The canvas v5 API supports hit testing regions. http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-addhitregion http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#hit-regions This probably will include subtasks for cursors, exposing to controls, etc.
<rdar://problem/11159264>