Ok, so after a little bit more tinkering, it appears that this function is used to set the title of the window in xterm for instance, and is not used in more “advanced” terminal emulator such as Konsole. Anyway, this was a nice discovery of the tput program, and I found this reference: https://www.gnu.org/software/termutils/manual/termutils-2.0/html_chapter/tput_1.html for those interested (I found the man entry, well… not comprehensive ).
I think “ppwd” supposed to “print present working directory”. It is used to generate the prompt, and that supposed to remind you where you are. The definition is a bit hard to follow. I think it is checking width to see if there is enough space on the command line. And for some terminals, it is instead used to put the directory in the title bar.