My C program uses a custom CSS file to define its GTK style:
GFile* style = g_file_new_for_path("style.css");
gtk_css_provider_load_from_file(GTK_CSS_PROVIDER(provider), style, NULL);
In this file, no font-family declaration is made.
When I inspect my application on Linux using GTK_DEBUG=interactive, I find that the program's font is set to my system default, "Ubuntu":
My question is: how can I change this default behavior and use a custom font imported from a .ttf file in my entire application?