LGTM to extend for 3 additional months/milestones (150 to 152
inclusive). But see below on the question of the spec PR.
On 5/19/26 3:19 p.m., Florin Malita wrote:
Thanks Vlad and Mike!
Replies inline.
On Tue, May 19, 2026 at 10:47 AM Vladimir Levin <[email protected]>
wrote:
On Mon, May 18, 2026 at 5:55 PM Mike Taylor
<[email protected]> wrote:
On 5/18/26 4:11 p.m., Florin Malita wrote:
*Contact emails*
[email protected], [email protected],
[email protected], [email protected]
*Explainer*
https://github.com/fserb/canvas2D/blob/master/spec/enhanced-textmetrics.md
https://github.com/Igalia/explainers/blob/main/canvas-formatted-text/text-metrics-additions.md
https://github.com/whatwg/html/issues/10677
*Specification*
https://github.com/whatwg/html/pull/11000
*Summary*
Expand the TextMetrics Canvas API to support selection
rectangles, bounding box queries, and glyph cluster-based
operations. This new functionality should enable complex text
editing applications with accurate selection, caret
positioning, and hit testing. Additionally, cluster-based
rendering facilitates sophisticated text effects such as
independent character animations and styling.
*Blink component*
Blink>Canvas
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECanvas%22>
*Web Feature ID*
/No information provided/
*TAG review*
https://github.com/w3ctag/design-reviews/issues/1095
*TAG review status*
Pending
*Origin Trial Name*
Enhanced Canvas TextMetrics
*Goals for experimentation*
Partners have implemented prototypes based on the available
runtime feature, with positive feedback. They are now
interested in expanding the scope, and testing the API with
real users. This experiment will provide valuable validation
in real-world use scenarios, and should help us gauge the
proposed API's fitness, ergonomics, and performance.
Can you also comment on progress in the following areas?
Draft spec (early draft is ok, but must be spec-like and
associated with the appropriate standardization venue, or WICG)
Just to add to Mike's question here, the last activity on this
HTML PR https://github.com/whatwg/html/pull/11000 seems to be from
roughly a year ago. Is this still under active discussion?
(Similar activity on https://github.com/whatwg/html/issues/10677)
The spec PR needs a couple of minor updates based on TAG feedback.
Beyond that, it is pending review and agreement on
https://github.com/whatwg/html/issues/10677. The main friction point
is the proposal
<https://github.com/whatwg/html/issues/10677#issuecomment-2787797845>
to significantly increase scope by exposing intermediate text shaping
stages and related info. We maintain that this is non-critical for
current use cases and can be deferred. schenney@ is engaging with
Apple engineers to reach a resolution.
Thanks - but please make progress here, one way or another. API OWNERs
are unlikely to approve another extension without spec progress and
instead encourage you to just ship the current shape at the end of the
OT. From my POV, you received feedback from Apple
<https://github.com/whatwg/html/issues/10677#issuecomment-2787797845> and
haven't had any responses in over 1 year when attempting to engage with
the feedback. If conversations and progress are happening in other
venues - that's great (and my apologies for missing it).
TAG review (see exceptions)
The TAG review offered some great feedback. One major focus was
accessibility, where the group’s position is to encourage more
accessible alternatives instead of expanding canvas APIs (which are
generally lacking). We discussed several alternatives, but
unfortunately none of them fulfill the low-level requirements we set
to solve with TextClusters. The upcoming HTML-in-Canvas should
address some of the general Canvas accessibility issues, and is a good
complement to Enhanced TextMetrics (an incremental Canvas API
extension focusing on low-level text rendering capabilities).
Tangentially, TAG and WHATWG feedback also led to the implementation
of language and text writing mode support for Canvas, which is tracked
through separate intents.
signals requests
Apple engineers were involved in the initial discussions. schenney@ is
reaching out to re-engage.
Outreach for feedback from the spec community
Feedback has been collected primarily through the spec PR and
associated discussions. Notably, Igalia/schenney@ have published blog
posts and explainers to socialise the proposal:
https://blogs.igalia.com/schenney/canvas-text-editing/
https://github.com/Igalia/explainers/blob/main/canvas-formatted-text/text-metrics-additions.md
WPT tests
WPT tests have been merged upstream as 'tentative' pending the
finalization of the spec:
https://wpt.fyi/results/html/canvas/offscreen/text?label=master&label=experimental&aligned&q=tentative
<https://wpt.fyi/results/html/canvas/offscreen/text?label=master&label=experimental&aligned&q=tentative>
*Chromium Trial Name*
ExtendedTextMetrics
*Origin Trial documentation link*
https://github.com/Igalia/explainers/blob/main/canvas-formatted-text/text-metrics-additions.md
*WebFeature UseCounter name*
kExtendedTextMetrics
*Risks*
*Interoperability and Compatibility*
These are new features and we will get vendor agreement at
WHATWG before shipping. So minimal interop risks beyond
platform-specific metrics differences.
/Gecko/: No
signal (https://github.com/mozilla/standards-positions/issues/1144)
/WebKit/: No
signal (https://github.com/WebKit/standards-positions/issues/436)
/Web developers/: Positive Developers want the ability to
animated glyphs independendly (such as exploding sentences)
and the ability to do e.g. selection on canvas text. The
proposed APIs support these use cases and more.
/Other signals/:
*Ergonomics*
None.
*Activation*
None.
*Security*
There is always a fingerprinting concern with HTML canvas.
THe new features expose no novel fingerprinting surface (text
metrics are already a fingerprinting concern).
*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/
*Reason this experiment is being extended*
Flutter Web has provided positive initial feedback based on
internal testing. To validate the feature at scale, they
require additional time to expose it to external developers
via their own experimentation infrastructure.
The goal of this extension is to gather telemetry and
feedback from real-world applications, allowing us to
identify and address any remaining rough edges before
proceeding with a formal launch.
*Ongoing technical constraints*
/No information provided/
*Debuggability*
DevTools supports querying the APIs by default.
*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>?*
Yes
html/canvas/[element|offscreen]/text...
2d.text.measure.index-from-offset*
2d.text.measure.selection-rects*
2d.text.measure.text-clusters*
https://wpt.fyi/results/html/canvas/element/text?label=master&label=experimental&aligned&q=tentative
<https://wpt.fyi/results/html/canvas/element/text?label=master&label=experimental&aligned&q=tentative>https://wpt.fyi/results/html/canvas/offscreen/text?label=master&label=experimental&aligned&q=tentative
<https://wpt.fyi/results/html/canvas/offscreen/text?label=master&label=experimental&aligned&q=tentative>
I see there are some tests that pass in all browsers - that
suggests the test isn't working as intended?
e.g.,
https://wpt.fyi/results/html/canvas/offscreen/text/2d.text.measure.strokeTextCluster-font-change.tentative.html?label=master&label=experimental&aligned&q=tentative
<https://wpt.fyi/results/html/canvas/offscreen/text/2d.text.measure.strokeTextCluster-font-change.tentative.html?label=master&label=experimental&aligned&q=tentative>
Thanks, agreed, that's unexpected. I filed a bug
<https://issues.chromium.org/issues/514632337> to investigate.
*Flag name on about://flags*
Experimental Web Platform Features
*Finch feature name*
ExtendedTextMetrics
*Requires code in //chrome?*
False
*Tracking bug*
https://issues.chromium.org/issues/341213359
*Measurement*
UMA counters will be added for the new APIs.
*Estimated milestones*
Origin trial desktop first 144
Origin trial desktop last 149
Origin trial extension 1 end milestone 155
DevTrial on desktop 141
Origin trial Android first 144
Origin trial Android last 149
DevTrial on Android 141
*Link to entry on the Chrome Platform Status*
https://chromestatus.com/feature/5075532483657728?gate=5178855770947584
*Links to previous Intent discussions*
Intent to Prototype:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CADgYMVdqo4PBs4OkGqVncRizs8vtX4YtFLDcK%2BRxdYo_wnaRJQ%40mail.gmail.com
Ready for Trial:
https://groups.google.com/a/chromium.org/g/blink-dev/c/OLCCI0ExvIk
Intent to Experiment:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CADgYMVfC-Naw8pFVaUUPMSfW-u3kC7SMdDeHJgwU5YmSHOOeeA%40mail.gmail.com
This intent message was generated by Chrome Platform Status
<https://chromestatus.com/>.
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