Canvas diff analysis for 14 APR 2014

Some talking points for tonight's agenda item on WHAT WG/W3C diff analysis:

*To be considered during Canvas Sub Group call on 14 APR 2014*

## Summary of features we will not be supporting in L1

Since we are removing these features from L1, but they still existing in L2,
there is no need to file any bugs.

* Nested Regions (ref to parentID, a count of hit regions)
* Custom Cursors
* Unbacked Regions (label)
* fillRule (should we support this, at least nonzero, how are we currently
determining pixels in path?)
* Support for Touch events

## Summary of broad changes to W3C spec

* Changed references to 'pixels' to 'paths'
* Changed references to 'scratch bitmap' to 'canvas element'
* No restrictions of allowable control elements
* Added method clearHitRegions()
<http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas_CR/#dom-context-2d-clearhitregions>
* Mouse events, reordered processing algorithm (for review)
<http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas_CR/#dom-mouseevent-region>

*Do we want to file bug reports on WHAT WG for any/all of these?*

## Features found only in WHAT WG we might consider in W3C spec

*Items that exist in [WHAT
WG](http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#hit-regions)
spec that do not exist in W3C and are not related to features we removed.*

<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#hit-regions>

### The control represented by a region (not in L2 either)###

<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#the-control-represented-by-a-region>

* If control is no longer a supported interactive canvas fallback element, then
return nothing and abort these steps. *(we would remove the "supported"
distinction)*

### Clear regions that cover the pixels ###

<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#clear-regions-that-cover-the-pixels>

* entire section

### Garbage collect the regions ###

<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#garbage-collect-the-regions>

* entire section

### addHitRegion() ###

<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-addhitregion>

* Do we want to add support for Transforms back in?
* We do not address clipping the region at all (not in L2 either)

## Editorial bug ##

### The region for a pixel

<http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas_CR/#the-region-for-a-pixel>

* Should the phrase "set of pixels" be "path"?

-- 
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