起始行：

用EM_GETFIRSTVISIBLELINE消息即可。

结束行：

Var

   r: TRect;

   lastvisibleline, lastlineindex: Integer;

 Begin

   richedit1.perform( EM_GETRECT, 0, longint( @r ));

   r.left := r.left+1;

   r.top  := r.bottom - 2;

   lastlineindex := richedit1.perform( EM_CHARFROMPOS, 0,integer(@r.topleft));

   lastvisibleline := richedit1.perform( EM_EXLINEFROMCHAR, 0,lastlineindex);

end;

************************

function RE_GetLastVisibleLine ( RichEdit : TRichEdit ): Integer ;

const

 EM_EXLINEFROMCHAR = WM_USER + 54 ;

var

 r : TRect ;

 i : Integer ;

begin

  {

  The EM_GETRECT message retrieves the formatting rectangle

  of an edit control.

 }

 RichEdit . Perform ( EM_GETRECT , 0 , Longint (@ r ));

 r . Left := r . Left + 1 ;

 r . Top   := r . Bottom - 2 ;

  {

   The EM_CHARFROMPOS message retrieves information about the character

   closest to a specified point in the client area of an edit control

 }

 i := RichEdit . Perform ( EM_CHARFROMPOS , 0 , Integer (@ r . topleft ));

  {

   The EM_EXLINEFROMCHAR message determines which

   line contains the specified character in a rich edit control

 }

 Result := RichEdit . Perform ( EM_EXLINEFROMCHAR , 0 , i );

end ;

{

 Sending the EM_GETFIRSTVISIBLELINE message to a multi-line edit control

 finds out which line is the first line visible.

 This is the line that is currently displayed at the top of the control.

}

function RE_GetFirstVisibleLine ( RichEdit : TRichEdit ): Integer ;

begin

 Result := RichEdit . Perform ( EM_GETFIRSTVISIBLELINE , 0 , 0 );

end ;

procedure TForm1 . Button1Click ( Sender : TObject );

begin

 Caption := Format ( '%d,%d' ,[ RE_GetFirstVisibleLine ( RichEdit1 ), RE_GetLastVisibleLine ( RichEdit1 )]);

end ;