W3C home > Mailing lists > Public > www-style@w3.org > January 2010

Re: Making pt a non-physical unit

From: David Singer <singer@apple.com>
Date: Thu, 14 Jan 2010 11:58:05 -0800
Cc: robert@ocallahan.org, www-style <www-style@w3.org>
Message-Id: <BECCD9A2-2B69-4EC0-9FA9-8BF363BC5830@apple.com>
To: Brad Kemper <brad.kemper@gmail.com>

On Jan 14, 2010, at 10:38 , Brad Kemper wrote:

> On Jan 14, 2010, at 2:21 AM, Robert O'Callahan wrote:
>> On Thu, Jan 14, 2010 at 2:02 PM, Robert O'Callahan <robert@ocallahan.org> wrote:
>> Our experience is that users do not expect the size of a CSS pixel to be different from one screen pixel by default. They do expect that content such as form controls will be displayed consistently inside the browser and outside it. Therefore attempts to automatically have CSS pixels approximate a particular subtended angle (which we have tried) are not appealing.
> I find myself in complete agreement with you here, Robert (shocking, isn't it?). I know it is taboo to suggest that unzoomed CSS pixels should be based on device pixels, but I think it is the most reasonable thing to do, at least on non-print media, or at least on monitors (projection, handheld, or otherwise) where there is no reliable way to know the exact or average viewing distance (especially with things like movie theater screens, where there can be huge differences in viewing distance between front and back rows and between different theaters).
> As an evil idiot author, I feel much of the value of high resolution monitors would be wasted if I cannot e.g. draw a border that is one device pixel in width while still maintaining the proportion between that 1px measure and other measures.

I think that that should be within the definition of CSS Pixel if a manufacturer wanted to go that way, either making that choice themselves or offering it to their users.

> I don't like that part. If I know that a scoreboard at the ball park is 800 pixels wide, with pixels the size of lightbulbs or whatever, I should be able to use that information to create borders that are one or two or three device pixels in width. It shares the same characteristics as other screen media.

There is a huge assumption here of a tie between the designer and the output device, which is very rare.

David Singer
Multimedia and Software Standards, Apple Inc.

Received on Thursday, 14 January 2010 19:58:38 UTC

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