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Re: Final changes to Hit Regions before return to Last Call

From: Mark Sadecki <mark@w3.org>
Date: Wed, 16 Apr 2014 16:40:44 -0400
Message-ID: <534EEACC.20005@w3.org>
To: "public-canvas-api@w3.org" <public-canvas-api@w3.org>, Jay Munro <jaymunro@microsoft.com>
Hey Jay,

This looks good with the following exceptions:

I think we agreed to link the word "path" to
 <http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas_CR/#hit-region%27s-path> in Step 2 of "The region for a pixel"

After reading it through, i think the MouseEvent processing algorithm needs a
final step.  I propose:

7. Dispatch the event, but with the updated event object as given in the above

I took out the phrase "Continue dispatching" because we are not continuing any
dispatch event and removed reference to "target" because we are not changing the
default target at all, we are just updating event.region to include the ID of
the region that was under the mouse when the event was fired.


On 4/15/14, 3:53 PM, Mark Sadecki wrote:
> The following changes were discussed during the canvas accessibility sub group
> call on 14 APR 2014
> <http://www.w3.org/2014/04/14-html-a11y-minutes.html>
> ## The region representing the control
> * Add a step that handles a null value for control, similar to the one that is
> defined for ID, just before the existing step 1.
>> "If control is null, return nothing and abort these steps."
> ## The region for a pixel
> * Change "set of pixels" to "path" in step 2 and link "path" to
> <http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas_CR/#hit-region%27s-path>
> ## addHitRegion()
> * add the following step after step 3 (Let specified pixels be the pixels
> contained in source path.)
>> "Remove from specified pixels any pixels not contained within the clipping
> region."
> ## clearHitRegions()
> * Remove Step 2 RE: Garbage Collection
> ## MouseEvent
> We agreed that we would eliminate event retargeting altogether and just pass the
> event.region to the canvas element.  This would require the following changes:
> * Revert order of steps and add step for handling a canvas element with no hit
> region list.  The first 4 steps should read as follows:
>    1. If the pointing device is not indicating a pixel on the canvas, act as
> normal and abort these steps.
> -> 2. If the canvas element has no hit region list, act as normal and abort
> these steps.
>    3. Let pixel be the pixel indicated by the pointing device.
>    4. Let region be the hit region that is the region for the pixel pixel on
> this canvas element's bitmap, if any.
> * The following steps are no longer required (the numbers will be shifted by one
> if the above steps have been followed) and should be removed:
> 7. Let control be the region's control, if any.
> 8. Let the canvas element be the target of the event object, unless there is a
> control, then target the control instead.
> 9. Continue dispatching the event, but with the updated event object and target
> as given in the above steps.

Mark Sadecki
Web Accessibility Engineer
World Wide Web Consortium, Web Accessibility Initiative
Telephone: +1.617.715.4017
Email: mark@w3.org
Web: http://w3.org/People/mark
Received on Wednesday, 16 April 2014 20:40:43 UTC

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