AtkText attributes

[Bill Haneman <bill haneman sun com>]

Hi:

We've had a couple of conversations about removing our current Pango
dependency from ATK.  Though we think Pango is great and will of
course depend on it heavily in GAIL, the only pango dependency that I
know of in ATK is the use of PangoAttributeSet as the means of
indicating text attributes.

In point of fact, it's not clear that this is the "best" way to expose
text attributes, certainly it's not the way to expose them to adaptive
technologies in the general-case SPI.  In that latter case it seems
almost certain that exposing them as "String" name-value pairs is the
best and most extensible approach... in most cases the AT will present
these attributes, if at all, in readable form (if they are strings
they even can be localized readily).  Since the presentation format
will ultimately be strings, it makes sense to move towards a string
N-V pair representation in ATK.  That's of course trivial extensible,
and we are unlikely to be able to make semantic use of the information
in the first place.  It also eases implementation for HTML and XML
markup, etc.

I asked Brian to look into GTK N-V pair support.  Since we are not
using semantic info and are storing only strings, existing things like
ghash might not be the best implementation, we may be better off
creating a trivial N-V pair structure ourselves.  I expect that since
the strings will not be consts in the general case, we should inherit
our N-V pair from GObject so that we can do ref counts and finalizers,
to free up the string memory , manage NV pair lifecycles, etc.  I
think this is also important since the attribute-getting API will
almost certainly return transient attribute sets rather than
persistent objects (the API now allows you to ask for the set of
attributes which is the same over a range of text).

I think that we also probably need a new boundary enumeration type,
ATTRIBUTES, so that we can easily get a range of text over which the
attributes are unchanged.

After a little more discussion, maybe, I'd like to make these changes
to AtkText, after which I think we can remove the pango dependency.

-Bill
-- 
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Bill Haneman
Gnome Accessibility / Batik SVG Toolkit
Sun Microsystems Ireland