Чужое окно

var
  buffer : array[0..1024] of Char;
begin
  SendMessage(Handle, WM_GETTEXT, SizeOf(buffer), Integer(@buffer));
...
end;

  Handle := FindWindow('Искомое окно', NIL);

procedure TForm1.Button2Click(Sender: TObject);
var wnd: hwnd;
    buff: array [0..127] of char;
begin
ListBox1.clear;
wnd := GetWindow(handle, gw_hwndfirst);
while wnd <> 0 do
begin // не показываем:
if (wnd <> Application.Handle)//собственное
and IsWindowVisible(wnd) // невидимые
and (GetWindow(wnd, gw_owner) = 0) //дочерние
and (GetWindowText(wnd, buff, SizeOf(buff)) <> 0) then
begin
GetWindowText(wnd, buff, SizeOf(buff));
ListBox1.Items.Add(StrPas(buff));
end;
wnd := GetWindow(wnd, gw_hwndnext);
end;
ListBox1.ItemIndex := 0;
end;
 
procedure TForm1.Button1Click(Sender: TObject);
var h:thandle;
buf:array[0..200] of char;
begin
h:=findwindow('Notepad',nil);
if h<>0 then
SendMessage(h,wm_gettext,200,Integer(@buf));
Caption:=buf;
Memo1.Lines.Add(buf);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  h   : HWND;
  buf : array[Byte] of Char;
  St  : String;
begin
  h := FindWindow('Notepad', NIL);
  if h <> 0 then
  begin
    SendMessage(h, WM_GETTEXT, SizeOF(buf), Integer(@buf));
    St := buf;
    Memo1.Lines.Add(St);
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
var wnd: hwnd;
    buff: array [0..127] of char;
begin
ListBox1.clear;
wnd := GetWindow(handle, gw_hwndfirst);
while wnd <> 0 do
begin // не показываем:
if (wnd <> Application.Handle)//собственное
and IsWindowVisible(wnd) // невидимые

and (GetWindowText(wnd, buff, SizeOf(buff)) <> 0) then
begin
GetWindowText(wnd, buff, SizeOf(buff));
ListBox1.Items.Add(StrPas(buff));
end;
wnd := GetWindow(wnd, gw_hwndnext);
end;
ListBox1.ItemIndex := 0;
end;

function EnumChildFunc(Child: HWND; lParam : Longint) : BOOL; stdcall;
var
  szClass : array[0..63] of Char;
  buf     : array[Byte] of Char;
  St      : String;
begin
  GetClassName(Child, szClass, SizeOf(szClass));
  if lstrcmpi(szClass, 'EDIT') = 0 then
  begin
    SendMessage(Child, WM_GETTEXT, SizeOF(buf), Integer(@buf));
    St := buf;
    Form1.Memo1.Lines.Add(St);
  end;
 
  Result := True;
end;
 
procedure TForm1.Button2Click(Sender: TObject);
var
  h   : HWND;
  buf : array[Byte] of Char;
  St  : String;
begin
  h := findwindow('Notepad', NIL);
  if h <> 0 then
  begin
    SendMessage(h, WM_GETTEXT, SizeOF(buf), Integer(@buf));
    St := buf;
    Memo1.Lines.Add(St);
  end;
 
  EnumChildWindows(h, @EnumChildFunc, 0);
end;