The WHATWG Blog — thisweekinhtml5

This Week in HTML 5 – Episode 28

Thursday, April 2nd, 2009

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 23^rd 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.

Defined <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 async="" or 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]
The <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 action, enctype, method, novalidate, and target, which exactly mirrored the attribute names that could be declared on the <form> element.

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.add(e) and 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 document.cookie and .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.cookie needs 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."

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This Week in HTML 5 – Episode 27

Thursday, April 2nd, 2009

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. In this episode, I'd like to highlight some of the discussions that I've missed in previous episodes.

Greg Millam writes, "I'm one of the main engineers responsible for captioning support on YouTube, and I've joined the Chrome team at Google to attempt to help drive video captions and subtitling forward." Henri Sivonen replies, "I agree it makes sense to start with something simple. The markupless flavor of SRT would be such a format. However, supporting the formatting tags in later flavors of SRT is a can of worms." [full thread: Captions, Subtitles, and the Video Element]
Robert O'Rourke writes, "Are there any plans to bring list headers from HTML3 into HTML5?" Ian Hickson replies, "You can do this in HTML5, using <figure> and <legend>." The thread continues in a number of directions. Marcus Ernst writes, "Anyway I would consider it even more appropriate to allow the list inside a paragraph," to which Ian replies, "We had this in the spec originally, but we dropped it due to a variety of issues (it made life harder for editors, it didn't work in text/html even when it looked like it did, people got confused...)." [full thread: List Headers]
Drew Wilson writes, "There's currently no way to set or get cookies from workers, which makes various types of cookie-based operations problematic." Jonas Sicking replies, "Allowing cookie to be set would unfortunately create a synchronous communication channel between the worker and the main window." The discussion continues, focusing on issues of multi-threaded updates to document.cookie. Drew Wilson again: "Following up on this. I created two pages, one that tests cookies in a loop, and one that sets cookies in a loop, and ran them in separate windows in Firefox 3, IE7, and Chrome. Chrome and IE7 currently allow concurrent modification of document.cookies (i.e. the test loop throws up an alert). Firefox does not." [full thread: Accessing cookies from workers]
There have been a number of overlapping discussions on whether and how to allow authors to embed RDFa in HTML 5 documents. See 1, 2, 3, and followups. Besides the technical arguments about how it would work, much of the discussion centers around the concept of distributed extensibility, which I've touched on before. For example, here is Chris Wilson (of the Microsoft IE development team): "We have had (in the past as well, imo, in the future) a requirement for decentralized extensibility - that is, that document/content authors can extend the set of elements with their own semantic or behavioral elements. I continue to think there is a requirement for that. (One might well ask why we didn't implement full XML in that case; I'll politely not answer from a historical context, but will point out that the draconian error handling and poor fallback story make delivering content in XML in the browser a poor solution in the ecosystem today.)"
Steven Faulkner writes, "I have ... taken a stab at a RFC 2119 compatible definition for table summaries: http://esw.w3.org/topic/HTML/SummaryForTABLE/SummarySpecification." [full thread: Draft text for summary attribute definition, continued in March archives]

There has also been a vigorous debate about the license of the specification itself.

Sam Ruby writes, "In my discussions with Ian and at Mozilla, I gathered that it was a shared understanding that by October that the license for the W3C license would be somehow open source friendly, and specifically that a Creative Commons Attribution license was something that was of common and general interest." The "open source friendly" clause is a reference to the fact that the spec does actually contain some code (in the form of WebIDL declarations), and vendors of open source browsers would like to include this code (or derive code from it) into their products.
After much discussion, Philippe Le Hegaret (of the W3C) writes, "In response to requests from developers to make it easier to include portions of W3C specifications in software documentation, bug reports, code, and test cases, W3C have drafted a new Excerpt & Citation License. ... Uses like forking of a specification would remain prohibited to protect the due process and the consensus found in a chartered Working Group."
Ian Hickson immediately replies, "Increasing license proliferation is a really bad idea here. I would be opposed to introducing yet another license. ... [The forking] use case is the main one that I'm concerned about, FWIW."
Jonas Sicking explains his reasoning about allowing forking: "I think it would gain W3C a tremendous amount of trust if it were to allow [forking]. To many people, me included, having the gurentee that W3C can't go off 'into the weeds' means that I have don't have to worry about my time being wasted when I contribute. I think many people feel the same when they contribute to the forkable software I represent."
Philippe notes that the W3C "isn't used to the concept of allowing a fork" of their specifications, which is one of the requirements of any "open source friendly" license.
I believe Maciej Stachowiak (WebKit developer at Apple) best summarized the group's objections: "1) Preventing specification forks is not achievable through license terms; a sufficiently motivated party can create a new spec from scratch. 2) Preventing specification forks is probably not necessary; the one time it happened, the outcome was good and the effort merged back into a realigned W3C. 3) Due to 1 and 2, we should give more consideration to LGPL/GPL compatibility than prevention of forks via licensing terms."
Ian Hickson agrees: "I do agree that the original use cases are (intentionally and explicitly) not all met by the proposal that was put forward, and I do think the original use cases were an accurate portrayal of the use cases that this working group has consensus on. Compatibility with open source (including GPL and LGPL projects), clear license terms (ideally reusing an existing license), and the ability to fork are all issues that working group members discussed and considered important previously."

[Further reading: Discussions with plh, Draft W3C Excerpt License]

Tune in next week for another exciting episode of "This Week in HTML 5."

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This Week in HTML 5 – Episode 26

Thursday, April 2nd, 2009

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 16^th is this announcement from Ian Hickson:

I've now split out the Server-sent Events and Storage APIs out of HTML5, and I've removed the text for Web Sockets, which was split out earlier. By popular demand I've also done some tweaks to the styling of these specs.

HTML5

http://dev.w3.org/html5/spec/

Server-Sent Events

http://dev.w3.org/html5/eventsource/

Web Storage

http://dev.w3.org/html5/webstorage/

Web Workers

http://dev.w3.org/html5/workers/

Web Sockets

http://dev.w3.org/html5/websockets/
http://tools.ietf.org/html/draft-hixie-thewebsocketprotocol

It is my understanding that the desire is to publish the Server-Sent Events, Web Storage, Web Workers, and Web Sockets specs through the Web Apps working group, so that is what I put into the "status of this document" sections.

I would like to be able to put more permissive licenses (ideally MIT) on these drafts, rather than the W3C license.

The following sections still haven't been split out:

URLs

I'll remove this section as soon as DanC's draft is published.

Content-Type sniffing

I'll remove this section once Adam's draft is on a standards track.

Timeout API

This section is lacking an active editor.

Origin

I'm unsure what will happen with this section.

In IRC, Ian explained that all of these documents are generated from one master file:

# [21:02] <hixie> the source document is run through a bunch of scripts to generate the output documents
# [21:03] <hixie> from that one file i now generate one whatwg spec, four w3c specs, and an rfc

In other news, r2876 (WARNING: VERY LARGE) adds user stylesheets to the HTML 5 specification itself. If you view it in a browser that support switching stylesheets (such as Firefox, under the View → Page Style submenu), you can choose between "Complete specification" (default), "Author documentation only," or "Highlight implementation requirements." The "Author documentation only" stylesheet hides all of the client parsing algorithms and focuses on the elements, attributes, and scripting features that web authors need to know about.

For example, the "author documentation" of the <img> element highlights the required attributes, how to create a new Image() dynamically, and the detailed requirements for providing alternate text, while completely hiding any mention of how image fetching fits into the client's task queue, the gory details of how clients resolve image URLs, or the security risks of allowing pages on the public internet to attempt to load images on the local network. On the flip side, "highlight implementation requirements" highlights these exact issues.

Critics who complained that the HTML 5 specification should be "just a markup language" will be able to have their cake and eat it too. Those who complained that HTML 5 was "too bloated" will have a little less to complain about now that several parts of it have been published as separate documents. On the other hand, critics who complained about these things as a cover for other agendas will have to continue complaining a little while longer.

Tune in next week for another exciting episode of "This Week in HTML 5."

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This Week in HTML 5 – Episode 25

Tuesday, March 31st, 2009

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 February 23^rd (yes, I'm that far behind) is a collection of changes about how video is processed. The changes revolve around the resource selection algorithm to handle cases where the src attribute of a <video> element is set dynamically from script.

Background reading on the resource selection algorithm: Re: play() sometimes doesn't do anything now that load() is async, r2849: "Change the way resources are loaded for media elements to make it actually work", r2873: "make all invokations of the resource selection algorithm asynchronous."

This Week Day in HTML 5 – Episode 24

Tuesday, March 10th, 2009

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 pace of HTML 5 changes has reached a fever pitch, so I'm going to split out these episodes into daily (!) rather than weekly summaries until things calm down.

The big news for February 13, 2009 is r2814/r2815, which adds a .value property on file upload controls:

On getting, [the .value property] must return the string "C:\fakepath\" followed by the filename of the first file in the list of selected files, if any, or the empty string if the list is empty. On setting, it must throw an INVALID_ACCESS_ERR exception.

According to bug 6529, Opera already implements something close to this, and is willing to modify their implementation to match the spec text.

The other big news of the day is r2804/r2805, which defines what happens when a focused element becomes hidden.

For example, this might happen because the element is removed from its Document, or has a hidden attribute added. It would also happen to an input element when the element gets disabled.

But let's back up a step. What does it mean for an element to be "focused" in the first place? The spec has a whole section on the concept of focus. The short answer is that focus is just what you think it is: it's the element that responds when you type. As you tab around a form, the focus moves between form fields, where you can type information; as you tab around a page, the focus moves between links, which you can follow; if you tab long enough, focus moves out of the page and back to the location bar, and so forth.

The not-so-short answer that everything in the previous paragraph is platform-specific and, depending on your browser, highly customizable. The HTML 5 spec respects these platform differences, and defers the definition of what elements should be focusable to the browser, which ultimately respects the conventions of the underlying operating system.

The long answer is that virtually anything can be focusable, because HTML 5 standardizes a crucial accessibility feature that most modern browsers now implement, namely that any element can have a tabindex attribute.

It may not sound like it, but this is a really, really important feature for building accessible web applications. HTML 4 restricted the tabindex attribute to links and form fields. For reasons unknown, Internet Explorer ignored that and respected a tabindex attribute on any element. Starting with Firefox 2, Mozilla co-opted this implementation and wrote up a rough "standard" about using the tabindex attribute on anything. Once it was implemented in the browser, IBM contracted with major screenreader vendors to support Firefox's (and IE's) behavior. This provided the foundation for pure-Javascript widgets to become keyboard-accessible (also implemented by IBM). Not just theoretically, but actually, in real shipping browsers and real shipping screenreaders. Under the covers, Dojo's complex widgets are marked up with semantically meaningless <div>s and <span>s, yet they are still focusable and keyboard-navigable. The controls are in the tab order, so you can focus with the keyboard, then you can use the keyboard to further manipulate them, change their state, and so forth.

In HTML 4, there was no way to put custom controls into the tab order without breaking markup validity (unless you futzed around with custom DTDs or scripting hacks), because the tabindex attribute could only be used on links and form fields. HTML 5 "paves the cowpaths" and standardizes this definition and behavior of tabindex-on-anything. This is a huge step forward for web accessibility. The concept of focus is central to accessibility, and HTML 5 gives it the attention it deserves. (There's more to making controls accessible than just keyboard navigability, but if you don't have keyboard navigability, nothing else really matters. If you're creating your own custom Javscript widgets, you must read the (non-vendor-specific) DHTML Style Guide for implementing keyboard accessibility in custom controls.)

Now then, why is r2804 important? Well, if the element that has focus suddenly can't have focus anymore -- because it was programmatically hidden or disabled, or it was removed from the DOM altogether -- then it is vitally important to specify where the focus goes. So the HTML 5 specification lays it all out:

When an element that is focused stops being a focusable element, or stops being focused without another element being explicitly focused in its stead, the user agent should run the focusing steps for the body element, if there is one; if there is not, then the user agent should run the unfocusing steps for the affected element only.

[Background reading: Re: Lose Focus When Hidden? (SVG ISSUE-2031)]

Other interesting changes of the day:

r2807 simplifies the definition of window.onerror.
r2810 makes the presence of a <noframes> element a non-ignoreable error for validators. (It was previously a "downplayed error.")
r2811 defines that "this" in the Javascript global scope, should return a WindowProxy object instead of a Window object. I confess I have no idea what that means or why it's important. Perhaps a commenter could enlighten me?
r2812 updates the way browsers should determine character encoding (using known aliases of common encodings).
r2817 adds "transparent" to the list of colors that need to be parsed in an IE-compatible way.
r2818 notes that putting a document in designMode does not actually prevent it from executing scripts.

Tune in... well, sometime soon-ish for another exciting episode of "This ~~Week~~ Day In HTML 5."

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