How to get the player screen size and postion related to viewport?

I am constrain my camera’s ratio to 16:9, resulting the the player screen only occupy a part of space of viewport.
What I want to do, is placing the UMG widget on the player screen rather than whole game viewport, and draw lines in the player screen. The problem comes because currently UMG DPI calculation seems depending on
viewport size, not player screen, So I need a way to get the player screen’s size and position in viewport. How could I got those data at runtime?