The a11y machinery is using signal subscription to get notified of size
changes and notify listeners in turn. This is suboptimal for a couple of
reasons:
- if something connects to the GtkWidget::size-allocate signal we need
to emit it; currently, we have an optimization in place that will
skip the signal emission if there are no handlers, and it would be
nice to go through the fast path
- the accessibility implementation is part of GTK, and should not go
through additional hoops like any out-of-tree API consumer
Since we are going to install these headers soon, we need
to make their mutual includes work in the installed location
as well. Also, avoid including individual gtk headers, to
avoid trouble with single-include guards.
This commit exposes the get_type() functions and standard
headers for accessible implementations. This makes it possible
to derive from the GTK accessible implementations without
GType magic tricks. This is necessary, because we require the
a11y type hierarchy to be parallel to the widget type hierarchy.
So, if you derive a widget and need to adjust its a11y implementation,
you have to be able to derive its accessible implementation.
This commit probably exposes more than is absolutely necessary,
it also exposes accessibles of widgets that are unlikely candidates
for deriving from.
