles(Form.Handle, 1)
Form.WndProc = FormWndProc
Form.ShowModal

SUB FormWndProc (Hwnd&, uMsg&, wParam&, lParam&)
    IF uMsg& = WM_DROPFILES THEN
       DragQueryPoint(wParam&, Point)
       IF Point.X >= ListBox.Left AND Point.Y >= ListBox.Top AND _
          Point.X < ListBox.Width AND Point.Y < ListBox.Height THEN

           Count = DragQueryFile(wParam&, &HFFFFFFFF, VARPTR(S), 0)
           FOR I = 0 TO Count-1
              Length = DragQueryFile(wParam&, I, 0, 0)
              S = SPACE$(Length+1)
              DragQueryFile(wParam&, I, VARPTR(S), Length+1)
              ListBox.AddItems(S)
           NEXT
       ELSE
           ShowMessage("Try dragging the files to the listbox")
       END IF
       DragFinish(wParam&)
    END IF
END SUB