- From: Ambrose LI <ambrose.li@gmail.com>
- Date: Tue, 12 Jan 2010 14:02:20 -0500
- To: Boris Zbarsky <bzbarsky@mit.edu>
- Cc: "Linss, Peter" <peter.linss@hp.com>, www-style W3C Group <www-style@w3.org>
2010/1/12 Boris Zbarsky <bzbarsky@mit.edu>: > On 1/12/10 1:15 PM, Linss, Peter wrote: > The point (no pun intended) is that there is such a reason: doing it is not > compatible with most of the web content out there. > >> I do see a use case for a device pixel unit, but it still scares me as >> it's ripe for abuse and will likely be misunderstood. The best use case I >> can come up with for it is a hairline border, where I want it to be the >> thinnest possible line that the output device can render. If there's really >> a compelling need for that, I think I'd rather have a "hairline" unit than >> device pixel. > > Indeed, since it may well be that the thinnest possible line the output > device can render is actually invisible to human eyes. For example, a > 1-pixel line on a 2400-dpi printer is nominally 0.01mm == 10um wide; > http://en.wikipedia.org/wiki/10_micrometres and > http://en.wikipedia.org/wiki/1_micrometre have some things in this range > (e.g. very very fine human hairs, cotton/silk/nylon fibers, 1/10 the > thickness of a typical sheet of paper, two red blood cells next to each > other, that sort of thing). I suspect that most papers wouldn't actually > show that line at that width, but if they did it would be below even the > theoretical maximum visual acuity of human eyes (.35mm at 1m viewing > distance according to <http://en.wikipedia.org/wiki/Eye#Acuity>) if held at > normal reading distance. > > I might be ok with a "hairline" width for this use case, with the UA trying > to do something sane with it, I guess. FWIW, in PostScript this "thinnest possible width" is represented by 0 (points). Whether it can be seen or not, it can be represented. -- cheers, -ambrose
Received on Tuesday, 12 January 2010 19:02:52 UTC