narrow, tall GtkTextView trap faults
Probably to do with the size allocation warnings "Allocating size to GtkWindow without calling gtk_widget_get_preferred_size"
If you make a GtkTextView that's very tall and narrow, it causes a trap fault in X, and it's a little difficult to diagnose why. I think it's something like a 10 character by over 2100 line GtkTextView.
Calling this ahead of time prevents the trap fault, presumably it's something to do with the way gtk guesses at allocation sizes while tracking width and height.
gtk_widget_set_size_request((GtkWidget *)textview, width * 5, lines * 10);
Perhaps there is a preferred way to do this, pre-allocation stuff, but it's not mentioned anywhere that I saw.