The framework calls this member function when the user presses XBUTTON1 or XBUTTON2 of the mouse while the cursor is in the nonclient area of a window.
A value of XBUTTON1 if the first mouse X button is pressed, or XBUTTON2 if the second X button is pressed.
A CPoint object that specifies the x and y coordinates of the cursor relative to the upper-left corner of the screen.
This method receives the WM_NCXBUTTONDOWN notification, which is described in the Windows SDK. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.
This method is supported in Windows Vista and later.
Additional requirements for this method are described in Build Requirements for Windows Vista Common Controls.