Re: AtkText attributes

[Peter Korn <peter korn sun com>]

Hi Brian, Bill, 

> [...discussion about attributes and text ranges...]

I think the basic tension here is between efficiency and complexity.  It's
inefficient to look at attributes a single character at a time, but simple. 
It's more efficient to look at ranges of characters (or runs as they are often
called), but then we run into interface complexity problems if we want to convey
all of the attribute information.

Perhaps there is a third way?  What about enumerating the unique attribute runs
and then allowing the AT to get information about those runs, in addition to
doing so a character at a time?  Thus, the text:

 <font="times">This <bold>bold, <italic>itali</bold>ziced </italic> text</font>

would contain 5 runs: [0-4], [5-10], [11-15], [16-21], and [22-26].

An AT gets the following information when querying about text attributes for a
given character index: the attributes for that index, and the range containing
that index of similarly attributed text.  Thus, to acquire all of the
information for the full string, the at would start at index 0, get the
attribute set and range [0-4], then ask for character index 5 (getting
attributes and range [5-10]), etc.  If a screen reader were doing an attribute
search (a feature of outSPOKEN for Windows), they might start from the caret and
go in run chunks.

Another benefit of this approach is that it layers nicely on top of the Java
Accessibility API which doesn't provide range information: all ranges are simply
the index in question (so if you ask about index 5, the range you get back is
[5-5]).  So this approach would work well in the AT SPI.


Regards,

Peter Korn
Sun Accessibility team