Re: Making pt a non-physical unit

On Jan 15, 2010, at 1:24 PM, Ambrose LI <ambrose.li@gmail.com> wrote:

> 2010/1/15 Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
> On Fri, Jan 15, 2010 at 9:25 PM, Robert O'Callahan <robert@ocallahan.org 
> > wrote:
> > On Sat, Jan 16, 2010 at 7:50 AM, David Singer <singer@apple.com>  
> wrote:
> >>
> >> a) on most screens a CSS pixel and a device pixel normally match
> >> b) on most physical screens, actual lengths and CSS lengths (for  
> example,
> >> inch) normally match;  exceptions include at least the case where  
> there is
> >> no physical surface at all (projection glasses)
> >> c) there are 96 CSS pixels to the CSS inch.
> >
> >
> > b) loses.
>
> Agreed, modulo setting in the UAs to choose a default zoom that
> prefers b) over a).
>
>
> I actually expect (b), though I know that (b) is not achievable  
> because even word processors and page layout programs can't do it  
> correctly.

Sorry for the slow response (was traveling). I violently agree that  
(b) looses in screen, projection, etc. My experience is similar to  
Ambrose's, which is part of the reason I feel this way. The other part  
is the viewing distance thing for goggles, retinal imaging, movie  
screens, blimp screens, etc.

I also agree with Giuseppe about zoom, but only if it is something  
that authors can set a value on to override the default, and relates  
to the zoom level controls in the browsers (that is, users can  
override). Probably should not be called 'zoom' though, since a lot of  
pages have 'zoom:1' to put IE into HasLayout, and the way I see it  
working is multiplicatively (if body has 'pixel-zoom:2' and a child  
element has 'pixel-zoom:3', then that child element has 6 device  
pixels per CSS pixel; browser zoom controls are actually setting  
'pixel-zoom' on the root).

For print you get a, b, and c, because (b) is a gimme.