Declaration

TIEFileDragDrop = class(TComponent, IInterface, IDropTarget, IDropSource)
public
  constructor Create(AOwner: TComponent);
  destructor Destroy;

  // Allow dropping to "DropControl"
  property EnableDropping : Boolean;

  // Execute dragging at cursor
  function InitiateDragging(ssFilenames : TStrings; DragActions: TIEFileDragDropActions): TIEDragResult;

published
  // Supported actions when dropping files
  property DropActions : TIEFileDragDropActions;
  
  // Control to receive dropped files
  property DropControl : TWinControl;

  // Whether a preview of files is shown while dragging
  property ShowPreview: Boolean;

  // Size of preview image
  property PreviewWidth: Integer;
  property PreviewHeight: Integer;

  // Event that occurs as user starts dragging to our control
  property OnBeginFileDrop : TNotifyEvent;

  // Event that occurs while dragging over and dropping to allow effect to be customized
  property OnGetDragDropEffect: TIEDragDropEffectEvent;
  
  // Event that occurs when files are dropped
  property OnFileDrop : TIEFileDropEvent;
end;

Description

Class to provide support for dragging and dropping files from/to Windows Explorer (and other applications). Used by TImageEnFolderMView.

Demo

Drop Example

// Enable dropping of a file onto a TImageEnView (from Windows Explorer, for example)

procedure TForm1.FormCreate(Sender: TObject);
begin
  // These can also be set via published properties...
  IEFileDragDrop1.DropControl    := ImageEnView1;
  IEFileDragDrop1.OnFileDrop     := IEFileDragDrop1FileDrop;

  IEFileDragDrop1.EnableDropping := True;
end;

procedure TForm1.IEFileDragDrop1FileDrop(Sender: TObject; ssFiles: TStrings; dwEffect: Integer);
begin
  ImageEnView1.IO.LoadFromFile( ssFiles[0] );
end;

Drag Example

// Allow image to be dragged from a TImageEnView (to Windows Explorer, for example)
procedure TForm1.ImageEnView1MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
var
  ssFiles: TStringList;
begin
  if GetKeyState(VK_LBUTTON) < 0 then // Mouse left button is down
  begin
    ssFiles := TStringList.Create;
    ssFiles.Text := ImageEnView1.IO.Params.FileName;
    IEFileDragDrop1.InitiateDragging( ssFiles, [iedaCopy] );
    FreeAndNil(ssFiles);
  end;
end;

TImageEnMView Example

procedure TForm1.FormCreate(Sender: TObject);
begin
  AFileDrop := TIEFileDragDrop.Create(Self);
  AFileDrop.DropControl := ImageEnMView1;
  AFileDrop.OnFileDrop  := DropFiles;

  // Because we won't not explicity free the FileDrop object (let it free automatically on closure)
  RegisterExpectedMemoryLeak(AFileDrop);

  // Activate dropping
  AFileDrop.EnableDropping := True;
end;

procedure TForm1.DropFiles(Sender: TObject; ssFiles: TStrings; dwEffect: Integer);
var
  i: Integer;
  aFileName: string;
begin
  // Add the dropped image files to ImageEnMView
  for i := 0 to ssFiles.Count - 1 do
  begin
    aFileName := Trim(ssFiles[i]);
    ImageEnMView1.InsertImage(i, aFileName);
    ImageEnMView1.ImageBottomText[i] := ExtractFileName(aFileName);
  end;
  ImageEnMView1.SelectedImage := 0;
end;

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