RE: Graphics contrast comments overview

HI Mike,

Good point, the exception should match the opening statement, I'll correct that.

> I assume time-based media would have an out from the 'essential' wording?

Yes, I think that's in the 'moving pictures' category. Although I guess it would be possible to apply frame-by-frame for animated (non-real-life) graphics? I wasn't intending to though, I don't have that much time in my entire lifetime to test video that way!

> I continue to be a bit worried about the 'vagueness' of "adjacent color(s)". For controls, I really think we're talking about the colors adjacent to the outline of the control? Is something like "colour(s) adjacent to the perimetre" any better?

I think it works for graphical objects, let's try a few examples for controls:

  *   A standard input with a bottom border (James' example from before).
http://www.cssdesk.com/2g7MM

  *   A standard input with a different background
Search on www.Gov.uk<http://www.Gov.uk> homepage.

  *   A raised button from material design
https://storage.googleapis.com/material-design/publish/material_v_12/assets/0B7WCemMG6e0VbDh6YmNiYVc3SHM/components-buttons-usage2.png

  *   A flat button from material design
https://storage.googleapis.com/material-design/publish/material_v_12/assets/0B7WCemMG6e0VNDg3V3ZjU2hsNGc/components-buttons-usage3.png

(Examples from here: https://material.io/guidelines/components/buttons.html#buttons-button-types )

There are several examples there which have really good contrast (e.g. the gov.uk search), but no border as such.
I think a formulation like "color(s) adjacent to the visual indicator" is what works as it could be one or two, leaving it open enough for any of those (with contrast on the indicator) to pass, and that's pretty much what we have. Otherwise you get into defining whether it is inner, outer, etc.
If you focus on the search of Gov.uk, that also adds a yellow highlighter which  is quite obvious, so I'd want to avoid forcing people into multi-colour outlines when not needed. Given that it has two colours in the default state, and the third contrasts with outer background, I'd be happy for the focus indicator to contrast with either colour (outer or inner) so long as it appears on the contrasting colour.
Would examples & techniques be enough for that?
Cheers,
-Alastair