Stefan, this was just for "non-zero delay" timers? Are there still
potential issues there?
On Fri, Aug 5, 2022 at 1:19 PM Stefan Zager <sza...@chromium.org> wrote:
> This is a common programming pattern:
>
> requestAnimationFrame(() => {
> setTimeout(() => {
> // At this point, it's very likely that layout is clean,
> // because we *just* completed a rendering update.
> // Queries of layout information are very unlikely to
> // trigger a forced layout.
> document.body.offsetTop;
> });
> });
>
> Aligning timers will make this strategy for avoiding forced layout less
> effective, because other non-timer tasks may run ahead of the setTimeout
> and invalidate layout.
>
> Also: the rAF(setTimeout()) construct is used extensively in chromium's
> test corpus, to schedule work ASAP after a rendering update. Many of our
> tests use a synchronous compositor: rendering updates happen without delay
> whenever there are no other tasks ready to run. In other tests, we increase
> the frequency of rendering updates from 60Hz to 200Hz, just because we know
> there won't be any long-running tasks and we want the tests to run faster.
>
> So... I see potential issues here.
>
> On Wed, Aug 3, 2022 at 6:50 AM Etienne Pierre-doray <etien...@chromium.org>
> wrote:
>
>> etien...@chromium.org
>>
>> ExplainerNone
>>
>> Specification
>> https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html
>>
>> Design docs
>>
>> https://docs.google.com/document/d/1OjZoHNvn_vz6bhyww68B_KZBi6_s5arT8xMupuNEnDM/edit
>>
>> Summary
>>
>> Run all timers (with a few exceptions) with a non-zero delay on a regular
>> 8ms aligned wake up (125 Hz), instead of as soon as their delay has passed.
>> This affect DOM timers; On foreground pages, run DOM timers with a non-zero
>> delay on a regular 8ms aligned wake up, instead of as soon as their delay
>> has passed. On background pages, DOM timers already run on a regular 1s
>> aligned wake up (1 Hz), or even less frequently after 5 minutes.
>>
>>
>> Blink componentBlink>Scheduling
>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EScheduling>
>>
>> TAG review
>>
>> TAG review statusNot applicable
>>
>> Risks
>>
>>
>> Interoperability and Compatibility
>>
>> This feature changes the behavior of an existing API in a way that is
>> spec-compliant (the spec says "Optionally, wait a further
>> implementation-defined length of time", ref.:
>> https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html#run-steps-after-a-timeout).
>> Content that relies on precise timing for DOM Timers may stop working
>> properly in Chromium with this feature. The risk is mitigated by delaying
>> DOM Timers by at most 8 ms, and by disabling the feature when WebRTC has
>> active connections in the process. Content that cannot support a 8 ms delay
>> would probably be better served by alternative APIs described at
>> https://developer.chrome.com/blog/timer-throttling-in-chrome-88/#workarounds.
>> Due to the significant battery savings that come with this feature, we
>> expect that most browsers will decide to implement it after some time.
>>
>>
>> *Gecko*: No signal
>>
>> *WebKit*: No signal
>>
>> *Web developers*: No signals
>>
>> *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?
>>
>>
>>
>> Goals for experimentation
>>
>> Gain insight on potential compatibility issues and evaluate impact on
>> guardian metrics (page load, latency).
>>
>>
>> Reason this experiment is being extended
>>
>>
>>
>> Ongoing technical constraints
>>
>>
>>
>> Debuggability
>>
>> This changes the behavior of an existing API. No new debugging support is
>> added.
>>
>>
>> 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>
>> ?No
>>
>> DevTrial instructions
>> https://github.com/eti-p-doray/align-wakeups/blob/main/HOWTO.md
>>
>> Flag namealign-wakeups
>>
>> Requires code in //chrome?False
>>
>> Tracking bughttps://crbug.com/1153139
>>
>> Estimated milestones
>> OriginTrial desktop last 105
>> OriginTrial desktop first 105
>> DevTrial on desktop 105
>> OriginTrial Android last 105
>> OriginTrial Android first 105
>> DevTrial on Android 105
>> OriginTrial webView last 105
>> OriginTrial webView first 105We plan to do a 1% Stable experiment for
>> M105 stable.
>>
>> Link to entry on the Chrome Platform Status
>> https://chromestatus.com/feature/5680188671655936
>>
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>>
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