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LibGfx/OpenType: Get size of ValueRecord from PairPos valueFormat field

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The stored ValueRecord in the font file only contains the fields
specified in the valueFormat field of the PairPosFormat1 table.
This means we need to construct the ValueRecord dynamically at runtime
and cannot bit_cast it to a struct.
This commit is contained in:
LukasACH 2023-03-21 14:39:58 +01:00 • committed by Andreas Kling
parent 7eb5fa38c4
commit b6cfacfd9f
2 changed files with 30 additions and 22 deletions
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38
Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
View file

@ -1085,9 +1085,6 @@ Optional<i16> GPOS::glyph_kerning(u16 left_glyph_id, u16 right_glyph_id) const
dbgln_if(OPENTYPE_GPOS_DEBUG, " valueFormat2: {}", pair_pos_format1.value_format2);
dbgln_if(OPENTYPE_GPOS_DEBUG, " pairSetCount: {}", pair_pos_format1.pair_set_count);
if (pair_pos_format1.value_format1 == 0)
continue;
auto get_coverage_index = [&](u16 glyph_id, Offset16 coverage_format_offset) -> Optional<u16> {
auto coverage_format_slice = pair_pos_format_slice.slice(coverage_format_offset);
auto const& coverage_format = *bit_cast<BigEndian<u16> const*>(coverage_format_slice.data());
@ -1128,18 +1125,41 @@ Optional<i16> GPOS::glyph_kerning(u16 left_glyph_id, u16 right_glyph_id) const
return {};
}
size_t value1_size = popcount(static_cast<u32>(pair_pos_format1.value_format1 & 0xff)) * sizeof(u16);
size_t value2_size = popcount(static_cast<u32>(pair_pos_format1.value_format2 & 0xff)) * sizeof(u16);
dbgln_if(OPENTYPE_GPOS_DEBUG, "ValueSizes: {}, {}", value1_size, value2_size);
// Manually iterate over the PairSet table, as the size of each PairValueRecord is not known at compile time.
auto pair_set_offset = pair_pos_format1.pair_set_offsets[coverage_index.value()];
auto pair_set_slice = pair_pos_format_slice.slice(pair_set_offset);
auto const& pair_set = *bit_cast<GPOS::PairSet const*>(pair_set_slice.data());
FixedMemoryStream stream(pair_set_slice);
for (size_t k = 0; k < pair_set.pair_value_count; ++k) {
auto pair_value_record = pair_set.pair_value_records[k];
if (right_glyph_id == pair_value_record.second_glyph) {
dbgln_if(OPENTYPE_GPOS_DEBUG, "Returning x advance {}", pair_value_record.value_record1.x_advance);
return pair_value_record.value_record1.x_advance;
auto pair_value_count = stream.read_value<BigEndian<u16>>().release_value_but_fixme_should_propagate_errors();
bool found_matching_glyph = false;
for (size_t k = 0; k < pair_value_count; ++k) {
auto second_glyph = stream.read_value<BigEndian<u16>>().release_value_but_fixme_should_propagate_errors();
if (right_glyph_id == second_glyph) {
dbgln_if(OPENTYPE_GPOS_DEBUG, "Found matching second glyph {}", second_glyph);
found_matching_glyph = true;
break;
}
(void)stream.discard(value1_size + value2_size).release_value_but_fixme_should_propagate_errors();
}
if (!found_matching_glyph) {
dbgln_if(OPENTYPE_GPOS_DEBUG, "Did not find second glyph matching {}", right_glyph_id);
continue;
}
[[maybe_unused]] auto value_record1 = read_value_record(pair_pos_format1.value_format1, stream);
[[maybe_unused]] auto value_record2 = read_value_record(pair_pos_format1.value_format2, stream);
dbgln_if(OPENTYPE_GPOS_DEBUG, "Returning x advance {}", value_record1.x_advance);
return value_record1.x_advance;
}
else if (pair_pos_format == 2) {

14
Userland/Libraries/LibGfx/Font/OpenType/Tables.h
View file

@ -1,6 +1,7 @@
/*
* Copyright (c) 2020, Srimanta Barua <srimanta.barua1@gmail.com>
* Copyright (c) 2022, Jelle Raaijmakers <jelle@gmta.nl>
* Copyright (c) 2023, Lukas Affolter <git@lukasach.dev>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -637,19 +638,6 @@ public:
Offset16 y_advance_device_offset;
};
// https://learn.microsoft.com/en-us/typography/opentype/spec/gpos#pair-adjustment-positioning-format-1-adjustments-for-glyph-pairs
struct PairValueRecord {
BigEndian<u16> second_glyph;
ValueRecord value_record1;
ValueRecord value_record2;
};
// https://learn.microsoft.com/en-us/typography/opentype/spec/gpos#pair-adjustment-positioning-format-1-adjustments-for-glyph-pairs
struct PairSet {
BigEndian<u16> pair_value_count;
PairValueRecord pair_value_records[];
};
// https://learn.microsoft.com/en-us/typography/opentype/spec/gpos#pair-adjustment-positioning-format-2-class-pair-adjustment
struct PairPosFormat2 {
BigEndian<u16> pos_format;