Implement DisplayList canonicalization

[Kyle-Ye]

Summary

• normalize empty and identity display-list items while preserving required content
• collapse compatible paint, clip, mask, and color-filter paths
• add dual coverage across canonicalization branches and reuse the shared SwiftUI version gate

Validation

• all 40 parameterized canonicalization fixtures pass
• the DisplayList printer dual-test suite passes

[augmentcode]

^{PR Risk Analyzer Agent 🛡️}

👀 Human review needed

Justification

This is a type: feature change that introduces substantive new production logic in core rendering — Sources/OpenSwiftUICore/Render/DisplayList/DisplayList.swift (+250/−47).

The reworked DisplayList.Item.canonicalize(options:) implements non-trivial branching that rewrites how display-list items are normalized and collapsed: empty/identity normalization, unit/zero opacity folding, identity-transform and identity-filter collapsing, clip→shape paint substitution, mask→clip/filter fusion, backdrop color-matrix fusion, and required-content preservation. Supporting helpers (opaqueContentPath, paint(in:), colorMatrix(size:), backdropFilter(size:)) and an effect-protocol relocation are also added.

These transformations directly affect rendered output correctness and edge-case behavior (e.g. opacity thresholds, opaque-paint detection, frame/offset handling, .required feature gating). This is well outside any automatic low-risk change class, so per policy I fail closed and route it to human review. The accompanying dual-test suite (40 canonicalization fixtures) is helpful signal but does not by itself substitute for human review of the core logic.

_{Reviewed commit bc9c273}

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[augmentcode]

🤖 Augment PR Summary

Summary: This PR implements canonicalization for DisplayList.Item values.

Changes:

• Removes empty content and effect items when they do not carry required content.
• Flattens identity effects, unit opacity, identity affine transforms, and identity filters.
• Collapses compatible clip-and-paint paths into shape content.
• Converts eligible opaque masks into clips and masked backdrop filters into vibrant color-matrix filters.
• Fuses nested compatible color-matrix filters.
• Moves effect-animation protocols and transform accessors into focused extensions without behavior changes.
• Adds a Darwin symbol stub and parameterized dual tests covering canonicalization branches.
• Reuses the shared SwiftUI 6.5-to-before-7.0 runtime gate in printer dual tests.

Technical Notes: Rewrites preserve item identity/frame/version handling where identity effects are eliminated and honor `.disableCanonicalization` plus required-content features.

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_{Reviewed commit: bc9c273}

[codecov]

Codecov Report

❌ Patch coverage is 0% with 164 lines in your changes missing coverage. Please review.
✅ Project coverage is 14.61%. Comparing base (c343337) to head (bc9c273).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...enSwiftUICore/Render/DisplayList/DisplayList.swift	0.00%	164 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #986      +/-   ##
==========================================
- Coverage   14.66%   14.61%   -0.05%     
==========================================
  Files         690      690              
  Lines       47615    47762     +147     
==========================================
- Hits         6983     6982       -1     
- Misses      40632    40780     +148     

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[tuist]

🛠️ Tuist Run Report 🛠️

Tests 🧪

Scheme	Status	Cache hit rate	Tests	Skipped	Ran	Commit
OpenSwiftUI	❌	0 %	1012	0	1012	931fdf8b7

Failed Tests ❌

• OpenSwiftUI: 6 failed tests (View all)

• viewListUsageRendersStaticAndOptionalAliasSources() · OpenSwiftUITests · ViewAliasTests
  (optionalPresentDisplayList → "(display-list (item #:identity 8 #:version 17 (frame (0.0 0.0; 100.0 100.0)) (content-seed 33) (color #000000FF)))"…

• nestedUnaryViewRoot() · OpenSwiftUICoreTests · VariadicViewTests
  (displayList.description → "(display-list (item #:identity 7 #:version 1005 (frame (0.0 0.0; 100.0 100.0)) (effect (item #:identity 10 #:version…

• nestedMultiViewRoot() · OpenSwiftUICoreTests · VariadicViewTests
  (displayList.description → "(display-list (item #:identity 14 #:version 1008 (frame (0.0 0.0; 100.0 100.0)) (content-seed 2015) (color #FF3B30FF))…

• optionalViewAliasDynamicProperty() · OpenSwiftUITests · ViewAliasTests
  (displayList → "(display-list (item #:identity 4 #:version 10 (frame (0.0 0.0; 100.0 100.0)) (content-seed 19) (color #000000FF)))").contains(effe…

• optionalViewAliasUsage(sourceIsPresent:) · OpenSwiftUITests · ViewAliasTests
  (displayList → "(display-list (item #:identity 1 #:version 3 (frame (0.0 0.0; 100.0 100.0)) (content-seed 5) (color #000000FF)))").contains(effect…

Showing 5 of 6 failed tests. See links above for full details.

Builds 🔨

Scheme	Status	Duration	Commit
OpenSwiftUI	✅	1m 38s	931fdf8b7