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Re: Making pt a non-physical unit

From: David Singer <singer@apple.com>
Date: Wed, 20 Jan 2010 16:56:34 +0900
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, "robert@ocallahan.org" <robert@ocallahan.org>, www-style <www-style@w3.org>
Message-Id: <EF86A775-4214-46ED-B1FC-57AA09AA51CA@apple.com>
To: Brad Kemper <brad.kemper@gmail.com>
I think I would be surprised, as a user, if I set zoom 2:1, and find no change, because that was the 'default' zoom for the UA I was using.  I think the user expects 'twice as large as normal' under those circumstances.

Or am I misunderstanding the way it would work?

On Jan 20, 2010, at 16:50 , Brad Kemper wrote:

> 
> 
> On Jan 19, 2010, at 9:31 PM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote:
> 
>> On Mon, Jan 18, 2010 at 6:04 PM, David Singer <singer@apple.com> wrote:
>>> ...
>>> Manufacturers may choose how these units map to their device, and may also offer users control over the mapping.
>>> 
>>> 
>>> * * * *
>> 
>> 
>> Two, Brad has suggested a slightly different take on the matter, that
>> ends up having the same effect.  For screen media, still use the ratio
>> of 96px to the in, as suggested here.  However, he suggests mapping 1
>> css pixel to 1 device pixel, and then assuming a >1 zoom value for all
>> elements by default when the dpi is high enough.  The only noticeable
>> difference is that in Brad's suggestion the author could easily get
>> access to device pixels in an element by setting zoom:1 on it.
> 
> Yes, and that author-set zoom on the root, default zoom by the UI (when the dpi is high enough), and user-set magnification through the UI (as it's done already) or through user style sheets, are all manipulations of the same property. So the author can override the UA, and the user can easily override the author and/or the UA.
> 
> I am also thinking that if a parent had a used zoom value of 2, and a child had 'zoom:3', then the parent would have 2x2 device pixels per px, and the child would have 6x6 device pixels per px (2*3=6).     

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Wednesday, 20 January 2010 07:57:08 GMT

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