OnMouseMove中的nFlags的意义何在呢？检测当前我们说产生的动作是如何

The framework calls this member function when the mouse cursor moves.

afx_msg void OnMouseMove( UINT nFlags, CPoint point );

Parameters

nFlags
Indicates whether various virtual keys are down. This parameter can be any combination of the following values:

MK_CONTROL Set if the CTRL key is down.

MK_LBUTTON Set if the left mouse button is down.

MK_MBUTTON Set if the middle mouse button is down.

MK_RBUTTON Set if the right mouse button is down.

MK_SHIFT Set if the SHIFT key is down.

point
Specifies the x- and y-coordinate of the cursor. These coordinates are always relative to the upper-left corner of the window.

Remarks

If the mouse is not captured, the WM_MOUSEMOVE message is received by the
CWnd object beneath the mouse cursor; otherwise, the message goes to the window that has captured the mouse.

Note

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.