pdfcpu / pdfcpu / 18786914678

62%

Build Type

push

github

Committed by hhrutter

Commit Message

Implement lazy font loading to reduce memory footprint

This change defers font loading until fonts are actually needed, reducing
memory usage for operations that don't require fonts (merge, split, etc.).

Changes:
- pkg/font/metrics.go: Add lazy loading with sync.Once pattern
  - doLoadUserFonts(): Actual loading implementation
  - LoadUserFonts(): Idempotent wrapper using sync.Once
  - ensureUserFontsLoaded(): Convenience wrapper for error-free calls
- pkg/pdfcpu/model/configuration.go: Replace eager font loading with
  ensureFontDirInitialized() that only sets up directories

Design:
- Uses sync.Once for clean, idiomatic lazy initialization
- Separates loading synchronization (Once) from map access (RWMutex)
- Error from first load attempt is cached and returned to all callers
- Thread-safe and efficient (atomic operations in sync.Once)

Benefits:
- Reduces minimum virtual memory requirement from ~800MB to ~720MB
- Eliminates unnecessary 16MB font allocation for common operations
- No impact on operations that need fonts (loaded on first use)
- Improves startup time when fonts aren't needed

Testing:
- Operations without fonts (merge, split, validate) now work with 720MB VSZ
- Operations with fonts (stamps, forms) load fonts lazily on first access
- LoadUserFonts() is idempotent and thread-safe

Related to #1169

Coverage Stats

22 of 33 new or added lines in 2 files covered. (66.67%)

9 existing lines in 1 file now uncovered.

44728 of 71752 relevant lines covered (62.34%)

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