From a28f035d76f0dbd4684b20b131ed700037b135c2 Mon Sep 17 00:00:00 2001
From: Sam Atkins <atkinssj@serenityos.org>
Date: Wed, 1 Nov 2023 15:23:29 +0000
Subject: [PATCH] LibGfx: Reduce bit casting in OpenType CBLC table after
 construction

The subtables are still read at use-time for now. I'm sure we could
build some kind of wrapper structures for them though.
---
 .../Libraries/LibGfx/Font/OpenType/Tables.cpp    |  6 ++++--
 Userland/Libraries/LibGfx/Font/OpenType/Tables.h | 16 ++++++++--------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Tables.cpp b/Userland/Libraries/LibGfx/Font/OpenType/Tables.cpp
index d96db972be..1d1a347e9d 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Tables.cpp
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Tables.cpp
@@ -451,12 +451,14 @@ ErrorOr<CBLC> CBLC::from_slice(ReadonlyBytes slice)
     if (slice.size() < total_size)
         return Error::from_string_literal("CBLC table too small");
 
-    return CBLC { slice };
+    ReadonlySpan<BitmapSize> bitmap_sizes { bit_cast<BitmapSize const*>(slice.data() + sizeof(CblcHeader)), num_sizes };
+
+    return CBLC { slice, header, bitmap_sizes };
 }
 
 Optional<CBLC::BitmapSize const&> CBLC::bitmap_size_for_glyph_id(u32 glyph_id) const
 {
-    for (auto const& bitmap_size : this->bitmap_sizes()) {
+    for (auto const& bitmap_size : m_bitmap_sizes) {
         if (glyph_id >= bitmap_size.start_glyph_index && glyph_id <= bitmap_size.end_glyph_index) {
             return bitmap_size;
         }
diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Tables.h b/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
index 97b97d0fa1..80520a67d0 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
@@ -549,26 +549,26 @@ public:
         BigEndian<u16> major_version;
         BigEndian<u16> minor_version;
         BigEndian<u32> num_sizes;
-        BitmapSize bitmap_sizes[];
+        // Stored in a separate span:
+        // BitmapSize bitmap_sizes[];
     };
     static_assert(AssertSize<CblcHeader, 8>());
 
-    CblcHeader const& header() const { return *bit_cast<CblcHeader const*>(m_slice.data()); }
-    ReadonlySpan<BitmapSize> bitmap_sizes() const { return { header().bitmap_sizes, header().num_sizes }; }
-    Optional<BitmapSize const&> bitmap_size_for_glyph_id(u32 glyph_id) const;
-
     static ErrorOr<CBLC> from_slice(ReadonlyBytes);
-    ReadonlyBytes bytes() const { return m_slice; }
-
+    Optional<BitmapSize const&> bitmap_size_for_glyph_id(u32 glyph_id) const;
     Optional<EBLC::IndexSubHeader const&> index_subtable_for_glyph_id(u32 glyph_id, u16& first_glyph_index, u16& last_glyph_index) const;
 
 private:
-    explicit CBLC(ReadonlyBytes slice)
+    explicit CBLC(ReadonlyBytes slice, CblcHeader const& header, ReadonlySpan<BitmapSize> bitmap_sizes)
         : m_slice(slice)
+        , m_header(header)
+        , m_bitmap_sizes(bitmap_sizes)
     {
     }
 
     ReadonlyBytes m_slice;
+    CblcHeader const& m_header;
+    ReadonlySpan<BitmapSize> m_bitmap_sizes;
 };
 
 // https://learn.microsoft.com/en-us/typography/opentype/spec/ebdt