Hi all, Over the holidays, some developers experienced the 0.000015% of pages impacted by skipped cancel events on <dialog>s, and filed a regression bug <https://bugs.chromium.org/p/chromium/issues/detail?id=1512224>. Out of an abundance of caution, we disabled this feature remotely using Finch for M120 and M121, and then disabled it in the codebase for M122.
In the subsequent discussions, we discovered two possible spec changes we could make to drive down that 0.000015% even further: - A bug fix to allow cancel events to fire for the first-created close watcher, as long as it was created by user activation. Even if the user never interacts with the <dialog>. Spec issue <https://github.com/whatwg/html/issues/10046>, spec PR <https://github.com/whatwg/html/pull/10048>, wip CL <https://chromium-review.googlesource.com/c/chromium/src/+/5187183>. - A more significant change, to consider firing cancel events even if you cannot call preventDefault(). Spec issue <https://github.com/whatwg/html/issues/10047>. Our plan is to implement the first of these bug fixes, which will address the cases reported on the Chromium bug tracker so far, and then re-enable the feature starting in M122. In parallel we'll explore fast-following with the second change, after a bit more discussion with the community. (The main goal of the second change is to enable a use case; we don't think the compat improvement is urgent. See more discussion on the spec issue.) Let me know if there are any concerns, -Domenic On Thu, Oct 19, 2023 at 12:59 AM Yoav Weiss <yoavwe...@chromium.org> wrote: > LGTM3 > > I agree that introspection can be additive on top of what we want to ship > here. > > On Wed, Oct 18, 2023 at 5:48 PM Philip Jägenstedt <foo...@chromium.org> > wrote: > >> The spec change has now landed, LGTM2. >> >> More introspection could possibly be useful >> <https://github.com/whatwg/html/pull/9462#discussion_r1361110313>, but >> without a concrete use case, example code, or developer feedback, I think >> it's hard to do a good job. Having reviewed the spec change, I'm confident >> that exposing more information is technically straightforward if the need >> arises. >> >> On Thu, Oct 12, 2023 at 1:59 AM Domenic Denicola <dome...@chromium.org> >> wrote: >> >>> >>> >>> On Thu, Oct 12, 2023 at 12:51 AM Yoav Weiss <yoavwe...@chromium.org> >>> wrote: >>> >>>> >>>> >>>> On Friday, October 6, 2023 at 12:34:21 AM UTC+2 Chris Harrelson wrote: >>>> >>>> Hi, >>>> >>>> While Alex's concerns are totally valid to consider from a feature >>>> design perspective, I think they are better to be discussed on the WHATWG >>>> issues for this feature. I chatted offline with Alex and he agreed about >>>> that point, and agreed to post comments and questions there. >>>> >>>> So from an API owners perspective LGTM1 modulo considering and taking >>>> into account all comments and feedback from Alex on the spec (as we should >>>> for all such feedback from anyone, of course!). >>>> >>>> >>>> On Wed, Oct 4, 2023 at 8:28 AM Domenic Denicola <dome...@chromium.org> >>>> wrote: >>>> >>>> >>>> >>>> 2023年10月4日(水) 8:16 Alex Russell <slightly...@chromium.org>: >>>> >>>> >>>> >>>> On Monday, October 2, 2023 at 10:16:53 AM UTC-7 Domenic Denicola wrote: >>>> >>>> >>>> >>>> 2023年10月2日(月) 10:11 Alex Russell <slightly...@chromium.org>: >>>> >>>> >>>> >>>> On Sunday, October 1, 2023 at 9:08:57 PM UTC-7 Domenic Denicola wrote: >>>> >>>> On Sat, Sep 30, 2023 at 5:01 AM Alex Russell <slightly...@chromium.org> >>>> wrote: >>>> >>>> The implicit behaviours based on construction order in this API are >>>> very strange and seem like footguns. >>>> >>>> >>>> I don't understand why you find this strange, or a footgun. It's >>>> intended to be the opposite: it guides developers toward creating the >>>> experience the user expects, where when the user requests to close >>>> something, the last thing that was opened, is what closes. >>>> >>>> >>>> Chris Palmer covered this pretty well recently, so I'll defer to his >>>> more eloquent writeup: >>>> >>>> https://noncombatant.org/2023/05/29/complexities-of-allocation/ >>>> >>>> Basically, this is spooky action at a distance and without _at least_ >>>> some reflection and manipulation surface (via DOM, probably), it's hard to >>>> understand how this won't turn into a footgun. >>>> >>>> As a separate note, I'm disappointed in the proliferation of APIs that >>>> affect DOM but have no API and reflection. Import Maps spring to mind, but >>>> there are other recent examples too. If manual disposal is going to be >>>> required for this, we should at least make it possible to introspect >>>> outside the scope in which an object that defines this behaviour is >>>> allocated. >>>> >>>> >>>> In what way does this API affect the DOM? No parts of the DOM tree are >>>> modified by CloseWatcher. The same is true for import maps... >>>> >>>> >>>> This is view state, which is frequently reflected via DOM. The primary >>>> concern here is that there's no way to inspect and/or modify the stack >>>> (attached to Node instances or not) independently of closure-scoped object >>>> lifetimes. >>>> >>>> >>>> It's not clear to me what definition of "view state" you are using, >>>> such that it encompasses things like the module specifier resolution >>>> algorithm or the routing of Android back gestures. >>>> >>>> Maybe, if this is a principle you believe in, you could file it as a >>>> suggestion on the w3ctag/design-principles repository, ideally with a clear >>>> explanation of what the boundaries of this "view state" concept are. >>>> (Including what, in your view, would *not* quality as view state.) >>>> >>>> >>>> >>>> The TAG feedback didn't touch on this very much, AFAICT, but it's >>>> somewhat surprising that the stack of close actions isn't inspectable. >>>> >>>> >>>> I can't speak for the TAG, but here are the reasons why the stack of >>>> close watchers isn't inspectable: >>>> >>>> - We received no developer or partner feedback requesting this >>>> capability >>>> - This could cause potential forward-compat problems without >>>> careful design. E.g., it could make it possible for developers to write >>>> code that assumes that only CloseWatchers, dialogs, and popover="" >>>> elements >>>> are close watchers, and thus make it hard for the web platform to >>>> introduce >>>> a fourth close watcher (e.g., <selectlist>) in the future. >>>> - This would be somewhat of an encapsulation leak between different >>>> parts of the application, making it harder to write resilient >>>> components. >>>> (This is not a strong argument, but rather a bias toward waiting for a >>>> use >>>> case instead of just exposing the information automatically.) >>>> >>>> Thanks, I appreciate the context, and I am impressed by the >>>> thoroughness of the design artifacts. >>>> >>>> >>>> What's the behaviour of non-`destroy()`'d watchers; e.g. if a developer >>>> forgets to dispose of one correctly? Can users get stuck? >>>> >>>> >>>> Non-destroy()ed is the default state of a CloseWatcher, so such >>>> CloseWatchers will respond to the next close request if they are on the top >>>> of the stack. The user cannot really get stuck, as every close request will >>>> either destroy the topmost close watcher on the stack, or possibly trigger >>>> (at most once) a preventDefault()ed cancel event. See >>>> https://github.com/WICG/close-watcher/blob/main/README.m >>>> d#abuse-analysis for more details. >>>> >>>> >>>> Also helpful; thank you! >>>> >>>> >>>> Note that the API generally guides you away from this possibility by >>>> making the simpler code be the one that automatically calls destroy() for >>>> you: https://github.com/WICG/close-watcher/blob/main/README. >>>> md#requesting-close-yourself . >>>> >>>> >>>> >>>> On Wednesday, September 27, 2023 at 7:43:49 PM UTC-7 Domenic Denicola >>>> wrote: >>>> >>>> Contact emailsjap...@chromium.org, dome...@chromium.org, jarhar@chro >>>> mium.org >>>> >>>> Explainerhttps://github.com/WICG/close-watcher/blob/main/README.md >>>> >>>> Specificationhttps://github.com/whatwg/html/pull/9462 >>>> >>>> >>>> What's preventing the PR from landing? >>>> >>> >>> It needs review, and none of the other editors have made the time yet. >>> (Maybe +Philip Jägenstedt <foo...@chromium.org> could help?) >>> >>> >>>> >>>> >>>> >>>> >>>> Summary >>>> >>>> "Close requests" are a new concept that encompasses user requests to >>>> close something currently open, using the Esc key on desktop or the back >>>> gesture/button on Android. Integrating them into Chromium comes with two >>>> changes: * CloseWatcher, a new API for directly listening and responding to >>>> close requests. * Upgrades to <dialog> and popover="" to use the new close >>>> request framework, so that they respond to the Android back button. >>>> >>>> >>>> Blink componentBlink >>>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink> >>>> >>>> TAG reviewhttps://github.com/w3ctag/design-reviews/issues/594 >>>> >>>> TAG review statusIssues addressed >>>> >>>> Risks >>>> >>>> >>>> Interoperability and Compatibility >>>> >>>> This API is designed to have an interoperable surface for web >>>> developers, to help them avoid platform-specific code. So, if it were >>>> implemented across browsers, it would be a positive for interoperability. >>>> Otherwise, it has the usual risks of not getting adopted by other vendors. >>>> Compatibility: To avoid allowing CloseWatchers, dialogs, and popovers >>>> ("close watchers") to prevent the Android back gesture/button from >>>> navigating through history, how close watchers respond to close requests >>>> depends on user activation. If no user activation occurs between opening, >>>> and the user issuing a close request, this can cause a >>>> CloseWatcher/dialog's cancel event to be skipped, or cause multiple close >>>> watchers to be closed at once. Although this behavior is meant to prevent >>>> back-trapping on Android specifically, it applies to desktop as well, for >>>> interoperability reasons. This change is a compatibility risk. However, use >>>> counters show it to be an acceptable one: - 0.000015% of pages impacted by >>>> skipped cancel events - 0.000007% of pages impacted by skipped cancel >>>> events that would otherwise call preventDefault() - between 0.000000% and >>>> 0.000001% of pages impacted by multiple dialogs closed >>>> >>>> >>>> *Gecko*: Positive (https://github.com/mozilla/st >>>> andards-positions/issues/604) >>>> >>>> *WebKit*: No signal (https://github.com/WebKit/sta >>>> ndards-positions/issues/215) >>>> >>>> *Web developers*: Positive (https://github.com/w3ctag/des >>>> ign-reviews/issues/594#issuecomment-890257686) See also >>>> https://bugs.chromium.org/p/chromium/issues/detail?id=1319915 >>>> >>>> *Other signals*: >>>> >>>> Activation >>>> >>>> The CloseWatcher API is meant to be usable as a progressive >>>> enhancement; if developers use it with feature detection, then their app >>>> will be able to watch for unusual close watchers in supporting browsers, >>>> while falling back to listening for the Esc key in browsers that haven't >>>> implemented the API. It would benefit from a conditional polyfill that >>>> translates the Esc key into a close signal, so that then developers don't >>>> even have to have feature detection and fallback logic, but can just use >>>> the CloseWatcher API surface. One such polyfill is available in the demo: >>>> https://close-watcher-demo.glitch.me/ >>>> >>>> >>>> Security >>>> >>>> The main security-related concern in this API is preventing it from >>>> being usable for back-trapping, i.e. disabling the Android back >>>> gesture/button. Although this is already possible in Chromium and other >>>> browsers due to bugs, we worked to ensure CloseWatcher and close request >>>> integration to dialogs/popups does not increase the size of the problem, by >>>> gating repeated use of these behind transient user activation checks: see >>>> https://github.com/WICG/close-watcher#abuse-analysis >>>> >>>> >>>> WebView application risks >>>> >>>> Does this intent deprecate or change behavior of existing APIs, such >>>> that it has potentially high risk for Android WebView-based applications? >>>> >>>> Beyond the low risks already listed in the Compat section, we do not >>>> anticipate any WebView-specific risks. A base::Feature killswitch is >>>> available just in case. >>>> >>>> >>>> Debuggability >>>> >>>> No special DevTools support is required. >>>> >>>> >>>> Will this feature be supported on all six Blink platforms (Windows, >>>> Mac, Linux, Chrome OS, Android, and Android WebView)?Yes >>>> >>>> Is this feature fully tested by web-platform-tests >>>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> >>>> ?Yes >>>> >>>> Flag name on chrome://flagsCloseWatcher >>>> >>>> Finch feature nameCloseWatcher >>>> >>>> Requires code in //chrome?False >>>> >>>> Tracking bughttps://bugs.chromium.org/p/chromium/issues/detail?id=117 >>>> 1318 >>>> >>>> Non-OSS dependencies >>>> >>>> Does the feature depend on any code or APIs outside the Chromium open >>>> source repository and its open-source dependencies to function? >>>> No. >>>> >>>> Sample links >>>> https://close-watcher-demo.glitch.me >>>> >>>> Estimated milestonesShipping on desktop119DevTrial on desktop97Shipping >>>> on Android119DevTrial on Android97Shipping on WebView119 >>>> >>>> Anticipated spec changes >>>> >>>> Open questions about a feature may be a source of future web compat or >>>> interop issues. Please list open issues (e.g. links to known github issues >>>> in the project for the feature specification) whose resolution may >>>> introduce web compat/interop risk (e.g., changing to naming or structure of >>>> the API in a non-backward-compatible way). >>>> None. >>>> >>>> Link to entry on the Chrome Platform Statushttps://chromestatus.com/ >>>> feature/4722261258928128 >>>> >>>> Links to previous Intent discussionsIntent to prototype: >>>> https://groups.google.com/a/chromium.org/g/blink-dev/c/NA5NC16OmsU >>>> >>>> This intent message was generated by Chrome Platform Status >>>> <https://chromestatus.com/>. >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "blink-dev" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to blink-dev+unsubscr...@chromium.org. >>>> To view this discussion on the web visit https://groups.google.com/a/ >>>> chromium.org/d/msgid/blink-dev/CAM0wra-SULEU6D-HmDDuf% >>>> 3D5T9faNVk_LcqjKxY%3Do%3Du-vqTzaag%40mail.gmail.com >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra-SULEU6D-HmDDuf%3D5T9faNVk_LcqjKxY%3Do%3Du-vqTzaag%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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