draft of hit testing on active regions (actually paths) in canvas

Hi Frank,

Thank you for the call today. I am glad we are on the same page on the
three basic methods for hit testing. I took the basic methods that Jonas
had put out earlier on the list and the discussion we had in San Diego and
put together an active regions and hit testing section. I also agree with
you this is for when we have multiple interactive elements within canvas. I
was glad to see that customers are starting to come to Microsoft to talk
about building more interactive widgets with canvas - not because I want
them to but more because it shows we are making the right moves to address
canvas accessibility.

Jonas, Charles, Frank, David, Cynthia

This is a first draft and the section I would like you to look at is
section 16. We can change the names to whatever we want. I have not yet
added spec. information as to how existing functions like
scrollElementIntoView should work on these elements as they should be
included in the layout engine positioning per Jonas earlier feedback. I
have also not stated how we would convert the paths to rectangles for the
underlying OS platform accessibility APIs. We could either do this in the
canvas spec. or in the accessibility API mapping guide that Cynthia is
leading. We just need to decide. Personally, I prefer the one stop
shopping.

I am sure Ian will want to tweak or rewrite the algorithm section
processing as he has his own consistent way of doing that but I took my
best shot at it.

Please review section 16.

(See attached file: clickableregion.html)

Since, like many of you I am going to TPAC, I will not have time to make
changes prior to the face to face. Janina please put a link to this
document in your canvas agenda for TPAC.

See you all in California.

Rich Schwerdtfeger