[jawsscripts] Opinion post: Time to change where new scripters begin
- From: Doug Lee <doug.lee@xxxxxxxxxxxxxxxx>
- To: jawsscripts@xxxxxxxxxxxxx
- Date: Thu, 27 Feb 2014 09:49:54 -0500
For years I have complained, as many probably have, that it is hard to
know how to start off a new JAWS scripter in a way that will empower
him or her to script the average application without getting
hopelessly lost or buried in details. A common initial approach has
been to teach window hierarchy navigation and cursor manipulation, but
these techniques increasingly fail to be sufficient to fix major
problems in current applications. This leaves new scripters stuck in
dead ends wondering where to go next. I believe it is time to change
where we start them off.
I believe, starting in recent JAWS 15 updates, that we finally have
one consistent, all-empowering path for scripters to take. There are of
course caveats, but I'll get to that. This path will give scripters
access to many things that previously required entire different
sets of function calls - window tree functions here, MSAA functions
there, HTML DOM access, etc.
JAWS 15, particularly starting with the 15.0.5056 update, introduces
direct scripter access to the Microsoft User Interface Automation (UIA)
API. This single API provides a way to get to pretty much everything
else one would usually need: window tree information, MSAA properties,
information from HTML nodes, and of course, native UIA support for newer
platforms like WPF and Silverlight. I regard the current interface as
complicated, I admit; but I think it is worth learning for any JAWS
scripter because of how much it can do.
Wherever JAWS itself provides ways to get information not provided by
this UIA interface, the UIA interface can help you find where to start
using other methods. For example, if you need to test the style bits of
a window though the UIA interface does not provide a means for this,
you can find the window's UIA object via the UIA interface, get the
nativeWindowHandle for it, and then call the JAWS getWindowStyleBits()
function on that handle. In other words, whereas we used to think of
navigating the window tree as the first step to finding things, I now
think we should consider navigating the UIA tree the first step. What
we do from there, in both cases, will depend on what we need.
The definitive reference document for the JAWS UIA interface is located at
http://www.freedomscientific.com/documentation/scripts/JAWS-UIAScriptAPI.asp.
It is likely to be a tough read for anyone who is not already familiar
with objects and object-oriented programming, so I imagine my post is
going to start a lot of chatter on this list about how this system
works.
The caveats:
1. As I said, it's complicated: Scripters must understand some
concepts of object-oriented programming and COM in order to use this
system. Objects, in JAWS scripting at least, have long been considered
an advanced topic. I say it's time to consider them central to
scripting.
2. It can be slow. Wise scripters should minimize UIA queries because
of this, by caching results, asking for as few nodes as possible by
crafting searches carefully, etc.
3. As already mentioned, this system will not work before JAWS
15.0.5056. (The fine print: Some of this works as far back as JAWS 14,
but several things aren't there that far back, some key items are
there but with different names, etc.) This means that you can't write
scripts this way if you want compatibility with old JAWS versions.
4. As the aforementioned Freedom Scientific reference document for the
UIA script API says, some of the features of UIA do not work on all
Windows versions. The document implies that support for this system
may start in Windows 7, but I have successfully used much of this
under Windows Vista and even XP.
In conclusion:
I do not think we are at the point of saying the old ways of
navigating window trees, working directly with MSAA objects, etc. are
obsolete and useless. I simply think the new UIA interface is the
single most promising place for a new scripter to begin, since it
doesn't miss much in terms of what it can let you find. Direct window
tree traversal and FindWindow calls, MSAA getFocusObject calls and
direct MSAA object access, etc., will sometimes run faster and should
not be dismissed as valid pursuits. The UIA interface, though,
certainly seems sufficient for solving many current scripting
problems, even if in a "fix first, optimize later" sort of way.
--
Doug Lee, Senior Accessibility Programmer
SSB BART Group - Accessibility-on-Demand
mailto:doug.lee@xxxxxxxxxxxxxxxx http://www.ssbbartgroup.com
"While they were saying among themselves it cannot be done,
it was done." --Helen Keller
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