[MacOS] GtkTreeView resets the selection on ctrl-GDK_BUTTON_PRIMARY instead of opening the context menu.
There are two ways to fix this. One would be to special-case gtk_tree_view_multipress_gesture_pressed to ignore GDK_BUTTON_PRIMARY if GDK_CONTROL_MASK is set and the backend is quartz.
A more general and IMO more correct approach would be to change gdk_mouse_button_from_ns_event to return 3 for case 0 with the control key pressed.