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[css-device-adapt] preferred way to make text bigger/smaller

From: Peter Sorotokin <psorotok@adobe.com>
Date: Fri, 28 Oct 2011 11:35:42 -0700
To: "www-style@w3.org" <www-style@w3.org>
Message-ID: <CAD0440E.16453%psorotok@adobe.com>
There are two possible ways to make text bigger (or smaller):
1. Change the default font size (say, from 16px to 20px)
2. Layout the content into smaller logical viewport and then scale the
layout up to fill up the original viewport

The second method is widely used by the browsers. It only depends on the
content being able to adapt to the different viewport sizes and allows
authors to conveniently use absolute units to style the content (including
the font sizes).

The second approach is also implemented by some browsers (I believe). It
is potentially more flexible, since it allows authors to select which
content will become bigger with text (by sizing it with em units) and
which content should stay the same size. (This method is commonly used for
ebook content).

Of these two approaches, there is no right or wrong one, it depends on the
content. It also interacts with logical viewport size: the first approach
relies on ability to resize it. Having the info on the preferred text size
change method would be a valuable for the UA and I think it would go
naturally into @viewport rule.

I propose the following descriptor for use only inside @viewport:

text-zoom: scale | font-size

scale is default value that corresponds to the second method, font-size
corresponds to the first. UA is still free to choose either method, or
something else altogether, of course (e.g. scaling without layout).

Peter
Received on Friday, 28 October 2011 18:36:15 GMT

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