Yes, on top of. startTime is defined in terms of renderTime which is now defined in terms of paint/presentation times.
So this just exposes the individual values that were already used for the calculations. On Wednesday, December 3, 2025 at 10:51:35 AM UTC-5 Yoav Weiss wrote: > I should know this but do I understand correctly and this is adding > `paintTime` and `presentationTime` *on top* of existing attributes such as > `renderTime`/`startTime`/etc? > > On Thursday, November 27, 2025 at 11:49:01 AM UTC+1 Chromestatus wrote: > >> *Contact emails* >> [email protected], [email protected] >> >> *Explainer* >> https://github.com/w3c/paint-timing/blob/main/presentation-timestamps.md >> >> *Specification* >> https://w3c.github.io/paint-timing/#painttimingmixin >> >> *Summary* >> Expose "paintTime" and "presentationTime" in element timing, LCP, long >> animation frames, and paint timing. "paintTime" means the time when the >> rendering phase ended and the browser started the paint phase. >> "presentationTime" means the time when the "pixels reached the screen", >> which is somewhat implementation-defined. This feature entry omits event >> timing, which would be done separately. >> >> *Blink component* >> Blink>PerformanceAPIs >> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EPerformanceAPIs%22> >> >> *Web Feature ID* >> performancetiming <https://webstatus.dev/features/performancetiming> >> >> *Motivation* >> So far the spec defined the paint time as the time after the "rendering >> update", when the document hands over rendering to the UA. However, in >> chromium the exposed paint time (in event timing, element timing, LCP and >> paint-timing) was different - the approximated VSync time from the >> compositor, which is important in terms of UX. This created confusion and >> incompatibility This proposal defines both these timestamps, and exposes >> them in an identical way in all the relevant entries. >> >> *Initial public proposal* >> https://github.com/w3c/paint-timing/issues/62 >> >> *TAG review* >> https://github.com/w3ctag/design-reviews/issues/1013 >> >> *TAG review status* >> Pending >> >> *Risks* >> >> >> *Interoperability and Compatibility* >> *No information provided* >> >> *Gecko*: Positive ( >> https://github.com/mozilla/standards-positions/issues/1110) Firefox >> folks took part of the WebPerfWG meeting where this was discussed/resolved. >> >> *WebKit*: In development ( >> https://github.com/WebKit/standards-positions/issues/426) >> >> *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? >> *No information provided* >> >> >> *Debuggability* >> *No information provided* >> >> *Will this feature be supported on all six Blink platforms (Windows, Mac, >> Linux, ChromeOS, 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 >> >> >> *Flag name on about://flags* >> *No information provided* >> >> *Finch feature name* >> PaintTimingMixin >> >> *Rollout plan* >> Will ship enabled for all users >> >> *Requires code in //chrome?* >> False >> >> *Tracking bug* >> https://issues.chromium.org/issues/378827535 >> >> *Estimated milestones* >> Shipping on desktop 144 >> Shipping on Android 144 >> Shipping on WebView 144 >> >> *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. This is already part of interop 2025. Note that the TAG review was >> delayed because some things in the explainer were missing initially. >> >> *Link to entry on the Chrome Platform Status* >> https://chromestatus.com/feature/5162859838046208?gate=5137700305502208 >> >> *Links to previous Intent discussions* >> Intent to Prototype: >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/67347e70.2b0a0220.3644d.01e9.GAE%40google.com >> >> >> 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 [email protected]. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/af7e59c1-fcdd-4452-ac61-1778a5d03b2cn%40chromium.org.
