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Re: [css-size-adjust] Specifying text-size-adjust: <percentage>

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Mon, 4 Jan 2016 13:13:13 -0800
Message-ID: <CAAWBYDC-hbNK3HtqjWNdUvgjkW2tV608=kCxdw0cTJzNjJPkHA@mail.gmail.com>
To: Philip Rogers <pdr@chromium.org>
Cc: www-style <www-style@w3.org>
On Mon, Jan 4, 2016 at 10:22 AM, Philip Rogers <pdr@chromium.org> wrote:
> The text-size-adjust CSS keyword has a prefixed implementation in most major
> engines today (an exception being chromium) which lets authors control how
> adjustment works. The <percentage> value is currently underspecified and I'd
> like to spec it to match both Trident and WebKit.
>
> Ideally, we'd remove <percentage> but the httparchive data shows percentage
> values are pretty common (1.2% of all files [1]). Because the implementation
> is not too onerous and supporting percentages with ease the transition to
> unprefixed properties, I'd like to spec it instead of remove it.
>
> I'd like to define <percentage> as a set value that gets multiplied by the
> specified font size. Percentage values are not relative to any other
> adjustment and text-size-adjust: 100% is equivalent to text-size-adjust:
> none. Trident and WebKit appear use this logic [2] and it is compatible with
> existing pages and MS/MDN documentation [3,4]. For posterity, Gecko does not
> support <percentage> and Chromium does not yet implement text-size-adjust at
> all.
>
> I have a preview of this change at:
> https://github.com/progers/csswg-drafts/commit/1f80533bc0f5eb8e97fbf4ae113af5f731756140
> And a preview of the updated spec at:
> https://rawgit.com/progers/csswg-drafts/master/css-size-adjust/Overview.html#adjustment-control

I recommend instead writing:

> User agents must not do automatic size adjustment.  The computed value of font-size must be multiplied by the percentage.
>
> Note: This means that ''font-size-adjust: 100%;'' is equivalent to ''font-size-adjust: none;''.

~TJ
Received on Monday, 4 January 2016 21:14:00 UTC

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