LibGfx: Define and use OpenType data types for struct definitions

A few closely-related changes:
- Move our definitions of the OpenType spec's "data types" into their
  own header file.
- Add definitions for the integer types there too, for completeness.
  (Plus Uint16 matches the spec term, and is less verbose than
  BigEndian<u16>.)
- Include Traits for the non-BigEndian types so that we can read them
  from Streams. (BigEndian<integer-type> already has this.)
- Use the integer types in our struct definitions.

As a bonus, this fixes a bug in Hmtx, which read the left-side bearings
as i16 instead of BigEndian<i16>.

Userland/Libraries/LibGfx/Font/OpenType/DataTypes.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2020, Srimanta Barua <[email protected]>
+ * Copyright (c) 2022, Jelle Raaijmakers <[email protected]>
+ * Copyright (c) 2023, Lukas Affolter <[email protected]>
+ * Copyright (c) 2023, Sam Atkins <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Endian.h>
+#include <AK/Types.h>
+
+// https://learn.microsoft.com/en-us/typography/opentype/spec/otff#data-types
+namespace OpenType {
+
+using Uint8 = u8;
+using Int8 = i8;
+using Uint16 = BigEndian<u16>;
+using Int16 = BigEndian<i16>;
+// FIXME: Uint24
+using Uint32 = BigEndian<u32>;
+using Int32 = BigEndian<i32>;
+
+struct [[gnu::packed]] Fixed {
+ BigEndian<u16> integer;
+ BigEndian<u16> fraction;
+};
+static_assert(AssertSize<Fixed, 4>());
+
+using FWord = BigEndian<i16>;
+using UFWord = BigEndian<u16>;
+
+// FIXME: F2Dot14
+
+struct [[gnu::packed]] LongDateTime {
+ BigEndian<u64> value;
+};
+static_assert(AssertSize<LongDateTime, 8>());
+
+using Tag = BigEndian<u32>;
+
+using Offset16 = BigEndian<u16>;
+// FIXME: Offset24
+using Offset32 = BigEndian<u32>;
+
+struct [[gnu::packed]] Version16Dot16 {
+ BigEndian<u16> major;
+ BigEndian<u16> minor;
+};
+static_assert(AssertSize<Version16Dot16, 4>());
+
+}
+
+namespace AK {
+template<>
+struct Traits<OpenType::Fixed const> : public GenericTraits<OpenType::Fixed const> {
+ static constexpr bool is_trivially_serializable() { return true; }
+};
+template<>
+struct Traits<OpenType::LongDateTime const> : public GenericTraits<OpenType::LongDateTime const> {
+ static constexpr bool is_trivially_serializable() { return true; }
+};
+template<>
+struct Traits<OpenType::Tag const> : public GenericTraits<OpenType::Tag const> {
+ static constexpr bool is_trivially_serializable() { return true; }
+};
+template<>
+struct Traits<OpenType::Version16Dot16 const> : public GenericTraits<OpenType::Version16Dot16 const> {
+ static constexpr bool is_trivially_serializable() { return true; }
+};
+}

Userland/Libraries/LibGfx/Font/OpenType/Tables.cpp

@@ -145,16 +145,16 @@ u16 Maxp::num_glyphs() const
 
 ErrorOr<Hmtx> Hmtx::from_slice(ReadonlyBytes slice, u32 num_glyphs, u32 number_of_h_metrics)
 {
- if (slice.size() < number_of_h_metrics * sizeof(LongHorMetric) + (num_glyphs - number_of_h_metrics) * sizeof(i16))
+ if (slice.size() < number_of_h_metrics * sizeof(LongHorMetric) + (num_glyphs - number_of_h_metrics) * sizeof(Int16))
  return Error::from_string_literal("Could not load Hmtx: Not enough data");
 
- // The Horizontal Metrics table is LongHorMetric[number_of_h_metrics] followed by i16[num_glyphs - number_of_h_metrics];
+ // The Horizontal Metrics table is LongHorMetric[number_of_h_metrics] followed by Int16[num_glyphs - number_of_h_metrics];
  ReadonlySpan<LongHorMetric> long_hor_metrics { bit_cast<LongHorMetric*>(slice.data()), number_of_h_metrics };
- ReadonlySpan<i16> left_side_bearings {};
+ ReadonlySpan<Int16> left_side_bearings {};
  auto number_of_left_side_bearings = num_glyphs - number_of_h_metrics;
  if (number_of_left_side_bearings > 0) {
  left_side_bearings = {
- bit_cast<i16*>(slice.offset(number_of_h_metrics * sizeof(LongHorMetric))),
+ bit_cast<Int16*>(slice.offset(number_of_h_metrics * sizeof(LongHorMetric))),
  number_of_left_side_bearings
  };
  }