layout: Consider Text as LCP candidate by shubhamg13 · Pull Request #47212 · servo/servo

shubhamg13 · 2026-08-13T08:31:32Z

Since the spec says, for text nodes we need to do union of border box per element.

Adding containing_element_tag for making this union.
Adding TextRecord to store TextNodes related to an Element.

Note: Please view using Hide whitespace option.

Testing: More WPT Passed

Added a specific test to verify union logic of rect - size calculation is correct in WPT
- tests/wpt/tests/largest-contentful-paint/text-fragment-union.html- Added a test for LCP text fragment union. web-platform-tests/wpt#61873
- (TODO: set loadTime to zero for text, other failing tests will also pass loadTime inconsistent in LargestContentfulPaint #47315)

Fixes: Part of #42000

servo-wpt-sync · 2026-08-13T08:36:13Z

🤖 Opened new upstream WPT pull request (web-platform-tests/wpt#61911) with upstreamable changes.

servo-wpt-sync · 2026-08-13T08:50:50Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

servo-wpt-sync · 2026-08-13T09:10:40Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

Adding a struct `PendingImageRecord`. Add complimentary `W3C` spec steps. Pre-requisite for servo#47212 Testing: WPT Unchanged. Fixes: Part of servo#42000 --------- Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com> Signed-off-by: Shubham Gupta <shubham.gupta@chromium.org>

servo-wpt-sync · 2026-08-17T07:32:25Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

servo-wpt-sync · 2026-08-17T07:35:57Z

✍ Updated existing upstream WPT pull request (web-platform-tests/wpt#61911) title and body.

servo-wpt-sync · 2026-08-17T07:53:46Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

servo-wpt-sync · 2026-08-17T07:58:19Z

✍ Updated existing upstream WPT pull request (web-platform-tests/wpt#61911) title and body.

servo-wpt-sync · 2026-08-17T08:34:41Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

servo-wpt-sync · 2026-08-17T09:35:15Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com>

servo-wpt-sync · 2026-08-17T09:58:58Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

shubhamg13 · 2026-08-17T09:59:56Z

        // Width of at least 100 px.
        // TODO: find a good way to bound text width.
        assert_greater_than_equal(entry.size, 1200);
        assert_equals(entry.loadTime, 0);


Still Fails because of loadTime. It will be fixed in follow-up

servo-wpt-sync · 2026-08-17T10:00:32Z

✍ Updated existing upstream WPT pull request (web-platform-tests/wpt#61911) title and body.

shubhamg13 · 2026-08-17T13:15:49Z

@@ -0,0 +1,3 @@
+[transparent-text.html]


as earlier text was not considered so it passed.

Now, text is considered but transparent is not checked.

This will be fixed soon.

jdm · 2026-08-17T16:49:05Z

@@ -1,4 +1,4 @@
 [larger-text.html]
-  expected: TIMEOUT
+  expected: ERROR


Can you wrap the forEach callback at

servo/tests/wpt/tests/largest-contentful-paint/larger-text.html

Line 51 in 518078c

entryList.getEntries().forEach(entry => {

in a t.step_func to make this test behave better when it fails?

Quite Insightful suggestion :)

jdm · 2026-08-17T16:50:50Z

@@ -1,4 +1,4 @@
 [text-fragment-union.html]
-  expected: TIMEOUT
+  expected: ERROR


Same here for a t.step_func:

servo/tests/wpt/tests/largest-contentful-paint/text-fragment-union.html

Line 24 in 518078c

new PerformanceObserver((entryList, observer) => {

jdm · 2026-08-17T16:53:40Z


        // PaintTimingMixin
-        assert_greater_than_equal(entry.paintTime, beforeRender, 'paintTime should represent the time when the UA started painting');
+        if ("paintTime" in entry && entry.paintTime !== null) {


This change isn't great, because it silently ignores a feature if it's not supported. We should either accept that the test will fail until we implement this feature, or we should split it out into a separate test that we will fail.

It is same for presentationTime below.

paintTime and presentationTime are in same interface and treated together under PaintTimingMixin IIRC.

That's why I did this. WDYS?

Huh. Ok, no objection if there's prior art in the same test file, I guess!

web-platform-tests/wpt@20ded9e and web-platform-tests/wpt@35cc694 is the original justification.

jdm

These changes look good to me, but I'd like someone more experienced with layout to verify the logic for the new containing_element_tag.

servo-wpt-sync · 2026-08-18T01:47:19Z

✍ Updated existing upstream WPT pull request (web-platform-tests/wpt#61911) title and body.

Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com>

servo-wpt-sync · 2026-08-18T02:09:12Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

servo-wpt-sync · 2026-08-18T02:13:51Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#61911).

servo-wpt-sync · 2026-08-18T02:19:22Z

✍ Updated existing upstream WPT pull request (web-platform-tests/wpt#61911) title and body.

shubhamg13 · 2026-08-18T14:41:29Z

Yayyyyy! Thanks

shubhamg13 · 2026-09-09T08:23:48Z

@servo-highfive monthly update

servo-highfive · 2026-09-09T08:23:54Z

Someone thinks this change could be added to the monthly blog post! To help with this, we need someone to answer the following questions: 😄

Who is most impacted by this change: users, Servo developers, embedders, or some other group?
What observable difference does this change make?
What preferences (if any) need to be enabled to observe this difference?
What (if any) specific URLs are affected?

If this change is part of a broader feature/project please make sure the PR description contains a Fixes: #12345 or Part of: #12345 issue reference.

Please add @servo-highfive monthly update answer when answering these questions so the bot notices your answer (or just quote this comment).

Thanks for helping us prepare the monthly blog post! ❤️

shubhamg13 · 2026-09-09T08:31:00Z

@servo-highfive monthly update answer

Web Developers and performance tooling that consume LCP
Text prominent Pages, pages whose LCP is text.
largest_content_paint_enabled
No particular domains — any page where the largest contentful item is text can be affected.

Adding a struct `PendingImageRecord`. Add complimentary `W3C` spec steps. Pre-requisite for servo#47212 Testing: WPT Unchanged. Fixes: Part of servo#42000 --------- Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com> Signed-off-by: Shubham Gupta <shubham.gupta@chromium.org>

Since the spec says, for text nodes we need to do union of border box per element. - Adding `containing_element_tag` for making this union. - Adding `TextRecord` to store `TextNodes` related to an `Element`. > Note: Please view using `Hide whitespace` option. Testing: More WPT Passed - Added a specific test to verify union logic of rect - size calculation is correct in WPT - `tests/wpt/tests/largest-contentful-paint/text-fragment-union.html`- web-platform-tests/wpt#61873 - (_TODO: set loadTime to zero for text, other failing tests will also pass #47315_) Fixes: Part of servo#42000 --------- Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com>

shubhamg13 requested review from Loirooriol and mrobinson as code owners August 13, 2026 08:31

servo-highfive added the S-awaiting-review There is new code that needs to be reviewed. label Aug 13, 2026

servo-wpt-sync mentioned this pull request Aug 13, 2026

layout: Consider Text as LCP candidate web-platform-tests/wpt#61911

Merged

shubhamg13 marked this pull request as draft August 13, 2026 08:36

shubhamg13 force-pushed the lcp_text branch from 22af1e9 to 8774322 Compare August 13, 2026 08:46

shubhamg13 force-pushed the lcp_text branch from 8774322 to e5a030b Compare August 13, 2026 09:06

shubhamg13 mentioned this pull request Aug 13, 2026

layout: Wrap up LCP Image things into PendingImageRecord #47215

Merged

shubhamg13 force-pushed the lcp_text branch from e5a030b to ed05f13 Compare August 17, 2026 07:25

shubhamg13 changed the title ~~Consider Text as LCP candidate~~ layout: Consider Text as LCP candidate Aug 17, 2026

shubhamg13 force-pushed the lcp_text branch from ed05f13 to 1055530 Compare August 17, 2026 07:45

shubhamg13 force-pushed the lcp_text branch from bc28c4a to 99446dc Compare August 17, 2026 09:30

shubhamg13 force-pushed the lcp_text branch from 99446dc to ee1a955 Compare August 17, 2026 09:54

shubhamg13 added 2 commits August 17, 2026 17:57

Consider Text as LCP candidate

6385505

Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com>

Add check for paintTime in observe-text.html

7ff35f7

Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com>

shubhamg13 force-pushed the lcp_text branch from ee1a955 to 21e8fa0 Compare August 17, 2026 09:58

shubhamg13 commented Aug 17, 2026

View reviewed changes

shubhamg13 marked this pull request as ready for review August 17, 2026 10:00

shubhamg13 commented Aug 17, 2026

View reviewed changes

jdm reviewed Aug 17, 2026

View reviewed changes

shubhamg13 mentioned this pull request Aug 18, 2026

Feature: LargestContentfulPaint #42000

Open

shubhamg13 added 2 commits August 18, 2026 09:57

Use t.step_func to make failures explicit

a5d7cc7

Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com>

New Expectations

2767525

Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com>

shubhamg13 force-pushed the lcp_text branch from ec38b7d to 2767525 Compare August 18, 2026 02:04

Update Manifest again

3d829b6

Signed-off-by: Shubham Gupta <shubhamg13.work@gmail.com>

mrobinson approved these changes Aug 18, 2026

View reviewed changes

servo-highfive removed the S-awaiting-review There is new code that needs to be reviewed. label Aug 18, 2026

jdm added this pull request to the merge queue Aug 18, 2026

servo-highfive added the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Aug 18, 2026

Merged via the queue into servo:main with commit 6de1edc Aug 18, 2026
34 checks passed

servo-highfive removed the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Aug 18, 2026

shubhamg13 deleted the lcp_text branch August 19, 2026 01:10

mrobinson mentioned this pull request Aug 19, 2026

Intermittent TIMEOUT in /largest-contentful-paint/performance-entry-sequence.html #47373

Closed

servo-highfive added the monthly update label Sep 9, 2026

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