/usr/share/man/man3/Tk_GetFontMetrics.3tk.gz is in tk8.4-doc 8.4.20-8.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man3/Tk_FontId.3tk.gz
/usr/share/man/man3/Tk_FontId.3tk.gz