1722322 - [meta] Largest Contentful Paint (LCP) implementation

Status: RESOLVED FIXED

(Core :: Performance, enhancement)

Description

[Benjamin De Kosnik [:bdekoz]]

The Largest Contentful Paint (aka LCP) metric is one of three core metrics in Google's web vitals suite of analytic tools for web performance.

More information can be found here: https://web.dev/lcp/

This bug tracks the status and implementation of this metric in Gecko.

Dependencies include the W3C Element Timing API, and the specification can be found in the Largest Contentful Paint API ((https://wicg.github.io/largest-contentful-paint/)

Comment 1

[Sean Feng [:sefeng]]

Attachment: WIP: Bug 1722322 - Refactor get-an-element algorithm to a static method

So that it can be reused.

Comment 2

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Add some minor tweaks to LargestContentfulPaint WPTs r=emilio

This patch mainly just adds hide_test_state: true to
LargestContentfulPaint related tests because the intermittent
test status can be considered as painted elements, which
may interfere the test results.

Plus a few minor tweaks.

Depends on D151073

Comment 3

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Convert two intersection algorithm related functions to static r=emilio

Depends on D151074

Comment 4

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Adjust the ini files for LargestContentfulPaint implementation accordingly r=emilio

With the implementation many tests start to pass, so we adjust
the ini files accordingly.

Depends on D151075

Comment 5

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Rename some contentful paint related variables/functions to make it clear they are based on FirstContentfulPaint r=emilio

Depends on D151076

Comment 6

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Fix two bugs in nsContentSecurityManager::GetSerializedOrigin r=#necko

According to
https://fetch.spec.whatwg.org/#serializing-a-request-origin,
the algorithm should return "null" if the request has a
redirected-tainted origin.

Depends on D151077

Comment 7

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Implement LargestContentfulPaint r=emilio

Spec: https://w3c.github.io/largest-contentful-paint

Depends on D151078

Comment 8

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Refactor get-an-element algorithm to a static method r=emilio

So that it can be reused.

Comment 9

[Phabricator Automation]

Comment on attachment 9284231 [details]
Bug 1722322 - Refactor get-an-element algorithm to a static method r=emilio

Revision D151081 was moved to bug 1778345. Setting attachment 9284231 [details] to obsolete.

Comment 10

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Add the WebIDL support for LargestContentfulPaint r=emilio

Comment 11

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Add a LCP test for generated css image r=emilio

We have tests that use content to generate text, however it looks like
we miss the one for images.

Comment 12

[Emilio Cobos Álvarez (:emilio)]

Did another review pass, sorry for the lag again.

Comment 13

[Phabricator Automation]

Comment on attachment 9284222 [details]
Bug 1722322 - Add some minor tweaks to LargestContentfulPaint WPTs r=emilio

Revision D151074 was moved to bug 1829388. Setting attachment 9284222 [details] to obsolete.

Comment 14

[Phabricator Automation]

Comment on attachment 9284226 [details]
Bug 1722322 - Rename some contentful paint related variables/functions to make it clear they are based on FirstContentfulPaint r=emilio

Revision D151077 was moved to bug 1830778. Setting attachment 9284226 [details] to obsolete.

Comment 15

[Phabricator Automation]

Comment on attachment 9314038 [details]
Bug 1722322 - Add the WebIDL support for LargestContentfulPaint r=emilio

Revision D167816 was moved to bug 1830794. Setting attachment 9314038 [details] to obsolete.

Comment 16

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Add two more tests for LCP r=emilio

• added one to ensure elements rendered by MathML are observable
• added one to ensure elements created in different namespaces are observable

Comment 17

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Add tests to ensure no LCP entries are generated for ChromeAccessOnly elements r=emilio

Comment 18

[Sean Feng [:sefeng]]

Attachment: Bug 1722322 - Update image-not-fully-visible.html to make it work on Firefox Android r=emilio

The meta tags for width and height are needed to make sure the
calculation for the image position uses device sizes
rather than virtual sizes.

minimum-scale is used to ensure the overflow:hidden content
is not scrollable on Firefox Android, so that the LCP size can
be computed correctly.

Comment 19

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0121c8cf5d2f
Adjust the ini files for LargestContentfulPaint implementation accordingly r=emilio
https://hg.mozilla.org/integration/autoland/rev/f52b1f28f753
Fix two bugs in nsContentSecurityManager::GetSerializedOrigin r=necko-reviewers,dragana
https://hg.mozilla.org/integration/autoland/rev/37fccb407777
Add a LCP test for generated css image r=emilio
https://hg.mozilla.org/integration/autoland/rev/9955756855bd
Implement LargestContentfulPaint r=emilio
https://hg.mozilla.org/integration/autoland/rev/c2a6440a83d7
Add two more tests for LCP r=emilio
https://hg.mozilla.org/integration/autoland/rev/7a75717f127c
Update image-not-fully-visible.html to make it work on Firefox Android r=emilio
https://hg.mozilla.org/integration/autoland/rev/0ebd32e273b8
apply code formatting via Lando

Comment 20

[Web Platform Test Sync Bot (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/42926 for changes under testing/web-platform/tests

Comment 21

[Sandor Molnar[:smolnar]]

Backed out for causing bp-nu bustages

Backout link: https://hg.mozilla.org/integration/autoland/rev/e90489c6f69d4b0ddfa6d953958c4ffd9db36cf9

Push with failures

Failure log -> build bustage

Comment 22

[Web Platform Test Sync Bot (Matrix: #interop:mozilla.org)]

Upstream PR was closed without merging

Comment 23

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/db558fea2a7c
Adjust the ini files for LargestContentfulPaint implementation accordingly r=emilio
https://hg.mozilla.org/integration/autoland/rev/a3ad0e6a7e2e
Fix two bugs in nsContentSecurityManager::GetSerializedOrigin r=necko-reviewers,dragana
https://hg.mozilla.org/integration/autoland/rev/ad5e97f0e18a
Add a LCP test for generated css image r=emilio
https://hg.mozilla.org/integration/autoland/rev/9e951b5150b8
Implement LargestContentfulPaint r=emilio
https://hg.mozilla.org/integration/autoland/rev/1b569e5741f1
Add two more tests for LCP r=emilio
https://hg.mozilla.org/integration/autoland/rev/1adce8bfea68
Update image-not-fully-visible.html to make it work on Firefox Android r=emilio
https://hg.mozilla.org/integration/autoland/rev/19a29adcc44d
apply code formatting via Lando

Comment 24

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/db558fea2a7c
https://hg.mozilla.org/mozilla-central/rev/a3ad0e6a7e2e
https://hg.mozilla.org/mozilla-central/rev/ad5e97f0e18a
https://hg.mozilla.org/mozilla-central/rev/9e951b5150b8
https://hg.mozilla.org/mozilla-central/rev/1b569e5741f1
https://hg.mozilla.org/mozilla-central/rev/1adce8bfea68
https://hg.mozilla.org/mozilla-central/rev/19a29adcc44d

Comment 25

[Web Platform Test Sync Bot (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot

Comment 26

[Ryan VanderMeulen [:RyanVM]]

Please add a relnote nomination for this when you get a chance.

Comment 27

[Sean Feng [:sefeng]]

Relnote nomination is added in bug 1866266.