How to view and learn font character codes using fontello.ttf example in Ubuntu?

Question

Fonts

Greetings!
In the built-in viewer, only a part of the characters without codes is displayed.
We need all the characters that are in the font with their codes.
I tried: Font Manage, Fonty python, Spicemen
does not display exactly the characters available in the font anywhere.

Answer 1

In general, everything turned out to be simpler:
in the Gnomish character table (gucharmap)
view -> Show images of characters only from this font
view -> For Unicode blocks
, select the "User area" block
at the bottom left will be the code of the selected character.