And let GtkPopover use it as its GtkAccessible implementation, this
accessible sets the POPUP_FOR relationship to the relative-to widget,
and keeps track of changes there.
https://bugzilla.gnome.org/show_bug.cgi?id=725864
The button now claims its menu as a child for a11y purposes,
which makes it possible for ATs to see it when the navigate
the tree top-down.
Update the a11y test to match.
GtkFlowBox is a container that its children in a reflowing
grid, which can be oriented horizontally or vertically.
It is similar to GtkListBox in that the children can
be sorted and filtered, and by requiring a dedicated child
widget type, GtkFlowBoxChild. It is similar to GtkTreeView
in that is supports a full set of selection modes, including
rubberband selection.
This is the culmination of work that has happened in the
egg-list-box module, and earlier in libegg. The origins of
this code are the EggSpreadTable in libegg, which was written
by Tristan van Berkom. It was moved to egg-list-box and
renamed EggFlowBox by Jon McCann, and I gave it some finishing
touched in the flowbox-improvements branch of that module.
We add a separate gtk-a11y.h single-include header for
them. This header will work much the same as gtkx.h. It
will be installed in /usr/include/gtk-3.0/gtk, but you
have to include it separately.
