LGTM2
On 4/7/23 11:34 AM, Yoav Weiss wrote:
LGTM1
On Thu, Apr 6, 2023 at 2:01 AM Chris Harrelson <chris...@chromium.org>
wrote:
Contact emails
chris...@chromium.org
Specification
https://drafts.csswg.org/css-overflow-3/#valdef-overflow-auto
Summary
Removes the overflow:overlay scrolling mode, and makes
overlay a legacy alias of auto. overflow:overlay is the
same as overflow:auto, except that it does not prevent
content from extending into the scrollbar gutter, in cases
where non-overlay OS scrollbars are present. (If overlay
scrollbars are present, there is no effect.) Example: With
overflow:overlay: https://output.jsbin.com/yujenuq/quiet
With overflow:auto: https://output.jsbin.com/ruzogaf/quiet
Blink component
Blink>Scroll
<https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EScroll>
TAG review
None
TAG review status
Not applicable
Risks
Interoperability and Compatibility
Developers currently relying on content overlapping the
scrollbar gutter would instead see some additional line
wrapping. Users, on the other hand, would be able to see
more content that is currently invisible underneath a
scrollbar. On platform configurations with overlay
scrollbars in the OS, this change has no effect; it only
applies to situations where a non-overlay scrollbar is
configured by the browser. Use counter:
https://chromestatus.com/metrics/feature/timeline/popularity/2995
Adoption is more than 2% of page loads. However: * I don't
think any sites will break for users. * Some sites will
improve because they are currently preventing users from
seeing some content that is accidentally underneath a
non-overlay scrollbar. * Interop will be achieved with
Webkit and Gecko. I reviewed
<https://docs.google.com/document/d/1KA-eavI44Vc6WTDDlAKvUfv7x2BThTeEY9-bw69Jj2Q/edit#>
20 sites listed from the HTTPArchive and found nothing
broken. The only "downside" was that the visible spacing
between content and the scrollbar increased by a few
pixels in some cases. In none of these cases was it a
significant change to the user experience. On two of the
sites, -webkit-scrollbar was also used to make the
scrollbar narrower when not hovered, in conjunction with
overflow:overlay to reduce the gutter spacing. On those
sites, the gutter got a bit wider but the user experience
was not materially affected.
/Gecko/: Shipped/Shipping
(https://github.com/mozilla/standards-positions/issues/768)
/WebKit/: Shipped/Shipping
(https://github.com/WebKit/standards-positions/issues/157)
/Web developers/: No signals
/Other signals/:
Ergonomics
After this change, sites will no longer be able to avoid
reserving space for the scrollbar. However, this is good,
because the scrollbar does take up space and it's bad for
users not to be able to read content obscured by it. The
CSSWG has in the past considered all of this and resolved
not to let developers prevent a scrollbar gutter, because
overlay scrollbars are an OS feature, and it's more
important for users to see content than for developers to
micro-manage an important user affordance. See
https://github.com/w3c/csswg-drafts/issues/4501 for
example. I found three use cases developers seemed to want
to achieve on these sites: * Reduce scrollbar gutter size
* "force" overlay scrollbars (there is no way to do that,
but overflow:overlay might lead them to that conclusion) *
Reduce the gutter when used in conjunction with a custom
scrollbar via -webkit-scrollbar that reduces its width
when not hovered. Use case 3 is better solved by shipping
scrollbar-width in the future
(https://developer.mozilla.org/en-US/docs/Web/CSS/scrollbar-width)
Activation
None
Security
None
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
Sites might not know why their line wrapping changed to
exclude the scrollbar gutter. However, this is the
existing behavior in Firefox and Safari, so they would get
interop by default.
Will this feature be supported on all six Blink platforms
(Windows, Mac, Linux, Chrome OS, Android, and Android
WebView)?
Yes
N/A
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/css/css-overflow/overflow-overlay.html?label=experimental&label=master&aligned>
Flag name
OverflowOverlayAliasesAuto
Requires code in //chrome?
False
Tracking bug
https://bugs.chromium.org/p/chromium/issues/detail?id=554361
Sample links
https://output.jsbin.com/yujenuq/quiet
https://output.jsbin.com/ruzogaf/quiet
Estimated milestones
Shipping on desktop 114
DevTrial on desktop 114
Shipping on Android 114
DevTrial on Android 114
Shipping on WebView 114
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/5194091479957504
Links to previous Intent discussions
Intent to prototype:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAOMQ%2Bw-F4mOhUMuU3nw423C8CurZKX_wxQvXRPv-XT4Zhsm-XQ%40mail.gmail.com
This intent message was generated by Chrome Platform
Status <https://chromestatus.com/>.
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