We've started to turns containers into widgets which
just happen to have children, and some of these need
to be exposed to the a11y stack.
This adds a very minimal implementation, it does not
currently emit change notification when children are
added or removed.
This commit introduces GtkPicture, which is supposed to complement
GtkImage.
GtkImage will be adapted to always display an icon, while
GtkPicture displays regular imagery.
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.
