Mega Code Archive
Implement Drag&Drop from an external application to your own application
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Title: implement Drag&Drop from an external application to your own application?
{
The following example demonstrates the Drag&Drop machanism from an external
application (Wordpad, Microsoft,..) to a TMemo in your own application.
{
Das folgende Beispiel demonstriert der Drag&Drop Maechanismus
aus externen Anwendungen (wie zum Beispiel WordPad oder Microsoft Word)
in ein TMemo des eigenen Delphi-Programms.
}
unit TMemoDragDropFrm;
{ ****************************************************************
Source File Name : TMemoDragDropFrm.pas
Typ : Hauptformular
Autor : Andreas Kosch
Compiler : Delphi 4.02 CSS
Betriebssystem : Windows 98
Beschreibung : Text via OLE Drag&Drop bernehmen aus einer
anderen Anwendung (wie zum Beispiel WordPad)
bernehmen.
16.01.2003: Test mit Delphi 7 und Microsoft Word XP unter Windowx XP
**************************************************************** }
{ Comments by Thomas Stutz }
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ComCtrls, ActiveX, ShlObj, ComObj, StdCtrls;
type
// TForm1's declaration indicates that it's a TForm and that
// it supports the IDropTarget interface:
{
IDropTarget
Any application wanting to accept drop operations must
implement the IDropTarget interface.
Methods of the IDropTarget interface:
DragEnter
Dragged item has just been moved into the application's window,
return the relevant icon.
DragOver
Dragged item is being moved over the application's window,
return the relevant icon.
DragLeave
Dragged item has just moved out of the application's window.
Drop
The dragged item has been dropped on this application.
}
TForm1 = class(TForm, IDropTarget)
Memo1: TMemo;
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
private
{ Private declarations }
// IDropTarget
function DragEnter(const dataObj: IDataObject;
grfKeyState: Longint;
pt: TPoint;
var dwEffect: Longint): HResult; stdcall;
function DragOver(grfKeyState: Longint;
pt: TPoint;
var dwEffect: Longint): HResult; stdcall;
function DragLeave: HResult; stdcall;
function Drop(const dataObj: IDataObject;
grfKeyState: Longint; pt: TPoint;
var dwEffect: Longint): HResult; stdcall;
// IUnknown
// Ignore referance counting
function _AddRef: Integer; stdcall;
function _Release: Integer; stdcall;
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
uses
ShellAPI;
// In the OnCreate event handler, two important methods are called.
// First, OleInitalize is called. This initializes the OLE libraries and should always be
// called before your application uses any OLE functions.
// RegisterDragDrop registers the window as a valid drop target.
// If this isn't called, the window will never receive any drop events.
procedure TForm1.FormCreate(Sender: TObject);
begin
OleInitialize(nil);
{Allow window to accept drop events}
OleCheck(RegisterDragDrop(Handle, Self));
{ Execute Wordpad for testing }
ShellExecute(Handle, 'open', 'wordpad', 'c:\Test.doc', nil, SW_SHOW);
end;
// OnDestroy does the exact opposite. It calls RevokeDropTarget to indicate that
// drop events are no longer accepted.
// It then calls OleUninitialize, since the application is finished using all OLE functions.
procedure TForm1.FormDestroy(Sender: TObject);
begin
{Finished accepting drops}
RevokeDragDrop(Handle);
OleUninitialize;
end;
{-----------------------------------------------------------------}
{ IDropTarget-Implementierung }
{-----------------------------------------------------------------}
function TForm1.DragEnter(const dataObj: IDataObject;
grfKeyState: Longint;
pt: TPoint;
var dwEffect: Longint): HResult;
begin
dwEffect := DROPEFFECT_COPY;
Result := S_OK;
end;
function TForm1.DragOver(grfKeyState: Longint;
pt: TPoint;
var dwEffect: Longint): HResult;
begin
dwEffect := DROPEFFECT_COPY;
Result := S_OK;
end;
function TForm1.DragLeave: HResult;
begin
Result := S_OK;
end;
function TForm1._AddRef: Integer;
begin
Result := 1;
end;
function TForm1._Release: Integer;
begin
Result := 1;
end;
function TForm1.Drop(const dataObj: IDataObject;
grfKeyState: Longint;
pt: TPoint;
var dwEffect: Longint): HResult;
var
aFmtEtc: TFORMATETC;
aStgMed: TSTGMEDIUM;
pData: PChar;
begin
{Make certain the data rendering is available}
if (dataObj = nil) then
raise Exception.Create('IDataObject-Pointer is not valid!');
with aFmtEtc do
begin
cfFormat := CF_TEXT;
ptd := nil;
dwAspect := DVASPECT_CONTENT;
lindex := -1;
tymed := TYMED_HGLOBAL;
end;
{Get the data}
OleCheck(dataObj.GetData(aFmtEtc, aStgMed));
try
{Lock the global memory handle to get a pointer to the data}
pData := GlobalLock(aStgMed.hGlobal);
{ Replace Text }
Memo1.Text := pData;
finally
{Finished with the pointer}
GlobalUnlock(aStgMed.hGlobal);
{Free the memory}
ReleaseStgMedium(aStgMed);
end;
Result := S_OK;
end;
end.
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