Fix noisy missing font fallback logging

[jfversluis]

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Fixes #28502
Fixes #24059

Related reports: #19774, #17872, #13239. Related to the embedded-font warning symptom in #19804, but not the broader NuGet asset packaging issue there.

Description

This reduces noisy missing-font fallback logging when an unregistered font family is resolved as a platform/system fallback rather than as an app font asset.

• Avoids warning/error log noise for unregistered missing font fallback names on Windows and Android.
• Avoids Android asset-warning noise for embedded-resource fonts that have already been extracted to the file system.
• Keeps registered missing fonts logging as warnings so real app font registration issues remain visible.
• Adds regression coverage for OpenSansRegular and Segoe UI on the affected Windows/Android font manager paths.

Scope

This PR intentionally covers the proven Windows and Android root causes. iOS/MacCatalyst was investigated separately, but the current tests pass without the fix there, so this PR no longer changes iOS/MacCatalyst font manager behavior or claims an iOS/MacCatalyst fix.

Validation

• dotnet build src\Core\tests\DeviceTests\Core.DeviceTests.csproj -f net10.0-windows10.0.19041.0 -p:WindowsPackageType=None --no-restore -v:minimal
• Previous Windows repro validation confirmed the patched font manager removes the noisy missing-font fallback errors while preserving fallback source behavior.
• Previous Android build validation confirmed the font manager changes compile and keep registered missing-font warnings while suppressing unregistered fallback/embedded-resource asset-warning noise.

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.sh | bash -s -- 35963

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.ps1) } 35963"

[kubaflo]

/review -b feature/enhanced-reviewer

[MauiBot]

AI Review Summary

@jfversluis — new AI review results are available based on this last commit: 6e8408a. To request a fresh review after new comments or commits, comment /review rerun.

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🗂️ Review Sessions — click to expand

🚦 Gate — Test Before & After Fix

Gate Result: ⚠️ SKIPPED

Gate skipped (SkipUITests fast test mode). No UI/device tests were run for this pipeline invocation.

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📋 Pre-Flight — Context & Validation

Issue: #28502 - Log - Missing Fonts report; #24059 - [Android] AddEmbeddedResourceFont Shows Exception Warning in Output Window
PR: #35963 - Fix noisy missing font fallback logging
Platforms Affected: Windows, Android; iOS requested for this review but PR description explicitly says iOS/MacCatalyst are not in scope after prior investigation.
Files Changed: 3 implementation, 4 test

Key Findings

• PR suppresses noisy missing-font fallback logging for unregistered/system font names while preserving warnings for registered missing app fonts.
• Android fix moves extracted-file handling before asset probing and only logs asset warnings when the font came from a registrar mapping.
• Windows fix avoids LocalPath on relative URIs and uses app-package resolution before Win2D probing.
• Prior iOS gate evidence says candidate tests passed both with and without the PR fix, so iOS does not currently demonstrate this bug.
• GitHub CLI is unauthenticated in this environment; public API/local branch were used for context, and CI status remains undetermined.

Code Review Summary

Verdict: NEEDS_DISCUSSION
Confidence: low
Errors: 0 | Warnings: 0 | Suggestions: 0

Key code review findings:

• Prior gate/test concern remains unresolved/undetermined: public review evidence reports iOS tests pass without the fix and with the fix, so they do not prove the bug.
• Prior inline logger brittleness feedback is fixed: FontManagerLoggerProvider.IsEnabled captures warning-and-above only.
• No high-confidence code defects found in the current Windows/Android implementation.

Fix Candidates

#	Source	Approach	Test Result	Files Changed	Notes
PR	PR #35963	Platform-specific Windows/Android suppression of unregistered fallback font logging while preserving registered missing-font warnings	⚠️ Gate skipped/no iOS repro in current prompt	FontManager.Android.cs, FontManager.Windows.cs, FontImageSourceService.Windows.cs, device tests	Original PR; no iOS code changes.

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🔬 Code Review — Deep Analysis

Code Review — PR #35963

Independent Assessment

What this changes: Reduces noisy font fallback logging on Android/Windows by only warning for registered app-font failures, handling embedded-file paths before Android asset loading, and avoiding Windows relative-URI LocalPath failures for font fallback probing.

Inferred motivation: Unregistered/system fallback names like Segoe UI/OpenSansRegular should not be treated as missing app assets.

Reconciliation with PR Narrative

Author claims: Matches: fixes noisy Windows/Android missing-font fallback logging and Android embedded-resource warnings; no iOS/MacCatalyst scope.
Agreement/disagreement: Code matches the stated scope.

Prior Review Reconciliation

Prior ❌ Error Finding	Source	Status	Evidence
Gate/tests pass without fix or are insufficient	MauiBot/kubaflo	❌ Unresolved/undetermined	Latest public reviews still show gate failure on current head; no authenticated CI/test verification available.
Inline logger brittleness	Copilot	✅ Fixed	FontManagerLoggerProvider.IsEnabled now captures warning+ only.

Blast Radius Assessment

• Runs for all instances: Yes, platform FontManager/font image paths affect all Windows/Android font resolution.
• Startup impact: Possible where controls resolve fonts during initialization.
• Static/shared state: Existing per-manager caches only; no new global state.

CI Status

• Required-check result: undetermined/tool-unavailable (gh unauthenticated).
• Classification: undetermined. Public check-runs show failing maui-pr, with visible infra-like failures, but required-check status could not be authenticated.
• Action taken: attempted ci-analysis (unavailable), used azdo-build-investigator context/public API; capped confidence.

Findings

No high-confidence ❌ Error or ⚠️ Warning code findings found.

Failure-Mode Probing

• Unregistered fallback font: returns fallback candidates without warning.
• Registered missing font: still logs warning.
• Relative Windows font source: no longer calls LocalPath on relative URI.
• Embedded Android extracted font path: File.Exists path loads before asset warning.

Verdict: NEEDS_DISCUSSION

Confidence: low — platform font plumbing plus unauthenticated/undetermined required CI and unresolved test-gate concern. Code approach appears sound, but this should not be treated as merge-ready without CI/test reconciliation.

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🛠️ Fix — Analysis & Comparison

Fix Candidates

#	Source	Approach	Test Result	Files Changed	Notes
1	maui-expert-reviewer	iOS-only registered-font warning gating: only log UIKit font-load warnings when the family resolves through IFontRegistrar.	❌ Not selected; iOS build-only passed but does not validate the Windows/Android bug	1 file (FontManager.iOS.cs)	Different from PR, but PR intentionally removed iOS scope because tests passed without the fix. Not demonstrably better.
2	maui-expert-reviewer	Windows generation-layer filtering: only emit generated Assets/Fonts/*.ttf/.otf fallback candidates when the package asset exists.	⚠️ Blocked; Windows build proxy blocked by NETSDK1005; iOS build-only passed but did not compile Windows code	1 file (FontManager.Windows.cs)	Higher-level than PR, but behavior riskier because it removes fallback candidates instead of tolerating them.
3	maui-expert-reviewer	Android asset-existence preflight: use AssetManager.List before Typeface.CreateFromAsset so missing candidates are not exception-driven.	❌ Not selected; Android build-only passed after namespace fix, iOS build-only passed, but no Android behavioral tests ran	1 file (FontManager.Android.cs)	Strongest alternative idea, but still not demonstrably better than PR without device-test proof and carries asset-list semantics risk.
PR	PR #35963	Platform-specific Windows/Android suppression/tolerance: Android checks registrar/file path before asset probing and logs only registered misses; Windows tolerates relative/unresolved font candidates without noisy errors.	⚠️ Gate skipped/no tests detected in prompt; prior public iOS gate did not reproduce the bug	3 implementation files + tests	Original PR remains selected because alternatives were unproven or riskier under available validation.

Cross-Pollination

Model/Reviewer	Round	New Ideas?	Details
maui-expert-reviewer	1	Yes	Proposed provenance-classified lookup; implemented as try-fix-1 iOS warning gating due requested iOS platform.
maui-expert-reviewer	2	Yes	Proposed suppressing invalid probes at Windows asset-candidate generation layer after try-fix-1 failed to prove value.
maui-expert-reviewer	3	Yes	Proposed Android AssetManager.List preflight after try-fix-2 was Windows-validation blocked and potentially riskier.
orchestrator	4	No	Remaining meaningful approaches would be variations of the same three classes: warning gating, candidate generation filtering, or asset existence preflight. Given iOS cannot reproduce/compile the relevant Windows/Android paths, further variations would not be demonstrably better.

Exhausted: Yes — for this review environment and requested iOS test platform. The bug is Windows/Android-specific, and iOS builds cannot validate the affected code paths.
Selected Fix: PR's fix — it is narrower and less risky than candidate 2, avoids candidate 3's Android asset-list compatibility risk, and does not add unproven iOS behavior from candidate 1. Candidate 3 is the only alternative worth future consideration if Android behavioral tests can be run.

Per-Candidate Details

try-fix-1

See CustomAgentLogsTmp/PRState/35963/PRAgent/try-fix-1/content.md.

try-fix-2

See CustomAgentLogsTmp/PRState/35963/PRAgent/try-fix-2/content.md.

try-fix-3

See CustomAgentLogsTmp/PRState/35963/PRAgent/try-fix-3/content.md.

Environment Notes

• gh was unauthenticated, so PR context used public GitHub API plus the checked-out review branch.
• EstablishBrokenBaseline.ps1 could not run because unrelated dirty files already existed in the shared worktree. Candidate diffs were applied and restored manually without touching unrelated changes.
• The prompt-provided gate result was respected: gate verification was not rerun and gate/content.md was not modified.

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🏁 Report — Final Recommendation

Comparative Fix Report — PR #35963

Inputs

• pr: submitted PR fix on branch pr-review-35963
• pr-plus-reviewer: submitted PR fix plus expert reviewer feedback
• try-fix-1: Android asset-existence preflight from try-fix-1/content.md
• try-fix-2: iOS registered-font warning gating from try-fix-2/content.md
• try-fix-3: Windows asset-candidate filtering from try-fix-3/content.md

Note: the aggregate try-fix/content.md table conflicts with the individual try-fix-N/content.md files for candidate numbering. This report uses the individual try-fix-N files as authoritative for candidate IDs.

Candidate Ranking

Rank	Candidate	Regression status	Assessment
1	pr	⚠️ Gate skipped in prompt; prior targeted Windows/Android validation documented	Best balance of scope, risk, and relevance. Directly addresses the proven Windows/Android noisy logging roots while preserving registered missing-font warnings and existing fallback behavior.
2	pr-plus-reviewer	⚠️ Same as pr	Equivalent to pr because the expert reviewer produced no actionable findings and inline-findings.json is []. Ranked just below pr only because it adds no improvement over the raw submitted fix.
3	try-fix-1	⚠️ Android build-only and iOS build-only passed; no behavioral regression tests	Strongest alternate idea for Android because it avoids exception-driven asset miss probing. Still riskier than the PR because AssetManager.List must exactly match Typeface.CreateFromAsset lookup semantics for root and subfolder assets, and no Android behavioral tests proved it.
4	try-fix-3	⚠️ Windows validation blocked; iOS build-only passed but did not compile the Windows code	Plausible Windows-only alternative, but riskier because it removes speculative fallback asset candidates instead of tolerating unresolved ones. Environment did not prove the Windows behavior.
5	try-fix-2	❌ Not selected; iOS build-only passed but does not reproduce the Windows/Android bug	Does not address the PR's proven Windows/Android root causes. Since prior investigation found iOS tests pass without the fix, this candidate is unproven and out of scope.

No candidate has stronger regression evidence than the PR. Candidates with blocked, weak, or non-relevant validation are ranked lower than the submitted PR fix.

Winning Candidate

Winner: pr

The submitted PR is the best candidate because it is narrowly targeted to the Windows and Android code paths where the noisy logging root causes were identified. It suppresses unregistered fallback noise without hiding registered app-font registration problems, and it avoids the additional behavioral risk introduced by the alternatives.

Why the Alternatives Do Not Win

pr-plus-reviewer

The expert reviewer found no actionable issues, so this candidate is a no-op relative to pr. It is safe, but it is not a distinct improvement.

try-fix-1

The Android asset preflight approach could be worth future exploration, but it depends on AssetManager.List matching all successful Typeface.CreateFromAsset paths. Without Android behavioral tests for root assets, Fonts/, fonts/, registered misses, unregistered misses, and embedded-resource extraction, it is not safer than the PR.

try-fix-2

The iOS warning-gating approach is out of scope for the demonstrated bug. The PR intentionally removed iOS/MacCatalyst behavior changes because current tests pass without the fix there.

try-fix-3

The Windows asset-candidate filtering approach prevents nonexistent assets from reaching Win2D, but it changes fallback candidate generation itself. The PR's approach is more conservative because it keeps the existing fallback list and only avoids noisy family-name probing for unresolved package assets.

Recommendation

Proceed with the submitted PR fix. Keep inline-findings.json as an empty array and do not apply any reviewer-driven code changes.

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🧭 Next Steps — review latest findings

No alternative fix was selected for this run. Review the session findings and CI results before merging.

[kubaflo]

/azp run

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).

[rokmeglicbit]

@kubaflo I could not test my app, but I could test related issue #24059 and I still get the error.

Here is the test app with the 35963 PR included. Save and run on Android.
MauiSampleApplication (2).zip

[kubaflo]

@rokmeglicbit did you test with this: #35963 (comment) ?

[rokmeglicbit]

@kubaflo yes, it is in the zip project above, the include reference is 35963

<ItemGroup>
	  <PackageReference Include="Microsoft.Maui.Controls" Version="10.0.100-ci.pr35963.26372.101" />
</ItemGroup>

Please download .zip and try it yourself. Maybe I did something wrong :(

[jfversluis]

Probably already mitigated/fixed by #33919 lets wait for that to land and see if we then still need to do anything here.

[rokmeglicbit]

@jfversluis did you try the testing and it works?
What is the new PR version, so I can test the zip also?

I guess issue 23268 is duplicate of this pull/35963, so testing above .zip would also confirm issue 23268?