layout: Consider `iframe` for `first-paint` by shubhamg13 · Pull Request #42149 · servo/servo

shubhamg13 · 2026-01-26T03:06:10Z

iframe should be considered for first-paint.

TODO of: #42975
Synced: web-platform-tests/wpt#58243
Refer for some history: #42498

Testing:

wpt/paint-timing/first-paint-only/child-painting-first-image.html
wpt/paint-timing/first-paint-only/sibling-painting-first-image.html

Fixes: #42455

servo-wpt-sync · 2026-01-26T03:09:17Z

🤖 Opened new upstream WPT pull request (web-platform-tests/wpt#57329) with upstreamable changes.

tests/wpt/tests/paint-timing/no_paint_entry_basetest.html

servo-wpt-sync · 2026-01-27T08:06:39Z

📝 Transplanted new upstreamable changes to existing upstream WPT pull request (web-platform-tests/wpt#57329).

tests/wpt/tests/paint-timing/no_paint_entry_basetest.html

servo-wpt-sync · 2026-03-03T03:54:05Z

🤖 This change no longer contains upstreamable changes to WPT; closed existing upstream pull request (web-platform-tests/wpt#57329).

tests/wpt/meta/paint-timing/first-paint-only/first-paint-bg-color.html.ini

shubhamg13 · 2026-03-03T13:37:14Z

If this one good to go, please review and merge.

I will re-check specs and reviews comments for #42975

mrobinson · 2026-03-03T14:08:40Z

If this one good to go, please review and merge.

I will re-check specs and reviews comments for #42975

Please combine this with #42975. I think it makes sense to land a more complete implementation.

Signed-off-by: Shubham Gupta <[email protected]>

github-actions · 2026-03-22T15:45:06Z

🔨 Triggering try run (#23406570519) for Linux (WPT)

github-actions · 2026-03-22T16:15:21Z

Test results for linux-wpt from try job (#23406570519):

Flaky unexpected result (34)

OK /_mozilla/css/offset_properties_inline.html (#40543)

FAIL [expected PASS] subtest: offsetTop

assert_equals: offsetTop of #inline-1 should be 0. expected 0 but got -1

FAIL [expected PASS] subtest: offsetLeft

assert_equals: offsetLeft of #inline-2 should be 40. expected 40 but got 25

OK /_mozilla/mozilla/getBoundingClientRect.html (#39668)
- FAIL [expected PASS] subtest: getBoundingClientRect 1
```
assert_equals: expected 62 but got 60.35
```

OK /_webgl/conformance/textures/misc/texture-upload-size.html (#21770)

FAIL [expected PASS] subtest: WebGL test #45

assert_true: Texture was smaller than the expected size 2x2 expected true got false

FAIL [expected PASS] subtest: WebGL test #47

assert_true: getError expected: INVALID_VALUE. Was NO_ERROR : when calling texSubImage2D with the same texture upload with offset 1, 1 expected true got false

FAIL [expected PASS] subtest: WebGL test #49

assert_true: Texture was smaller than the expected size 2x2 expected true got false

FAIL [expected PASS] subtest: WebGL test #51

assert_true: getError expected: INVALID_VALUE. Was NO_ERROR : when calling texSubImage2D with the same texture upload with offset 1, 1 expected true got false

PASS [expected FAIL] subtest: WebGL test #53
PASS [expected FAIL] subtest: WebGL test #55
PASS [expected FAIL] subtest: WebGL test #57
PASS [expected FAIL] subtest: WebGL test #59

FAIL [expected PASS] subtest: WebGL test #61

assert_true: Texture was smaller than the expected size 2x2 expected true got false

FAIL [expected PASS] subtest: WebGL test #63

assert_true: getError expected: INVALID_VALUE. Was NO_ERROR : when calling texSubImage2D with the same texture upload with offset 1, 1 expected true got false

And 10 more unexpected results...

CRASH [expected OK] /_webgl/conformance2/wasm/readpixels-2gb-in-4gb-wasm-memory.html
CRASH [expected OK] /content-security-policy/meta/sandbox-iframe.html (#43478)
FAIL [expected PASS] /css/css-backgrounds/background-size-042.html
OK /fetch/metadata/generated/css-font-face.sub.tentative.html (#34624)
- PASS [expected FAIL] subtest: sec-fetch-storage-access - Not sent to non-trustworthy same-origin destination
- PASS [expected FAIL] subtest: sec-fetch-storage-access - Not sent to non-trustworthy same-site destination
- PASS [expected FAIL] subtest: sec-fetch-storage-access - Not sent to non-trustworthy cross-site destination
TIMEOUT /fetch/metadata/generated/css-images.sub.tentative.html (#29047)
- TIMEOUT [expected PASS] subtest: background-image sec-fetch-site - Not sent to non-trustworthy same-origin destination
```
Test timed out
```
ERROR [expected OK] /focus/focus-event-after-switching-iframes.sub.html (#40368)

OK /html/browsers/browsing-the-web/navigating-across-documents/refresh/same-document-refresh.html (#34597)

FAIL [expected PASS] subtest: Same-Document Referrer from Refresh

assert_equals: original page loads expected "http://web-platform.test:8000/html/browsers/browsing-the-web/navigating-across-documents/refresh/resources/refresh-with-section.sub.html?url=%23section" but got "http://web-platform.test:8000/html/browsers/browsing-the-web/navigating-across-documents/refresh/resources/refresh-with-section.sub.html?url=%23section#section"

CRASH [expected OK] /html/browsers/history/the-history-interface/004.html
OK /html/browsers/history/the-history-interface/traverse_the_history_2.html (#21383)
- PASS [expected FAIL] subtest: Multiple history traversals, last would be aborted
CRASH [expected OK] /html/browsers/history/the-location-interface/location-symbol-toprimitive.html
OK [expected TIMEOUT] /html/interaction/focus/the-autofocus-attribute/supported-elements.html (#24145)
- PASS [expected TIMEOUT] subtest: Non-HTMLElement should not support autofocus
- FAIL [expected NOTRUN] subtest: Host element with delegatesFocus should support autofocus
```
assert_equals: expected Element node &lt;div autofocus=""&gt;&lt;/div&gt; but got Element node &lt;body&gt;&lt;div autofocus=""&gt;&lt;/div&gt;&lt;/body&gt;
```
- FAIL [expected NOTRUN] subtest: Host element with delegatesFocus including no focusable descendants should be skipped
```
assert_equals: expected Element node &lt;input autofocus=""&gt;&lt;/input&gt; but got Element node &lt;body&gt;&lt;/body&gt;
```
- FAIL [expected NOTRUN] subtest: Area element should support autofocus
```
promise_test: Unhandled rejection with value: object "TypeError: can't access property "appendChild", w.document.querySelector(...) is null"
```
OK /html/semantics/document-metadata/the-meta-element/pragma-directives/attr-meta-http-equiv-refresh/allow-scripts-flag-changing-1.html (#39694)
- PASS [expected FAIL] subtest: Meta refresh is blocked by the allow-scripts sandbox flag at its creation time, not when refresh comes due
OK /html/semantics/document-metadata/the-meta-element/pragma-directives/attr-meta-http-equiv-refresh/allow-scripts-flag-changing-2.html (#39703)
- FAIL [expected PASS] subtest: Meta refresh of the original iframe is not blocked if moved into a sandboxed iframe
```
uncaught exception: Error: assert_unreached: The iframe into which the meta was moved must not refresh Reached unreachable code
```
OK /html/semantics/embedded-content/media-elements/media_fragment_seek.html (#24114)
- FAIL [expected PASS] subtest: Video should seek to time specified in media fragment syntax
```
assert_equals: expected 3 but got 0
```
OK [expected TIMEOUT] /html/semantics/embedded-content/media-elements/src_object_blob.html (#40340)
- PASS [expected TIMEOUT] subtest: HTMLMediaElement.srcObject blob
TIMEOUT [expected OK] /html/semantics/embedded-content/the-iframe-element/iframe_sandbox_navigate_other_frame_popup.sub.html (#39702)
- TIMEOUT [expected FAIL] subtest: Sandboxed iframe can not navigate other frame's popup
```
Test timed out
```

OK /html/semantics/scripting-1/the-script-element/execution-timing/077.html (#22139)

FAIL [expected PASS] subtest: adding several types of scripts through the DOM and removing some of them confuses scheduler

assert_array_equals: expected property 1 to be "Script #1 ran" but got "Script #3 ran" (expected array ["Script #2 ran", "Script #1 ran", "Script #3 ran", "Script #4 ran"] got ["Script #2 ran", "Script #3 ran", "Script #4 ran", "Script #1 ran"])

OK /html/semantics/scripting-1/the-script-element/module/dynamic-import/blob-url.any.worker.html (#33909)
- FAIL [expected PASS] subtest: Revoking a blob URL immediately after calling import will not fail
```
promise_test: Unhandled rejection with value: object "TypeError: Module fetching failed"
```
TIMEOUT [expected OK] /html/user-activation/navigation-state-reset-sameorigin.html
- TIMEOUT [expected PASS] subtest: Post-navigation state reset.
```
Test timed out
```
OK /mixed-content/tentative/autoupgrades/video-upgrade.https.sub.html (#41135)
- FAIL [expected PASS] subtest: Video of other host autoupgraded
```
assert_equals: Length. Other host expected 1 but got Infinity
```
TIMEOUT [expected OK] /preload/modulepreload-sri-importmap.html (#43354)
- TIMEOUT [expected PASS] subtest: Script should not be loaded if modulepreload's integrity is invalid
```
Test timed out
```
OK /resource-timing/buffer-full-add-then-clear.html (#40819)
- FAIL [expected PASS] subtest: Test that if the buffer is cleared after entries were added to the secondary buffer, those entries make it into the primary one
```
assert_equals: Number of entries does not match the expected value. expected 3 but got 0
```
CRASH [expected OK] /resource-timing/render-blocking-status-link.html (#41664)
TIMEOUT /trusted-types/trusted-types-navigation.html?06-10 (#37920)
- PASS [expected FAIL] subtest: Navigate a frame via anchor with javascript:-urls in report-only mode.
OK [expected TIMEOUT] /trusted-types/trusted-types-navigation.html?31-35 (#38034)
- PASS [expected TIMEOUT] subtest: Navigate a frame via form-submission with javascript:-urls w/ default policy in report-only mode.
- FAIL [expected NOTRUN] subtest: Navigate a window via form-submission with javascript:-urls w/ a default policy throwing an exception in enforcing mode.
```
promise_test: Unhandled rejection with value: "Unexpected message received: \"No securitypolicyviolation reported!\""
```
- FAIL [expected NOTRUN] subtest: Navigate a window via form-submission with javascript:-urls w/ a default policy throwing an exception in report-only mode.
```
promise_test: Unhandled rejection with value: "Unexpected message received: \"No securitypolicyviolation reported!\""
```
- FAIL [expected NOTRUN] subtest: Navigate a window via form-submission with javascript:-urls w/ a default policy making the URL invalid in enforcing mode.
```
promise_test: Unhandled rejection with value: "Unexpected message received: \"No securitypolicyviolation reported!\""
```
OK /webdriver/tests/classic/accept_alert/accept.py (#43194)
- FAIL [expected PASS] subtest: test_accept_in_popup_window
```
AssertionError: no such alert (404): No user prompt is currently active.
```
OK /webdriver/tests/classic/delete_cookie/delete.py
- FAIL [expected PASS] subtest: test_null_response_value
```
AssertionError: no such window (404): No such window
```
OK /webdriver/tests/classic/delete_cookie/user_prompts.py
- FAIL [expected PASS] subtest: test_accept[alert-None]
```
webdriver.error.NoSuchWindowException: no such window (404): No such window
```
OK /webdriver/tests/classic/element_clear/scroll_into_view.py
- FAIL [expected PASS] subtest: test_scroll_into_view
```
webdriver.error.NoSuchWindowException: no such window (404): No such window
```
OK [expected TIMEOUT] /webstorage/localstorage-about-blank-3P-iframe-opens-3P-window.partitioned.html (#29053)
- PASS [expected TIMEOUT] subtest: StorageKey: test 3P about:blank window opened from a 3P iframe
OK [expected ERROR] /webxr/render_state_update.https.html (#27535)

Stable unexpected results that are known to be intermittent (12)

FAIL [expected PASS] /_mozilla/mozilla/sslfail.html (#10760)
TIMEOUT [expected OK] /_mozilla/mozilla/window_resize_event.html (#36741)
- TIMEOUT [expected PASS] subtest: Popup onresize event fires after resizeTo
```
Test timed out
```
OK /css/css-cascade/layer-cssom-order-reverse.html (#36094)
- FAIL [expected PASS] subtest: Delete layer invalidates @font-face
```
assert_equals: expected "220px" but got "133px"
```
OK /css/css-fonts/generic-family-keywords-001.html (#37467)
- FAIL [expected PASS] subtest: @font-face matching for quoted and unquoted generic(khmer-mul)
```
assert_equals: quoted generic(khmer-mul) matches  @font-face rule expected 50 but got 30
```
OK /css/css-fonts/generic-family-keywords-003.html (#38994)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted math (drawing text in a canvas)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted generic(fangsong) (drawing text in a canvas)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted generic(khmer-mul) (drawing text in a canvas)
ERROR /fetch/metadata/generated/serviceworker.https.sub.html (#36247)
- PASS [expected FAIL] subtest: sec-fetch-site - Same origin, no options - registration
OK /fetch/metadata/window-open.https.sub.html (#40339)
- FAIL [expected PASS] subtest: Same-site window, forced, reloaded
```
The operation is insecure.
```

OK /html/browsers/browsing-the-web/navigating-across-documents/replace-before-load/a-click.html (#28697)

FAIL [expected PASS] subtest: aElement.click() before the load event must NOT replace

assert_equals: expected "http://web-platform.test:8000/common/blank.html?thereplacement" but got "http://web-platform.test:8000/html/browsers/browsing-the-web/navigating-across-documents/replace-before-load/resources/code-injector.html?pipe=sub(none)&amp;code=%0A%20%20%20%20const%20a%20%3D%20document.createElement(%22a%22)%3B%0A%20%20%20%20a.href%20%3D%20%22%2Fcommon%2Fblank.html%3Fthereplacement%22%3B%0A%20%20%20%20document.currentScript.before(a)%3B%0A%20%20%20%20a.click()%3B%0A%20%20"

OK /html/semantics/embedded-content/media-elements/audio_loop_seek_to_eos.html (#41226)
- PASS [expected FAIL] subtest: seeking to the end of looping audio
OK /navigation-timing/test-navigation-type-reload.html (#33334)
- PASS [expected FAIL] subtest: Reload domInteractive > Original domInteractive
TIMEOUT [expected OK] /preload/modulepreload-sri.html (#43354)
- TIMEOUT [expected PASS] subtest: Script should not be loaded if modulepreload's integrity is invalid
```
Test timed out
```
OK /touch-events/single-tap-when-touchend-listener-use-sync-xhr.html (#41175)
- FAIL [expected PASS] subtest: Click event should be fired when touchend opens synchronous XHR
```
assert_equals: expected "touchend@div, mousedown@div, mouseup@div, click@div" but got "touchend@div"
```

github-actions · 2026-03-22T16:15:29Z

✨ Try run (#23406570519) succeeded.

shubhamg13 · 2026-03-23T05:43:46Z

This PR has been rebased over WPT upstream sync of #43531.
And covers the expectations of affected tests in web-platform-tests/wpt#58243.

This adds the leftover TODO implementations of #42975. Please help to review.

servo-wpt-sync mentioned this pull request Jan 26, 2026

layout: Fix first-paint detection. web-platform-tests/wpt#57329

Closed

jdm reviewed Jan 26, 2026

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shubhamg13 force-pushed the fix_fp branch from c529502 to c45690f Compare January 27, 2026 08:03

shubhamg13 requested a review from jdm January 27, 2026 08:17

jdm reviewed Jan 27, 2026

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shubhamg13 force-pushed the fix_fp branch from c45690f to bca84c7 Compare March 3, 2026 03:47

shubhamg13 requested a review from jdm March 3, 2026 03:48

shubhamg13 marked this pull request as ready for review March 3, 2026 03:59

shubhamg13 requested review from Loirooriol and mrobinson as code owners March 3, 2026 03:59

servo-highfive added the S-awaiting-review There is new code that needs to be reviewed. label Mar 3, 2026

shubhamg13 mentioned this pull request Mar 3, 2026

layout: Fix first-paint detection #42975

Merged

shubhamg13 force-pushed the fix_fp branch 2 times, most recently from c4227b3 to dc9491f Compare March 3, 2026 04:25

mrobinson reviewed Mar 3, 2026

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tests/wpt/meta/paint-timing/first-paint-only/first-paint-bg-color.html.ini Outdated Show resolved Hide resolved

shubhamg13 requested a review from mrobinson March 3, 2026 08:31

shubhamg13 marked this pull request as draft March 4, 2026 03:48

shubhamg13 force-pushed the fix_fp branch from dc9491f to fffdfb5 Compare March 20, 2026 08:45

shubhamg13 added 2 commits March 22, 2026 23:26

Consider iframe as paintable

5def053

Signed-off-by: Shubham Gupta <[email protected]>

Update WPT expectations

6b55eb4

Signed-off-by: Shubham Gupta <[email protected]>

shubhamg13 force-pushed the fix_fp branch from fffdfb5 to 6b55eb4 Compare March 22, 2026 15:28

shubhamg13 changed the title ~~layout: Fix first-paint detection.~~ layout: Consider iframe for first-paint Mar 22, 2026

shubhamg13 marked this pull request as ready for review March 22, 2026 15:33

shubhamg13 mentioned this pull request Mar 22, 2026

Feature: PaintTiming #42623

Open

shubhamg13 added the T-linux-wpt Do a try run of the WPT label Mar 22, 2026

github-actions bot removed the T-linux-wpt Do a try run of the WPT label Mar 22, 2026

jdm approved these changes Mar 23, 2026

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jdm added this pull request to the merge queue Mar 23, 2026

servo-highfive added the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Mar 23, 2026

Merged via the queue into servo:main with commit 047e321 Mar 23, 2026
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servo-highfive removed the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Mar 23, 2026

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layout: Consider `iframe` for `first-paint`#42149

layout: Consider `iframe` for `first-paint`#42149
jdm merged 2 commits intoservo:mainfrom
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