windows API的帮助中看SendMessage的帮助,
LRESULT SendMessage(
HWND hWnd, // handle of destination window
UINT Msg, // message to send
WPARAM wParam, // first message parameter
LPARAM lParam // second message parameter
);
Parameters
hWnd
Identifies the window whose window procedure will receive the message. If this parameter is HWND_BROADCAST, the message is sent to all top-level windows in the system, including disabled or invisible unowned windows, overlapped windows, and pop-up windows; but the message is not sent to child windows.
如果hWnd是HWND_BROADCAST, 这条消息将发给所有的 top-level窗口,包括失效的和
隐藏,overlapped和pop-up 但是不包括子窗口