What is it and what vimscript functions are associated with it?

I was messing around with the phcs plugin. I made it so that the plugin calls bufwrite, but modified phsh to display only the quickfix window if any violations actually occurred.

I am having problems with the fact that when opening the quickfix window, the buffer does not display a gray canvas with red ">" error symbols, if I did not first move the cursor to the quick fix window and then back to the buffer.

I am looking for functions that I could call in my phpcs plugin so that after I open the quickfix window, I can update this gray bar to immediately display and show violations.