Drag and drop text from other programs (such as Web pages) into memo

You need to use the OLE drop target of the COM interface, the program creates a unittmydroptarget unit that supports the drag-and-drop target, creating a Tmydroptarget class in this unit.

This program enables you to drag a text block, such as WordPad or a Web page, into the Memo of the program and insert it into the Memo drag-and-drop position.

First look at how to use this Tmydroptarget class:

What you need to add to the header file (for example, Unit1.h) in the Form (the Blue section is new):

#include "UnitTMyDropTarget.h"
Class Tform1:public Tform
{
Private://User declarations
Tmydroptarget *dropmemo1; Custom drag-and-drop target classes
void __fastcall Dropmemo1text (idroptarget *sender, ansistring atext, DWORD keystate, Tpoint PT); Drag-and-drop events
Public://User declarations
__fastcall TForm1 (tcomponent* Owner);
__fastcall ~tform1 ();
};
In the From. cpp file (for example, Unit1.cpp), what you need to add (the Blue section is new):
__fastcall Tform1::tform1 (tcomponent* Owner)
: Tform (Owner)
{
OleInitialize (NULL);
DropMemo1 = new Tmydroptarget (MEMO1);
Dropmemo1->onprocesstext = Dropmemo1text;
}
//---------------------------------------------------------------------------
__fastcall Tform1::~tform1 ()
{
Dropmemo1->release ();//delete DropMemo1;
OleUninitialize ();
}
//---------------------------------------------------------------------------
void __fastcall TForm1::D ropmemo1text (IDropTarget *sender, ansistring atext, DWORD keystate, Tpoint PT)
{
POINTS P={pt.x,pt.y};
* (long*) &p=sendmessage (memo1->handle,em_charfrompos,0,* (long*) &p);
Memo1->selstart = p.x;
memo1->sellength = 0;
Memo1->seltext = Atext;
}
//---------------------------------------------------------------------------
Implementation of the Tmydroptarget class:
Contents of header File UnitTMyDropTarget.h:
//---------------------------------------------------------------------------
#ifndef Unittmydroptargeth
#define Unittmydroptargeth
//---------------------------------------------------------------------------
#include "oleidl.h"
#include "controls.hpp"
//---------------------------------------------------------------------------
Class Tmydroptarget:public IDropTarget
{
Public
__property void __fastcall (__closure *ongetformat) (IDropTarget *sender, IDataObject *dataobject, DWORD KeyState, TPoint PT, DWORD &DPE, bool &bdataok) = {read=_fgetformat, write=_fgetformat};
__property void __fastcall (__closure *onprocessdata) (IDropTarget *sender, IDataObject *dataobject, DWORD KeyState, Tpoint pt) = {read=_fprocessdata, write=_fprocessdata};
__property void __fastcall (__closure *onprocesstext) (IDropTarget *sender, ansistring atext, DWORD KeyState, TPoint pt) = {read=_fprocesstext, write=_fprocesstext};
Tmydroptarget (Twincontrol *aowner);
~tmydroptarget ();
HRESULT __stdcall QueryInterface (const GUID &iid, void **PPV);
ULONG __stdcall AddRef (void) {return ++_irefcount;}
ULONG __stdcall Release (void) {if (--_irefcount==0) {delete the;} return _irefcount;}
HRESULT __stdcall DragEnter (IDataObject *pdataobject, DWORD grfkeystate, Pointl PT, DWORD *pdweffect);
HRESULT __stdcall DragOver (DWORD grfkeystate, Pointl PT, DWORD *pdweffect);
HRESULT __stdcall DragLeave (void);
HRESULT __stdcall Drop (IDataObject *pdataobject, DWORD grfkeystate, Pointl PT, DWORD * pdweffect);
Private
ULONG _irefcount;
IDataObject *_lpdataobj;
Twincontrol *_ownercontrol;
void __fastcall (__closure *_fgetformat) (IDropTarget *sender, IDataObject *dataobject, DWORD keystate, TPoint PT, DWORD &A MP;DPE, bool &bdataok);
void __fastcall (__closure *_fprocessdata) (IDropTarget *sender, IDataObject *dataobject, DWORD keystate, TPoint PT);
void __fastcall (__closure *_fprocesstext) (IDropTarget *sender, ansistring atext, DWORD keystate, Tpoint PT);
BOOL __fastcall Fdataformatok (DWORD keystate, Pointl PT, DWORD &DPE);
void __fastcall Fprocessdata (DWORD keystate, Pointl PT);
};
//---------------------------------------------------------------------------
#endif
//---------------------------------------------------------------------------
Content of UnitTMyDropTarget.cpp:
//---------------------------------------------------------------------------
#include "UnitTMyDropTarget.h"
//---------------------------------------------------------------------------
Tmydroptarget::tmydroptarget (Twincontrol *aowner)
{
_ownercontrol = Aowner;
_irefcount = 0;
_lpdataobj = NULL;
_fgetformat = NULL;
_fprocessdata = NULL;
_fprocesstext = NULL;
Registerdragdrop (_ownercontrol->handle,this);
}
//---------------------------------------------------------------------------
Tmydroptarget::~tmydroptarget ()
{
Revokedragdrop (_ownercontrol->handle);
}
//---------------------------------------------------------------------------
HRESULT __stdcall tmydroptarget::queryinterface (const GUID &iid, void **PPV)
{
if ((Iid==iid_iunknown) | | (Iid==iid_idroptarget))
{
*ppv=this;
AddRef ();
}
Else
{
*ppv=null;
return e_nointerface;
}
return S_OK;
}
//---------------------------------------------------------------------------
HRESULT __stdcall Tmydroptarget::D ragenter (IDataObject *pdataobject, DWORD grfkeystate, Pointl PT, DWORD *pdweffect)
{
_lpdataobj = pDataObject;
Fdataformatok (Grfkeystate,pt,*pdweffect);
return S_OK;
}
//---------------------------------------------------------------------------
HRESULT __stdcall Tmydroptarget::D ragover (DWORD grfkeystate, Pointl PT, DWORD *pdweffect)
{
Fdataformatok (Grfkeystate,pt,*pdweffect);
return S_OK;
}
//---------------------------------------------------------------------------
HRESULT __stdcall Tmydroptarget::D ragleave (void)
{
return S_OK;
}
//---------------------------------------------------------------------------
HRESULT __stdcall Tmydroptarget::D rop (IDataObject *pdataobject, DWORD grfkeystate, Pointl PT, DWORD * pdweffect)
{
_lpdataobj = pDataObject;
if (Fdataformatok (Grfkeystate,pt,*pdweffect))
Fprocessdata (GRFKEYSTATE,PT);
return S_OK;
}
//---------------------------------------------------------------------------
BOOL __fastcall Tmydroptarget::fdataformatok (DWORD keystate, Pointl PT, DWORD &DPE)
{
FORMATETC Fetc={cf_text,0,dvaspect_content,-1,dword (-1)};
BOOL Bok=_lpdataobj->querygetdata (&FETC) ==s_ok;
DPE = BOK? Dropeffect_copy:dropeffect_none;
if (_fgetformat)
{
Tpoint Point (PT.X,PT.Y);
:: ScreenToClient (_ownercontrol->handle,&point);
_fgetformat (This,_lpdataobj,keystate,point,dpe,bok);
}
return BOK;
}
//---------------------------------------------------------------------------
void __fastcall Tmydroptarget::fprocessdata (DWORD keystate, Pointl PT)
{
if (_fprocessdata)
{
Tpoint Point (PT.X,PT.Y);
:: ScreenToClient (_ownercontrol->handle,&point);
_fprocessdata (This,_lpdataobj,keystate,point);
}
else if (_fprocesstext)
{
Stgmedium smed;
FORMATETC Fetc={cf_text,0,dvaspect_content,-1,dword (-1)};
BOOL bvalue= (_lpdataobj->getdata (&fetc,&smed) ==S_OK);
if (bvalue)
{
Hglobal hdata = GlobalLock (Smed.hglobal);
if (Hdata)
{
Tpoint Point (PT.X,PT.Y);
:: ScreenToClient (_ownercontrol->handle,&point);
_fprocesstext (this, (char*) hdata,keystate,point);
GlobalUnlock (Hdata);
GlobalFree (Hdata);
}
}
}
}
//---------------------------------------------------------------------------