Re: Be notified when any of the windows is activated
<yvzsahin@gmail.com> wrote in message
news:1173075386.552830.277160@p10g2000cwp.googlegroups.com...
There are 3 methods (as far as I could find) to get the active window
all the time
a) Place a timer and check with GetForeGroundWindow(), but you
will get NULL for the windows not created by your thread because their
input state is different from yours. Use AttachThreadInput() to attach
your input state with the thread whose windows you want to analyze.
http://www.microsoft.com/msj/0397/Win32/Win320397.aspx will be
helpful.
No, this is not true. You can call GetForegroundWindow(), and it will
return the HWND of the foreground window, it doesn't matter whose thread it
belongs to. AttachThreadInput() is useful for things like GetFocus(), not
GetForegroundWindow().
b) Place a hook using SetWindowsHookEx. Types of hooks you can
use is on documentation page. But again the above problem occurs, you
get only events related to your thread because windows don't let you
interrupt other threads input states.
No, this is not true. Using a WH_SHELL hook you can definitely get
HSHELL_ACTIVATED notifications regardless of thread input state.
Using this method you can use a
callback method of your own thread or a method from a DLL and to place
a system-wide hook like I wanted you should use a dll callback
function. Which is not a desirable solution for me.
Yes, you would need a system-wide hook to use SetWindowsHookEx (WH_SHELL,
.....).
c) Place a hook using SetWinEventHook. Using this method you can
specify the thread or process whose events you want to get, or place
simply 0 and get the system-wide events.
This is the simplest and most promising. Use SetWinEventHook() to capture
EVENT_SYSTEM_FOREGROUND events.
There may be issues relating to new privilege mechanism of Vista,
which is out of my scope.
SetWindowsHookEx() fails if the injector app (yours) has a lower priviledge
than the injectee app (theirs). This is because Vista prevents your DLL
from being injected into their process.
However, SetWinEventHook() has the option of receiving callbacks out of
process, so your DLL does not need to be injected into their process. I'm
not sure if you will get EVENT_SYSTEM_FOREGROUND events in this case. The
MSDN doc says HWND info is read-only to lower-priviledged processes, and it
seems which window is the foreground is read only. You can try
SetWinEventHook() and see if it works.
-- David (MVP)