winscp/source/packages/dragndrop/DragDropFilesEx.pas

unit DragDropFilesEx;
{
  Description
  ===========
     TDragDropFilesEx is a comfortable and powerful component for COM/OLE
     drag&drop operations with files and supports completely the namespace of
     Windows (PIDL). The component is a child-class from TDragDrop.


  Disclaimer
  ==========
    The author disclaims all warranties, expressed or implied, including,
    without limitation, the warranties of merchantability and of fitness
    for any purpose. The author assumes no liability for damages, direct or
    consequential, which may result from the use of this component/unit.


  Restrictions on Using the Unit / Components
  ===========================================
      This unit/component is copyright 1998 by Dieter Steinwedel. ALL RIGHTS
    ARE RESERVED BY DIETER STEINWEDEL. You are allowed to use it freely
    subject to the following restrictions:

    • You are not allowed delete or alter the author's name and
      copyright in any manner

    • You are not allowed to publish a copy, modified version or
      compilation neither for payment in any kind nor freely

    • You are allowed to create a link to the download in the WWW

    • These restrictions and terms apply to you as long as until
      I alter them. Changes can found on my homepage
}

{$ALIGN ON}
{$ASSERTIONS OFF}
{$BOOLEVAL OFF}
{$DENYPACKAGEUNIT OFF}
{$EXTENDEDSYNTAX ON}
{$HINTS ON}
{$IMPORTEDDATA ON}
{$LONGSTRINGS ON}
{$OPTIMIZATION ON}
{$TYPEDADDRESS OFF}
{$TYPEINFO OFF}
{$WARNINGS ON}

interface

uses DragDrop, Windows, Classes, SysUtils, ActiveX, PIDL, ShlObj, ComObj,
   Registry;

type
  PDropFiles = ^TDropFiles;
  TDropFiles = packed record
    pFiles: DWORD;                       { offset of file list }
    pt: TPoint;                          { drop point (client coords) }
    fNC: BOOL;                           { is it on NonClient area }
    fWide: BOOL;                         { WIDE character switch }
  end;

  PItemIDList=ShlObj.PItemIDList;
  TFileExMustDnD=(nvFilename, nvPIDL);
  TFileExMustDnDSet = set of TFileExMustDnD;
  TOnSpecifyDropTarget = procedure(Sender: TObject; DragDropHandler:boolean;
     pt: TPoint; var pidlFQ:PItemIDList; var Filename:string) of object;


  PFDDListItem = ^TFDDListItem;
  TFDDListItem = record
     pidlFQ: PItemIDList;
     Name:string;
     MappedName:string;
  end;

  PCMListItem = ^TCMListItem;
  TCMListItem = record
     FirstCmd:integer;
     LastCmd:integer;
     CM:IContextMenu;
  end;

  TFileList = class(TList)
  private
     function Get(Index: Integer): PFDDListItem;
     procedure Put(Index: Integer; Item: PFDDListItem);
  public
     constructor Create;
     destructor Destroy; override;
     procedure Clear; override;
     procedure Delete(Index:Integer);
     function Remove(Item: PFDDListItem): Integer;
     function First: PFDDListItem;
     function Last: PFDDListItem;
     function AddItem(ApidlFQ:PItemIDList; AName:String):integer;
     function AddItemEx(ApidlFQ:PItemIDList; AName, AMappedName:String):integer;
     function RenderPIDLs:boolean;
     function RenderNames:boolean;
     property Items[Index:integer]:PFDDListItem read get write put;
  end;

  TDataObjectFilesEx = class(TDataObject)
  private
     pidlStream:TMemoryStream;
     HDropStream:TMemoryStream;
     FilenameMapList:TStringList;
     FilenamesAreMapped:boolean;
     FOnRelease: TNotifyEvent;
  public
     constructor Create(AFileList:TFileList; RenderPIDL, RenderFilename: boolean);
     destructor Destroy; override;
     function RenderData(FormatEtc:TFormatEtc;
        var StgMedium: TStgMedium):HResult; override;
     function IsValid(Formatpidl, FormatHDrop:boolean):boolean;
     property OnRelease: TNotifyEvent read FOnRelease write FOnRelease;
  end;

  TDropTargetFilesEx = class(TDropTarget)
  protected
     procedure AcceptDataObject(DataObj: IDataObject; var Accept:boolean); override;
  public
     constructor Create(AOwner: TDragDrop);
     destructor Destroy; override;
     procedure RenderDropped(DataObj: IDataObject; grfKeyState: Longint;
        pt: TPoint; var dwEffect: longint); override;
  end;

  TShellExtension = class(TPersistent)
  private
    FDropHandler:boolean;
    FDragDropHandler:boolean;
  protected
    procedure AssignTo(Dest: TPersistent); override;
  published
    property DropHandler:boolean read FDropHandler write FDropHandler
       default false;
    property DragDropHandler:boolean read FDragDropHandler
       write FDragDropHandler default false;
  end;

  TDragDropFilesEx = class(TDragDrop)
  private
     FFileList:TFileList;
     FNeedValid: TFileExMustDnDSet;
     FCompleteFileList:boolean;
     FFileNamesAreMapped:boolean;
     FOnSpecifyDropTarget:TOnSpecifyDropTarget;
     FShellExtension:TShellExtension;
     FCMList:TList;
     FOnDataObjectRelease: TNotifyEvent;
  protected
     function CreateDataObject:TDataObject; override;
     procedure DataObjectRelease(Sender: TObject);
     procedure DoMenuPopup(Sender: TObject; AMenu: HMenu; DataObj: IDataObject;
        AMinCustCmd:integer; grfKeyState: Longint; pt: TPoint); override;
     function DoMenuExecCmd(Sender: TObject; AMenu: HMenu; DataObj:IDataObject;
       Command:integer; var dwEffect: longint):boolean; override;
     procedure DoMenuDestroy(Sender:TObject; AMenu: HMenu); override;
     function DropHandler(const dataObj: IDataObject; grfKeyState: Longint;
       pt: TPoint; var dwEffect: Longint): boolean; override;
  public
     constructor Create(AOwner: TComponent); override;
     destructor Destroy; override;
     function TargetHasDropHandler(pidlFQ:PItemIDList; Filename:string;
        var dwEffect: longint): boolean;
     property FileList: TFileList read FFileList write FFileList;
     property FileNamesAreMapped: boolean read FFileNamesAreMapped;
  published
     property NeedValid: TFileExMustDnDSet read FNeedValid write FNeedValid;
     property CompleteFileList: boolean read FCompleteFileList
       write FCompleteFileList default true;
     property ShellExtensions:TShellExtension read FShellExtension write FShellExtension;
     property OnSpecifyDropTarget:TOnSpecifyDropTarget read FOnSpecifyDropTarget
       write FOnSpecifyDropTarget;
     property OnDropHandlerSucceeded;
     property OnDataObjectRelease: TNotifyEvent read FOnDataObjectRelease write FOnDataObjectRelease;
  end;

procedure Register;

implementation

uses
  Types;

const
  {$EXTERNALSYM IID_IDropTarget}
  IID_IDropTarget: TGUID = (
    D1:$00000122;D2:$0000;D3:$0000;D4:($C0,$00,$00,$00,$00,$00,$00,$46));

type PByte=^byte;

// some local functions --------------------------------------------------------

procedure CopyHDropToFilelist(var List: TFileList; HDropPtr: PAnsiChar; HDropSize: LongInt);
var s:string;
    DropFiles: PDropFiles;
    ws: WideString;
// List must be empty, before calling ...
begin
     if (HDropPtr<>nil) and (HDropSize>0) then
     begin
          PAnsiChar(DropFiles):=HDropPtr;
          inc(HDropPtr,DropFiles^.pFiles);
          if DropFiles^.FWide then
          begin
               while HDropPtr^<>#0 do
               begin
                    ws := PWideChar(HDropPtr);
                    inc(HDropPtr,(Length(ws)+1)*2);
                    List.AddItem(nil,ws);
               end;
          end
          else
          begin
               while HDropPtr^<>#0 do
               begin
                    s:=string(HDropPtr);
                    inc(HDropPtr, Length(s)+1);
                    List.AddItem(nil,s);
               end;
          end;
     end;
end;

procedure CopyFilenameMapToFilelist(var List:TFileList; FilenameMapPtr:PChar;
   FilenameMapSize:longint; IsWideChar:boolean);
var s:string;
    idx:longint;
    ws:WideString;
// should be only called after "CopyHDropToFilelist" ...
begin
     if (FilenameMapPtr<>nil) and (FilenameMapSize>0) then
     begin
          idx:=0;
          if IsWideChar then
          begin
               while FilenameMapPtr^<>#0 do
               begin
                    ws:=WideCharToString(PWideChar(FilenameMapPtr));
                    inc(FilenameMapPtr,(Length(ws)+1)*2);
                    if Idx>=0 then List.Items[Idx]^.MappedName:=ws
                    else raise Exception.Create('A non-existing filename is mapped');
                    inc(Idx);
               end;
          end
          else
          begin
               while FilenameMapPtr^<>#0 do
               begin
                    s:=StrPas(FilenameMapPtr);
                    inc(FilenameMapPtr, Length(s)+1);
                    if Idx>=0 then List.Items[Idx]^.MappedName:=s
                    else raise Exception.Create('A non-existing filename is mapped');
                    inc(Idx);
               end;
          end;
     end;
end;

procedure CopyPIDLsToFilelist(var List:TFileList; pidlPtr:PByte; pidlSize:longint);
var size,i,Idx,Count:longint;
    pidl, pidlRoot:PItemIDList;
    LIPtr:^longint;
    AddToList:boolean;
begin
     if (pidlPtr<>nil) and (pidlSize>0) then
     begin
          PByte(LIPtr):=pidlPtr;
          count:=LIPtr^;
          AddToList:=List.Count=0;
          Idx:=0;
          inc(LIPtr);
          inc(pidlPtr,LIPtr^);
          i:=LIPtr^; // mempos
          pidlRoot:=nil;
          inc(LIPtr);
          while (Count>Idx) and (i<pidlSize) do
          begin
               PByte(pidl):=pidlPtr;
               size:=PIDL_GetSize(pidl);
               if i=LIPtr^ then
               begin // is an item pidl ...
                    if AddToList then
                       List.AddItem(PIDL_Concatenate(pidlRoot,pidl),'')
                    // PIDL_Concatenate --> waste of memory
                    else List.Items[Idx]^.pidlFQ:=PIDL_Concatenate(pidlRoot,pidl);
                    inc(Idx);
                    inc(LIPtr);
               end
               else pidlRoot:=pidl; // is a root pidl ...
               inc(i,size);
               inc(pidlPtr,size);
          end;
     end;
end;

// TFileList -------------------------------------------------------------------

constructor TFileList.Create;
begin
     inherited Create;
end;

destructor TFileList.Destroy;
begin
     Clear;
     inherited Destroy;
end;

function TFileList.Get(Index: Integer): PFDDListItem;
begin
     Result:=inherited Items[Index];
end;

procedure TFileList.Put(Index: Integer; Item: PFDDListItem);
begin
     inherited Items[Index]:=Item;
end;


procedure TFileList.Clear;
var Item:PFDDListItem;
    i:integer;
begin
     if Count>0 then
        for i:=0 to Count-1 do
        begin
             Item:=inherited Items[i];
             if Item<>nil then
             begin
                  PIDL_Free(Item^.pidlFQ);
                  dispose(Item);
             end;
        end;
     inherited Clear;
end;

procedure TFileList.Delete(Index:Integer);
var Item:PFDDListItem;
begin
     Item:=inherited Items[Index];
     if Item<>nil then
     begin
          PIDL_Free(Item^.pidlFQ);
          dispose(Item);
     end;
     inherited Delete(Index);
end;

function TFileList.Remove(Item: PFDDListItem): Integer;
begin
     Result:=inherited Remove(Item);
     if Item<>nil then
     begin
          PIDL_Free(Item^.pidlFQ);
          dispose(Item);
     end;
end;

function TFileList.First: PFDDListItem;
begin
     Result:=inherited First;
end;

function TFileList.Last: PFDDListItem;
begin
     Result:=inherited Last;
end;

function TFileList.AddItem(ApidlFQ:PItemIDList; AName:String):integer;
var LI:PFDDListItem;
begin
     New(LI);
     LI^.Name:=AName;
     LI^.MappedName:='';
     LI^.pidlFQ:=PIDL_Copy(ApidlFQ);
     Result:=Add(LI);
end;

function TFileList.AddItemEx(ApidlFQ:PItemIDList; AName, AMappedName:String):integer;
var LI:PFDDListItem;
begin
     New(LI);
     LI^.Name:=AName;
     LI^.MappedName:=AMappedName;
     LI^.pidlFQ:=PIDL_Copy(ApidlFQ);
     Result:=Add(LI);
end;

function TFileList.RenderPIDLs:boolean;
var i:integer;
    piDesktop: IShellFolder;
    olePath: WideString;
    ulEaten, ulAttribs:ULong;
begin
     if Failed(SHGetDesktopFolder(piDesktop)) then
     begin
          Result:=false;
          exit;
     end;
     Result:=true;
     if Count>0 then
        for i:=0 to Count-1 do
            if (Items[i]<>nil) and (Items[i]^.pidlFQ=nil) then
            begin
                 if Items[i]^.Name='' then Result:=false
                 else
                 begin
                      olePath := Items[i]^.Name;
                      ulAttribs := 0;
                      if Failed(piDesktop.ParseDisplayName(0, nil, POleStr(olePath), ulEaten,
                         Items[i]^.pidlFQ, ulAttribs)) then Result:=false;
                 end;
            end;
end;

function TFileList.RenderNames:boolean;
var i:integer;
    SF:IShellFolder;
    pc:array[0..1024] of char;
    ppidlRoot, ppidlItem: PItemIDList;
begin
     Result:=true;
     if Count>0 then
        for i:=0 to Count-1 do
            if (Items[i]<>nil) and (Items[i]^.Name='') then
            begin
                 if Items[i]^.pidlFQ=nil then Result:=false
                 else
                 begin
                      PIDL_GetRelative(Items[i]^.pidlFQ, ppidlRoot, ppidlItem);
                      if PIDL_GetFileFolder(ppidlRoot,SF) then
                      begin
                           if PIDL_GetDisplayName(SF, ppidlItem,
                              SHGDN_FORPARSING,pc,sizeof(pc)) then
                              Items[i]^.Name:=StrPas(pc)
                           else
                           begin
                                Items[i]^.Name:='';
                                Result:=false;
                           end;
                           PIDL_Free(ppidlRoot);
                           PIDL_Free(ppidlItem);
                      end
                      else Result:=false;
                 end;
            end;
end;

// TDataObjectFilesEx -------------------------------------------------------------

constructor TDataObjectFilesEx.Create(AFileList: TFileList; RenderPIDL, RenderFilename: Boolean);
var
  i: DWORD;
  FE: TFormatEtc;
  SM: TStgMedium;
  LastpidlRoot, pidlRoot, pidlItem: PItemIDList;
  Pos: DWORD;
  df: TDropFiles;
  pc: array[0..1024] of Char;
begin
     inherited Create;
     pidlStream:=TMemoryStream.Create;
     HDropStream:=TMemoryStream.Create;
     FilenameMapList:=TStringList.Create;
     FilenamesAreMapped:=false;
     if RenderPIDL then
     begin
          LastpidlRoot:=nil;
          pidlStream.SetSize(AFileList.count*4+8);
          pidlStream.Seek(0,0);
          i:=AFileList.count;
          pidlStream.Write(i,4);
          i:=pidlStream.Size;
          pidlStream.Write(i,4);
          pidlStream.Seek(0,2);
          for i:=0 to AFileList.count-1 do
          begin
               if AFileList.Items[i]^.pidlFQ=nil then
               begin
                    pidlStream.SetSize(0);
                    break;
               end;
               PIDL_GetRelative(AFileList.Items[i]^.pidlFQ,
                 pidlRoot, pidlItem);
               if (LastpidlRoot=nil) or (PIDL_Equal(LastpidlRoot,pidlRoot)=false) then
               begin
                    if LastpidlRoot<>nil then PIDL_Free(LastpidlRoot);
                    LastpidlRoot:=PIDL_Copy(pidlRoot);
                    pidlStream.Write(pidlRoot^,PIDL_GetSize(pidlRoot));
               end;
               pos:=pidlStream.Position;
               pidlStream.Write(pidlItem^,PIDL_GetSize(pidlItem));
               pidlStream.seek(8+4*i,soBeginning);
               pidlStream.Write(pos,4);
               pidlStream.Seek(0,2);
               PIDL_Free(pidlRoot);
               PIDL_Free(pidlItem);
          end;
          PIDL_Free(LastpidlRoot);
          if pidlStream.Size<>0 then
          begin
               with FE do
               begin
                    cfFormat:=CF_SHELLIDLIST;
                    ptd:=nil;
                    dwAspect:=DVASPECT_CONTENT;
                    lindex:=-1;
                    tymed:=TYMED_HGLOBAL;
               end;
               SetData(FE,SM,false);
          end;
     end;
     if RenderFilename then
     begin
          with df do
          begin
               pfiles:=sizeof(Tdropfiles);
               pt.x:=0;
               pt.y:=0;
               longint(fnc) := 0;
               longint(Fwide) := 1;
          end;
          HDropStream.Write(df,sizeof(df));
          for i:=0 to AFileList.count-1 do
          begin
               if AFileList.Items[i]^.Name='' then
               begin
                    HDropStream.SetSize(0);
                    break;
               end;
               strPcopy(pc,AFileList.Items[i]^.Name+#0);
               HDropStream.Write(pc,(length(AFileList.Items[i]^.Name)+1) * sizeof(pc[0]));
               FilenameMapList.Add(AFileList.Items[i]^.MappedName);
               if FilenameMapList[i]<>'' then FilenamesAreMapped:=true;
          end;
          if HDropStream.Size<>0 then
          begin
               with FE do
               begin
                    cfFormat:=cf_HDrop;
                    ptd:=nil;
                    dwAspect:=DVAspect_Content;
                    lindex:=-1;
                    tymed:=tymed_HGlobal;
               end;
               SetData(FE,SM,false);
               pc[0]:=#0;
               HDropStream.Write(pc,sizeof(pc[0]));
          end;
          if FilenamesAreMapped then
          begin
                with FE do
                begin
                     cfFormat:=CF_FILENAMEMAPW;
                     ptd:=nil;
                     dwAspect:=DVASPECT_CONTENT;
                     lindex:=-1;
                     tymed:=TYMED_HGLOBAL;
                end;
                SetData(FE,SM,false);
          end;
     end;
end;

destructor TDataObjectFilesEx.Destroy;
begin
     if Assigned(OnRelease) then OnRelease(Self);
     pidlStream.Free;
     HDropStream.Free;
     FilenameMapList.Free;
     inherited Destroy;
end;

function TDataObjectFilesEx.RenderData(FormatEtc:TFormatEtc;
        var StgMedium: TStgMedium):HResult;
var h: HGlobal;
    p:pointer;
    FilenameMapStream:TMemoryStream;
    i:integer;
    pc:array[0..1024] of char;
begin
     Result:=E_Fail;
     if FormatEtc.cfFormat=CF_SHELLIDLIST then
     begin
          h := GlobalAlloc(GHND or GMEM_SHARE, pidlStream.Size);
          if h = 0 then
          begin
               Result:= E_OUTOFMEMORY;
               Exit;
          end;
          p:=globallock(h);
          pidlStream.Seek(0,0);
          pidlStream.Read(p^,pidlStream.Size);
          globalunlock(h);
          with StgMedium do
          begin
               tymed:=TYMED_HGLOBAL;
               hGlobal := h;
               unkForRelease := nil;
          end;
          result:=S_OK;
     end;
     if FormatEtc.cfFormat=cf_HDrop then
     begin
          h := GlobalAlloc(GHND or GMEM_SHARE, HDropStream.Size);
          if h = 0 then
          begin
               Result:= E_OUTOFMEMORY;
               Exit;
          end;
          p:=globallock(h);
          HDropStream.Seek(0,0);
          HDropStream.Read(p^,HDropStream.Size);
          globalunlock(h);
          with StgMedium do
          begin
               tymed:=TYMED_HGLOBAL;
               hGlobal := h;
               unkForRelease := nil;
          end;
          Result:=S_OK;
     end;
     if (FormatEtc.cfFormat=CF_FILENAMEMAP) or (FormatEtc.cfFormat=CF_FILENAMEMAPW) then
     begin
          FilenameMapStream:=TMemoryStream.Create;
          if (FormatEtc.cfFormat=CF_FILENAMEMAPW) then
          begin
               for i:=0 to FilenameMapList.count-1 do
               begin
                    StringToWideChar(FilenameMapList[i],PWideChar(@pc),sizeof(pc));
                    FilenameMapStream.Write(pc,Length(WideString(PWideChar(@pc)))*2+2);
               end;
               pc[0]:=#0; pc[1]:=#0;
               FilenameMapStream.Write(pc,2);
          end
          else
          begin
               for i:=0 to FilenameMapList.count-1 do
               begin
                    strPcopy(pc,FilenameMapList[i]+#0);
                    FilenameMapStream.Write(pc,length(FilenameMapList[i])+1);
               end;
               pc[0]:=#0;
               FilenameMapStream.Write(pc,1);
          end;
          h := GlobalAlloc(GHND or GMEM_SHARE, FilenameMapStream.Size);
          if h = 0 then
          begin
               Result:= E_OUTOFMEMORY;
               FilenameMapStream.Free;
               Exit;
          end;
          p:=globallock(h);
          FilenameMapStream.Seek(0,0);
          FilenameMapStream.Read(p^,FilenameMapStream.Size);
          FilenameMapStream.Free;
          globalunlock(h);
          with StgMedium do
          begin
               tymed:=TYMED_HGLOBAL;
               hGlobal := h;
               unkForRelease := nil;
          end;
          result:=S_OK;
     end;
end;

function TDataObjectFilesEx.IsValid(Formatpidl, FormatHDrop:boolean):boolean;
begin
     Result:= not ((Formatpidl and (pidlStream.Size=0)) or (FormatHDrop and (HDropStream.Size=0)));
end;

// TDropTargetFilesEx -------------------------------------------------------------

constructor TDropTargetFilesEx.Create(AOwner: TDragDrop);
begin
     inherited Create(AOwner);
end;

destructor TDropTargetFilesEx.Destroy;
begin
     inherited Destroy;
end;

procedure TDropTargetFilesEx.AccepTDataObject(DataObj: IDataObject;
   var Accept:boolean);
var  FE:TFormatEtc;
     HasHDrop, HasIDList:boolean;
begin
     Accept:=false;
     with FE do
     begin
          cfFormat:=cf_HDrop;
          ptd:=nil;
          dwAspect:=DVASPECT_CONTENT;
          lindex:=-1;
          tymed:=TYMED_HGLOBAL;
     end;
     HasHDrop:=DataObj.QueryGetData(FE)=S_OK;
     if (HasHDrop=false) and (nvFilename in TDragDropFilesEx(FOwner).FNeedValid) then exit;
     with FE do
     begin
          cfFormat:=CF_SHELLIDLIST;
          ptd:=nil;
          dwAspect:=DVASPECT_CONTENT;
          lindex:=-1;
          tymed:=TYMED_HGLOBAL;
     end;
     HasIDList:=DataObj.QueryGetData(FE)=S_OK;
     if (HasIDList=false) and (nvPIDL in TDragDropFilesEx(FOwner).FNeedValid) then exit;
     Accept:=HasIDList or HasHDrop;
end;

procedure TDropTargetFilesEx.RenderDropped(DataObj: IDataObject; grfKeyState: Longint;
        pt: TPoint; var dwEffect: longint);
var FormatEtc: TFormatEtc;
    StgMedium: TStgMedium;
    HDropSize, pidlSize, FileNameMapSize: longint;
    HDropPtr, pidlPtr, FileNameMapPtr: pointer;
    HDropHandle,pidlHandle, FileNameMapHandle: THandle;
    IsWideChar:boolean;
begin
     TDragDropFilesEx(FOwner).FFileList.Clear;
     // get "cf_HDrop" items
     with FormatEtc do
     begin
          cfFormat:=cf_HDrop;
          ptd:=nil;
          dwAspect:=DVASPECT_CONTENT;
          lindex:=-1;
          tymed:=TYMED_HGLOBAL;
     end;
     if DataObj.GetData(FormatEtc, StgMedium)=S_Ok then HDropHandle:=StgMedium.HGlobal
     else HDropHandle:=0;
     if HDropHandle<>0 then
     begin
          try
             HDropSize:=GlobalSize(HDropHandle);
             HDropPtr:=GlobalLock(HDropHandle);
             CopyHDropToFilelist(TDragDropFilesEx(FOwner).FFileList,
                HDropPtr, HDropSize);
          finally
             GlobalUnLock(HDropHandle);
             ReleaseStgMedium(StgMedium);
          end;
          // CF_FILENAMEMAP makes only sense if cf_HDrop exists ...
          // get "CF_FILENAMEMAP" or "CF_FILENAMEMAPW" items
          with FormatEtc do
          begin
               cfFormat:=CF_FILENAMEMAP;
               ptd:=nil;
               dwAspect:=DVASPECT_CONTENT;
               lindex:=-1;
               tymed:=TYMED_HGLOBAL;
          end;
          IsWideChar:=false;
          FileNameMapHandle:=0;
          if DataObj.GetData(FormatEtc, StgMedium)=S_Ok then FileNameMapHandle:=StgMedium.HGlobal
          else
          begin
               with FormatEtc do
               begin
                    cfFormat:=CF_FILENAMEMAPW;
                    ptd:=nil;
                    dwAspect:=DVASPECT_CONTENT;
                    lindex:=-1;
                    tymed:=TYMED_HGLOBAL;
               end;
               if DataObj.GetData(FormatEtc, StgMedium)=S_Ok then
               begin
                    FileNameMapHandle:=StgMedium.HGlobal;
                    IsWideChar:=true;
               end;
          end;
          if FileNameMapHandle<>0 then
          begin
               TDragDropFilesEx(FOwner).FFileNamesAreMapped:=true;
               try
                  FileNameMapSize:=GlobalSize(FileNameMapHandle);
                  FileNameMapPtr:=GlobalLock(FileNameMapHandle);
                  CopyFileNameMapToFilelist(TDragDropFilesEx(FOwner).FFileList,
                    FileNameMapPtr, FileNameMapSize,IsWideChar);
              finally
                  GlobalUnLock(FileNameMapHandle);
                  ReleaseStgMedium(StgMedium);
               end;
          end
          else TDragDropFilesEx(FOwner).FFileNamesAreMapped:=false;
     end
     else TDragDropFilesEx(FOwner).FFileNamesAreMapped:=false;
     // get "CF_SHELLIDLIST" items
     with FormatEtc do
     begin
          cfFormat:=CF_SHELLIDLIST;
          ptd:=nil;
          dwAspect:=DVASPECT_CONTENT;
          lindex:=-1;
          tymed:=TYMED_HGLOBAL;
     end;
     if DataObj.GetData(FormatEtc, StgMedium)=S_Ok then pidlHandle:=StgMedium.HGlobal
     else pidlHandle:=0;
     if pidlHandle<>0 then
     begin
          try
             pidlSize:=GlobalSize(pidlHandle);
             PidlPtr:=GlobalLock(pidlHandle);
             CopyPIDLsToFilelist(TDragDropFilesEx(FOwner).FFileList,
                pidlPtr, pidlSize);
          finally
             GlobalUnLock(pidlHandle);
             ReleaseStgMedium(StgMedium);
          end;
     end;
end;

// TShellExtension ---------------------------------------------------

procedure TShellExtension.AssignTo(Dest: TPersistent);
begin
     if Dest is TShellExtension then
        with TShellExtension(Dest) do
        begin
             FDropHandler:=Self.FDropHandler;
             FDragDropHandler:=Self.FDragDropHandler;
        end
        else inherited AssignTo(Dest);
end;

// TDragDropFilesEx ---------------------------------------------------------------

constructor TDragDropFilesEx.Create(AOwner: TComponent);
begin
     inherited Create(AOwner);
     FFileList:=TFileList.Create;
     FDropTarget._Release;
     FDropTarget:=TDropTargetFilesEx.Create(self);
     FCompleteFileList:=true;
     SourceCompatibility:=[];
     FFileNamesAreMapped:=false;
     FCMList:=TList.Create;
     FShellExtension:=TShellExtension.Create;
end;

destructor TDragDropFilesEx.Destroy;
begin
     FCMList.Free;
     FFileList.Free;
     FShellExtension.Free;
     inherited destroy;
end;

procedure TDragDropFilesEx.DataObjectRelease(Sender: TObject);
begin
  if Assigned(OnDataObjectRelease) then OnDataObjectRelease(Self);
end;

function TDragDropFilesEx.CreateDataObject:TDataObject;
var DataObject:TDataObjectFilesEx;
    RFName,RPidl:boolean;
begin
     Result:=nil;
     if FCompleteFileList then
     begin
          RFName:=FFileList.RenderNames;
          RPidl:=FFileList.RenderPIDLs;
          if ((nvFilename in FNeedValid) and (RFName=false)) or
             ((nvPIDL in FNeedValid) and (RPidl=false)) then exit;
     end
     else
     begin
          RFName:=true;
          RPidl:=true;
     end;
     if FFileList.Count>0 then
     begin
          DataObject:=TDataObjectFilesEx.Create(FFileList, RPidl, RFname);
          DataObject.OnRelease := DataObjectRelease;
          if DataObject.IsValid((nvPIDL in FNeedValid),
             (nvFilename in FNeedValid))=false then DataObject._Release
          else Result:=DataObject;
     end;
end;

procedure TDragDropFilesEx.DoMenuPopup(Sender: TObject; AMenu: HMenu;
   DataObj: IDataObject; AMinCustCmd:integer; grfKeyState: Longint; pt: TPoint);
var StringList:TStringList;
    Reg:TRegistry;
    pidlFQ:PItemIDList;
    FileName:string;

    procedure CreateDragDropHandler(GUID:string);
    var Unknown:IUnknown;
        ShellExtInit:IShellExtInit;
        CMListItem:PCMListItem;
    begin
         try
            Unknown:=CreateComObject(StringToGUID(GUID));
         except
            Unknown:=nil;
         end;
         try
            if assigned(Unknown) and
               (Unknown.QueryInterface(IID_IShellExtInit, ShellExtInit)=S_OK) then
            begin
                 if ShellExtInit.Initialize(pidlFQ, DataObj, 0)=NoError then
                 begin
                      New(CMListItem);
                      if ShellExtInit.QueryInterface(IID_IContextMenu,
                         CMListItem^.CM)=S_Ok then
                      begin
                           CMListItem^.FirstCmd:=AMinCustCmd;
                           CMListItem^.LastCmd:=AMinCustCmd;
                           inc(CMListItem^.LastCmd,CMListItem^.CM.QueryContextMenu(
                              AMenu, 0, CMListItem^.FirstCmd, $7FFF, CMF_NORMAL));
                           if CMListItem^.LastCmd=CMListItem^.FirstCmd then
                              Dispose(CMListItem)
                           else
                           begin
                                AMinCustCmd:=CMListItem^.LastCmd;
                                FCMList.Add(CMListItem);
                           end;
                      end;
                 end;
            end;
         finally
            Unknown:=nil;
            ShellExtInit:=nil;
         end;
    end;

begin
     if assigned(FOnSpecifyDropTarget) and FShellExtension.FDragDropHandler then
     begin
          pidlFQ:=nil;
          FOnSpecifyDropTarget(self, true, DragDropControl.ScreenToClient(pt),
             pidlFQ, Filename);
          if pidlFQ=nil then pidlFQ:=PIDL_GetFromPath(PChar(Filename))
          else pidlFQ:=PIDL_Copy(pidlFQ);
          StringList:=TStringList.Create;
          Reg:=TRegistry.Create;
          try
             Reg.RootKey:=HKEY_CLASSES_ROOT;
             if Reg.OpenKey('Folder\ShellEx\DragDropHandlers', false) then
             begin
                  Reg.GetKeyNames(StringList);
                  Reg.CloseKey;
                  while StringList.Count>0 do
                  begin
                       { The documentation for the drag-and-drop handlers varies
                         between many registry-keys, where you find the handlers.
                         I think, the correct position is "Folder"; "Directory"
                         should be the key for system-folders! Even, I have found
                         in the documentation, that you can define drag-and-drop
                         handlers for the system-folder "printers". Till now, it
                         doesn't make sense to me. Therefore, I haven't implemented
                         it }
                       if Reg.OpenKey('Folder\ShellEx\DragDropHandlers\'+
                          StringList[StringList.Count-1], false) then
                       begin
                            CreateDragDropHandler(Reg.ReadString(''));
                            Reg.CloseKey;
                       end;
                       StringList.Delete(StringList.Count-1);
                   end;
             end;
          finally
             Stringlist.Free;
             Reg.Free;
             PIDL_Free(pidlFQ);
          end;
     end;
     inherited DoMenuPopup(Sender, AMenu, DataObj, AMinCustCmd,
        grfKeyState, pt);
end;

function TDragDropFilesEx.DoMenuExecCmd(Sender: TObject; AMenu: HMenu;
   DataObj:IDataObject; Command:integer; var dwEffect: longint):boolean;
var ICM: TCMInvokeCommandInfo;
    i:integer;
    CMListItem:PCMListItem;
begin
     Result:=false;
     try
        if FCMList.Count>0 then
           for i:=0 to FCMList.Count-1 do
           begin
                CMListItem:=FCMList.Items[i];
                if (CMListItem^.FirstCmd<=Command) and
                   (CMListItem^.LastCmd>Command) then
                begin
                     FillChar(ICM,SizeOf(TCMInvokeCommandInfo),#0);
                     ICM.cbSize:=SizeOf(TCMInvokeCommandInfo);
                     ICM.hwnd:=DragDropControl.Handle;
                     ICM.lpVerb:=MakeIntResourceA(Command-CMListItem^.FirstCmd);
                     ICM.nShow:=SW_SHOWNORMAL;
                     Result:=CMListItem^.CM.InvokeCommand(ICM)=NOERROR;
                     break;
                end;
           end;
     finally
        if Result=false then
           Result:=inherited DoMenuExecCmd(Sender, AMenu, DataObj, Command, dwEffect);
     end;
end;

procedure TDragDropFilesEx.DoMenuDestroy(Sender:TObject; AMenu: HMenu);
var CMListItem:PCMListItem;
begin
     while FCMList.Count>0 do
     begin
          CMListItem:=FCMList.Items[FCMList.Count-1];
          CMListItem^.CM:=nil;
          Dispose(CMListItem);
          FCMList.Delete(FCMList.Count-1);
     end;
     inherited DoMenuDestroy(Sender, AMenu);
end;

function TDragDropFilesEx.TargetHasDropHandler(pidlFQ:PItemIDList; Filename:string;
   var dwEffect: longint): boolean;
var ppidlFQ, ppidlRoot, ppidlItem:PItemIDList;
    SF:IShellFolder;
    DT:IDropTarget;
begin
     try
        Result:=false;
        ppidlFQ:=nil;
        ppidlRoot:=nil;
        ppidlItem:=nil;
        if pidlFQ=nil then ppidlFQ:=PIDL_GetFromPath(PChar(Filename))
        else ppidlFQ:=PIDL_Copy(pidlFQ);
        PIDL_GetRelative(ppidlFQ, ppidlRoot, ppidlItem);
        PIDL_GetFileFolder(ppidlRoot, SF);
        if assigned(SF) then
        begin
             SF.GetUIObjectOf(0,1,ppidlItem,IID_IDropTarget,nil,Pointer(DT));
             Result:=Assigned(DT) and FileExists(Filename);
             if Assigned(DT) and (dwEffect and not
                (DropEffect_Scroll or DropEffect_Link)=DropEffect_None) then
             dwEffect:=dwEffect and not DropEffect_Link;
        end;
     finally
        SF:=nil;
        DT:=nil;
        PIDL_Free(ppidlRoot);
        PIDL_Free(ppidlItem);
        PIDL_Free(ppidlFQ);
     end;
end;

function TDragDropFilesEx.DropHandler(const dataObj: IDataObject; grfKeyState: Longint;
       pt: TPoint; var dwEffect: Longint): boolean;
var pidlFQ, ppidlFQ, ppidlRoot, ppidlItem:PItemIDList;
    SF:IShellFolder;
    DT:IDropTarget;
    Filename:string;
    pc:array[0..1024] of char;
begin
     try
        Result:=false;
        ppidlRoot:=nil;
        ppidlItem:=nil;
        ppidlFQ:=nil;
        if (ShellExtensions.FDropHandler=false) or
           (assigned(FOnSpecifyDropTarget)=false) then exit;
        pidlFQ:=nil;
        FOnSpecifyDropTarget(self, false, DragDropControl.ScreenToClient(pt),
           pidlFQ, Filename);
        if pidlFQ=nil then ppidlFQ:=PIDL_GetFromPath(PChar(Filename))
        else ppidlFQ:=PIDL_Copy(pidlFQ);
        PIDL_GetRelative(ppidlFQ, ppidlRoot, ppidlItem);
        PIDL_GetFileFolder(ppidlRoot, SF);
        if assigned(SF) then
        begin
             if (Filename='') and PIDL_GetDisplayName(SF, ppidlItem, SHGDN_FORPARSING,
                pc, sizeof(pc)) then Filename:=StrPas(pc);
             SF.GetUIObjectOf(0,1,ppidlItem,IID_IDropTarget,nil,Pointer(DT));
             if FileExists(Filename) and Assigned(DT) then
             begin
                  DT.DragEnter(DataObj, grfKeyState, pt, dwEffect);
                  Result:=DT.Drop(DataObj, grfKeyState, pt, dwEffect)=NOERROR;
             end;
        end;
     finally
        SF:=nil;
        DT:=nil;
        PIDL_Free(ppidlRoot);
        PIDL_Free(ppidlItem);
        PIDL_Free(ppidlFQ);
     end;
end;

// Register Component ----------------------------------------------------------

procedure Register;
begin
  {MP}RegisterComponents({'Shell32'}'DragDrop', [TDragDropFilesEx]);
end;

end.