Canvas W3C/WHAT WG 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 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"?