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LibGfx: Add spec links for cmap table formats

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Nico Weber 2023-10-26 08:12:40 -07:00 • committed by Andreas Kling
parent 864172084b
commit 2ef24e883c
1 changed files with 4 additions and 0 deletions
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4
Userland/Libraries/LibGfx/Font/OpenType/Cmap.cpp
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@ -96,6 +96,7 @@ u32 Cmap::Subtable::glyph_id_for_code_point(u32 code_point) const
u32 Cmap::Subtable::glyph_id_for_code_point_table_0(u32 code_point) const
{
// https://learn.microsoft.com/en-us/typography/opentype/spec/cmap#format-0-byte-encoding-table
if (code_point > 255)
return 0;
@ -104,6 +105,7 @@ u32 Cmap::Subtable::glyph_id_for_code_point_table_0(u32 code_point) const
u32 Cmap::Subtable::glyph_id_for_code_point_table_4(u32 code_point) const
{
// https://learn.microsoft.com/en-us/typography/opentype/spec/cmap#format-4-segment-mapping-to-delta-values
u32 segcount_x2 = be_u16(m_slice.offset((u32)Table4Offsets::SegCountX2));
if (m_slice.size() < segcount_x2 * (u32)Table4Sizes::NonConstMultiplier + (u32)Table4Sizes::Constant)
return 0;
@ -135,6 +137,7 @@ u32 Cmap::Subtable::glyph_id_for_code_point_table_4(u32 code_point) const
u32 Cmap::Subtable::glyph_id_for_code_point_table_6(u32 code_point) const
{
// https://learn.microsoft.com/en-us/typography/opentype/spec/cmap#format-6-trimmed-table-mapping
u32 first_code = be_u16(m_slice.offset((u32)Table6Offsets::FirstCode));
if (code_point < first_code)
return 0;
@ -149,6 +152,7 @@ u32 Cmap::Subtable::glyph_id_for_code_point_table_6(u32 code_point) const
u32 Cmap::Subtable::glyph_id_for_code_point_table_12(u32 code_point) const
{
// https://learn.microsoft.com/en-us/typography/opentype/spec/cmap#format-12-segmented-coverage
u32 num_groups = be_u32(m_slice.offset((u32)Table12Offsets::NumGroups));
VERIFY(m_slice.size() >= (u32)Table12Sizes::Header + (u32)Table12Sizes::Record * num_groups);
for (u32 offset = 0; offset < num_groups * (u32)Table12Sizes::Record; offset += (u32)Table12Sizes::Record) {