Embedding window into another process

Question

I have read some posts here on StackOverflow, but none has worked for me. Here is the code I am using to display the window of the standard Calculator on my form:

procedure TForm1.Button1Click(Sender: TObject);
var
  Tmp: Cardinal;
  R: TRect;
begin
  CalcWindow := FindWindow(nil, 'Calculator');
  if (CalcWindow <> 0) then
  begin
    GetWindowThreadProcessID(CalcWindow, CalcProcessID);

    Tmp := GetWindowLong(CalcWindow, GWL_STYLE);
    Tmp := (Tmp and not WS_POPUP) or WS_CHILD;
    SetWindowLong(CalcWindow, GWL_STYLE, Tmp);
    GetWindowRect(CalcWindow, R);

    SetForegroundWindow(CalcWindow);
    Windows.SetParent(CalcWindow, Panel1.Handle);
    SetWindowPos(CalcWindow, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOSIZE or SWP_FRAMECHANGED);

    AttachThreadInput(GetCurrentThreadID(), CalcWindow, True);
  end;
end;

It does display the window on my form, but the glass border is lost and sometimes (especially when I move my form), it is hard to restore the focus to the embedded window (I need to click several times).

What may be causing this? Also, do you see any potential issues I may get into with using this method?

Thank you for your time.

Answer 1

Try this code. I took it from one of my older source codes. You will lose glass frame, but main menu is visible, and I didn't notice any problem in setting focus back to the embedded app. You should be able to do so using SetForegroundWindow() API function. Whenever you move your container form, your embedded app loses focus, so you need to call SetForegroundWindow again to restore focus :

procedure ShowAppEmbedded(WindowHandle: THandle; Container: TWinControl);
var
  WindowStyle : Integer;
  FAppThreadID: Cardinal;
begin
  /// Set running app window styles.
  WindowStyle := GetWindowLong(WindowHandle, GWL_STYLE);
  WindowStyle := WindowStyle
                 - WS_CAPTION
                 - WS_BORDER
                 - WS_OVERLAPPED
                 - WS_THICKFRAME;
  SetWindowLong(WindowHandle,GWL_STYLE,WindowStyle);

  /// Attach container app input thread to the running app input thread, so that
  ///  the running app receives user input.
  FAppThreadID := GetWindowThreadProcessId(WindowHandle, nil);
  AttachThreadInput(GetCurrentThreadId, FAppThreadID, True);

  /// Changing parent of the running app to our provided container control
  Windows.SetParent(WindowHandle,Container.Handle);
  SendMessage(Container.Handle, WM_UPDATEUISTATE, UIS_INITIALIZE, 0);
  UpdateWindow(WindowHandle);

  /// This prevents the parent control to redraw on the area of its child windows (the running app)
  SetWindowLong(Container.Handle, GWL_STYLE, GetWindowLong(Container.Handle,GWL_STYLE) or WS_CLIPCHILDREN);
  /// Make the running app to fill all the client area of the container
  SetWindowPos(WindowHandle,0,0,0,Container.ClientWidth,Container.ClientHeight,SWP_NOZORDER);

  SetForegroundWindow(WindowHandle);
end;

You can call it this way:

  ShowAppEmbedded(FindWindow(nil, 'Calculator'), Panel1);