script: Populate `document.fonts` with web fonts from CSS by simonwuelker · Pull Request #46509 · servo/servo

simonwuelker · 2026-07-14T22:06:48Z

Previously document.fonts only contained font faces explicitly added to it via javascript, but each valid @font-face rule should also have an entry here. This fixes intermittency in one test that reads document.fonts to wait for web fonts to load, but previously waited on nothing because document.fonts was empty.

Testing: New tests start to pass
Fixes #46434

Signed-off-by: Simon Wülker <[email protected]>

simonwuelker · 2026-07-14T22:08:57Z

@@ -1,9 +1,10 @@
 [font-unicode-PUA.html]
+  expected: TIMEOUT


This timeout represents progress: The test runs

promise_setup(_ => Promise.all([...document.fonts].map(f => f.load())));

which previously waited on nothing because document.fonts was always empty. That caused intermittent passes. Now it waits forever because we never mark FontFaces backed by @font-face rules as loaded. We can fix that in a later change.

github-actions · 2026-07-14T22:13:26Z

🔨 Triggering try run (#29372221445) for Linux (WPT)

github-actions · 2026-07-14T23:40:41Z

Test results for linux-wpt from try job (#29372221445):

Flaky unexpected result (31)

TIMEOUT /FileAPI/url/url-in-tags-revoke.window.html (#19978)
- PASS [expected TIMEOUT] subtest: Fetching a blob URL immediately before revoking it works in <script> tags.
CRASH [expected OK] /_webgl/conformance/glsl/misc/shader-uniform-packing-restrictions.html
TIMEOUT [expected OK] /_webgl/conformance/textures/misc/texture-video-transparent.html
- NOTRUN [expected PASS] subtest: Overall test
TIMEOUT [expected OK] /_webgl/conformance/uniforms/no-over-optimization-on-uniform-array-06.html
- NOTRUN [expected PASS] subtest: Overall test
CRASH [expected OK] /_webgl/conformance/uniforms/no-over-optimization-on-uniform-array-14.html
TIMEOUT [expected OK] /_webgl/conformance/uniforms/no-over-optimization-on-uniform-array-17.html
- NOTRUN [expected PASS] subtest: Overall test
TIMEOUT [expected OK] /_webgl/conformance2/state/gl-object-get-calls.html
- NOTRUN [expected PASS] subtest: Overall test
TIMEOUT [expected OK] /_webgl/conformance2/transform_feedback/transform_feedback.html
OK /cookies/partitioned-cookies/partitioned-cookies-samesite-attribute.https.html (#45255)
- FAIL [expected PASS] subtest: In embedded cross-site contexts, partitioned cookies can only be set with explicit SameSite=None
```
assert_equals: expected 0 but got 3
```
CRASH [expected OK] /css/compositing/canvas-composite-modes.html
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 "122.8px"
```
OK /css/css-fonts/variations/at-font-face-font-matching.html (#20684)
- FAIL [expected PASS] subtest: Matching font-style: 'oblique -20deg' should prefer 'oblique -20deg' over 'oblique -60deg -40deg'
```
assert_equals: Unexpected font on test element expected 487 but got 532
```

OK /css/css-grid/alignment/grid-alignment-implies-size-change-005.html

FAIL [expected PASS] subtest: .before 1

assert_equals: 
&lt;div data-expected-width="100" id="item" class=" before" data-expected-height="100"&gt;XX X&lt;br&gt;X XXX&lt;br&gt;X&lt;br&gt;XX XXX&lt;/div&gt;
height expected 100 but got 80

FAIL [expected PASS] /css/css-sizing/dynamic-available-size-iframe.html (#45763)
TIMEOUT [expected OK] /fetch/content-encoding/br/big-br-body.https.any.worker.html
- TIMEOUT [expected PASS] subtest: large br data should be decompressed successfully
```
Test timed out
```
- NOTRUN [expected FAIL] subtest: large br data should be decompressed successfully with byte stream
TIMEOUT [expected OK] /fetch/content-encoding/gzip/big-gzip-body.https.any.worker.html
- TIMEOUT [expected PASS] subtest: large gzip data should be decompressed successfully
```
Test timed out
```
- NOTRUN [expected FAIL] subtest: large gzip data should be decompressed successfully with byte stream
TIMEOUT [expected OK] /fetch/content-encoding/zstd/big-zstd-body.https.any.html
OK /html/browsers/history/the-history-interface/traverse_the_history_5.html (#21383)
- PASS [expected FAIL] subtest: Multiple history traversals, last would be aborted
TIMEOUT [expected OK] /html/browsers/origin/cross-origin-objects/cross-origin-objects.html
TIMEOUT [expected OK] /html/interaction/focus/the-autofocus-attribute/autofocus-dialog.html (#29087)
- TIMEOUT [expected PASS] subtest: <dialog>-contained autofocus element gets focused when the dialog is shown
```
Test timed out
```
TIMEOUT [expected OK] /html/interaction/focus/the-autofocus-attribute/update-the-rendering.html (#24145)
- TIMEOUT [expected FAIL] subtest: "Flush autofocus candidates" should be happen before a scroll event and animation frame callbacks
```
Test timed out
```
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 1 but got 0
```

OK /html/semantics/embedded-content/media-elements/seeking/seek-to-currentTime.html (#46014)

FAIL [expected PASS] subtest: seek to currentTime

assert_array_equals: fired events lengths differ, expected array ["seeking", "timeupdate", "seeked"] length 3, got ["seeking", "timeupdate", "timeupdate", "seeked"] length 4

OK /html/semantics/forms/form-submission-0/jsurl-form-submit.tentative.html (#36489)
- PASS [expected FAIL] subtest: Verifies that form submissions scheduled inside javascript: urls take precedence over the javascript: url's return value.
TIMEOUT [expected OK] /html/syntax/parsing/html5lib_write_single.html?file=entities02
- TIMEOUT [expected PASS] subtest: <div bar="ZZ&gt;YY"></div>
```
Test timed out
```
- TIMEOUT [expected PASS] subtest: <div bar="ZZ&"></div>
```
Test timed out
```
- TIMEOUT [expected PASS] subtest: <div bar='ZZ&'></div>
```
Test timed out
```
- TIMEOUT [expected PASS] subtest: <div bar=ZZ&></div>
```
Test timed out
```
- TIMEOUT [expected PASS] subtest: <div bar="ZZ&gt=YY"></div>
```
Test timed out
```
- TIMEOUT [expected PASS] subtest: <div bar="ZZ&gt0YY"></div>
```
Test timed out
```
- TIMEOUT [expected PASS] subtest: <div bar="ZZ&gt9YY"></div>
```
Test timed out
```
- TIMEOUT [expected PASS] subtest: <div bar="ZZ&gtaYY"></div>
```
Test timed out
```
- NOTRUN [expected PASS] subtest: <div bar="ZZ&gtZYY"></div>
- NOTRUN [expected PASS] subtest: <div bar="ZZ&gt YY"></div>
- And 16 more unexpected results...
TIMEOUT [expected OK] /html/user-activation/navigation-state-reset-sameorigin.html (#45151)
- TIMEOUT [expected FAIL] subtest: Post-navigation state reset.
```
Test timed out
```
TIMEOUT [expected OK] /pointerevents/compat/pointerevent_touch-action_two-finger_interaction.html (#44693)
- NOTRUN [expected PASS] subtest: touch two-finger pan on 'touch-action: pan-x pan-y'
- NOTRUN [expected FAIL] subtest: touch two-finger pan on 'touch-action: pinch-zoom'

OK [expected CRASH] /resource-timing/render-blocking-status-link.html (#41664)

FAIL [expected PASS] subtest: Validate render blocking status of link resources in PerformanceResourceTiming

assert_equals: render blocking status for http://web-platform.test:8000/resource-timing/resources/empty_style.css?stylesheet-head-dynamic-docWrite should be blocking expected (string) "blocking" but got (undefined) undefined

CRASH [expected OK] /trusted-types/script-enforcement-016.html
OK [expected TIMEOUT] /trusted-types/trusted-types-navigation.html?01-05 (#38975)
- PASS [expected TIMEOUT] subtest: Navigate a window via anchor with javascript:-urls in report-only mode.
- PASS [expected NOTRUN] subtest: Navigate a window via anchor with javascript:-urls w/ default policy in report-only mode.
- PASS [expected NOTRUN] subtest: Navigate a frame via anchor with javascript:-urls in enforcing mode.
CRASH [expected OK] /webstorage/storage_local_setitem_quotaexceedederr.window.html

Stable unexpected results that are known to be intermittent (18)

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...

OK /beacon/beacon-basic.https.window.html (#41723)
- FAIL [expected PASS] subtest: Payload size restriction should be accumulated: type = string
```
assert_false: expected false got true
```
- PASS [expected FAIL] subtest: Payload size restriction should be accumulated: type = arraybuffer
TIMEOUT /content-security-policy/inheritance/auxiliary-blank-document.html (#44821)
- FAIL [expected PASS] subtest: For transient doc, violation event occurs in auxiliary, not opener window.
```
assert_equals: expected Document node with 1 child but got Document node with 1 child
```
OK [expected TIMEOUT] /fetch/api/redirect/redirect-keepalive.https.any.html (#32153)
- PASS [expected TIMEOUT] subtest: [keepalive][iframe][load] mixed content redirect; setting up
OK [expected ERROR] /fetch/fetch-later/quota/same-origin-iframe/multiple-iframes.https.window.html (#35176)
OK /html/browsers/browsing-the-web/navigating-across-documents/navigation-unload-same-origin.window.html (#29049)
- FAIL [expected PASS] subtest: Same-origin navigation started from unload handler must be ignored
```
assert_equals: expected "?pass" but got "?fail"
```
TIMEOUT [expected OK] /html/browsers/browsing-the-web/navigating-across-documents/replace-before-load/form-requestsubmit.html (#44098)
- TIMEOUT [expected FAIL] subtest: Replace before load, triggered by formElement.requestSubmit()
```
Test timed out
```
OK [expected TIMEOUT] /html/syntax/parsing/html5lib_write.html?file=processing-instructions (#46205)
OK /paint-timing/with-lcp/fcp-document-opacity-image.html (#43068)
- PASS [expected FAIL] subtest: Test that FCP after opacity change is not a larger value than LCP
OK /pointerevents/pointerevent_pointercapture_in_frame.html?touch (#45445)
- PASS [expected FAIL] subtest: Test touchpointer capture in same-origin frame: Pointer down at inner frame and set pointer capture.
- PASS [expected FAIL] subtest: Test touchpointer capture in same-origin frame: Pointer down at inner frame and set pointer capture to outer frame should not capture.
OK /resource-timing/test_resource_timing.https.html (#25216)
- FAIL [expected PASS] subtest: PerformanceEntry has correct name, initiatorType, startTime, and duration (xmlhttprequest)
```
assert_equals: expected 47.160000000000004 but got 47.15
```
OK /sanitizer-api/sanitizer-inert-document.html (#45260)
- FAIL [expected PASS] subtest: Test whether setHTML loads the image.
```
promise_test: Unhandled rejection with value: "The server observed a request. It shouldn't have."
```
- PASS [expected FAIL] subtest: Test whether setHTMLUnsafe loads the image.
OK /touch-events/single-tap-when-touchend-listener-use-sync-xhr.html (#41175)
- PASS [expected FAIL] subtest: Click event should be fired when touchend opens synchronous XHR
TIMEOUT /trusted-types/trusted-types-navigation.html?06-10 (#37920)
- TIMEOUT [expected PASS] subtest: Navigate a frame via anchor with javascript:-urls in report-only mode.
```
Test timed out
```
- NOTRUN [expected TIMEOUT] subtest: Navigate a frame via anchor with javascript:-urls w/ default policy in report-only mode.
TIMEOUT [expected OK] /trusted-types/trusted-types-navigation.html?16-20 (#44835)
- TIMEOUT [expected PASS] subtest: Navigate a frame via area with javascript:-urls w/ default policy in enforcing mode.
```
Test timed out
```
- NOTRUN [expected PASS] subtest: Navigate a frame via area with javascript:-urls in report-only mode.
- NOTRUN [expected PASS] subtest: Navigate a frame via area with javascript:-urls w/ default policy in report-only mode.
TIMEOUT [expected OK] /trusted-types/trusted-types-navigation.html?26-30 (#38807)
- TIMEOUT [expected PASS] subtest: Navigate a window via form-submission with javascript:-urls in report-only mode.
```
Test timed out
```
- NOTRUN [expected PASS] subtest: Navigate a window via form-submission with javascript:-urls w/ default policy in report-only mode.
- NOTRUN [expected PASS] subtest: Navigate a frame via form-submission with javascript:-urls in enforcing mode.
- NOTRUN [expected PASS] subtest: Navigate a frame via form-submission with javascript:-urls w/ default policy in enforcing mode.
TIMEOUT /trusted-types/trusted-types-navigation.html?31-35 (#38034)
- PASS [expected TIMEOUT] subtest: Navigate a frame via form-submission with javascript:-urls in report-only mode.
- TIMEOUT [expected NOTRUN] subtest: Navigate a frame via form-submission with javascript:-urls w/ default policy in report-only mode.
```
Test timed out
```
OK [expected TIMEOUT] /webstorage/localstorage-about-blank-3P-iframe-opens-3P-window.partitioned.html (#29053)
- FAIL [expected TIMEOUT] subtest: StorageKey: test 3P about:blank window opened from a 3P iframe
```
assert_true: about:blank window opened by 3P iframe does not inherit 3P iframe's StorageKey expected true got false
```

github-actions · 2026-07-14T23:40:48Z

✨ Try run (#29372221445) succeeded.

TimvdLippe

Nice work. Appreciate all the spec comments to be able to follow the code. Only two clarifying questions

TimvdLippe · 2026-07-15T06:56:20Z

@@ -1092,17 +1089,23 @@ impl LayoutThread {

        // Load new @font-face rules and remove old ones if necessary.
        // TODO: Can we make the invalidation set tell us whether any @font-face rules changed?


Is this TODO still relevant? I am not intimately familiar with this code, but I think it does now.

Its still relevant. Ideally stylo could tell us whether a stylesheet that was added to the page and then we might not have to call rebuild_font_face_set at all.

TimvdLippe · 2026-07-15T06:59:41Z

+                .iter()
+                .find(|entry| entry.is_connected_to_font_face_rule(removed_font_face_rule))
+            else {
+                if cfg!(debug_assertions) {


Is this a pattern we use? It's the first time I see it and usually we unconditionally call unreachable.

I think for bugs that are minor (don't affect soundness, and likely won't break any other assumptions related to soundess) this is preferable to avoid panics (DOS) in production.
The problem with always only logging a warning is that its easy to ignore, so adding a debug assertion is a middle ground that helps fix such minor bugs (and i guess unconditional debug_assert!(true, ..) might be linted against?)

I think for bugs that are minor (don't affect soundness, and likely won't break any other assumptions related to soundess) this is preferable to avoid panics (DOS) in production.

Yes, that is the intention.

and i guess unconditional debug_assert!(true, ..) might be linted against?

I've tried it just now and it doesn't trigger lints. I don't have a strong preference on what we should use (but I have used if cfg!(debug_assertions) { unreachable!() } in a couple of places before).

@font-face

servo#46537) I wasn't sure how to approach this in servo#46509 but it turns out the necessary code already exists, so it is quite trivial. Changes to these descriptors do not yet reflect in the actual @font-face rule. Testing: This change adds a test --------- Signed-off-by: Simon Wülker <[email protected]>

simonwuelker added 2 commits July 15, 2026 00:06

script: Populate document.fonts with font faces from CSS

244f65b

Signed-off-by: Simon Wülker <[email protected]>

Update wpt expectations

924c2ff

Signed-off-by: Simon Wülker <[email protected]>

simonwuelker requested review from Loirooriol, gterzian, mrobinson and nicoburns as code owners July 14, 2026 22:06

servo-highfive added the S-awaiting-review There is new code that needs to be reviewed. label Jul 14, 2026

simonwuelker added the A-platform/fonts label Jul 14, 2026

simonwuelker commented Jul 14, 2026

View reviewed changes

simonwuelker added the T-linux-wpt Do a try run of the WPT label Jul 14, 2026

github-actions Bot removed the T-linux-wpt Do a try run of the WPT label Jul 14, 2026

TimvdLippe approved these changes Jul 15, 2026

View reviewed changes

servo-highfive removed the S-awaiting-review There is new code that needs to be reviewed. label Jul 15, 2026

simonwuelker added this pull request to the merge queue Jul 15, 2026

servo-highfive added the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Jul 15, 2026

Merged via the queue into servo:main with commit e4a1464 Jul 15, 2026
76 checks passed

simonwuelker deleted the populate-document-fonts branch July 15, 2026 13:41

servo-highfive removed the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Jul 15, 2026

simonwuelker mentioned this pull request Jul 15, 2026

script: Initialize descriptor fields of css-connected FontFace objects #46537

Merged

servo-wpt-sync mentioned this pull request Jul 15, 2026

script: Initialize descriptor fields of css-connected FontFace objects web-platform-tests/wpt#61324

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script: Populate `document.fonts` with web fonts from CSS - #46509

script: Populate `document.fonts` with web fonts from CSS#46509
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		@@ -1092,17 +1089,23 @@ impl LayoutThread {

		// Load new @font-face rules and remove old ones if necessary.
		// TODO: Can we make the invalidation set tell us whether any @font-face rules changed?

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