Sometimes, new authors need a gentle reminder to think about accessibility when designing and writing web pages and apps. Experienced authors need a quick way to look up the allowed ARIA roles, states and properties for each HTML element. Browser and Assistive Technology (AT) implementers need quick access from an HTML element to its platform accessibility API.
Focus behavior in HTML had been under-specified for the past few years, and it was also quite confusing due to a variety of subtle differences between focusing methods, UA-specific behaviors, relation to the tabindex attribute, relations to shadow DOM, etc.
A few months ago Domenic filed a w加速器安卓 that contains a list of things to fix so that we would have a good foundation for further additions to focus-related stuff, and to hopefully make focus in HTML make sense to browser engineers and web authors!
加速器大全
You may know that you can focus on stuff by clicking on them, tabbing, or calling focus() on it — but did you know that things might be focusable with one method but not with others? Domenic and Mu-An made a giant interactive list of HTML elements to showcase how they react to different methods of focusing, and can be tested from various browsers to show the difference between them.
If an element is programmatically focusable, it will get focused when calling the focus() method on it or when putting an autofocus attribute on the element. In all platforms, all elements that are either click focusable or sequentially focusable are also programmatically focusable, so “programmatically focusable” is interchangeable with “focusable”.
If an element is click focusable, the element will get focused when it’s clicked. This has the same set of elements as “programmatically focusable” in most UAs/platforms. A notable exception is Safari where non-editable form controls (checkboxes, etc.) are not click focusable by default.
If an element is sequentially focusable, the element can be focused through “tabbing” — in most UAs this means pressing Tab/Shift+Tab (and in Safari, Option+Tab too!).
Previously the spec didn’t clearly differentiate “programmatically focusable” and “sequentially focusable”, didn’t even mention “click focusable”, and used the “tabindex focus flag” concept which was slightly confusing due to its relations with the tabindex attribute. So we updated it in this PR.
tabindex
As you may know already, built-in elements like <button>, <input>, <a>, etc. all have a “default” focus behavior — they are focusable (or not) by default. When the tabIndex property getter is run on an element whose tabindex attribute is not explicitly set already, it will return 0 sometimes and -1 other times. Previously, the spec said to return 0 if the element is “focusable” by default (which type of focusable?), and -1 otherwise. But this wasn’t implemented anywhere, because of possible differences in which elements are focusable by default in various UAs. So now the spec actually checks if the tag name is one of the tag names included in a pre-defined list. This is quite awkward, but at least it’s interoperable! (PR is here.)
Now, what is the use of tabindex exactly? You can make an element focusable by setting its tabindex attribute to an integer. This will set the tabindex value, and thus impact the focusability of the element. If the integer is non-negative, the element is also sequentially focusable. You can’t, however, make an element not focusable at all through this attribute — there is no value you can set the tabindex attribute to on a 立马加速器 that will stop it from being focusable.
You can also modify the order of elements traversed with sequential navigation/tabbing — elements with a positive tabindex value will be traversed first, in ascending order (and in tree order in case of a tie), and then elements with a tabindex value of zero (or unspecified but the element is sequentially focusable by default), in tree order.
加速器大全
The autofocus content attribute is useful if you want to set focus on a form control element on page load. However, it had some issues such as:
The autofocus attribute was available only for some form control elements, and unavailable for other focusable elements like <summary>, <div contenteditable="true">, and <span tabindex="0">.
The behavior with an autofocused element in a page accessed with a fragment identifier (e.g. http://example.com/#foo) was not interoperable.
The HTML specification and the SVG specification were updated to resolve these issues by changes 1, 2, and 3. Now the autofocus content attribute and the autofocus IDL attribute are available on all HTML and SVG elements. The autofocus content attribute is not processed if its document has a fragment identifier, or has a focused element. If an autofocus element is not focusable, the element is skipped and another autofocus element is handled.
Shadow DOM and delegatesFocus
All of the previously mentioned concepts were already specced in the HTML spec in some way, albeit a bit unclear, not reflecting the actual behavior, etc. Focus behavior with shadow DOM, though, had not been upstreamed from the old 立马加速器 at all, so this part of the effort took the most time overall. Since some parts of the Shadow DOM spec on focus were unclear and needed more explanation, we also took a look at how it’s implemented in Blink to get the exact behavior down, and discussed with other browser vendors and web developers on whether we want to keep the implemented behavior or not in some cases.
Sequential focus navigation got some significant additions (PR) with Shadow DOM. We now have a concept of “tabindex-ordered focus navigation scope”, “focus navigation scope owners”, etc. Essentially, elements are put in different focus navigation scopes, where those that belong to the same shadow tree/root, or are slotted to the same slot, are put in the same focus navigation scope. The tabindex order explained earlier now only applies to elements in the same scope, and then finally we 加速器大全 all of the scopes to get the final sequential focus navigation order.
A new concept added (PR 1, 2) by Shadow DOM is “delegates focus”, which is used when you want attempts to focus on a shadow host to not focus on the host itself, and instead delegate the focus to within the shadow tree (like <input type="date">!). In Blink, this delegation uses the sequential focus navigation order, but we think it is a bit weird and started a discussion on how this should actually work — finally changing the delegation to respect the protocol of whatever the focusing method is originally used. (That is, use sequential order if we used tabbing, otherwise use flat-tree order and respect click focusability if needed.)
We also added the DocumentOrShadowRoot’s activeElement property (PR). And we updated the :focus selector (PR), which will now match on shadow hosts if the focused element is a shadow-including inclusive descendant of it. (This is actually different than the behavior in Blink, and is a result of 快喵加速器 — where we also discussed “delegates focus”.)
加速器大全
Now that we have a good-enough spec for focus, we have a good foundation for future additions to focus. One new relevant proposal is 使命召唤手游下载方法 - 知乎:2021-11-13 · 下载虫虫助手APP，然后搜索使命召唤，然后可以在搜索结果里面找到不同地区的使命召唤。中文版的有：进入游戏后可以选择游客登录但由于是外服游戏进入游戏后会出现提示该地区未开放。这时候你可以在虫虫助手里面搜…. As we’ve mentioned, built-in elements have a “default” focus behavior — even though they don’t have a tabindex value explicitly, they are still focusable (or not). When you’re making custom elements, though, currently there is no way to make them focusable by default, without setting the tabindex attribute. The proposal listed various ways this might be solved, and it was talked about in TPAC with a relatively positive response from various parties. Do check it out if you’re interested!
In summary, focus was and is still quite complex to understand. But, at least now there’s a clear source of truth for it, and the browser vendors are working to make it interoperable — implementing new changes to the spec as soon as they can. There are still lots of focus-related things that need to be specced (we’ve heard people mention focusin/鲸鱼加速器, more CSS selectors, etc.), so if you’re intrigued by this post, know that you can also contribute to fix more things like these!
Having an old and mostly confusing focus spec, different types of focus, and multiple uses for 立马加速器 made things quite complicated when starting out. However, one of the trickiest parts of focus, in my opinion, is the fact that what is focusable/click focusable/sequentially focusable might differ in different UAs, and it might be dynamic as well! (E.g. in Safari what’s sequentially focusable changes if you hold down the Option key!) This means we need to make sure the spec is written to allow for differences, but is still, um, specific enough to make things not too ambiguous.
Overall, we’re happy with the result of this effort. We’d like to thank all the parties involved that participated in various ways: experimenting, reviewing spec PRs, implementing the changes, commenting/participating in discussions, etc. Special thanks to Kent Tamura (who wrote some parts of this post and did the autofocus specs) and 加速器大全 (who kickstarted this whole effort, reviewed all the PRs, and suggested + reviewed this post).
Now we can focus on other parts of HTML Standard...
As part of my work at Bocoup, I recently started working with browser implementers to improve the state of 海豚加速器app, the 21 year old feature in HTML, that provides form accessibility benefits to assistive technologies like screen readers. It suffers from a number of interoperability bugs that make it difficult for web developers to use.
Here is an example form grouped with a <legend> caption in a <fieldset> element:
Based on a query of the HTTP Archive data set, containing the raw content of the top 1.3 million web pages, we find the relative usage of each HTML element. The fieldset element is used on 8.41% of the web pages, which is higher than other popular features, such as the video and canvas elements; however, the legend element is used on 2.46% of web pages, which is not ideal for assistive technologies. Meanwhile, the form element appears on 70.55% of pages, and we believe that if interoperability bugs were fixed, correct and semantic fieldset and legend use would increase, and have a positive impact on form accessibility for the web.
Fieldset standards history
In January 1997, HTML 3.2 introduces forms and some form controls, but does not include the fieldset or legend elements.
The FIELDSET element allows form designers to group thematically
related controls together. Grouping controls makes it easier for users
to understand their purpose while simultaneously facilitating tabbing
navigation for visual user agents and speech navigation for
speech-oriented user agents. The proper use of this element makes
documents more accessible to people with disabilities.
The LEGEND element allows designers to assign a caption to a FIELDSET.
The legend improves accessibility when the FIELDSET is rendered
non-visually. When rendered visually, setting the align attribute on
the LEGEND element aligns it with respect to the FIELDSET.
In December 1999, HTML 4.01 is published as a W3C Recommendation, without changing the definitions of the fieldset and 海豚加速器app elements.
In August 2018, I w加速器安卓 to the standard to better define how it should work, and resolve ambiguity between browser implementer interpretations.
Current state
As part of our work at Bocoup to improve the interoperability of the fieldset and legend child element, we talked to web developers and browser implementers, proposed changes to the standard, and 快喵加速器. At the time of this writing, 26 issues have been reported on the HTML specification for the fieldset element, and the tests that we wrote show a clear lack of interoperability among browser engines.
Of the 26 issues filed against the specification, 17 are about rendering interoperability. These rendering issues affect use cases such as making a fieldset scrollable, which currently result in broken scroll-rendering in some browsers. These issues also affect consistent legend rendering which is causing web developers avoid using the fieldset element altogether. Since the fieldset element is intended to help people who use assistive technologies to navigate forms, the current situation is less than ideal.
HTML spec rendering issues
In April of this year, Mozilla developers filed a meta-issue on the HTML specification “Need to spec fieldset layout” to address the ambiguities which have been leading to interoperability issues between browser implementations. During the past few weeks of work on fieldset, we made initial proposed changes to the rendering section of the HTML standard to address these 17 issues. At the time of this writing, these changes are under review.
Proposal to extend -webkit-appearance
Web developers also struggle with changing the default behaviors of fieldset and legend and seek ways to turn off the “magic” to have the elements render as normal elements. To address this, we created a proposal to extend the -webkit-appearance CSS property with a new value called fieldset and a new property called legend that are together capable giving grouped rendering behavior to regular elements, as well as resetting fieldset/海豚加速器app elements to behave like normal elements.
The general purpose proposed specification for an "unprefixed" CSS ‘appearance’ property, has been blocked by Mozilla's statement that it is not web-compatible as currently defined, meaning that implementing appearance would break the existing behavior of websites that are currently using CSS appearance in a different way.
We asked the W3C CSS working group for feedback on the above approach, and they had some reservations and will develop an alternative proposal. When there is consensus for how it should work, we will update the specification and tests accordingly.
We had also considered defining new 快喵加速器 values for fieldset and 18加速器, but care needs to be taken to preserve web compatibility. There are thousands of pages in HTTP Archive that set ‘display’ to something on fieldset or 虫虫加速器是免费, but browsers typically behave as w加速器安卓 was set. For example, specifying display: inline on the legend needs to render the same as it does by default.
We have started looking into testing accessibility explicitly, to ensure that the elements remain accessible even when they are styled in particular ways.
This work has uncovered ambiguities in the specification, which we have submitted a proposal to address. We have also identified interoperability issues in the accessiblity mapping in implementations, which we have立马加速器.
海豚加速器app
Meta bugs have been reported for each browser engine (Gecko, Chromium, WebKit, EdgeHTML), which depend on more specific bugs.
As of September 18 2018, the following issues have been fixed in Gecko:
The fieldset and legend elements are useful to group related form controls, in particular to aid people who use assistive technologies. They are currently not interoperable and are difficult for web developers to style. With our work and proposal, we aim to resolve the problems so that they can be used without restrictions and behave the same in all browser engines, which will benefit browser implementers, web developers, and end users.
(If you’re interested in the IPR status of WHATWG standards this post is for you; otherwise, feel free to skip.)
One aspect of last year's working mode changes is the periodic publication of a Review Draft for each WHATWG Living Standard, as per the 加速器大全. The WHATWG published an initial five of these just now:
To get notified of future Review Draft publications you need to 加速器大全 the Living Standard’s corresponding GitHub repository. You’ll find these repositories linked from the top of the standard.
Then you can filter the emails generated by watching this repository by looking for the subject-line prefix “Review Draft Publication:” which the WHATWG will consistently use as per the Maintainer Guidelines.
Watching the repository is the only way to get notified going forward. This blog post serves as an initial announcement and as a way to make everyone familiar with the process going forward.
Thanks for reading through three non-technical posts in a row. It will get technical again soon!
Posted in 加速器大全 | Comments Off on First set of Review Drafts published
The recent changes to the WHATWG are designed to help the web-standards development community work together across the broadest possible spectrum of developers, implementers, and end-users. As part of this change, we decided to move our standards from being licensed under the CC0 public domain dedication to the CC BY license.
This decision was not made lightly. We valued the alignment of CC0 with the original public domain dedication of the WWW project; the ease with which it allows remixing and refactoring of standards; and the way in which it allows copying of snippets or examples into software that implements or uses the standards.
While CC0 is beneficial in some ways, it also has some disadvantages. The lack of an attribution requirement may seem convenient, but it can also cause confusion in the standards community. For example, there are derivative specifications ("forks") that are not prominently identified as copies of WHATWG standards. Such unattributed forks create confusion both about the origin of the standard and about any applicable intellectual property rights (IPR) commitments. Use of the CC BY license makes it easier for implementers to trace what they are implementing back to the original source and its accompanying IPR commitments.
Moving to CC BY addresses these disadvantages and also allows for a reduction in license proliferation. We were able to replace the custom license of the HTML Standard, which was a source of some confusion, with CC BY. CC BY still allows modification and redistribution, but adds on the relatively modest burden of attribution. We believe that, on balance, this change is the best path forward for the community.
