Is d-pad for logitech f310 programmed as a joystick or buttons? In the c++ reference I can’t find anything that be used to program d-pad.
I think the simplest way to find out what axis and button numbers correspond to the controls on a joystick or gamepad is to hook it up and see what you get. In LabVIEW, it’s as easy as creating an indicator on the Axes and Buttons outputs of the Joystick Get vi. In C++, you’ll want code to continuously display all the axis and button values.
In my experience, the d-pad typically shows up on joystick axes 5 and 6.
It may fall under the same umbrella as the POV hat on most flight stick style joysticks; however, I don’t know if the Joystick class has the POV hat, since we don’t use ours 
It doesn’t, but our XBox controllers read the point of view hat as a single axis with 3 values, -1.0, 0, 1.0. It’s only vertical, no horizontal.
This is how the F310 behaves as well.