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Re: ISMAP-class problem with script

From: Jon Gunderson <jongund@staff.uiuc.edu>
Date: Mon, 05 Oct 1998 09:29:26 -0500
Message-Id: <199810051430.JAA18119@staff2.cso.uiuc.edu>
To: Al Gilman <asgilman@access.digex.net>, w3c-wai-ua@w3.org
Instead of an ISMAP view of looking for mouse positions, the author could
have associated IDs with each of the images.  The event handler could get
the ID of the object and know which of the images was clicked on without
needing to compare mouse coordinates with image coordinates (although the
later could also be done).  

One way to partically identify elements that respond to events is to
require that they define the ID attribute.   But, IDs can also be used to
manipulate an element in response to another elements reponse to a DHTML
event, so this is not necessarily a definitive identification that the
element responds to an event.

Does this make sense?


At 03:40 PM 10/3/98 -0400, Al Gilman wrote:
>Chuck described a problem event-handling script for us in the
>User Agent telecon a week or so ago.  As I understood the 
>scenario, it is "the same class of object as the deprecated
>server-side sensitive image map."
>I want to build on this analogy in our WAI-PF dialog with the
>DOM group about accessibility requirements.  But I owe the
>example to Chuck and that meeting, so I am writing it down
>here first.
>There is a table.  in the table cells there are images.  There is
>no on-mouse-down event handler bound to any of the images, but
>there is one on the table.  The script which handles
>on-mouse-down for the table, however, inspects the current mouse
>location to decide what to do.
>To perfect the ISMAP analogy, let us just say that it compares
>the mouse position with a disjoint set of rectangles falling
>entirely within the table and each one completely enclosing one
>image.  This is a control morphology identical to a sensitive
>map.  Now, we have established accessibility standards that say a
>sensitive map should be done on the user side because then the
>user agent can give the user verbal information about the
>available control actions and their prospective outcomes.  In a
>sense, the DOM question is "Is the DOM a frame of reference where
>we can recognize that this is the same thing as the server-side
>image map pathology?"
>Jon has done a good job in his note about "DHTML Issues"
>that this is the basic usability/accessibility problem:
>how can the user have adequate visibility over the potential
>consequences of actions so that the UI merits being rated
>as "exhibiting predictable response?"
>To the user, the on-mouse-down handler is a method associated
>with an object, the table.  I suspect that DOM 1 only covers the
>information associated with the table that the HTML tells us, not
>the behavior of its methods that the script tells us.
>When and how to get the model to cover and discipline what
>actually bites the user is one of the things that WAI-PF
>and the DOM WG need to discuss.
Jon Gunderson, Ph.D., ATP
Coordinator of Assistive Communication and Information Technology
Division of Rehabilitation - Education Services
University of Illinois at Urbana/Champaign
1207 S. Oak Street
Champaign, IL 61820

Voice: 217-244-5870
Fax: 217-333-0248
E-mail: jongund@uiuc.edu
WWW:	http://www.staff.uiuc.edu/~jongund
Received on Monday, 5 October 1998 10:30:27 UTC

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