RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-26 11:57:34 +00:00
Code Issues Activity Actions

LibGfx: Determine slope attributes for TrueTypeFonts from tables

Browse source 
First checks the OS/2 table for an oblique selection flag before
falling back on italic flags.
This commit is contained in:
thankyouverycool 2022-01-31 20:10:30 -05:00 • committed by Andreas Kling
parent a79e730839
commit 87a149c9a4
5 changed files with 29 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

2
Userland/Libraries/LibGfx/BitmapFont.h
View file

@ -37,7 +37,7 @@ public:
u16 weight() const override { return m_weight; }
void set_weight(u16 weight) { m_weight = weight; }
u8 slope() const { return m_slope; }
virtual u8 slope() const override { return m_slope; }
void set_slope(u8 slope) { m_slope = slope; }
Glyph glyph(u32 code_point) const override;

1
Userland/Libraries/LibGfx/Font.h
View file

@ -101,6 +101,7 @@ public:
FontMetrics metrics(u32 code_point) const;
virtual u8 presentation_size() const = 0;
virtual u8 slope() const = 0;
virtual u16 weight() const = 0;
virtual Glyph glyph(u32 code_point) const = 0;

23
Userland/Libraries/LibGfx/TrueTypeFont/Font.cpp
View file

@ -474,6 +474,24 @@ u16 Font::weight() const
return 400;
}
u8 Font::slope() const
{
// https://docs.microsoft.com/en-us/typography/opentype/spec/os2
constexpr u16 italic_selection_bit { 1 };
constexpr u16 oblique_selection_bit { 512 };
// https://docs.microsoft.com/en-us/typography/opentype/spec/head
constexpr u16 italic_style_bit { 2 };
if (m_os2.selection() & oblique_selection_bit)
return 2;
if (m_os2.selection() & italic_selection_bit)
return 1;
if (m_head.style() & italic_style_bit)
return 1;
return 0;
}
bool Font::is_fixed_width() const
{
// FIXME: Read this information from the font file itself.
@ -549,6 +567,11 @@ u16 OS2::weight_class() const
return be_u16(m_slice.offset_pointer((u32)Offsets::WeightClass));
}
u16 OS2::selection() const
{
return be_u16(m_slice.offset_pointer((u32)Offsets::Selection));
}
i16 OS2::typographic_ascender() const
{
return be_i16(m_slice.offset_pointer((u32)Offsets::TypographicAscender));

2
Userland/Libraries/LibGfx/TrueTypeFont/Font.h
View file

@ -57,6 +57,7 @@ public:
String family() const;
String variant() const;
u16 weight() const;
u8 slope() const;
bool is_fixed_width() const;
private:
@ -122,6 +123,7 @@ public:
// Gfx::Font implementation
virtual NonnullRefPtr<Font> clone() const override { return *this; } // FIXME: clone() should not need to be implemented
virtual u8 presentation_size() const override { return m_point_height; }
virtual u8 slope() const override { return m_font->slope(); }
virtual u16 weight() const override { return m_font->weight(); }
virtual Gfx::Glyph glyph(u32 code_point) const override;
virtual bool contains_glyph(u32 code_point) const override { return m_font->glyph_id_for_code_point(code_point) > 0; }

2
Userland/Libraries/LibGfx/TrueTypeFont/Tables.h
View file

@ -133,12 +133,14 @@ class OS2 {
public:
enum class Offsets {
WeightClass = 4,
Selection = 62,
TypographicAscender = 68,
TypographicDescender = 70,
TypographicLineGap = 72,
};
u16 weight_class() const;
u16 selection() const;
i16 typographic_ascender() const;
i16 typographic_descender() const;
i16 typographic_line_gap() const;