RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-27 15:27:35 +00:00
Code Issues Activity Actions

LibPDF: Don't crash on fixed-width type 1 fonts that use /MissingWidth

Browse source 
Type 1 fonts usually have a m_font_program and no m_font -- they only
have m_font if we're using a replacement font for the fonts that
were built-in to PDFs before Acrobat 4.0 (and must still work to
show existing files).

However, SimpleFont::get_glyph_width() used to always return a
float, which in Type1Font was only implemented if m_font was set.

Per spec, we're supposed to just use /MissingWidth for fonts that
are missing an entry in the descriptor's /Width array. However, for
built-in fonts, no explicit /Width array is needed (PDF 1.7 spec,
Appendix H.3, 5.5.1). So if we just always use /MissingWidth,
then PDFs that use a built-in font draw all their text on top
of each other (e.g. 000333.pdf from stillhq.com-pdfdb).

So change get_glyph_width() to return Optional<float>, return
it only in Type1Font if m_font is set, and use MissingWidth
if it isn't set.

That way, replacement fonts still return a width, and real
fonts that are supposed to have /Width and use /MissingWidth
for missing entries do what they're supposed to too, instead
of crashing.

From 20 (6%) to 16 (5%) crashes on the 300 first PDFs, and from
39 (7.8%) to 31 (6.2%) on the 500-random PDFs test.
This commit is contained in:
Nico Weber 2023-10-22 23:34:14 -04:00 • committed by Tim Flynn
parent 52afa936c4
commit 11bee7a075
6 changed files with 12 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

4
Userland/Libraries/LibPDF/Fonts/SimpleFont.h
View file

@ -17,7 +17,7 @@ public:
protected:
PDFErrorOr<void> initialize(Document* document, NonnullRefPtr<DictObject> const& dict, float font_size) override;
virtual float get_glyph_width(u8 char_code) const = 0;
virtual Optional<float> get_glyph_width(u8 char_code) const = 0;
virtual void draw_glyph(Gfx::Painter& painter, Gfx::FloatPoint point, float width, u8 char_code, Color color) = 0;
RefPtr<Encoding>& encoding() { return m_encoding; }
RefPtr<Encoding> const& encoding() const { return m_encoding; }
@ -26,7 +26,7 @@ private:
RefPtr<Encoding> m_encoding;
RefPtr<StreamObject> m_to_unicode;
HashMap<u8, u16> m_widths;
u16 m_missing_width;
u16 m_missing_width { 0 };
};
}