[web] Capture pointers to the Flutter view so drags survive platform view iframes - #195187

flutter/flutter@d4c8577...0c2473c

2026-10-28 [email protected] Roll Packages from a8549ae to 13d38e0 (9 revisions) (flutter/flutter#195488)
2026-10-28 [email protected] Use int.oneBitCount in PersistentHashMap and scope 53-bit caps to JS (flutter/flutter#195005)
2026-10-28 [email protected] Roll pub packages (flutter/flutter#195483)
2026-10-28 [email protected] [iPhone Duo] Use the correct UIScreen to report the display size and update when fold/unfold (flutter/flutter#195199)
2026-10-28 [email protected] [fuchsia] Fix portable_ui_test.h includes for newer Fuchsia SDKs (flutter/flutter#195420)
2026-10-28 [email protected] Change default pipeline options to match production draw calls (flutter/flutter#194597)
2026-10-28 [email protected] Roll Fuchsia Test Scripts from 2T18KC7-LDQtmQiLP... to xl1LWBuppzu-BnOzV... (flutter/flutter#195450)
2026-10-27 [email protected] [flutter_tools] Inject dependencies into Darwin build targets, native assets, and Xcode build settings (flutter/flutter#194052)
2026-10-27 [email protected] Revert: Reland square corners fix (flutter/flutter#195436)
2026-10-27 [email protected] [flutter_tools] Add DeviceService app launch and flutter run support for tool extensions (flutter/flutter#194589)
2026-10-27 [email protected] [engine] Honor targetWidth/targetHeight for animated images (flutter/flutter#194615)
2026-10-27 [email protected] [Android][a11y] Set visibleToUser=false for hidden semantics nodes (flutter/flutter#194411)
2026-10-27 [email protected] Fix repo deletion test flake (flutter/flutter#195349)
2026-10-27 [email protected] Roll Packages from 23a05b6 to a8549ae (10 revisions) (flutter/flutter#195434)
2026-10-27 [email protected] [web] Capture pointers to the Flutter view so drags survive platform view iframes (flutter/flutter#195187)
2026-10-27 [email protected] [web] Add opt-in raw samples, measured sample count and warm-up phase hook to the web benchmark recorder (flutter/flutter#195118)
2026-10-27 [email protected] Link migration guide in deprecation messages (flutter/flutter#195361)
2026-10-27 [email protected] Pin basic_material_app_macos__compile to macOS 26 (flutter/flutter#195429)
2026-10-27 [email protected] Add benchmark for warmed pipeline usage (flutter/flutter#195001)
2026-10-27 [email protected] [flutter_tools] Add device log streaming support to DeviceService and ExtensionBackedDevice (flutter/flutter#194964)
2026-10-27 [email protected] Roll Dart SDK from 1d16c04dc346 to 65fc979759ca (4 revisions) (flutter/flutter#195383)

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…view iframes (flutter#195187)

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On Flutter Web, a drag that starts on Flutter content stops receiving
`pointermove` events when the pointer moves over an `<iframe>` platform
view, because the browser routes those events to the iframe document
instead of the host window. As a result, the dragged widget freezes over
the iframe and jumps when the pointer re-enters Flutter content.

This PR captures the pointer to the `<flutter-view>` root on
`pointerdown` when the press targets Flutter content (`_viewTarget` or
`flt-glass-pane`, to which events inside the scene's shadow root are
retargeted), and cancels still-pressed pointers if capture on the view
root is involuntarily lost (`lostpointercapture`). Presses on platform
views, the text-editing host, and the semantics host are excluded so
native HTML interactions, text selection, and `ClickDebouncer`
accessibility clicks continue to work on their original targets.

This change ships separately from automatic pointer interceptors so that
pointer-routing changes for all Flutter web apps can be reviewed and
reverted independently.

**Review hot spots**

- **Boundary events during a captured drag:**
`pointerover`/`out`/`enter`/`leave` on other elements (including
`pointerleave` on the view root when dragging outside the window) are
suppressed until release.
- **Involuntary capture loss (`lostpointercapture`):** cancels active
presses if capture on `_viewTarget` is lost before
`pointerup`/`pointercancel` (e.g. window blur or
`releasePointerCapture`), while ignoring `lostpointercapture` after
normal release or bubbling from platform view descendants.
- **Clicks and semantics:** after a captured press, `click` lands on the
view root. `semanticsHost` is excluded from capture so `ClickDebouncer`
and assistive-technology `flt-tappable` activation remain unchanged
(drags starting on semantics nodes remain uncaptured over iframes).
- **Touch, pen, and multi-view:** touch already has implicit capture
(moving it to the view root is benign), pen drags gain capture alongside
mouse drags, and each view captures to its own root.

Fixes flutter#141307

Related: flutter#157968,
flutter#134652

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