- From: Gregg C Vanderheiden <greggvan@umd.edu>
- Date: Tue, 10 Jan 2017 18:14:08 -0500
- To: "Patrick H. Lauke" <redux@splintered.co.uk>
- Cc: GLWAI Guidelines WG org <w3c-wai-gl@w3.org>
Gregg C Vanderheiden greggvan@umd.edu > On Jan 10, 2017, at 6:04 PM, Patrick H. Lauke <redux@splintered.co.uk> wrote: > > On 10/01/2017 22:55, Gregg C Vanderheiden wrote: > >> 2) I agree with Patrick that 10 degrees of visual field won’t work >> >> 1. you can’t calculate that unless you know a) how far the person is >> from the screen b) the size of the screen and c) the pixel >> resolution of the screen d) the scaling of the screen. None of >> these are known to the author and change from user to user >> 2. (Most people couldn’t calculate it if they did know those things) > > Related to this, is there any chance the definition "general flash and red flash thresholds" currently in WCAG 2.0 can also be somehow changed/simplified for 2.1 according to whatever is decided here, as it presents exactly the same problems? That one is worse and also has 40% in the middle. But that is what the research base is for it was. But there is a tool that automatically does the analysis for you — so that is not a problem. Perhaps making a test tool for this one would help as well. > >> 3) You can’t use 1/3 of web page because >> >> 1. a web page could be 500 ‘pages’ long so nothing would be 1/3 of it. >> 2. and you can’t use 1/3 of screen for the same reason as #2 above. >> >> >> 4) I THINK — Doing it in CSS pixels (aka David) is the best bet but >> remember that a large blinking “O" only changes a relatively small >> number of pixels -- so you might look at pixel area rather than pixels. > > What about simply percentage of overall screen/viewport size? It's still an approximation, as some users will be closer/further away from their screen so even the full screen/viewport will in fact occupy different angle of their full field of view, but it's at least something that can be consistently queried and tested (though in context of responsive design, it'll need to be tested for each breakpoint/common device screen resolution). for instance, simply saying "more than 1/4 of the viewport" or similar? Same problem as above. You have absolutely no idea how large that is without knowing a bunch of things about the screen (see #2 above) however — you might do something like base it on a typical screen size and resolution and scaling etc — and then set your threshold there. This was done for Flash. > >> 5) I wouldn't ban it - but rather ban anything the has a duration longer >> than say three seconds that can’t be stopped. Such animations are >> very useful for directing attention for people with cognitive >> disabilities. Also important sometimes for warnings. > > Agree in part, though certain very extreme animations, even if shorter than 3 seconds, may cause issues for certain user groups (e.g. vertigo / motion sensitivity) if it will end - they might just close their eyes for a second or two. Don’t like that approach but only other alternative is to ban it — and that is not good for other people. Ideas anyone? > > P > -- > Patrick H. Lauke > > www.splintered.co.uk | https://github.com/patrickhlauke > http://flickr.com/photos/redux/ | http://redux.deviantart.com > twitter: @patrick_h_lauke | skype: patrick_h_lauke >
Received on Tuesday, 10 January 2017 23:14:46 UTC