paint: Correctly apply viewport <meta> initial-scale by shubhamg13 · Pull Request #43160 · servo/servo

shubhamg13 · 2026-03-11T02:16:54Z

Instead of applying initial scale to page.

An initial-scale should directly affect the visualviewport.scaleas it is layer that manages zoom factor [css-viewport] How to determine minimum-scale and layout viewport size? w3c/csswg-drafts#9004
initial-scale should be considered with device_pixel_ratio while calculating layout_viewport as per following spec gudelines.

Specs: https://www.w3.org/TR/css-viewport-1/#the-viewport

This specification introduces a way of overriding the size of the viewport provided by the user agent (UA). Because of this, we need to introduce the difference between the initial viewport and the actual viewport.

initial viewport
This refers to the viewport before any UA or author styles have overridden the viewport given by the window or viewing area of the UA. Note that the initial viewport size will change with the size of the window or viewing area.
actual viewport
This is the viewport you get after processing the viewport tag.

Sample Page: viewport_meta_with_style_2.html

Testing: tests/webview.rs: test_viewport_meta_tag_initial_scale

Fixes: #39002

codecov-commenter · 2026-03-11T02:38:08Z

⚠️ JUnit XML file not found

The CLI was unable to find any JUnit XML files to upload.
For more help, visit our troubleshooting guide.

xiaochengh · 2026-03-12T07:47:48Z

components/servo/tests/webview.rs

-    let load_webview = webview.clone();
-    let _ = servo_test.spin(move || load_webview.load_status() != LoadStatus::Complete);
+    show_webview_and_wait_for_rendering_to_be_ready(&servo_test, &webview, &delegate);
+    let eval_visual_viewport = |attr: &str| {


This function is not used in this PR.

xiaochengh · 2026-03-12T07:53:30Z

@stevennovaryo might know better about this one.

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

github-actions · 2026-03-26T13:48:59Z

🔨 Triggering try run (#23597795448) for Linux (WPT)

github-actions · 2026-03-26T14:39:54Z

Test results for linux-wpt from try job (#23597795448):

Flaky unexpected result (33)

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
```
CRASH [expected ERROR] /_webgl/conformance2/misc/uninitialized-test-2.html (#41656)
TIMEOUT [expected OK] /content-security-policy/inheritance/document-write-iframe.html (#41195)
- TIMEOUT [expected PASS] subtest: document.open() keeps inherited CSPs on transient about:blank.
```
Test timed out
```
CRASH [expected OK] /content-security-policy/meta/sandbox-iframe.html (#43478)
FAIL [expected PASS] /css/css-backgrounds/background-size-042.html
OK [expected ERROR] /fetch/fetch-later/quota/same-origin-iframe/multiple-iframes.https.window.html (#35176)
TIMEOUT /fetch/metadata/generated/css-images.sub.tentative.html (#29047)
- FAIL [expected PASS] subtest: content sec-fetch-site - HTTPS downgrade-upgrade
```
assert_unreached: Reached unreachable code
```
OK /fetch/metadata/window-open.https.sub.html (#40339)
- FAIL [expected PASS] subtest: Cross-site window, forced, reloaded
```
The operation is insecure.
```
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
CRASH [expected OK] /html/browsers/browsing-the-web/unloading-documents/beforeunload-canceling.html
CRASH [expected OK] /html/browsers/sandboxing/sandbox-initial-empty-document-toward-same-origin.html (#35948)
OK [expected TIMEOUT] /html/infrastructure/urls/base-url/document-base-url-window-initiator-is-not-opener.https.window.html (#30970)
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/audio_loop_seek_to_eos.html (#41226)
- PASS [expected FAIL] subtest: seeking to the end of looping audio
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/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.
CRASH [expected ERROR] /html/semantics/forms/the-select-element/customizable-select/select-appearance-button-after-span.html

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"])

TIMEOUT [expected OK] /html/user-activation/navigation-state-reset-sameorigin.html
- TIMEOUT [expected PASS] subtest: Post-navigation state reset.
```
Test timed out
```
PASS [expected FAIL] /png/apng/acTL-plays-two.html (#41191)
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
```
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 /resource-timing/test_resource_timing.html (#25720)
- PASS [expected FAIL] subtest: PerformanceEntry has correct name, initiatorType, startTime, and duration (xmlhttprequest)
OK /resource-timing/test_resource_timing.https.html (#25216)
- PASS [expected FAIL] subtest: PerformanceEntry has correct name, initiatorType, startTime, and duration (xmlhttprequest)
OK [expected TIMEOUT] /trusted-types/trusted-types-navigation.html?26-30 (#38807)
- PASS [expected TIMEOUT] subtest: Navigate a window via form-submission with javascript:-urls in report-only mode.
- PASS [expected NOTRUN] subtest: Navigate a window via form-submission with javascript:-urls w/ default policy in report-only mode.
- PASS [expected NOTRUN] subtest: Navigate a frame via form-submission with javascript:-urls in enforcing mode.
- PASS [expected NOTRUN] 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)
- TIMEOUT [expected PASS] subtest: Navigate a frame via form-submission with javascript:-urls in report-only mode.
```
Test timed out
```
- NOTRUN [expected TIMEOUT] subtest: Navigate a frame via form-submission with javascript:-urls w/ default policy in report-only mode.
PASS [expected TIMEOUT] /visual-viewport/viewport-apply-initial-scale-after-navigation.html (#41582)
OK /webdriver/tests/classic/element_click/scroll_into_view.py
- FAIL [expected PASS] subtest: test_scroll_into_view
```
webdriver.error.NoSuchElementException: no such element (404)
```
OK /webdriver/tests/classic/element_click/shadow_dom.py
- FAIL [expected PASS] subtest: test_shadow_element_click[host_element]
```
webdriver.error.NoSuchWindowException: no such window (404): No such window
```
OK /webdriver/tests/classic/fullscreen_window/from_minimized_window.py
- ERROR [expected FAIL] subtest: test_fullscreen_from_minimized_window
```
setup error: webdriver.error.NoSuchWindowException: no such window (404): No such window
```
OK /xhr/send-redirect.htm (#32026)
- FAIL [expected PASS] subtest: XMLHttpRequest: send() - Redirects (basics) (302, GET, content.py)
```
assert_equals: expected (string) "GET" but got (object) null
```

Stable unexpected results that are known to be intermittent (19)

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.
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 /_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 14 more unexpected results...

TIMEOUT [expected OK] /credential-management/credentialscontainer-frame-basics.https.html (#39430)
- TIMEOUT [expected FAIL] subtest: navigator.credentials should be undefined in documents generated from data: URLs.
```
Test timed out
```
OK /css/css-fonts/generic-family-keywords-001.html (#37467)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted generic(fangsong)
OK /css/css-fonts/generic-family-keywords-003.html (#38994)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted sans-serif (drawing text in a canvas)
- 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(kai) (drawing text in a canvas)
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted generic(khmer-mul) (drawing text in a canvas)
- FAIL [expected PASS] subtest: @font-face matching for quoted and unquoted generic(nastaliq) (drawing text in a canvas)
```
assert_equals: quoted generic(nastaliq) matches  @font-face rule expected 125 but got 40
```
- PASS [expected FAIL] subtest: @font-face matching for quoted and unquoted ui-serif (drawing text in a canvas)
ERROR [expected OK] /fetch/fetch-later/quota/same-origin-iframe/accumulated-oversized-payload.https.window.html (#41705)
OK [expected ERROR] /fetch/fetch-later/quota/same-origin-iframe/sandboxed-iframe.https.window.html (#41704)
OK /fetch/metadata/generated/css-font-face.https.sub.tentative.html (#32732)
- PASS [expected FAIL] subtest: sec-fetch-dest
- PASS [expected FAIL] subtest: sec-fetch-user
- PASS [expected FAIL] subtest: sec-fetch-storage-access - Same site
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/history/the-history-interface/traverse_the_history_4.html (#21383)
- PASS [expected FAIL] subtest: Multiple history traversals, last would be aborted

OK /html/browsers/windows/embedded-opener-remove-frame.html (#23867)

FAIL [expected PASS] subtest: opener of discarded auxiliary browsing context

assert_object_equals: property "get" expected function "function opener() {
    [native code]
}" got function "function opener() {
    [native code]
}"

TIMEOUT /html/interaction/focus/the-autofocus-attribute/supported-elements.html (#24145)
- TIMEOUT [expected FAIL] subtest: Element with tabindex should support autofocus
```
Test timed out
```
- NOTRUN [expected TIMEOUT] subtest: Non-HTMLElement should not support autofocus
TIMEOUT /html/semantics/embedded-content/media-elements/preserves-pitch.html (#40352)
- PASS [expected TIMEOUT] subtest: Speed-ups should not change the pitch when preservesPitch=true
- PASS [expected NOTRUN] subtest: Slow-downs should not change the pitch when preservesPitch=true
- TIMEOUT [expected NOTRUN] subtest: Speed-ups should change the pitch when preservesPitch=false
```
Test timed out
```
OK /html/webappapis/dynamic-markup-insertion/document-write/iframe_005.html (#43671)
- FAIL [expected PASS] subtest: document.write external script into iframe write back into parent
```
assert_array_equals: lengths differ, expected array [1, 2, 3, 4, 5] length 5, got [1, 2] length 2
```
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, mousedown@div"
```
OK [expected TIMEOUT] /webmessaging/with-ports/018.html (#24485)
- PASS [expected TIMEOUT] subtest: origin of the script that invoked the method, javascript:
OK [expected TIMEOUT] /webmessaging/without-ports/018.html (#24485)
- PASS [expected TIMEOUT] subtest: origin of the script that invoked the method, javascript:

github-actions · 2026-03-26T14:40:04Z

✨ Try run (#23597795448) succeeded.

stevennovaryo · 2026-03-30T08:32:27Z

components/paint/webview_renderer.rs

+        self.adjust_pinch_zoom(
+            self.viewport_description.initial_scale.get(),
+            DevicePoint::origin(),
+        );


I am unsure whether we should apply this directly into the pinch zoom. From a simple demo it seems to affect layout like page zoom, but it also adds on into VisualViewport.scale.

For example, lets consider the following HTML:

<!DOCTYPE html> <html lang="en"> <head> <meta name="viewport" content="initial-scale=1.0"> <style> #target { background-color: green; padding: 20px; border-radius: 8px; max-width: 220px; word-wrap: break-word; } .child { background-color: palegreen; display: inline-block; width: 50px; height: 50px; padding: 10px; } </style> </head> <body> <div id="target"> <div class="child"></div> <div class="child"></div> <div class="child"></div> <div class="child"></div> <div class="child"></div> <div class="child"></div> </div> </body> </html>

If we change the initial-scale to a certain amount, the layout will follow the available space and the values returned by layout queries will be different as well.

Yes, some values will be different as we skip parsing device-width from meta and its application in any calculation. I checked with your sample with scale 2.0 it works consistent.

As far as considering current architecture of Servo and broken bits of specs, it felt right to apply to pinch-zoom and resize layout viewport accordingly.

If you have any suggestions, I'm open to it.

) Scenario proposed should be best tested using unit tests. Testing: TODO (Waiting for #43160) Fixes: #41582 Signed-off-by: Shubham Gupta <[email protected]>

shubhamg13 requested review from mrobinson and xiaochengh March 11, 2026 02:17

shubhamg13 force-pushed the veiwport_resize branch 3 times, most recently from 4f0c72f to 81110a7 Compare March 11, 2026 04:45

shubhamg13 marked this pull request as ready for review March 11, 2026 04:46

servo-highfive added the S-awaiting-review There is new code that needs to be reviewed. label Mar 11, 2026

shubhamg13 force-pushed the veiwport_resize branch from 81110a7 to b2e38b2 Compare March 11, 2026 09:18

xiaochengh reviewed Mar 12, 2026

View reviewed changes

xiaochengh requested a review from stevennovaryo March 12, 2026 07:53

shubhamg13 force-pushed the veiwport_resize branch from b2e38b2 to e681974 Compare March 26, 2026 09:25

shubhamg13 marked this pull request as draft March 26, 2026 09:25

shubhamg13 force-pushed the veiwport_resize branch from e681974 to efc3412 Compare March 26, 2026 10:09

shubhamg13 self-assigned this Mar 26, 2026

shubhamg13 marked this pull request as ready for review March 26, 2026 10:09

shubhamg13 force-pushed the veiwport_resize branch from efc3412 to a035223 Compare March 26, 2026 10:21

shubhamg13 requested a review from xiaochengh March 26, 2026 10:21

shubhamg13 marked this pull request as draft March 26, 2026 10:21

shubhamg13 force-pushed the veiwport_resize branch from a035223 to e75f69f Compare March 26, 2026 10:27

shubhamg13 added 2 commits March 26, 2026 18:42

Affect device-pixel-ratio using initial scale instead of rect.

17b46b1

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

Update unit test for viewport meta.

5909efd

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

shubhamg13 force-pushed the veiwport_resize branch from e75f69f to 5909efd Compare March 26, 2026 10:43

shubhamg13 changed the title ~~paint: Resize layout viewport according to viewport <meta> initial-scale~~ paint: Correctly apply viewport <meta> initial-scale Mar 26, 2026

shubhamg13 marked this pull request as ready for review March 26, 2026 11:00

shubhamg13 added the T-linux-wpt Do a try run of the WPT label Mar 26, 2026

github-actions bot removed the T-linux-wpt Do a try run of the WPT label Mar 26, 2026

This was referenced Mar 27, 2026

wpt: Delete viewport-apply-initial-scale-after-navigation.html #43701

Merged

Feature: <meta name="viewport"> #36159

Closed

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paint: Correctly apply viewport <meta> initial-scale#43160

paint: Correctly apply viewport <meta> initial-scale#43160
shubhamg13 wants to merge 2 commits intoservo:mainfrom
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