When using twm as window manager, right-clicking on a character pops up a window
to show the enlarged glyph that is the only place that the font being used is
listed.  twm then shows a frame and the user is supposed to place the window,
placing the window by clicking then triggers mouse-up event that closes the
popup shortly after actually showing it.

The problem may be fixed by using correct wm hints, or may not.  It would be
better if user right-clicks and the enlarging feature triggers and enlarges as
you move over the characters, and right-clicks again to turn it off.  That's the
Windows behavior IIRC.

BTW, the font being used should be listed in the Character Detail tab.  Better
yet, all fonts that contain the glyph should be listed, in the order preferred
by fontconfig.