I cannot build a working program (lissajous) against the dynamic library, I get the message "GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported" . GTK init code runs until a call to gtk_databox_create_box_with_scrollbars_and_rulers(). The example code (build during initial make) runs but these do not seem to use the dynamic library. GTK ver 3.22.30-1ubuntu4
Solving my own... There was a old lingering 64 bit version from ubuntu. I killed the old version and put the proper gtkdatabox,.pc file in place so pkg-config can find the correct headers and lib. I can build against dynamic libs.