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LibPDF: Cache fonts per page

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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.)
This commit is contained in:
Nico Weber 2023-10-10 13:55:35 -04:00 • committed by Andreas Kling
parent e6d9bb0774
commit c8510b58a3
2 changed files with 37 additions and 5 deletions
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19
Userland/Libraries/LibPDF/Renderer.h
View file

@ -99,6 +99,13 @@ class Renderer {
public:
static PDFErrorsOr<void> render(Document&, Page const&, RefPtr<Gfx::Bitmap>, RenderingPreferences preferences);
struct FontCacheKey {
DeprecatedString font_dictionary_key;
float font_size;
bool operator==(FontCacheKey const&) const = default;
};
private:
Renderer(RefPtr<Document>, Page const&, RefPtr<Gfx::Bitmap>, RenderingPreferences);
@ -139,6 +146,8 @@ private:
Gfx::AffineTransform const& calculate_text_rendering_matrix();
Gfx::AffineTransform calculate_image_space_transformation(int width, int height);
PDFErrorOr<NonnullRefPtr<PDFFont>> get_font(FontCacheKey const&, Optional<NonnullRefPtr<DictObject>> extra_resources);
RefPtr<Document> m_document;
RefPtr<Gfx::Bitmap> m_bitmap;
Page const& m_page;
@ -153,12 +162,22 @@ private:
bool m_text_rendering_matrix_is_dirty { true };
Gfx::AffineTransform m_text_rendering_matrix;
HashMap<FontCacheKey, NonnullRefPtr<PDFFont>> m_font_cache;
};
}
namespace AK {
template<>
struct Traits<PDF::Renderer::FontCacheKey> : public GenericTraits<PDF::Renderer::FontCacheKey> {
static unsigned hash(PDF::Renderer::FontCacheKey const& key)
{
return pair_int_hash(key.font_dictionary_key.hash(), int_hash(bit_cast<u32>(key.font_size)));
}
};
template<>
struct Formatter<PDF::LineCapStyle> : Formatter<StringView> {
ErrorOr<void> format(FormatBuilder& builder, PDF::LineCapStyle const& style)