WM_NOTIFY is a notification message sent to its parent window, has never thought of the problem of changing the parent window of the control, until you want to achieve this problem when you want to implement a VC's docking toolbar. When the toolbar is stopped, its parent window is the program main window, dragging the toolbar out, that is, dragging the main window or dragging to the client area, you must create a popup window, the parent window of the toolbar becomes this Popup window. According to MSDN, WM_NOTIFY is sent to the parent window, and should be sent to this Popup window, and the Popup window does not cut this message or sends it to the main window. After study, I found that the WM_NOTIFY message sent only the main window when the control is created, and pay attention, huh, huh.
