Fix mounting anywidget CSS in cross-realm roots#10136
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A widget's `_css` was only mounted when its view root passed an `instanceof Document | ShadowRoot` check. That is `false` for a cross-realm root such as a Document Picture-in-Picture window, so a composed child rendered there got no styles. Guard on nodeType instead, and construct the stylesheet in the root's own realm so it applies there.
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mscolnick
approved these changes
Jul 10, 2026
mscolnick
approved these changes
Jul 10, 2026
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Pull request overview
This PR fixes anywidget CSS injection for views rendered into cross-realm DOM roots (e.g., Document Picture-in-Picture windows), where instanceof Document | ShadowRoot fails and where constructing a CSSStyleSheet in the wrong realm prevents styles from applying.
Changes:
- Replace realm-sensitive
instanceofchecks with realm-independentnodeType-based guards forDocument/ShadowRoot. - Construct
CSSStyleSheetinstances from the target root’s realm (doc.defaultView.CSSStyleSheet) so adopted stylesheets apply in cross-realm contexts. - Ensure
<style>element fallback is also created from the target document (doc.createElement("style")).
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🚀 Development release published. You may be able to view the changes at https://marimo.app?v=0.23.14-dev61 |
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Follow up to #10127
A widget's
_csswas only mounted when its view root passed aninstanceof Document | ShadowRootcheck. That isfalsefor a cross-realm root such as a Document Picture-in-Picture window, so a composed child rendered there got no styles.Guard on nodeType instead, and construct the stylesheet in the root's own realm so it applies there. Styles now apply in different realms: