Nico Weber c8510b58a3 LibPDF: Cache fonts per page ...

Previously, every time a page switched fonts, we'd completely
re-parse the font.

Now, we cache fonts in Renderer, effectively caching them per page.

It'd be nice to have an LRU cache across pages too, but that's a
bigger change, and this already helps a lot.

Font size is part of the cache key, which means we re-parse the same
font at different font sizes. That could be better too, but again,
it's a big help as-is already.

Takes rendering the 1310 pages of the PDF 1.7 reference with

    Build/lagom/bin/pdf --debugging-stats \
        ~/Downloads/pdf_reference_1-7.pdf

from 71 s to 11s :^)

Going through pages especially in the index is noticeably snappier.

(On the PDF 2.0 spec, ISO_32000-2-2020_sponsored.pdf, it's less
dramatic: From 19s to 16s.)

2023-10-11 07:10:19 +02:00

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