From e6551e685d7db43786398d24b715ce3cc3c573a8 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 19 Dec 2022 15:03:03 +0100
Subject: [PATCH] LibGfx/OpenType: Clean up "htmx" table reading

Use a C++ struct to read out the LongHorMetrics, and make the rest of
the code more idiomatic.
---
 .../Libraries/LibGfx/Font/OpenType/Font.cpp   | 19 ++++++++-----------
 .../Libraries/LibGfx/Font/OpenType/Tables.h   |  6 +++---
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp b/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
index 807aae833f..d2ab082778 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
@@ -153,7 +153,7 @@ u16 Maxp::num_glyphs() const
 
 Optional<Hmtx> Hmtx::from_slice(ReadonlyBytes slice, u32 num_glyphs, u32 number_of_h_metrics)
 {
-    if (slice.size() < number_of_h_metrics * (u32)Sizes::LongHorMetric + (num_glyphs - number_of_h_metrics) * (u32)Sizes::LeftSideBearing) {
+    if (slice.size() < number_of_h_metrics * sizeof(LongHorMetric) + (num_glyphs - number_of_h_metrics) * sizeof(u16)) {
         return {};
     }
     return Hmtx(slice, num_glyphs, number_of_h_metrics);
@@ -335,21 +335,18 @@ DeprecatedString Name::string_for_id(NameId id) const
 GlyphHorizontalMetrics Hmtx::get_glyph_horizontal_metrics(u32 glyph_id) const
 {
     VERIFY(glyph_id < m_num_glyphs);
+    auto const* long_hor_metrics = bit_cast<LongHorMetric const*>(m_slice.data());
     if (glyph_id < m_number_of_h_metrics) {
-        auto offset = glyph_id * (u32)Sizes::LongHorMetric;
-        u16 advance_width = be_u16(m_slice.offset_pointer(offset));
-        i16 left_side_bearing = be_i16(m_slice.offset_pointer(offset + 2));
         return GlyphHorizontalMetrics {
-            .advance_width = advance_width,
-            .left_side_bearing = left_side_bearing,
+            .advance_width = static_cast<u16>(long_hor_metrics[glyph_id].advance_width),
+            .left_side_bearing = static_cast<i16>(long_hor_metrics[glyph_id].lsb),
         };
     }
-    auto offset = m_number_of_h_metrics * (u32)Sizes::LongHorMetric + (glyph_id - m_number_of_h_metrics) * (u32)Sizes::LeftSideBearing;
-    u16 advance_width = be_u16(m_slice.offset_pointer((m_number_of_h_metrics - 1) * (u32)Sizes::LongHorMetric));
-    i16 left_side_bearing = be_i16(m_slice.offset_pointer(offset));
+
+    auto const* left_side_bearings = bit_cast<BigEndian<u16> const*>(m_slice.offset_pointer(m_number_of_h_metrics * sizeof(LongHorMetric)));
     return GlyphHorizontalMetrics {
-        .advance_width = advance_width,
-        .left_side_bearing = left_side_bearing,
+        .advance_width = static_cast<u16>(long_hor_metrics[m_number_of_h_metrics - 1].advance_width),
+        .left_side_bearing = static_cast<i16>(left_side_bearings[glyph_id - m_number_of_h_metrics]),
     };
 }
 
diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Tables.h b/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
index 728d1856f5..1668f0e191 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
@@ -177,9 +177,9 @@ public:
     GlyphHorizontalMetrics get_glyph_horizontal_metrics(u32 glyph_id) const;
 
 private:
-    enum class Sizes {
-        LongHorMetric = 4,
-        LeftSideBearing = 2
+    struct LongHorMetric {
+        BigEndian<u16> advance_width;
+        BigEndian<i16> lsb;
     };
 
     Hmtx(ReadonlyBytes slice, u32 num_glyphs, u32 number_of_h_metrics)