Avoid application activation and focus in when clicking buttons on it - Windows API or Qt

Question

Situation: A border-less QDialog stays successfully on top of other applications.

The problem is when clicking on this always-on-top application window, the following occurs:

• The clicked always-on-top application gets activated
• The clicked always-on-top application window steals the focus of previous active/focused app

Is there a possibility that when clicking on this always-on-top inactive and unfocused application window,

• the current application does not loose activation and focus
• while user being still able to interact with the always-on-top application (hitting buttons or drop-down menus, dragging the window)?

I'm working with Qt but there's no problem about using native Windows API.

I tried the following Qt windowFlag:

• Qt::WindowDoesNotAcceptFocus but it does not work: the always-on-top application is activated, focused.
• Qt::WindowTransparentForInput, the always-on-top application is really transparent to clicks: not activated and not focused in but buttons are unfortunately not triggered when hit.

Answer 1

It is possible to make a window unactivable and unfocusable when clicking on it by using Windows flags (#include <qt_windows.h>). The following has to be used after the window is created and shown:

HWND winHandle = (HWND)winId();
ShowWindow(winHandle, SW_HIDE);
SetWindowLong(winHandle, GWL_EXSTYLE, GetWindowLong(winHandle, GWL_EXSTYLE)
    | WS_EX_NOACTIVATE | WS_EX_APPWINDOW);
ShowWindow(winHandle, SW_SHOW);

Answer 2

I don't know about QDialog, I'm using just a QWidget for similar purpose (displaying a Windows 8 style notification).

Try setting:

dialog->setFocusPolicy(Qt::NoFocus);
dialog->setAttribute(Qt::WA_ShowWithoutActivating); 

maybe you'll have to set focus policy on all children.