September 2020 - webkit-dev - lists.webkit.org

Request for position on @font-face descriptors ascent/descent/line-gap-override to override font metrics
by Xiaocheng Hu 23 Sep '20

23 Sep '20

Hi webkit-dev, I'd like to request an official position on @font-face descriptors `ascent-override`, `descent-override` and `line-gap-override` for overriding the default font metrics. Explainer: https://gist.github.com/xiaochengh/da1fa52648d6184fd8022d7134c168c1 Spec: https://drafts.csswg.org/css-fonts-4/#font-metrics-override-desc Chromestatus: https://www.chromestatus.com/feature/5651198621253632 Other information: These descriptors are newly added into CSS Fonts Level [1], following a recent resolution [2]. Chromium has already implemented them in M86 behind a flag [3]. [1] https://github.com/w3c/csswg-drafts/pull/5521 [2] https://github.com/w3c/csswg-drafts/issues/4792#issuecomment-693528301 [3] https://chromium-review.googlesource.com/q/hashtag:%22font-metrics-override… Thanks, Xiaocheng

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Requesting a position on Document Policy
by Ian Clelland 22 Sep '20

22 Sep '20

Hi WebKit! I'm building out the infrastructure in Blink for Document Policy, and would like to ship at least part of it in Chrome for developers to take advantage of. I'd like to get an official position from WebKit leads on this. I'm also interested in getting thoughts from other WebKit folks about the design or implementation. Some details: Document Policy explainer: https://github.com/w3c/webappsec-permissions-policy/blob/master/document-po… Document Policy spec: https://w3c.github.io/webappsec-permissions-policy/document-policy.html GitHub Repository (shared with Permissions Policy (previously Feature Policy)): https://github.com/w3c/webappsec-permissions-policy Blink intent-to-ship discussion: https://groups.google.com/a/chromium.org/g/blink-dev/c/Za159T1QOek/m/lewQUF… Also previously discussed at the TAG: https://github.com/w3ctag/design-reviews/issues/408 I think that the last time I brought this to WebKit engineers would have been at TPAC last year, where it was discussed in the WebAppSec meetings as a way to provide a general configuration mechanism for documents, splitting off of ideas that had been floating around at the time for Feature Policy. While Document Policy itself doesn't prescribe any actual features, it could eventually be used to configure the behaviour of different web-platform features, such as: - Restricting the use of poorly-performing images - Disabling slow synchronous JS APIs - Configuring frame, image, or script loading styles - Restricting overall document sizes or network usage - Restricting patterns which cause page re-layout The initial intent, though, is to ship part of this in Chrome to support an opt-out for the Scroll-to-text-fragment feature. Document Policy has two different mechanisms which can work in conjunction with each other: The first is the Document-Policy (and Document-Policy-Report-Only) HTTP header, which just sets the policy on the document it ships with. The other is a negotiation mechanism between an embedder and its embedded content, which uses an Iframe attribute and an additional request header. I'm currently interested in shipping just the first of these mechanisms in Chrome. The second may warrant more discussion and review, and isn't needed for the Scroll-to-text-fragment opt-out. The details are in the Chrome Platform Status entry: https://www.chromestatus.com/feature/5756689661820928 Feel free to ask any questions; I'm happy to discuss this in whatever forum works best for folks, Thanks! Ian

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Request for position on the aspect-ratio CSS property
by Christian Biesinger 22 Sep '20

22 Sep '20

Hello, I'd like to request an official position the aspect-ratio CSS property, as both Gecko and Blink are currently implementing it, and ideally we'd like to ship it soonish. https://drafts.csswg.org/css-sizing-4/#aspect-ratio https://docs.google.com/document/d/1VqD0mfkIDyCxQBrrvDw5wEbhXBsmEYIhk6ahiX_… Thanks, Christian

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Could use some help from people who care about the WinCairo port
by Darin Adler 13 Sep '20

13 Sep '20

The patch for this bug https://bugs.webkit.org/show_bug.cgi?id=216428 <https://bugs.webkit.org/show_bug.cgi?id=216428> is failing to build on WinCairo because of some kind of precompiled header problem. I could use some help figuring out what I did wrong. — Darin

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Request for position on Heavy Ad Intervention
by John Delaney 09 Sep '20

09 Sep '20

Hi webkit-dev, I'd like to request an official position on the Heavy Ad Intervention. Explainer: https://github.com/johnivdel/heavy-ad-intervention/blob/master/README.md WICG/Interventions Issue: https://github.com/WICG/interventions/issues/68 HTML Spec PR: https://github.com/whatwg/html/pull/5885 Chromestatus: https://www.chromestatus.com/feature/4800491902992384 Other information: This is a browser intervention which unloads ads that use an egregious amount of system resources. While we aren't proposing a full spec for this intervention, we are proposing an update to the HTML spec which allows user agents to unload iframes/embeds at will. Any feedback is appreciated. Thanks, John

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EWS now cq- the patches with build or layout test failure
by Aakash Jain 09 Sep '20

09 Sep '20

Hi All, From now on, whenever EWS detects any build failure or layout test failure caused by a patch, it will mark the patch cq-. If the patch was in commit queue at the time it was marked cq-, commit queue would not land it. You can always mark the patch cq+ again (if you think that EWS was incorrect), and commit queue would land the patch. Reference: https://bugs.webkit.org/show_bug.cgi?id=214194 Please let me know if you notice any issue or have any feedback. Thanks Aakash

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PSA: Bit fields won't be packed on Windows if you mix types
by Ryosuke Niwa 04 Sep '20

04 Sep '20

Hi, Unlike gcc and clang, MSVC pads each consecutive member variables of the same type in bitfields. e.g. if you have: struct AB { unsigned m_1 : 31; bool m_2 : 1; } then *MSVC pads m_1 and allocates sizeof(unsigned) * 2 for AB* whereas gcc and clang only allocate sizeof(unsigned) * 1 for AB. This is *not a compiler bug*. It's a spec. compliant behavior, and may in fact have a better run-time performance in some situations. However, for core objects like RenderObject and InlineBox, allocating extra 4-8 bytes per each object is prohibitory expensive. In such cases, please *use the same POD type for all bitfield member variables*. (Storage class classifiers and variable qualifiers seem to have no effect on how variables are packed; e.g. mutable, const, etc...). For example, MSVC will allocate sizeof(unsigned) * 1 for AB if we rewrite the above code as: struct AB { unsigned m_1 : 31; unsigned m_2 : 1; } When you're making this change, *be sure to audit all code that assigns a non-boolean value to m_2* because implicit type coercion into boolean is no longer in effect. For example, AB ab; ab.m_2 = 2; puts(ab.m_2 ? "true" : "false"); will print "true" before the change and will print "false" after the change. An easy way to ensure you've audited all such code is to add getters and setters for all bitfield member variables or wrap them in a special structure or class as done in http://trac.webkit.org/changeset/103353 and http://trac.webkit.org/changeset/104254. Best regards, Ryosuke Niwa Software Engineer Google Inc.

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PSA: Flatpak WPE/GTK SDK upgrade to version 0.3
by Philippe Normand 02 Sep '20

02 Sep '20

Hi, This mail is mostly for WPE/GTK port developers. Feel free to skip if you're not part of that group. In r266455[0] the SDK build definitions were updated along with a major upgrade to the FDO SDK version 20.08. Compared with 19.08, this new version breaks ABI, that means applications built for 19.08 will not work in 20.08 and need to be rebuilt. So if you are working with the GTK and/or WPE ports and using the Flatpak SDK, you will need to remove your local build directories after this patch lands: https://bugs.webkit.org/show_bug.cgi?id=216073 Additionally, you will need to run `Tools/Scripts/update-webkitgtk- libs` or `Tools/Scripts/update-webkitwpe-libs` so that version 0.3 is locally installed on your workstation. We plan to land this patch soon, during the early European morning, in order to avoid major service disruption on the bots and EWS. Philippe [0] https://trac.webkit.org/r266455

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Request for position on hasDroppedEntry in PerformanceObserverCallback
by Nicolás Peña 01 Sep '20

01 Sep '20

Hi, We'd like to request an official position on a very small addition to PerformanceTimeline specification. We've added a hasDroppedEntry parameter to PerformanceObserverCallback, which is in https://w3c.github.io/performance-timeline/#the-performanceobserver-interfa…, and logic for it in https://w3c.github.io/performance-timeline/#queue-the-performanceobserver-t…. It lets a developer know when an entry has been dropped from a buffer that the PerformanceObserver cares about. We reached this solution when discussing https://github.com/w3c/performance-timeline/issues/169 in a WebPerf WG call.

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