I couldn't figure out why we had introduced gtk_style_context_set_background in commit 74dd32170d3aca20bbce1282bd24193807306603. I understood why GtkDrawingArea and others need to use it for compatibility, but GdNavBar uses gtk_render_background and chains up in its draw method.

At least it doesn't seem necessary today, and causes this deprecation warning:

lib/gd-nav-bar.c: In function ‘gd_nav_bar_realize’:
lib/gd-nav-bar.c:739:9: warning: ‘gtk_style_context_set_background’ is deprecated: Use 'gtk_render_background' instead [-Wdeprecated-declarations]
         gtk_style_context_set_background (gtk_widget_get_style_context (widget), window);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/gtk-3.0/gtk/gtkicontheme.h:27:0,
                 from /usr/include/gtk-3.0/gtk/gtk.h:123,
                 from lib/gd-nav-bar.h:23,
                 from lib/gd-nav-bar.c:24:
/usr/include/gtk-3.0/gtk/gtkstylecontext.h:1232:6: note: declared here
 void gtk_style_context_set_background       (GtkStyleContext *context,
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~