How can I tell if a Window has focus? (Win32 API)

Question

Using the Win32 API (in C, but that's inconsequential) how can I tell if a given window (identified by HWND) has focus? I'm hooking an application watching for an event, and when that event occurs I want to check if the application already has focus. If it doesn't, I want to flash the window until they give focus to it.

Alternately, does the FlashWindowEx struct flag FLASHW_TIMERNOFG that flashes until the window has focus just not flash if the window already has focus? I cannot test this now since I am not in my development environment, but I was under the impression that it would flash anyways, which is what I'm trying to avoid.

Edit: Also, if it matters, the application uses DirectX in this window.

Answer 1

Do you really mean "focus" or do you mean "active?"

One window has the focus -- the one that's first in line to get keyboard events. The outer window (that the user can drag around the screen) is "active" if one of its subwindows has the focus, but it might or might not have focus itself.

Answer 2

GetActiveWindow will return the top-level window that is associated with the input focus. GetFocus will return the handle of the window that has the input focus.

This article might help:
http://www.microsoft.com/msj/0397/Win32/Win320397.aspx