Re: AtkText attributes

[Brian Cameron <Brian Cameron sun com>]

Bill & Others:
 
> 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.

Aside from returning the data as name/value paris, there are some
issues with returning the attirbutes from the GtkTextWidget.

First of all, all PangoAttributes have a start_index and an end_index,
(for example describing that the text uses a certain font in this
range).  What if a TextBuffer has font 1 defined for characters
10-30, font2 defined for characters 31-50, and the user calls 
atk_text_get_range_attributes asking for the attributes between
characters 25 and 40.  The "Font" attribute will have two different
values within this range.  I'm not sure that this level of detail
is returned via the current atk_text_get_range_attributes interface.

Perhaps one step of the solution is to return something more complicated
than a (name value) pair, but instead something like a (name, value,
start position, end position) structure.  This way multiple "font"
attributes could be returned.

However, since font1 is used from position 10-30 and font2 is used
from position 31-50, and the user asked for info for positions 25-40,
does the function say font1 is used from 1-30 or from 25-30, and
that font2 is used from 31-40 or 31-50?  Not sure if I'm making sense
here, but it's not clear how the function should work.

One solution would be to make the function not range based.  If the
function were just a atk_text_get_attributes() and returned an array
of (name, value, start position, end position) structures for the
whole buffer, then this would resolve any potential confusion about
how to handle ranges.  This would pass all the info about the buffer
back to the user and let them extract what interests them.

Another problem is that the GtkTextWidget doesn't give easy access
to the Pango Attributes.  Instead it uses GtkTextTags to provide
a level of indirection between Pango and the GtkTextWidget.  If
you look at this website you can see what "tags" are supported.  See
section named Args.

  http://developer.gnome.org/doc/API/2.0/gtk/gtktexttag.html

This function would be much easier to code if we could just use
the tag information instead of the Pango information.  Is this
acceptable?  I might need some help defining which of these "tags"
are in fact useful ones that we want to make available through
this interface...unless we just blindly want to pass them all
through.

Let me know what you think.

Brian