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LibGfx: Read OpenType table directory using structs and streams

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Sam Atkins 2023-10-21 17:02:04 +01:00 committed by Andreas Kling
parent 5455ecf650
commit 1ab03ff963
3 changed files with 40 additions and 43 deletions
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56
Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
View file

@ -3,6 +3,7 @@
* Copyright (c) 2021-2023, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2022, Jelle Raaijmakers <jelle@gmta.nl>
* Copyright (c) 2023, Lukas Affolter <git@lukasach.dev>
* Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -111,11 +112,9 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_externally_owned_memory(Readonl
// FIXME: "loca" and "glyf" are not available for CFF fonts.
ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u32 offset)
{
if (Checked<u32>::addition_would_overflow(offset, (u32)Sizes::OffsetTable))
return Error::from_string_literal("Invalid offset in font header");
if (buffer.size() <= offset + (u32)Sizes::OffsetTable)
return Error::from_string_literal("Font file too small");
FixedMemoryStream stream { buffer };
TRY(stream.seek(offset, AK::SeekMode::SetPosition));
auto& table_directory = *TRY(stream.read_in_place<TableDirectory const>());
Optional<ReadonlyBytes> opt_head_slice = {};
Optional<ReadonlyBytes> opt_name_slice = {};
@ -144,54 +143,47 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
Optional<CBDT> cbdt;
Optional<GPOS> gpos;
auto num_tables = be_u16(buffer.offset(offset + (u32)Offsets::NumTables));
if (buffer.size() <= offset + (u32)Sizes::OffsetTable + num_tables * (u32)Sizes::TableRecord)
return Error::from_string_literal("Font file too small");
for (auto i = 0; i < table_directory.num_tables; i++) {
auto& table_record = *TRY(stream.read_in_place<TableRecord const>());
for (auto i = 0; i < num_tables; i++) {
u32 record_offset = offset + (u32)Sizes::OffsetTable + i * (u32)Sizes::TableRecord;
u32 tag = be_u32(buffer.offset(record_offset));
u32 table_offset = be_u32(buffer.offset(record_offset + (u32)Offsets::TableRecord_Offset));
u32 table_length = be_u32(buffer.offset(record_offset + (u32)Offsets::TableRecord_Length));
if (table_length == 0 || Checked<u32>::addition_would_overflow(table_offset, table_length))
if (table_record.length == 0 || Checked<u32>::addition_would_overflow(static_cast<u32>(table_record.offset), static_cast<u32>(table_record.length)))
return Error::from_string_literal("Invalid table offset or length in font");
if (buffer.size() < table_offset + table_length)
if (buffer.size() < table_record.offset + table_record.length)
return Error::from_string_literal("Font file too small");
auto buffer_here = ReadonlyBytes(buffer.offset(table_offset), table_length);
auto buffer_here = buffer.slice(table_record.offset, table_record.length);
// Get the table offsets we need.
if (tag == tag_from_str("head")) {
if (table_record.table_tag == tag_from_str("head")) {
opt_head_slice = buffer_here;
} else if (tag == tag_from_str("name")) {
} else if (table_record.table_tag == tag_from_str("name")) {
opt_name_slice = buffer_here;
} else if (tag == tag_from_str("hhea")) {
} else if (table_record.table_tag == tag_from_str("hhea")) {
opt_hhea_slice = buffer_here;
} else if (tag == tag_from_str("maxp")) {
} else if (table_record.table_tag == tag_from_str("maxp")) {
opt_maxp_slice = buffer_here;
} else if (tag == tag_from_str("hmtx")) {
} else if (table_record.table_tag == tag_from_str("hmtx")) {
opt_hmtx_slice = buffer_here;
} else if (tag == tag_from_str("cmap")) {
} else if (table_record.table_tag == tag_from_str("cmap")) {
opt_cmap_slice = buffer_here;
} else if (tag == tag_from_str("loca")) {
} else if (table_record.table_tag == tag_from_str("loca")) {
opt_loca_slice = buffer_here;
} else if (tag == tag_from_str("glyf")) {
} else if (table_record.table_tag == tag_from_str("glyf")) {
opt_glyf_slice = buffer_here;
} else if (tag == tag_from_str("OS/2")) {
} else if (table_record.table_tag == tag_from_str("OS/2")) {
opt_os2_slice = buffer_here;
} else if (tag == tag_from_str("kern")) {
} else if (table_record.table_tag == tag_from_str("kern")) {
opt_kern_slice = buffer_here;
} else if (tag == tag_from_str("fpgm")) {
} else if (table_record.table_tag == tag_from_str("fpgm")) {
opt_fpgm_slice = buffer_here;
} else if (tag == tag_from_str("prep")) {
} else if (table_record.table_tag == tag_from_str("prep")) {
opt_prep_slice = buffer_here;
} else if (tag == tag_from_str("CBLC")) {
} else if (table_record.table_tag == tag_from_str("CBLC")) {
cblc = TRY(CBLC::from_slice(buffer_here));
} else if (tag == tag_from_str("CBDT")) {
} else if (table_record.table_tag == tag_from_str("CBDT")) {
cbdt = TRY(CBDT::from_slice(buffer_here));
} else if (tag == tag_from_str("GPOS")) {
} else if (table_record.table_tag == tag_from_str("GPOS")) {
gpos = TRY(GPOS::from_slice(buffer_here));
}
}

11
Userland/Libraries/LibGfx/Font/OpenType/Font.h
View file

@ -68,17 +68,6 @@ private:
EmbeddedBitmapData embedded_bitmap_data_for_glyph(u32 glyph_id) const;
enum class Offsets {
NumTables = 4,
TableRecord_Offset = 8,
TableRecord_Length = 12,
};
enum class Sizes {
TTCHeaderV1 = 12,
OffsetTable = 12,
TableRecord = 16,
};
static ErrorOr<NonnullRefPtr<Font>> try_load_from_offset(ReadonlyBytes, unsigned index = 0);
Font(

16
Userland/Libraries/LibGfx/Font/OpenType/Tables.h
View file

@ -67,6 +67,22 @@ struct [[gnu::packed]] TableRecord {
};
static_assert(AssertSize<TableRecord, 16>());
}
template<>
class AK::Traits<OpenType::TableDirectory const> : public GenericTraits<OpenType::TableDirectory const> {
public:
static constexpr bool is_trivially_serializable() { return true; }
};
template<>
class AK::Traits<OpenType::TableRecord const> : public GenericTraits<OpenType::TableRecord const> {
public:
static constexpr bool is_trivially_serializable() { return true; }
};
namespace OpenType {
// https://learn.microsoft.com/en-us/typography/opentype/spec/head
// head: Font Header Table
class Head {