[webkit-dev] Considering a Touchhover

Charles Pritchard chuck at jumis.com
Fri Mar 11 09:43:40 PST 2011

Recently, while working on code review / accessibility for a large 
canvas application, I found that the iOS VoiceOver AT
does not play well with the html canvas element. It can work, but it's 
not a natural transition from html to
canvas (with "buttons" in it). Using transparent [button] tags work, but 
it is rather awkward.

It occurred to me that, when VoiceOver is on, on these mobile devices, 
that a new "touch" type is active.
For the time being, I'm proposing calling it "touchhover".

Currently, VoiceOver AT captures touch events, waiting until the user 
has set virtual focus to an element,
then tapped twice, to set event focus on that element. It works quite 
well for html elements.

My thinking is that this state, where it's not passing 
touchstart/touchmove/touchend events, is
very much like the traditional "hover" events we've used with mice.

If touchhover events were passed through Mobile Safari, I'd be able to 
use hit detection on canvas
elements, and set the canvas element to the appropriate title matching 
whatever the user has focus upon.

Does this make sense? Should I provide more examples? The purpose here 
is to enable UI elements
in Canvas to work appropriately with touch-based AT, such as the iOS 
VoiceOver extension.


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