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StandardFont built a new AFMFont for every document, rebuilding the glyph width and kerning tables from the same font data each time. AFMFont only reads that data, so keep one per font data in a WeakMap. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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What kind of change does this PR introduce?
Performance fix.
StandardFontbuilds a newAFMFontfor every document, so each document that uses e.g. Helvetica rebuilds its glyph width and kerning tables from the same font data.AFMFontonly reads that data after construction (nothing inlib/writes to it), so one instance per font data is now kept in aWeakMapand shared. Keying on the data object meansregisterStdFonts()with replacement data still gets a freshAFMFont.Measured on Node 26, Apple Silicon, 2 000 documents with one heading in Helvetica-Bold and a paragraph in Helvetica (after 200 warm-up documents), 3 runs each:
In a react-pdf HTML → PDF pipeline, profiling showed
AFMFontconstruction at ~7% of CPU, and the change cut total render time by ~10%.Checklist:
standard font metrics are shared across documentsfails without the change; fullyarn testpasses, 551 tests)🤖 Generated with Claude Code