[css-values] Ability to address actual physical size #614

[mrmazda]

Worked all day to prepare a response to issue #614 and finally got it ready only to have it closed/uncommentable without email notification of same less than 10 hours after previous comment. Then a few hours after I started this, more comment there, even though marked closed.

[astearns]

@mrmazda Copying the image then pasting into this edit field should work. You'll see a temporary "uploading" bit replaced by an ![image](https://user-images.githubusercontent.com/… link

[mrmazda]

Thanks to astearns! 23 years on the internet without ever needing to paste anything but text, so never "copied" an image to which a link refers before. Finally I saw "uploading" instead of mere text or nothing at all.

This image attempts to show the painfully dismal result of trying to use currently compliant web browsers to produce real life size objects on a screen with accurate display density, using a digital camera.

This shows a quite acceptable result of doing the same that is possible with web browsers not handicapped by current standards, letting the computer do the computing:

Either image will be an expected presentation if and only if for display it can be resized up or down such that the obvious included "yardstick" measures as indicated. When the logical display density and the physical display density match, then no adjustment is required for computed content. For images, rightly size a container in mozmm (instead of now "pointless" cm, in, mm, pt, etc. units), fill the container with an image, and the image will be right sized. To confirm, a ruler can be placed against the display screen, and accuracy will be reasonable, subject only to modest rounding error if on a lower density display.

Display dimensions are normally provided by EDID, which an OS or desktop can even now employ to make any adjustment required automatically, letting the computer do the computing instead of a web artiste. People who want reasonable accuracy can have it. Myopics, projectionists and mobile phone users that don't care, or don't want to, don't have to, except through fate.