Re: [CSS21] 4.3.2 Lengths (reference pixel?)

On Mon, Dec 13, 2010 at 11:40 AM, Anton Prowse <> wrote:
> On 13/12/2010 20:10, Tab Atkins Jr. wrote:
>> Those authors have never truly had good physical units.  I don't
>> recall the precise details of which browsers do what, but more than
>> one browser, at least, has done the "1in = 96px" thing for a long
>> time.
>> So there never was a way to do it "correctly" because the physical
>> units never were truly physical, in practice.
> Sure, but an author who attempted to do it correctly (testing on a monitor
> of a certain, common resolution) cannot be blamed much for not knowing that
> the software he relied upon was letting him down in practice on monitors of
> different resolution.

Sure.  But we similarly can't change all the pages written by authors
who used both pt and px in their pages and expected them to maintain a
steady ratio.

It appears that this group of authors is much larger than the group of
authors who wrote pages expecting an absolute length to exactly
correspond with the analogous real-world units (especially since they
never did, except perhaps by accident on some screens with particular

Further, absolute units *do* correspond closely to the analogous
real-world units in print media and other high-dpi media, and as
screen resolutions increase the same will happen there.  The
disconnect between CSS in and real-world inches is a temporary
aberration caused by the particular circumstances of how screens work
(requiring us to make CSS px correspond to integer multiples of screen
pixels) and the current common dpi ratio.


Received on Monday, 13 December 2010 19:57:12 UTC