compositing: Split out `Painter` from `IOCompositor` by mrobinson · Pull Request #40264 · servo/servo

mrobinson · 2025-10-29T11:47:04Z

This change splits IOCompositor into two structs: IOCompositor and
Painter. The idea is that Painter will be per-RenderingContext.
Currently there is only one, but when there is more than one there will
be one Painter per-RenderingContext. Therefore, everything that we
suspect will be managed this way is moved to Painter.

In addition, to avoid the risk of double-borrows, WebViewRender no
longer keeps a reference to any of the containing structs. Instead
necessary things are passed down when necessary or stored internally.

Testing: This should not change behavior and is thus covered by existing
tests.
Fixes: This is part of #40261.

github-actions · 2025-10-29T11:48:24Z

🔨 Triggering try run (#18906838540) for Linux (WPT)

github-actions · 2025-10-29T12:15:26Z

Test results for linux-wpt from try job (#18906838540):

Flaky unexpected result (24)

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
```
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 10 more unexpected results...
OK /content-security-policy/frame-ancestors/frame-ancestors-path-ignored.window.html (#36468)
- PASS [expected FAIL] subtest: A 'frame-ancestors' CSP directive with a URL that includes a path should be ignored.
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 "38.3166666666667px"
```
- FAIL [expected PASS] subtest: @font-face override update with appended sheet 2
```
assert_equals: expected "80px" but got "38.3166666666667px"
```
TIMEOUT [expected FAIL] /dom/xslt/encoding-single-chunk.html (#39983)
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/005.html (#27062)
- FAIL [expected PASS] subtest: Link with onclick navigation and href navigation
```
assert_equals: expected "href" but got "click"
```
OK /html/browsers/browsing-the-web/navigating-across-documents/initial-empty-document/iframe-src-aboutblank-navigate-immediately.html (#29048)
- PASS [expected FAIL] subtest: Navigating to a different document with form submission
OK /html/browsers/browsing-the-web/navigating-across-documents/initial-empty-document/load-pageshow-events-window-open.html (#28691)
- FAIL [expected PASS] subtest: load event does not fire on window.open('about:blank')
```
assert_unreached: load should not be fired Reached unreachable code
```

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"

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"
```
FAIL [expected PASS] /html/canvas/element/manual/text/canvas.2d.disconnected.html (#30063)
TIMEOUT [expected OK] /html/interaction/focus/the-autofocus-attribute/document-with-fragment-empty.html (#28259)
- TIMEOUT [expected FAIL] subtest: Autofocus elements in top-level browsing context's documents with empty fragments should work.
```
Test timed out
```
TIMEOUT [expected OK] /html/interaction/focus/the-autofocus-attribute/document-with-fragment-top.html (#28259)
- TIMEOUT [expected FAIL] subtest: Autofocus elements in top-level browsing context's documents with "top" fragments should work.
```
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/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/the-iframe-element/iframe-loading-lazy-nav-form-submit.html (#32607)

FAIL [expected PASS] subtest: Navigating iframe loading='lazy' before it is loaded: form submit

uncaught exception: Error: assert_equals: expected "http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/support/blank.htm?" but got "http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/support/blank.htm?src"

OK [expected TIMEOUT] /html/semantics/embedded-content/the-iframe-element/iframe_sandbox_navigate_other_frame_popup.sub.html (#39702)
- FAIL [expected TIMEOUT] subtest: Sandboxed iframe can not navigate other frame's popup
```
assert_equals: expected "cannot navigate" but got "can navigate"
```
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/scripting-1/the-script-element/module/dynamic-import/blob-url.any.html (#33948)
- FAIL [expected PASS] subtest: Revoking a blob URL immediately after calling import will not fail
```
promise_test: Unhandled rejection with value: object "TypeError: Dynamic import failed"
```

OK /html/webappapis/user-prompts/print-during-unload.html (#35944)

FAIL [expected PASS] subtest: print() during unload

assert_array_equals: expected property 1 to be "destination" but got "error: window.print is not a function" (expected array ["start", "destination"] got ["start", "error: window.print is not a function"])

OK [expected TIMEOUT] /webdriver/tests/classic/perform_actions/navigation.py (#38822)
OK [expected TIMEOUT] /webmessaging/without-ports/018.html (#24485)
- PASS [expected TIMEOUT] subtest: origin of the script that invoked the method, javascript:
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

Stable unexpected results that are known to be intermittent (22)

OK /FileAPI/url/url-with-fetch.any.worker.html (#21517)
- FAIL [expected PASS] subtest: Revoke blob URL after calling fetch, fetch should succeed
```
promise_test: Unhandled rejection with value: object "TypeError: Network error occurred"
```

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)
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 /css/css-fonts/generic-family-keywords-001.html (#37467)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted generic(fangsong)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted generic(kai)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted generic(khmer-mul)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted generic(nastaliq)
OK /custom-elements/form-associated/ElementInternals-setFormValue.html (#29174)
- FAIL [expected PASS] subtest: Single value - name is missing
```
assert_equals: expected "?name-pd1=value-pd1" but got ""
```
TIMEOUT [expected FAIL] /dom/xslt/large-cdata.html (#38029)
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
ERROR /fetch/metadata/generated/serviceworker.https.sub.html (#36247)
- PASS [expected FAIL] subtest: sec-fetch-site - Same origin, no options - registration
OK /html/browsers/browsing-the-web/navigating-across-documents/008.html (#24456)
- PASS [expected FAIL] subtest: Link with onclick form submit to javascript url and href navigation
OK /html/browsers/browsing-the-web/navigating-across-documents/navigation-unload-same-origin-fragment.html (#20768)
- PASS [expected FAIL] subtest: Tests that a fragment navigation in the unload handler will not block the initial navigation
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 2 (expected array [6, 3] got [6, 2])
```
TIMEOUT /html/interaction/focus/the-autofocus-attribute/supported-elements.html (#24145)
- TIMEOUT [expected NOTRUN] subtest: Non-HTMLElement should not support autofocus
```
Test timed out
```

OK /preload/preload-error.sub.html (#37177)

PASS [expected FAIL] subtest: success (fetch): main

FAIL [expected PASS] subtest: 404 (fetch): main

assert_greater_than: http://web-platform.test:8000/preload/resources/dummy.xml?pipe=status%28404%29&amp;label=fetch should be loaded expected a number greater than 0 but got 0

PASS [expected FAIL] subtest: CORS (fetch): main

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=da8a8661-d6f5-42e9-8248-ffbccf06c290 expected 1 but got 0
```
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.
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.

github-actions · 2025-10-29T12:15:35Z

✨ Try run (#18906838540) succeeded.

Narfinger · 2025-10-29T15:17:40Z

Awesome work!
I know most of it was just moving things around but I wanted to record some thoughts about it for this PR or for the future.
I was wondering about is painting order related methods in painter. To me they seem to be a bit out of place and should be in webviewmanager.
Also perhaps we should all it something to denote that it's main responsibility is sending events and handling the painting order.

mrobinson · 2025-10-29T15:34:07Z

I was wondering about is painting order related methods in painter. To me they seem to be a bit out of place and should be in webviewmanager.

The plan is to remove the concept of painting order entirely. In the future, when two WebViews share a RenderingContext, they would both be painted in creation order, if they are not hidden. In order to "switch" between WebViews in the same context an embedder would hide all of the other ones and ensure only one is showing.

This change splits `IOCompositor` into two structs: `IOCompositor` and `Painter`. The idea is that `Painter` will be per-`RenderingContext`. Currently there is only one, but when there is more than one there will be one `Painter` per-`RenderingContext`. Therefore, everything that we suspect will be managed this way is moved to `Painter`. In addition, to avoid the risk of double-borrows, `WebViewRender` no longer keeps a reference to any of the containing structs. Instead necessary things are passed down when necessary or stored internally. Co-authored-by: Mukilan Thiyagarajan <[email protected]> Signed-off-by: Martin Robinson <[email protected]>

Also clean up the code and remove unnecesary borrow in the `Painter::render` method. This was missed during code review of servo#40264. Signed-off-by: Mukilan Thiyagarajan <[email protected]>

…40302) Also clean up the code and remove unnecesary borrow in the `Painter::render` method. This was missed during code review of #40264. Testing: No testing. This is just a small code cleanup. Signed-off-by: Mukilan Thiyagarajan <[email protected]>

servo-highfive added the S-awaiting-review There is new code that needs to be reviewed. label Oct 29, 2025

mrobinson requested a review from mukilan October 29, 2025 11:47

mrobinson added the T-linux-wpt Do a try run of the WPT label Oct 29, 2025

github-actions bot removed the T-linux-wpt Do a try run of the WPT label Oct 29, 2025

mrobinson force-pushed the split-compositor-by-webrender-instance branch from a9a42f2 to c09893f Compare October 29, 2025 15:36

mukilan approved these changes Oct 29, 2025

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github-merge-queue bot removed this pull request from the merge queue due to a conflict with the base branch Oct 29, 2025

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mrobinson force-pushed the split-compositor-by-webrender-instance branch from c09893f to 373862e Compare October 29, 2025 18:16

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mrobinson force-pushed the split-compositor-by-webrender-instance branch from 373862e to b1bb7d3 Compare October 29, 2025 18:53

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Merged via the queue into servo:main with commit 15ad114 Oct 29, 2025
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mukilan mentioned this pull request Oct 31, 2025

compositor: use the Painter terminology in RefreshDriver traits #40302

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mrobinson mentioned this pull request Nov 3, 2025

Support multiple RenderingContexts #40261

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compositing: Split out `Painter` from `IOCompositor`#40264

compositing: Split out `Painter` from `IOCompositor`#40264
mrobinson merged 1 commit intoservo:mainfrom
mrobinson:split-compositor-by-webrender-instance

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