current_font(+Pattern, -Name)
     current_font(+Limit, +Pattern, -Name)
     current_font(+Display, +Limit, +Pattern, -Name)

Name is the name of a currently available font on Display (which defaults as usual). If Pattern is given, it restricts Name to fonts matching it. If Limit is given, it is an upper limit on the number of fonts that will be backtracked through (defaults to one million).