Font – GNU Radio Companion Toolbar (GRC) on HiDPI 16.04

I've tried to know how to increase the size of the toolbar with tiny icons in GNU Radio Companion (GRC, version 3.7.9.1-2ubuntu1), installed on Dell XPS 13, Ubuntu 16.04, with hiDPI . I found this page with recommendations:
https://wiki.gnuradio.org/index.php/Tips_for_MacBooks_and_other_HiDPI_displays
But I do not have the file in question, $ HOME / .gtkrc-2.0, and when it's created and saved with "gtk-font-name =" Without 14 "", that does not change anything. I tried to move it to other configuration and GTK folders, without success. Someone has an idea how to proceed?
At M