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Revert: Fix square corner issue - #193189

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Reverts: Fix square corner issue

Initiated by: @andywolff

Reason for reverting: seems to have caused a test order dependency #192992
Original PR Author: @andywolff

Reviewed By: @gaaclarke

The original PR description is provided below:

Fixes #190602, see my comment on that issue for details about the problems I identified.
Also fixes #162172

What changed

When a route contained rounded clips (such as CupertinoSheetRoute), intermediate child ink features, and a backdrop filter (such as a blurred app bar), the clip stack replay logic prematurely popped parent clips and exceeded the depth buffer budget across render pass splits, causing subsequent header draws to render with 90° square corners. This PR addresses both mechanisms:

First, EntityPassClipStack::RecordRestore was popping replay entities unconditionally whenever any clip was restored. In a sheet containing ink decorations (like list item ripple effects), child clip restores at deeper heights would prematurely discard the root parent clip. We now track clip_height in ReplayResult so that restorations only pop entities when clip_height > restore_height, preserving parent clips across sibling restores. When replaying those clips in ClipContents::Render, we also supply the entity's model matrix to properly recompute the MVP matrix against the new pass's orthographic projection instead of reusing the stale matrix from the prior pass.

Second, the pass depth budget was exhausting across backdrop splits. Canvas::kMaxDepth (1 << 24) was mismatched with Entity::kDepthEpsilon (1.0 / 262144.0, or 2^-18), allowing integer depths to exceed the 18-bit precision of the depth buffer. Aligning Canvas::kMaxDepth to 262,143 and capping depth allocations in Save/SaveLayer to min(current_depth_ + total_content_depth, parent_clip_depth) keeps clip replay and subsequent draw operations within valid precision bounds. In Canvas::Restore, we also prevent unconditional depth jumps to kMaxDepth for unclipped saves, preserving the allocated budget for subsequent sibling draws.

Testing

Reproducing this interaction in automated tests required testing the onscreen pass-splitting branch (IsOnscreen()), which normal offscreen unit tests bypass. We added a ScopedOnscreenOverride test hook in Canvas and constructed a multi-layer display list recreating the route clip, child ink items, blurred backdrop bar, and trailing app bar:

  • clip_stack_unittests.cc: Added EntityPassClipStackTest.RestoringChildClipPreservesParentReplayEntities to isolate parent clip retention across sibling restores.
  • canvas_unittests.cc: Added AiksTest.ClipDepthMaintainedAcrossBackdropFilterAndLayers to verify depth invariants and precision bounds (<= kMaxDepth), and AiksTest.ParentClipDepthBudgetPreservedAfterBackdropLayerRestore to verify parent depth budget restoration.
  • dl_golden_unittests.cc (impeller_golden_tests): Added DlGoldenTest.CanRenderClippedBackdropFilterWithSuperellipse for pixel-accurate golden image verification in CI against Skia Gold.

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Code Review

This pull request refactors and simplifies clip depth and clip stack management in Impeller. It increases the maximum canvas depth, simplifies clip depth tracking during save and restore operations, and removes clip height tracking from the entity pass clip stack and clip contents rendering. Additionally, several tests and unused mock dependencies are removed. There are no review comments to evaluate, so I have no feedback to provide.

@andywolff
andywolff requested review from flar and gaaclarke September 22, 2026 22:07
@github-actions github-actions Bot added engine flutter/engine related. See also e: labels. e: impeller Impeller rendering backend issues and features requests labels Sep 22, 2026
@andywolff andywolff added the autosubmit Merge PR when tree becomes green via auto submit App label Sep 23, 2026
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autosubmit label was removed for flutter/flutter/193189, because - The status or check suite Dashboard Checks has failed. Please fix the issues identified (or deflake) before re-applying this label.

@andywolff andywolff added the autosubmit Merge PR when tree becomes green via auto submit App label Sep 23, 2026
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@andywolff
Reland square corners fix (flutter#194314)
730d1b2 
Fixes flutter#192992
Relands flutter#191096
Fixes flutter#190602
Fixes flutter#162172

This PR relands flutter#191096, which
resolves the square corners regression in clipped backdrop filters. The
original PR was reverted in
flutter#193189 due to test flakiness and
order dependencies in CI, which were resolved and landed separately in
flutter#193497.

This is a pure reland.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [AI contribution guidelines] and understand my
responsibilities, or I am not using AI tools.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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LongCatIsLooong pushed a commit to LongCatIsLooong/flutter that referenced this pull request Oct 22, 2026
@andywolff @LongCatIsLooong
Reland square corners fix (flutter#194314)
433581c 
Fixes flutter#192992
Relands flutter#191096
Fixes flutter#190602
Fixes flutter#162172

This PR relands flutter#191096, which
resolves the square corners regression in clipped backdrop filters. The
original PR was reverted in
flutter#193189 due to test flakiness and
order dependencies in CI, which were resolved and landed separately in
flutter#193497.

This is a pure reland.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [AI contribution guidelines] and understand my
responsibilities, or I am not using AI tools.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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mdebbar pushed a commit to molchanovia/flutter that referenced this pull request Oct 27, 2026
@flutteractionsbot
Revert: Reland square corners fix (flutter#195436)
9ece365 
Reverts: [Reland square corners
fix](flutter#194314)

Initiated by: @andywolff

Reason for reverting: changed opacity behavior causing golden flakes
flutter#195423

Original PR Author: @andywolff

Reviewed By: @gaaclarke

The original PR description is provided below:

Fixes flutter#192992
Relands flutter#191096
Fixes flutter#190602
Fixes flutter#162172

This PR relands flutter#191096, which
resolves the square corners regression in clipped backdrop filters. The
original PR was reverted in
flutter#193189 due to test flakiness and
order dependencies in CI, which were resolved and landed separately in
flutter#193497.

This is a pure reland.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [AI contribution guidelines] and understand my
responsibilities, or I am not using AI tools.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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suryaKommana2662 pushed a commit to suryaKommana2662/flutter that referenced this pull request Oct 29, 2026
@andywolff @suryaKommana2662
Reland square corners fix (flutter#194314)
f9355e9 
Fixes flutter#192992
Relands flutter#191096
Fixes flutter#190602
Fixes flutter#162172

This PR relands flutter#191096, which
resolves the square corners regression in clipped backdrop filters. The
original PR was reverted in
flutter#193189 due to test flakiness and
order dependencies in CI, which were resolved and landed separately in
flutter#193497.

This is a pure reland.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [AI contribution guidelines] and understand my
responsibilities, or I am not using AI tools.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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suryaKommana2662 pushed a commit to suryaKommana2662/flutter that referenced this pull request Oct 29, 2026
@flutteractionsbot @suryaKommana2662
Revert: Reland square corners fix (flutter#195436)
ad8a038 
Reverts: [Reland square corners
fix](flutter#194314)

Initiated by: @andywolff

Reason for reverting: changed opacity behavior causing golden flakes
flutter#195423

Original PR Author: @andywolff

Reviewed By: @gaaclarke

The original PR description is provided below:

Fixes flutter#192992
Relands flutter#191096
Fixes flutter#190602
Fixes flutter#162172

This PR relands flutter#191096, which
resolves the square corners regression in clipped backdrop filters. The
original PR was reverted in
flutter#193189 due to test flakiness and
order dependencies in CI, which were resolved and landed separately in
flutter#193497.

This is a pure reland.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [AI contribution guidelines] and understand my
responsibilities, or I am not using AI tools.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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