Question

I use:

Hwnd hStart = ::FindWindow ("Shell_TrayWnd",NULL);  // get HWND of taskbar first
hStart = ::FindWindowEx (hStart, NULL,"BUTTON", NULL); // get HWND of start button

to get start button’s handle. It’s running properly on Windows XP,
but in Windows 7, ::FindWindowEx (hStart, NULL,"BUTTON", NULL) always returns 0, and GetLastError() returns 0, too.

Why is that?

Answer 1

In Windows 7 the start button, which has class name "Button", is a child of the desktop window. Your code assumes that the start button is a child of the window named "Shell_TrayWnd" which does indeed appear to be the way the taskbar and start menu were implemented on XP.

For Windows 7 you want to use something like this:

hStart = ::FindWindowEx(GetDesktopWindow(), NULL, "Button", NULL);

Although I think it would be better search for it by name to be sure that you get the right button.

hStart = ::FindWindowEx(GetDesktopWindow(), NULL, "Button", "Start");

I’m not sure how Vista implements its taskbar and start menu, but you can use Spy++ to find out.

Having said all of this, it would be much better if you can find a way to achieve your goals without poking around in such implementation specific details.