This Week in HTML 5 – Episode 28
Welcome back to "This Week in HTML 5," where I'll try to summarize the major activity in the ongoing standards process in the WHATWG and W3C HTML Working Group.
The big news for the week of March 23rd is that SVG can once again be included directly in HTML 5 documents served as text/html:
I've made the following changes to HTML5:
- Uncommented out the XXXSVG bits, reintroducing the ability to have SVG content in text/html.
<script>processing for SVG
<script>in text/html by deferring to the SVG Tiny 1.2 spec and blocking synchronous
document.write(). The alternative to this is to integrate the SVG script processing model with the (pretty complicated) HTML script processing model, which would require changes to SVG and might result in a dependency from SVG to HTML5. Anne would like to do this, but I'm not convinced it's wise, and it certainly would be more complex than what we have now. If we ever want to add
defer=""to SVG scripts, then this would probably be a necessary part of that process, though.
- Added a paragraph suggesting: "To enable authors to use SVG tools that only accept SVG in its XML form, interactive HTML user agents are encouraged to provide a way to export any SVG fragment as a namespace-well-formed XML fragment."
- Added a paragraph defining the allowed content model for SVG
<title>elements in text/html documents.
r2904 (and, briefly, r2910) give all the details of this solution. There are still a number of differences between the text in HTML 5 and the proposal brought by the SVG working group. Some of these are addressed further down in the announcement:
- SVG-in-XML is case-preserving; SVG-in-HTML is not.
- SVG-in-XML requires quoted attribute values; SVG-in-HTML does not.
- When SVG-in-XML uses CDATA blocks, they show up as CDATA nodes in the DOM; when SVG-in-HTML uses CDATA blocks, they show up in the DOM as conventional text nodes. [Clarified based on Henri's feedback]
<svg>element can not be the root element of a text/html document.
Doug Schepers, who has been the SVG working group's HTML 5 liason, does not like this solution:
To be honest, I think it's not a good use of the SVG WG's time to provide feedback when Ian already has his mind made up, even if I don't believe that he is citing real evidence to back up his decision. What I see is this: one set of implementers and authors (the SVG WG) and the majority of the author and user community (in public comments) asking for some sort of preservation of SVG as an XML format, even if it's looser and error-corrected in practice, and a few implementers (Jonas and Lachy, most notably) disagreeing, and Ian giving preference to the minority opinion. Maybe there is sound technical rationale for doing so, but I haven't been satisfied on that score.
Turning to technical matters, one of the features of web forms in HTML 5 is allowing the attributes for form submission on either the
<form> element (as in HTML 4) or on the submit button (new in HTML 5). Originally, the attributes for submit buttons were named
target, which exactly mirrored the attribute names that could be declared on the
However, in January 2008, Hallvord R. M. Steen (Opera developer) noted that "INPUT action [attribute] breaks web applications frequently. Both GMail and Yahoo mail (the new Oddpost-based version) use input/button.action and were seriously broken by WF2's action attribute."
Following up in November 2008, Ian Hickson replied, "I notice that Opera still supports 'action' and doesn't seem to have problems in GMail; is this still a problem?" to which Hallvord replied, "GMail fixed it on their side a while ago. It is still a problem with Yahoo mail, breaking most buttons in their UI for a browser that supports 'action'. We work around this with a browser.js hack. ('Still a problem' means 'I tested this again a couple of weeks ago and things were still broken without this patch'.)"
Ian replied, "This is certainly problematic. It's unclear what we should do. It's hard to use another attribute name, since the whole point is reusing existing ones... can we trigger this based on quirks mode, maybe? Though I hate to add new quirks." Hallvord did not like that idea: "In my personal opinion, I don't see why re-using attribute names is considered so important if we can find an alternative that feels memorable and usable. How does this look?
<input type="submit" formaction="http://www.example.com/">"
Finally, in March 2009, Ian replied:
That seems reasonable. I've changed "action", "method", "target", "enctype" and "novalidate" attributes on <input> and <button> to start with "form" instead: "formaction", "formmethod", "formtarget", "formenctype" and "formnovalidate".
And thus we have r2890: Rename attributes for form submission to avoid clashes with existing usage.
Other interesting changes this week:
- r2889 adds support for
select.options.add(e)with no second argument.
- r2888 defines how to determine the character encoding of Web Worker scripts. Briefly, it says to look for a Byte Order Mark, then look at the Content-Type HTTP header, then fall back to UTF-8.
- r2898, r2899, r2901, r2914, and r2916 define a locking mechanism to allow thread-safe read/write access to
.localStorage. The lock is acquired during page fetching (which sets the cookie based on HTTP headers) and released once the cookie is set. It is also released automatically whenever something modal happens (such as
window.alert()). (I first mentioned the discussion of this issue in episode 27. The problem is that Web Workers allows threaded client-side script execution, which means access to shared storage like
document.cookieneeds to be made explicitly thread-safe with some sort of locking mechanism.)
Tune in next week for another exciting episode of "This Week in HTML 5."
CDATA sections are supported as currently drafted in SVG-in-text/html. However, they do not generate CDATA section DOM nodes but conventional text nodes. Thus, the syntax works but the syntactic sugar doesn’t leak into the DOM representation.
Updated, thanks Henri.
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