slackbuilds_ponce/libraries/libfm

LibFM provides file management functions built on top of Glib/GIO, 
giving a convenient higher-level API.

vala is an optional dependency (for custom file manager actions).

you can choose between which version of gtk the library builds
against:
GTK=2  (default) link with gtk+2
GTK=3  link with gtk+3
GTK=0  don't link against gtk at all
pass the script the parameter you prefer, like

  GTK=3 ./pcmanfm.SlackBuild