[webkit-dev] Proposal: Move CSS3 Text Decoration properties out of CSS3_TEXT feature flag / remove vendor prefix

Tue Aug 20 16:11:32 PDT 2013

From: Ryosuke Niwa <ryosuke.niwa at gmail.com<mailto:ryosuke.niwa at gmail.com>>
Date: Tuesday, August 20, 2013 1:59 PM
To: Bruno de Oliveira Abinader <bruno.d at partner.samsung.com<mailto:bruno.d at partner.samsung.com>>
Subject: Re: [webkit-dev] Proposal: Move CSS3 Text Decoration properties out of CSS3_TEXT feature flag / remove vendor prefix

On Tue, Aug 20, 2013 at 10:08 AM, Bruno de Oliveira Abinader <bruno.d at partner.samsung.com<mailto:bruno.d at partner.samsung.com>> wrote:
The CSS Level 3 Text Decoration specification [1] has recently changed status to "W3C Candidate Recommendation", which means it has been widely reviewed and is ready for implementation (so we can expect no further syntax changes). So far the following properties from that specification are implemented behind a feature flag (CSS3_TEXT):

-webkit-text-decoration (shorthand)
-webkit-text-decoration-line
-webkit-text-decoration-style
-webkit-text-decoration-color
-webkit-text-underline-position

Please notice all of these properties are implemented with vendor prefix on WebKit. There are other properties implemented behind CSS3_TEXT feature flag that do not belong to CSS Level 3 Text Decoration specification and thus are not going to be handled in this proposal. Said this, I would like to propose the following changes:

I'd like to know how well these properties work well in contenteditable regions.  Namely, when a user edits text with text decoration color, line style, etc... would it properly preserve them?

I believe this requires some discussion – currently the HTML Editing APIs [1] specification does not provide methods for modifying text decoration's style and color. That said, these prefixed properties implementations are not currently handled in EditingStyle – but if you paste HTML code containing these on an editable element, it would preserve the properties information (I could write a test in editing/ to verify that).

1) Move the aforementioned properties out of CSS3_TEXT feature flag - currently it is enabled by default on EFL/GTK ports, must obtain acknowledgement from all other ports maintainers.

How complete and compatible is our implementation with other browsers and with respect to the W3C specification?  Does W3C have tests?  If so, do we pass all of them?

In terms of completeness, we are not providing support for all properties specified in CSS Level 3 Text Decoration specification, but for the ones we have implemented, those are full implementations (with exception of "blink" value from text-decoration-line which is valid but ignored, as in CSS 2.1 text-decoration implementation in WebKit).

Speaking of compatibility, besides WebKit, Gecko implements text-decoration shorthand unprefixed, text-decoration{-line,-style-color} prefixed (-moz-), and does not implement text-underline-position (which is only implemented on Trident). The syntax for values is the same for all implementations, and does so for visual expectations/computed styles.

As for W3C tests, according to [2] there are currently no tests for latest release, but on the nightly unstable [3] I could find at least 12 tests, all passing for now (w/ exception of text-decoration-line-014 which expects text to blink).

2) Remove the vendor prefix from these properties – probably the only side-effect that I see is that the current computed style from text-decoration (which is implemented according to CSS 2.1 specification) would change to support the shorthand implementation (as currently implemented on Blink), thus requiring us to modify some layout test results that depends on text-decoration computed style.

Do EFL and GTK ports not want to support the prefixed version?  It seems desirable to keep both the prefixed version and the unprefixed version.

I'd feel comfortable with whatever decision the port maintainers decide, though un-prefixing these properties would match Blink's implementation.

Links:
[1] https://dvcs.w3.org/hg/editing/raw-file/tip/editing.html
[2] http://www.w3.org/Style/CSS/Test/Overview.en.html
[3] http://test.csswg.org/suites/css-text-decor-3/nightly-unstable/

Best regards,
Bruno
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