fonts: Add WebFontDocumentContext for CSS Fonts 4 font fetching #40301

jdm · 2025-10-31T06:15:17Z

Rebase of #37021 with review comments applied. These changes bundle up the required information from the relevant global when a stylesheet is added so that any requests for web fonts match the specification.

Testing: Newly passing tests.
Fixes: #36590

github-actions · 2025-10-31T06:16:06Z

🔨 Triggering try run (#18964463483) for Linux (WPT)

TimvdLippe

Nice! I would expect some CSP tests to start passing as well.

components/fonts/font_context.rs

github-actions · 2025-10-31T08:19:56Z

⚠️ Try run (#18964463483) failed.

mrobinson

Looks good from the perspective of someone who worked on the font loader. I'm not sure about the origin request parameter.

github-actions · 2025-10-31T18:10:49Z

🔨 Triggering try run (#18981318512) for Linux (WPT)

github-actions · 2025-10-31T18:42:11Z

Test results for linux-wpt from try job (#18981318512):

Flaky unexpected result (26)

OK /IndexedDB/idbfactory_open.any.html
- FAIL [expected PASS] subtest: Calling open() with version argument 1.5 should not throw.
```
assert_equals: version expected 1 but got 9007199254740991
```
TIMEOUT [expected OK] /_mozilla/mozilla/window_resize_event.html (#36741)
- TIMEOUT [expected PASS] subtest: Popup onresize event fires after resizeTo
```
Test timed out
```
TIMEOUT [expected PASS] /_mozilla/shadow-dom/move-element-with-ua-shadow-tree-crash.html (#39473)
OK [expected TIMEOUT] /_webgl/conformance/textures/misc/tex-video-using-tex-unit-non-zero.html (#39735)
- PASS [expected NOTRUN] subtest: Overall test
- PASS [expected FAIL] subtest: WebGL test #0
OK /_webgl/conformance/textures/misc/texture-upload-size.html (#21770)
- PASS [expected FAIL] subtest: WebGL test #45
- PASS [expected FAIL] subtest: WebGL test #47
- PASS [expected FAIL] subtest: WebGL test #49
- PASS [expected FAIL] subtest: WebGL test #51
- FAIL [expected PASS] subtest: WebGL test #53
```
assert_true: Texture was smaller than the expected size 2x2 expected true got false
```
- FAIL [expected PASS] subtest: WebGL test #55
```
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 #57
```
assert_true: Texture was smaller than the expected size 2x2 expected true got false
```
- FAIL [expected PASS] subtest: WebGL test #59
```
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 #61
- PASS [expected FAIL] subtest: WebGL test #63
- And 6 more unexpected results...
OK /css/css-cascade/layer-font-face-override.html (#35935)
- FAIL [expected PASS] subtest: @font-face override update with appended sheet 1
```
assert_equals: expected "80px" but got "41.45px"
```
- FAIL [expected PASS] subtest: @font-face override update with appended sheet 2
```
assert_equals: expected "80px" but got "41.45px"
```
OK /css/css-fonts/generic-family-keywords-003.html (#38994)
- FAIL [expected PASS] subtest: @font-face matching for quoted and unquoted serif (drawing text in a canvas)
```
assert_equals: quoted serif matches  @font-face rule expected 125 but got 40
```
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted ui-sans-serif (drawing text in a canvas)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted ui-rounded (drawing text in a canvas)
TIMEOUT [expected OK] /fetch/api/redirect/redirect-keepalive.https.any.html (#32153)
- TIMEOUT [expected PASS] subtest: [keepalive][iframe][load] mixed content redirect; setting up
```
Test timed out
```
OK /html/browsers/browsing-the-web/navigating-across-documents/009.html (#24456)
- PASS [expected FAIL] subtest: Link with onclick form submit to javascript url with document.write and href navigation
OK /html/browsers/browsing-the-web/navigating-across-documents/navigation-unload-same-origin.window.html (#29049)
- PASS [expected FAIL] subtest: Same-origin navigation started from unload handler must be ignored

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"

OK /html/browsers/browsing-the-web/navigating-across-documents/replace-before-load/a-click.html (#28697)
- PASS [expected FAIL] subtest: aElement.click() before the load event must NOT replace
TIMEOUT /html/browsers/history/the-history-interface/001.html (#12580)
- FAIL [expected PASS] subtest: traversing history must also traverse hash changes
```
assert_equals: (this could cause other failures later on) expected "" but got "test"
```
OK /html/browsers/history/the-history-interface/traverse_the_history_3.html (#21383)
- FAIL [expected PASS] subtest: Multiple history traversals, last would be aborted
```
assert_array_equals: Pages opened during history navigation expected property 1 to be 3 but got 1 (expected array [6, 3] got [6, 1])
```
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 PASS] /html/browsers/origin/origin-keyed-agent-clusters/popups-crash.https.html
FAIL [expected PASS] /html/canvas/element/manual/text/canvas.2d.disconnected.html (#30063)
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/embedded-content/the-iframe-element/iframe-loading-lazy-reload-location-reload.html (#32595)
- FAIL [expected PASS] subtest: Reloading iframe loading='lazy' before it is loaded: location.reload
```
uncaught exception: Error: assert_equals: expected "http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/support/blank.htm?src" but got "about:blank"
```
OK /preload/preload-xhr.html (#39092)
- FAIL [expected PASS] subtest: Make an XHR request immediately after creating link rel=preload.
```
assert_equals: resources/dummy.xml?token=7ef7bd6e-d82c-4cdc-b654-9c725a045412 expected 1 but got 0
```
ERROR /service-workers/idlharness.https.any.html (#36250)
- PASS [expected TIMEOUT] subtest: ServiceWorkerContainer interface: operation register((TrustedScriptURL or USVString), optional RegistrationOptions)
- PASS [expected TIMEOUT] subtest: NavigationPreloadManager interface: operation enable()
- PASS [expected TIMEOUT] subtest: NavigationPreloadManager interface: operation disable()
- PASS [expected TIMEOUT] subtest: NavigationPreloadManager interface: operation setHeaderValue(ByteString)
- PASS [expected TIMEOUT] subtest: NavigationPreloadManager interface: operation getState()
OK /trusted-types/trusted-types-navigation.html?26-30 (#38807)
- PASS [expected FAIL] subtest: Navigate a window via form-submission with javascript:-urls in report-only mode.
- PASS [expected FAIL] subtest: Navigate a frame via form-submission with javascript:-urls in enforcing mode.
OK /trusted-types/trusted-types-navigation.html?31-35 (#38034)
- PASS [expected FAIL] subtest: Navigate a frame via form-submission with javascript:-urls in report-only mode.
OK [expected TIMEOUT] /webmessaging/with-ports/017.html (#24486)
- PASS [expected TIMEOUT] subtest: origin of the script that invoked the method, about:blank
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 (16)

OK /IndexedDB/idbcursor-continuePrimaryKey-exceptions.any.worker.html (#39277)

FAIL [expected PASS] subtest: IDBCursor continuePrimaryKey() on object store cursor

assert_throws_dom: continuePrimaryKey() should throw if source is not an index function "function() {
        cursor.continuePrimaryKey(2, 2);
      }" threw object "TypeError: cursor.continuePrimaryKey is not a function" that is not a DOMException InvalidAccessError: property "code" is equal to undefined, expected 15

OK /IndexedDB/idbobjectstore_getAll.any.html (#39276)
- PASS [expected FAIL] subtest: Get all values with transaction.commit()
OK /IndexedDB/idbobjectstore_getAll.any.worker.html (#39400)
- PASS [expected FAIL] subtest: Get all values with transaction.commit()

OK /IndexedDB/key-conversion-exceptions.any.html (#39305)

FAIL [expected PASS] subtest: IDBCursor continue() method with throwing/invalid keys

assert_throws_exactly: key conversion with throwing getter should rethrow function "() =&gt; {
      receiver[method](key);
    }" threw object "TypeError: receiver[method] is not a function" but we expected it to throw object "getter: throwing from getter"

OK /IndexedDB/key-conversion-exceptions.any.worker.html (#39284)

FAIL [expected PASS] subtest: IDBCursor continue() method with throwing/invalid keys

assert_throws_exactly: key conversion with throwing getter should rethrow function "() =&gt; {
      receiver[method](key);
    }" threw object "TypeError: receiver[method] is not a function" but we expected it to throw object "getter: throwing from getter"

FAIL [expected PASS] subtest: IDBCursor update() method with throwing/invalid keys

assert_throws_exactly: throwing getter should rethrow during clone function "() =&gt; {
      cursor.update(value);
    }" threw object "TypeError: cursor.update is not a function" but we expected it to throw object "getter: throwing from getter"

FAIL [expected PASS] /_mozilla/mozilla/sslfail.html (#10760)
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"
```
TIMEOUT [expected FAIL] /dom/xslt/large-cdata.html (#38029)
OK /fetch/metadata/generated/css-font-face.https.sub.tentative.html (#32732)
- PASS [expected FAIL] subtest: sec-fetch-mode
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-site destination
- PASS [expected FAIL] subtest: sec-fetch-storage-access - Not sent to non-trustworthy cross-site destination
TIMEOUT /html/interaction/focus/the-autofocus-attribute/supported-elements.html (#24145)
- PASS [expected NOTRUN] 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;
```
- TIMEOUT [expected NOTRUN] subtest: Host element with delegatesFocus including no focusable descendants should be skipped
```
Test timed out
```
OK /html/semantics/embedded-content/the-video-element/intrinsic_sizes.htm (#37173)
- FAIL [expected PASS] subtest: default object size after src is removed
```
assert_equals: expected "300px" but got "320px"
```
OK /html/semantics/forms/historical.html (#28568)
- PASS [expected FAIL] subtest: <input name=isindex> should not be supported
OK /preload/preload-error.sub.html (#37177)
- PASS [expected FAIL] subtest: CORS (fetch): main
OK /trusted-types/trusted-types-navigation.html?01-05 (#38975)
- PASS [expected FAIL] subtest: Navigate a window via anchor with javascript:-urls in enforcing mode.
- PASS [expected FAIL] subtest: Navigate a window via anchor with javascript:-urls in report-only mode.
- FAIL [expected PASS] subtest: Navigate a frame via anchor with javascript:-urls in enforcing mode.
```
promise_test: Unhandled rejection with value: "Unexpected message received: \"No securitypolicyviolation reported!\""
```
OK /webdriver/tests/classic/dismiss_alert/dismiss.py (#39098)
- FAIL [expected PASS] subtest: test_dismiss_in_popup_window
```
AssertionError: no such alert (404): No user prompt is currently active.
```

github-actions · 2025-10-31T18:42:24Z

✨ Try run (#18981318512) succeeded.

TimvdLippe · 2025-10-31T19:07:35Z

I am surprised this fixes zero tests. Shouldn't tests like https://wpt.fyi/results/content-security-policy/font-src/font-stylesheet-font-blocked.sub.html?product=servo or https://wpt.fyi/results/fetch/metadata/generated/css-font-face.sub.tentative.html?product=servo be affected?

jdm · 2025-11-02T18:39:05Z

Aha, the culprit is:

servo/components/fonts/font_context.rs

Line 931 in 2a18c6b

    
           FetchResponseMsg::ProcessCspViolations(..) => DownloaderResponseResult::InProcess,

. We drop the CSP notification on the ground.

github-actions · 2025-11-02T21:02:02Z

⚠️ Try run (#19017822404) failed.

jdm · 2025-11-02T23:27:20Z

If my try push in https://github.com/servo/servo/actions/runs/19019558687 goes well, I would like to split this work up into three PRs in sequence:

this PR without the CSP changes
make webfonts critical subresources that block load events and remove our Ahem.css user stylesheet injection (f363bc2)
the CSP webfont changes from this PR

That will hopefully put us in a position where reporting CSP violations for web fonts doesn't break tests that expect a particular CSP failure but see a violation from our injected Ahem.ttf instead.

TimvdLippe · 2025-11-03T06:54:08Z

Sounds like a good plan to me

mrobinson · 2025-11-03T08:05:37Z

Another alternative here would be to ensure that every platform has Ahem loaded into its system font cache before running the tests. It seems like this could be done by injecting it manually on Servo startup.

mrobinson · 2025-11-18T08:57:56Z

2. make webfonts critical subresources that block load events and remove our Ahem.css user stylesheet injection (f363bc2)

About this, I wonder why it is necessary? We are currently waiting for all web fonts to load before taking screenshots. Is there another case that I'm missing here?

jdm · 2025-11-18T14:18:02Z

make webfonts critical subresources that block load events and remove our Ahem.css user stylesheet injection (f363bc2)

About this, I wonder why it is necessary? We are currently waiting for all web fonts to load before taking screenshots. Is there another case that I'm missing here?

There's a window of time between finishing fetching an external style sheet and starting fetching any web fonts that it defines. Without our injected user style sheet present, we end up sometimes taking a screenshot during that window so the expected font is not applied.

Signed-off-by: Uthman Yahaya Baba <uthmanyahayababa@gmail.com>

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

TimvdLippe · 2025-11-23T07:45:00Z

components/script/dom/window.rs

+        }));
+    }
+
+    fn clone(&self) -> Box<dyn CspViolationHandler> {


Can't we derive Clone for this struct? It looks like the default implementation to me

We can derive Clone, I don't think it really helps us at all since we still need to write this method.

TimvdLippe · 2025-11-23T07:45:32Z

components/fonts/font_context.rs

+    pub csp_handler: Box<dyn CspViolationHandler>,
+}
+
+impl Clone for WebFontDocumentContext {


Same here, can't we derive Clone?

Nope—the presence of the trait object makes that impossible, and trying to use trait CspViolationHandler: Clone means it can't be used as a trait object.

jdm requested review from Loirooriol, gterzian, mrobinson and nicoburns as code owners October 31, 2025 06:15

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jdm mentioned this pull request Oct 31, 2025

Add WebFontDocumentContext for CSS Fonts 4 font fetching #37021

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jdm force-pushed the issue_36590 branch from e12720b to 60c4bfc Compare October 31, 2025 18:11

servo-highfive added the S-needs-rebase There are merge conflict errors. label Nov 2, 2025

jdm force-pushed the issue_36590 branch from 87a7b01 to 2c79583 Compare November 2, 2025 19:26

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servo-highfive removed the S-awaiting-review There is new code that needs to be reviewed. label Nov 2, 2025

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servo-highfive added the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Nov 2, 2025

jdm removed this pull request from the merge queue due to a manual request Nov 2, 2025

uthmaniv and others added 5 commits November 23, 2025 01:55

Add WebFontDocumentContext for CSS Fonts 4 font fetching

fc2fc30

Signed-off-by: Uthman Yahaya Baba <uthmanyahayababa@gmail.com>

Add Helper method for creating new WebFontDocumentContext

65a366e

Signed-off-by: Uthman Yahaya Baba <uthmanyahayababa@gmail.com>

Review fixes.

2e3403e

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

fonts: Set origin of web font requests.

cb298f8

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

script: Clean up repeated code.

d58239b

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

jdm force-pushed the issue_36590 branch from 2c79583 to 6a42beb Compare November 23, 2025 07:32

servo-highfive added the S-awaiting-review There is new code that needs to be reviewed. label Nov 23, 2025

jdm enabled auto-merge November 23, 2025 07:33

jdm disabled auto-merge November 23, 2025 07:35

fonts: Report CSP violations for web font downloads.

c210760

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

jdm force-pushed the issue_36590 branch from 6a42beb to c210760 Compare November 23, 2025 07:39

jdm enabled auto-merge November 23, 2025 07:39

jdm added this pull request to the merge queue Nov 23, 2025

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Merged via the queue into servo:main with commit bbbfe6d Nov 23, 2025
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jdm deleted the issue_36590 branch November 23, 2025 08:49

servo-highfive removed the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Nov 23, 2025

mrobinson mentioned this pull request Dec 19, 2025

Support cross-origin font loads #22694

Closed

This was referenced Dec 30, 2025

Support mixed content blocking for font resources #16353

Closed

Active mixed content should be blocked #8582

Closed

mrobinson mentioned this pull request Jan 2, 2026

/css/css-text/ test very flaky since August #40562

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fonts: Add WebFontDocumentContext for CSS Fonts 4 font fetching #40301

fonts: Add WebFontDocumentContext for CSS Fonts 4 font fetching #40301

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