> I assume cancelling the mousedown (but not the mousemove) still prevents selection and drag-and-drop in all browsers, is that right? That's the pattern I'd expect is most common. Also, what's the behavior of pointermove for mice today and after this change?
I just confirmed <https://codepen.io/mustaqahmed/full/wvNYGEP> that Chrome (and Firefox and Safari too) already prevents both selection and drag-and-drop when mousedown or pointerdown is cancelled. So sites canceling all the mouse events will work fine. > We have landed a metric which specifically checks for cases where the mousemove is preventDefaulted but a selection starts (i.e. selectstart wasn't prevented, there was no user-select: none, and so the selection does change). Right now this is a UMA but we could also add UKM and get sites from this. Mustaq WDYT about adding UKM for this and running the 1% finch trial? Adding UKM and running a 1% finch trial sounds good. Perhaps we can run a Canary/Dev/Beta trial even now (on M121)? On Wed, Dec 6, 2023 at 12:34 PM Robert Flack <fla...@chromium.org> wrote: > On Wed, Dec 6, 2023 at 12:18 PM Rick Byers <rby...@chromium.org> wrote: > >> API owners met and discussed this one briefly today. There was agreement >> that more work needs to be done to demonstrate the compat risk is low >> enough to ship this breaking change. A few points: >> >> - If you'd like to do a finch trial to gather data (up to stable 1%) >> we're supportive of that. >> - Mike Taylor argued that you're not likely to learn too much useful >> from a finch trial since people seem not to report bugs for things that >> fail for a seemingly random 1% of their users, and perhaps the idea of >> surveying a few sites would be more effective at finding real breakage. Of >> course UKM + Finch might be a good way to find URLs to test. >> >> We have landed a metric which specifically checks for cases where the > mousemove is preventDefaulted but a selection starts (i.e. selectstart > wasn't prevented, there was no user-select: none, and so the selection does > change). Right now this is a UMA but we could also add UKM and get sites > from this. Mustaq WDYT about adding UKM for this and running the 1% finch > trial? > >> >> - Mike also argued that in his experience, he'd expect sites like >> mapping apps to have engine-specific conditional code around their event >> handling, so that increases the risk. >> - Philip and I discussed that if there is evidence of real breakage >> we can't accept, we should propose changing the spec here - it seems like >> it would be very reasonable if cancelling the first mousemove event in a >> sequence canceled text selection (just like cancelling the first touchmove >> prevents scrolling). But if we have reasonable evidence that it's >> non-breaking, we're happy to just align with WebKit and Gecko for improved >> interoperability. >> >> Agreed, though it may be breaking for other engines to change behavior > too though, right? E.g. we are in a similar situation with > overscroll-behavior on the root element (crbug.com/954423 > <https://bugs.chromium.org/p/chromium/issues/detail?id=954423&q=overscroll-behavior%20root&can=2>) > where changing either behavior to the other will have compat risk. > >> >> - All agreed we're willing to take some risk here to achieve interop >> quickly and don't want to impose too much of a burden of proof, especially >> since the severity of breakage is likely low. We just need some more >> evidence that the risk is manageable. >> >> Perhaps the most pragmatic path would be something like: >> >> 1. Survey at least 5 sites with mouse drag involving DOM and explain >> why they're unimpacted (cancelling mousedown? cancelling selectionstart? >> or >> just user-select: none?). If you find one that is indeed broken, revisit >> plan. >> 2. Work with the enterprise team on release notes & plan - i.e. >> either finch roll out with commitment to killswitch if we get reports of >> enterprise breakage, or add a policy knob opt-out >> 3. Go for 100% but be prepared to killswitch if there are non-trivial >> reports of breakage, then revisit with either a migration plan (outreach, >> blog post) or proposed spec change >> >> WDYT? >> > > This sounds reasonable. I think running the 1% experiment with the > targeted metric (cases where selection now happens when it didn't used to) > should help us gain confidence. > > Rick >> >> On Tue, Dec 5, 2023 at 3:42 PM Rick Byers <rby...@chromium.org> wrote: >> >>> Hey Mustaq, >>> Thanks for pushing to get this long-time interop issue addressed! I >>> assume cancelling the mousedown (but not the mousemove) still prevents >>> selection and drag-and-drop in all browsers, is that right? That's the >>> pattern I'd expect is most common. Also, what's the behavior of pointermove >>> for mice today and after this change? >>> >>> What's your plan for if the UseCounter comes back high? FWIW, I'm >>> betting that it will. First I expect it'll be common for sites to >>> cancel all the mouse events. If my understanding above is correct, then >>> perhaps you want to exclude those from your UseCounter since the behavior >>> won't change in those cases? But secondly, given past history with some >>> major sites, I suspect there might be a long tail of sites that are lightly >>> broken here. Maybe worth doing a finch-based rollout to mitigate the risk? >>> I'd support going up to stable 1% now to see if we learn of any issues. I'm >>> particularly worried about enterprise (LOB) apps which are often >>> chromium-only. We'll see what Enterprise review says on the launch, but >>> they might want >>> <https://www.chromium.org/developers/enterprise-changes/> a mention in >>> the release notes and a policy opt-out. Then again perhaps since the >>> breakage is likely to be rare and cosmetic, just doing a finch-based >>> roll-out (and hitting a finch killswitch on reports of any issues) should >>> be enough to mitigate the risk. >>> >>> You might also consider enabling UKM support >>> <https://source.chromium.org/chromium/chromium/src/+/main:components/page_load_metrics/browser/observers/use_counter/ukm_features.cc?q=ukm_features&ss=chromium> >>> for >>> your UseCounter to get some sample URLs, though again I'd worry you might >>> get lots of hits but not be able to easily reproduce any obvious breakage. >>> Alternately it might be most useful to just spot check 5-10 major sites >>> which have mouse dragging behavior with DOM (not just canvas) and catalog >>> how they avoid getting unintended selection (eg. do they cancel selectstart >>> or use user-select: none). I think mapping sites are an obvious example, >>> gmail has some message dragging behavior I think, not sure what else. >>> >>> Rick >>> >>> On Mon, Dec 4, 2023 at 2:35 PM Mustaq Ahmed <mus...@chromium.org> wrote: >>> >>>> Contact emailsmus...@chromium.org, fla...@chromium.org >>>> >>>> ExplainerNone >>>> >>>> Specificationhttps://w3c.github.io/uievents/#event-type-mousemove >>>> >>>> Summary >>>> >>>> Canceling mousemove will not prevent text selection or drag-and-drop. >>>> Chrome allowed cancelling mousemove events to prevent other APIs like text >>>> selection (and even drag-and-drop in the past). This does not match other >>>> major browsers; nor does it conform to the UI Event spec: >>>> https://w3c.github.io/uievents/#event-type-mousemove Through this >>>> feature, the default-action of mousemove becomes none. Text selection and >>>> drag-and-drop can still be prevented through cancelling selectstart and >>>> dragstart events respectively, which are spec compliant and fully >>>> interoperable. >>>> >>>> >>>> Blink componentBlink>Input >>>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EInput> >>>> >>>> TAG reviewNone >>>> >>>> TAG review statusNot applicable >>>> >>>> Risks >>>> >>>> >>>> Interoperability and Compatibility >>>> >>>> This feature will make Chrome fully interoperable. Chrome is currently >>>> failing the corresponding WPT (a part of Interop 2023) while both Mozilla >>>> and WebKit have started passing the WPT recently. There is a bit of compat >>>> risk. We attempted it twice in the past but had to revert for two different >>>> reasons: in 2014 we faced a text-selection regression >>>> https://crbug.com/485892 on an app that no longer shows the problem >>>> (because app event handling changed), then in 2018 we faced a drag-and-drop >>>> regression https://crbug.com/878392 that is irrelevant now (because >>>> Chrome drag-and-drop changed). For our current attempt the risk from >>>> text-selection remains, and we need to expose the feature to be able to >>>> assess the risk. We have added a use-counter and turned on the feature as >>>> "experimental" on M121 to observe field data before shipping it. >>>> >>>> >>>> *Gecko*: Shipped/Shipping ( >>>> https://bugzilla.mozilla.org/show_bug.cgi?id=1823663) >>>> >>>> *WebKit*: Shipped/Shipping ( >>>> https://bugs.webkit.org/show_bug.cgi?id=262878) >>>> >>>> *Web developers*: Positive (https://crbug.com/346473#c6) >>>> >>>> *Other signals*: >>>> >>>> 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? >>>> >>>> None >>>> >>>> >>>> Debuggability >>>> >>>> None >>>> >>>> >>>> Will this feature be supported on all six Blink platforms (Windows, >>>> Mac, Linux, ChromeOS, Android, and Android WebView)?No >>>> >>>> Is this feature fully tested by web-platform-tests >>>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> >>>> ?Yes >>>> >>>> >>>> https://wpt.fyi/results/uievents/mouse/mousemove_prevent_default_action.tentative.html?label=experimental&label=master&aligned >>>> >>>> >>>> Flag name on chrome://flagsNone >>>> >>>> Finch feature nameMouseDragOnCancelledMouseMove >>>> >>>> Requires code in //chrome?False >>>> >>>> Tracking bughttps://crbug.com/346473 >>>> >>>> MeasurementWe have added the use-counter >>>> kMouseDragOnCancelledMouseMove to track possible regressions in the wild. >>>> >>>> Sample links >>>> https://codepen.io/mustaqahmed/full/wvNYGEP >>>> >>>> Estimated milestones >>>> Shipping on desktop 122 >>>> Shipping on Android 122 >>>> Shipping on WebView 122 >>>> >>>> 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 Status >>>> https://chromestatus.com/feature/5145305056280576 >>>> >>>> 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/CAB0cuO7reN%2B6Wb_N99jNm_aJY7fhhQ1ncCrh_J_%2BFCLdASm0eg%40mail.gmail.com >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAB0cuO7reN%2B6Wb_N99jNm_aJY7fhhQ1ncCrh_J_%2BFCLdASm0eg%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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