Until this commitment gui gave us segmentation fault in the case when no element was on graph_displayer_canvas and a map to visualize by a property has been changed.

open file from command line

compile with gtkmm 2.4

Alpar had the key, focus can be set in the window class. But it is not enough, the focused widget has to be activated, as well! Was a hard task to find out... By the way, two compilation warnings are removed.