setMode
Sets the GtkSizeGroupMode
of the size group.
The mode of the size group determines whether the widgets in the size group should all have the same horizontal requisition (%GTK_SIZE_GROUP_HORIZONTAL) all have the same vertical requisition (%GTK_SIZE_GROUP_VERTICAL), or should all have the same requisition in both directions (%GTK_SIZE_GROUP_BOTH).
Parameters
mode
the mode to set for the size group.