What would dx11 do when I change the desktop resolution!

Hi guys!

    The QA of  our company gives me bug, here is bug description.

    Reproducing steps are as follows,

1.    Open game with a large resolution;
2.   Change the resolution of desktop;

    Result:

      The ui was rendered correctly ,but user can not click the button ,

the hit area of button is mismatch.

My question is , what does the clent need to do when change to a desktop resolution smaller than current window of game. All I have learned is that dx11 will handle it by itself ,developpers need to do nothing .

Thanks!