Use threadsafe pooling for TrueType Interpreter #486
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Pull request overview
This pull request introduces thread-safe object pooling for TrueTypeInterpreter instances to fix concurrency issues when rendering fonts in parallel (Issue #484). The implementation adds a generic ObjectPool<T> class with an IPooledObjectPolicy<T> interface, and refactors StreamFontMetrics to use a bounded pool of interpreter instances instead of a single shared instance.
Key changes:
- New generic
ObjectPool<T>class for efficient, thread-safe object reuse with bounded capacity based on processor count - Refactored
ApplyTrueTypeHintingto borrow interpreters from pool with proper try-finally cleanup - Added comprehensive parallel rendering tests to validate thread-safety fixes
Reviewed changes
Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
src/SixLabors.Fonts/ObjectPool{T}.cs |
New generic object pool implementation with thread-safe get/return operations using lock-free primitives |
src/SixLabors.Fonts/StreamFontMetrics.cs |
Added interpreter pool initialization in CompactFont constructor |
src/SixLabors.Fonts/StreamFontMetrics.TrueType.cs |
Refactored hinting to use pooled interpreters; added CreateInterpreter factory method and pooling policy |
src/SixLabors.Fonts/Tables/TrueType/Hinting/TrueTypeInterpreter.cs |
Added TODO comment suggesting SIMD optimization for CVT initialization |
src/SixLabors.Fonts/Buffer{T}.cs |
Updated memory slicing to use modern range syntax |
tests/SixLabors.Fonts.Tests/Issues/Issues_484.cs |
Added parallel rendering tests to reproduce and validate the thread-safety fix |
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Pull request overview
Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.
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Prerequisites
Description
Fix #484
This pull request introduces a thread-safe object pooling mechanism for
TrueTypeInterpreterinstances in the font rendering pipeline, improving performance and correctness when rendering fonts in parallel. The main changes include implementing a generic object pool, refactoring howTrueTypeInterpreterinstances are managed and used, and adding targeted tests to ensure thread safety and correctness.Thread safety and performance improvements:
ObjectPool<T>class andIPooledObjectPolicy<T>interface to efficiently reuse objects and reduce allocation overhead, especially under concurrent workloads. (src/SixLabors.Fonts/ObjectPool{T}.cs)StreamFontMetricsto use a thread-safe, bounded pool ofTrueTypeInterpreterinstances (interpreterPool) instead of a single instance, preventing race conditions and improving performance in parallel scenarios. (src/SixLabors.Fonts/StreamFontMetrics.TrueType.cs,src/SixLabors.Fonts/StreamFontMetrics.cs) [1] [2] [3] [4]TrueTypeInterpreterPooledObjectPolicyto control creation and return behavior for pooled interpreters. (src/SixLabors.Fonts/StreamFontMetrics.TrueType.cs)Code quality and maintainability:
Buffer<T>constructor for clarity and modern C# idioms. (src/SixLabors.Fonts/Buffer{T}.cs)TrueTypeInterpretersuggesting possible SIMD optimization for control value table initialization. (src/SixLabors.Fonts/Tables/TrueType/Hinting/TrueTypeInterpreter.cs)Testing and validation:
tests/SixLabors.Fonts.Tests/Issues/Issues_484.cs)These changes collectively address concurrency issues in font rendering, improve resource management, and lay the groundwork for further performance optimizations.