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LibPDF: Don't crash on fixed-width type 1 fonts that use /MissingWidth
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.
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parent
52afa936c4
commit
11bee7a075
6 changed files with 12 additions and 8 deletions
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@ -53,8 +53,10 @@ PDFErrorOr<Gfx::FloatPoint> SimpleFont::draw_string(Gfx::Painter& painter, Gfx::
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float glyph_width;
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if (auto width = m_widths.get(char_code); width.has_value())
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glyph_width = font_size * width.value() / 1000.0f;
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else if (auto width = get_glyph_width(char_code); width.has_value())
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glyph_width = width.value();
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else
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glyph_width = get_glyph_width(char_code);
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glyph_width = m_missing_width;
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draw_glyph(painter, glyph_position, glyph_width, char_code, paint_color);
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@ -17,7 +17,7 @@ public:
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protected:
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PDFErrorOr<void> initialize(Document* document, NonnullRefPtr<DictObject> const& dict, float font_size) override;
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virtual float get_glyph_width(u8 char_code) const = 0;
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virtual Optional<float> get_glyph_width(u8 char_code) const = 0;
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virtual void draw_glyph(Gfx::Painter& painter, Gfx::FloatPoint point, float width, u8 char_code, Color color) = 0;
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RefPtr<Encoding>& encoding() { return m_encoding; }
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RefPtr<Encoding> const& encoding() const { return m_encoding; }
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@ -26,7 +26,7 @@ private:
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RefPtr<Encoding> m_encoding;
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RefPtr<StreamObject> m_to_unicode;
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HashMap<u8, u16> m_widths;
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u16 m_missing_width;
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u16 m_missing_width { 0 };
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};
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}
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@ -35,7 +35,7 @@ PDFErrorOr<void> TrueTypeFont::initialize(Document* document, NonnullRefPtr<Dict
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return {};
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}
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float TrueTypeFont::get_glyph_width(u8 char_code) const
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Optional<float> TrueTypeFont::get_glyph_width(u8 char_code) const
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{
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return m_font->glyph_width(char_code);
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}
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@ -14,7 +14,7 @@ namespace PDF {
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class TrueTypeFont : public SimpleFont {
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public:
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float get_glyph_width(u8 char_code) const override;
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Optional<float> get_glyph_width(u8 char_code) const override;
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void set_font_size(float font_size) override;
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void draw_glyph(Gfx::Painter&, Gfx::FloatPoint, float, u8, Color) override;
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Type type() const override { return PDFFont::Type::TrueType; }
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@ -49,9 +49,11 @@ PDFErrorOr<void> Type1Font::initialize(Document* document, NonnullRefPtr<DictObj
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return {};
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}
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float Type1Font::get_glyph_width(u8 char_code) const
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Optional<float> Type1Font::get_glyph_width(u8 char_code) const
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{
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return m_font->glyph_width(char_code);
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if (m_font)
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return m_font->glyph_width(char_code);
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return OptionalNone {};
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}
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void Type1Font::set_font_size(float font_size)
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@ -22,7 +22,7 @@ struct Type1GlyphCacheKey {
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class Type1Font : public SimpleFont {
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public:
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float get_glyph_width(u8 char_code) const override;
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Optional<float> get_glyph_width(u8 char_code) const override;
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void set_font_size(float font_size) override;
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void draw_glyph(Gfx::Painter& painter, Gfx::FloatPoint point, float width, u8 char_code, Color color) override;
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Type type() const override { return PDFFont::Type::Type1; }
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