The framework calls this member function when the user presses the middle mouse button while the cursor is within a nonclient area.
Specifies the hit-test code. A hit test is a test that determines the location of the cursor.
Specifies a CPoint object that contains the x and y screen coordinates of the cursor position. These coordinates are always relative to the upper-left corner of the screen.
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.