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[csswg-drafts] [css-values] Anthropometric length and time units

From: Christoph Päper via GitHub <sysbot+gh@w3.org>
Date: Tue, 27 Dec 2016 10:18:22 +0000
To: public-css-archive@w3.org
Message-ID: <issues.opened-197680703-1482833899-sysbot+gh@w3.org>
Crissov has just created a new issue for 
https://github.com/w3c/csswg-drafts:

== [css-values] Anthropometric length and time units ==
Extending the idea of a `tip` length unit 
[mentioned](https://github.com/w3c/csswg-drafts/issues/614#issuecomment-254956032)
 in #614, I hereby propose to add several units to CSS that are 
**based upon measures of the human body**. Where possible, 
implementations may adapt them to fit measured data of the actual 
active user. 

I am not discussing use cases, at least in this initial message, 
because most of these units are intended for future devices but are 
already applicable to styles build with existing CSS modules.

Anthropometric length units
---------------------------

All anthropometric [length 
units](https://drafts.csswg.org/css-values/#lengths) are defined as 
the diameter of the smallest circle that contains a touch print of a 
particular human body part. The default or fallback values provided 
are rough estimates, open to discussion. They are not (yet) based upon
 empiricial data, but approximate physical units that do *not* depend 
on the *anchor unit* (usually `px`) in recent levels of CSS. This 
makes them applicable to many scenarios that  “`realcm`” etc. have 
been proposed for in #614 and in older threads on www-style.

| Unit | Alternatives | Definition | Fallback |
|-----|-----------|------------|------------|
| `tip` |  | tip of index finger (or stylus) | 5 mm |
| `tap` |  | index finger print | 1 cm |
| `mark` | `push`, `thumb`, `toe` | thumb print | 2.5 cm |
| `pad` | `paw`, `palm`, `ball` | palm without fingers | 10 cm |
| `span` |  | open hand with splayed fingers | 20 cm |
| `sole` | `foot`, `shoe` | foot print (with shoe) | 30 cm |

Anthropometric time units
---------------------------

I’m proposing two *psychological* [temporal 
units](https://drafts.csswg.org/css-values/#time) and two 
*physiological* temporal units. 

In psychology, _instant_ and _moment_ have conventional absolute 
definitions. They are complicated to measure for an individual user in
 the current situation, but different values may apply for some age 
groups or users of certain assistive technology.

Recent advances in sensor technology have brought devices to the 
consumer market that are able to measure a user’s physiology, e.g. 
their pulse rate or heart beat (especially in “smart watches”) or the 
rate and duration of their eye blinks (expected for head gear like 
AR/VR goggles).

| Unit | Alternatives | Definition | Fallback |
|-----|-----------|------------|------------|
| `now`  | `inst` | perceived instant | `3s` |
| `mom` |  | perceived moment | `90s` |
| `beat` |  | heart beat interval | `0.8s` |
| `blink` |  | duration eye lid closes | `25ms` |


Please view or discuss this issue at 
https://github.com/w3c/csswg-drafts/issues/837 using your GitHub 
account
Received on Tuesday, 27 December 2016 10:18:29 UTC

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