BackdropFilter blur ignores ClipOval when a UiKitView is in the tree (Impeller, iOS, regression persists in 3.44.4)

On iOS with Impeller, a BackdropFilter wrapped in a ClipOval samples and
paints its blur over the widget's rectangular bounds — a square halo — as
soon as a UiKitView is present in the same scene. Without the platform
view the clip is honored. #175048 describes this family and was closed as
fixed via #115926's fix (available since 3.41), but this reproduces on
stable 3.44.4.

Repro

Stack(children: [
  const SizedBox.expand(
    child: UiKitView(viewType: 'any-registered-view-type'),
  ),
  Center(
    child: SizedBox(
      width: 60, height: 60,
      child: ClipOval(
        child: BackdropFilter(
          filter: ImageFilter.blur(sigmaX: 10, sigmaY: 10),
          child: const ColoredBox(color: Color(0x66000000)),
        ),
      ),
    ),
  ),
])

Square blur halo around the circle when the UiKitView renders bright
content beneath.
Replace the UiKitView with a bright ColoredBox → perfect circle.
BackdropFilter.grouped inside a BackdropGroup shows the same bleed.

Environment

Flutter 3.44.4 (stable), Impeller default renderer
iPhone 13 Pro Max, iOS 27.0
Hybrid composition platform view (AVFoundation video layer in our app)

Happy to provide captures of each variant (with/without platform view,
grouped/ungrouped).

@foux

@foux Thanks for the report. Can you verify if the issue persists in the latest master? If it does, can you provide a minimal reproducible example (MRE) or a self-contained main.dart to replicate the behavior as the provided sample in not enough?

@saurabh-mirajkar

@saurabh-mirajkar Thanks for looking at this. Verified on latest master — still reproduces, identical to stable.

master: Flutter 3.46.0-1.0.pre-423, revision a3222d4a24 (2026-07-06) → square blur halo
stable 3.44.4 → square blur halo (as reported)

Self-contained main.dart below. The only dependency is webview_flutter (flutter pub add webview_flutter), used purely as a convenient first-party platform view — any UiKitView triggers the bug (in our app it is an AVFoundation video layer). The FAB swaps the platform view for an identical Flutter-drawn stripe pattern; with the platform view gone the blur is correctly clipped to the circle, with it present the blur paints over the widget's full rectangular bounds.

main.dart

// Minimal reproduction for https://github.com/flutter/flutter/issues/188971
//
// A BackdropFilter wrapped in a ClipOval paints its blur over the widget's
// rectangular bounds (square halo) as soon as a UiKitView is present in the
// same scene. webview_flutter is used only as a convenient first-party
// platform view rendering bright content underneath the filter.
//
// Tap the FAB to swap the platform view for an identical Flutter-drawn
// stripe pattern: the blur is then correctly clipped to a circle.

import 'dart:ui';

import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';

void main() => runApp(const ReproApp());

class ReproApp extends StatefulWidget {
  const ReproApp({super.key});

  @override
  State<ReproApp> createState() => _ReproAppState();
}

class _ReproAppState extends State<ReproApp> {
  late final WebViewController _controller;
  bool _usePlatformView = true;

  @override
  void initState() {
    super.initState();
    _controller = WebViewController()
      ..loadHtmlString(
        '<body style="margin:0;height:100vh;background:'
        'repeating-linear-gradient(45deg,#000 0 20px,#fff 20px 40px)"></body>',
      );
  }

  // Same stripes as the HTML page, rendered by Flutter itself.
  static const _stripes = DecoratedBox(
    decoration: BoxDecoration(
      gradient: LinearGradient(
        begin: Alignment.topLeft,
        end: Alignment(-0.98, -0.96),
        colors: [Colors.black, Colors.black, Colors.white, Colors.white],
        stops: [0, 0.5, 0.5, 1],
        tileMode: TileMode.repeated,
      ),
    ),
  );

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Stack(
          children: [
            // Bright background: platform view (bug) or plain widget (OK).
            SizedBox.expand(
              child: _usePlatformView
                  ? WebViewWidget(controller: _controller)
                  : _stripes,
            ),
            Center(
              child: SizedBox(
                width: 120,
                height: 120,
                child: ClipOval(
                  child: BackdropFilter(
                    filter: ImageFilter.blur(sigmaX: 10, sigmaY: 10),
                    child: const ColoredBox(color: Color(0x66000000)),
                  ),
                ),
              ),
            ),
          ],
        ),
        floatingActionButton: FloatingActionButton.extended(
          onPressed: () =>
              setState(() => _usePlatformView = !_usePlatformView),
          label: Text(_usePlatformView
              ? 'platform view (bug)'
              : 'plain widget (OK)'),
        ),
      ),
    );
  }
}

	platform view in tree	plain widget (control)
stable 3.44.4
master `a3222d4a24`

Device: iPhone 13 Pro Max, iOS 27.0, Impeller (default renderer), hybrid composition.

To rule out the iOS 27 beta as a factor: re-ran the same main.dart on a second device running iOS 26.5.2 (stable) — iPad Pro 12.9" 3rd gen (iPad8,7), same master build (a3222d4a24). Identical result: square blur halo with the platform view in the tree, correct circular clip without it.

So the bug reproduces on both iOS 26 (stable) and iOS 27 (beta), and is not tied to the OS version.

@foux

@foux Thanks for the updated repro and verification on both stable and current master. Labeling and routing for further investigation.

@Hari-07

@Hari-07 you may be interested in this one 🙂

@foux

Ty for the mention.

This isn't a regression - with the reproducible main.dart shared by OP even though the bug is present, the linked issue was about ClipRRect which is indeed fixed

@foux as a workaround you can do ClipRRect (if a circle is fine) for the moment. Will get this working soon :)

Looks like the current internal implementation of ClipOval on a backdrop propogates as a ClipPath . We do already have an issue that for ClipPath this currently no ops. Which means this issue with get fixed automatically when #179127 is fixed.

Not sure if that counts as duplicate

@Hari-07

Makes sense as a duplicate, thanks @Hari-07!

A better fix for this is to actually add the optimization that'd make a ClipOval a ClipRRect under the hood since thats more efficient anyway. ApplyClip already has these optimizations so it makes sense that PushClipToEmbeddedNativeViewMutatorStack mirrors them.

Reopening this issue since that'd seperate the 2 issues

Add `ClipPath` optimizations to backdrop clips as well (flutter#189118)

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

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BackdropFilter blur ignores ClipOval when a UiKitView is in the tree (Impeller, iOS, regression persists in 3.44.4) #188971

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BackdropFilter blur ignores ClipOval when a UiKitView is in the tree (Impeller, iOS, regression persists in 3.44.4) #188971

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saurabh-mirajkar commented on Jul 6, 2026

foux commented on Jul 6, 2026

foux commented on Jul 6, 2026

saurabh-mirajkar commented on Jul 6, 2026

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jmagman commented on Jul 7, 2026

Hari-07 commented on Jul 7, 2026

Hari-07 commented on Jul 7, 2026

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