Sets whether child should appear in a secondary group of children.
A typical use of a secondary child is the help button in a dialog.
This group appears after the other children if the style
is GTK_BUTTONBOX_START, GTK_BUTTONBOX_SPREAD or
GTK_BUTTONBOX_EDGE, and before the other children if the style
is GTK_BUTTONBOX_END. For horizontal button boxes, the definition
of before/after depends on direction of the widget (see
Widget.setDirection). If the style is GTK_BUTTONBOX_START
or GTK_BUTTONBOX_END, then the secondary children are aligned at
the other end of the button box from the main children. For the
other styles, they appear immediately next to the main children.
Sets whether child should appear in a secondary group of children. A typical use of a secondary child is the help button in a dialog.
This group appears after the other children if the style is GTK_BUTTONBOX_START, GTK_BUTTONBOX_SPREAD or GTK_BUTTONBOX_EDGE, and before the other children if the style is GTK_BUTTONBOX_END. For horizontal button boxes, the definition of before/after depends on direction of the widget (see Widget.setDirection). If the style is GTK_BUTTONBOX_START or GTK_BUTTONBOX_END, then the secondary children are aligned at the other end of the button box from the main children. For the other styles, they appear immediately next to the main children.