LibGfx/OpenType: Add scaffolding for CBDT and CBLC tables

3 files changed, 177 insertions, 3 deletions

diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp b/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
index b8b9730809..4ad4debe58 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2020, Srimanta Barua <srimanta.barua1@gmail.com>
- * Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021-2023, Andreas Kling <kling@serenityos.org>
  * Copyright (c) 2022, Jelle Raaijmakers <jelle@gmta.nl>
  *
  * SPDX-License-Identifier: BSD-2-Clause
@@ -409,6 +409,8 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
     Optional<Kern> opt_kern = {};
     Optional<Fpgm> opt_fpgm = {};
     Optional<Prep> opt_prep = {};
+    Optional<CBLC> cblc;
+    Optional<CBDT> cbdt;
 
     auto num_tables = be_u16(buffer.offset_pointer(offset + (u32)Offsets::NumTables));
     if (buffer.size() < offset + (u32)Sizes::OffsetTable + num_tables * (u32)Sizes::TableRecord)
@@ -453,6 +455,10 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
             opt_fpgm_slice = buffer_here;
         } else if (tag == tag_from_str("prep")) {
             opt_prep_slice = buffer_here;
+        } else if (tag == tag_from_str("CBLC")) {
+            cblc = TRY(CBLC::from_slice(buffer_here));
+        } else if (tag == tag_from_str("CBDT")) {
+            cbdt = TRY(CBDT::from_slice(buffer_here));
         }
     }
 
@@ -537,7 +543,22 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
         }
     }
 
-    return adopt_ref(*new Font(move(buffer), move(head), move(name), move(hhea), move(maxp), move(hmtx), move(cmap), move(loca), move(glyf), move(os2), move(kern), move(fpgm), move(prep)));
+    return adopt_ref(*new Font(
+        move(buffer),
+        move(head),
+        move(name),
+        move(hhea),
+        move(maxp),
+        move(hmtx),
+        move(cmap),
+        move(loca),
+        move(glyf),
+        move(os2),
+        move(kern),
+        move(fpgm),
+        move(prep),
+        move(cblc),
+        move(cbdt)));
 }
 
 Gfx::ScaledFontMetrics Font::metrics([[maybe_unused]] float x_scale, float y_scale) const
diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Font.h b/Userland/Libraries/LibGfx/Font/OpenType/Font.h
index 86abc00b44..7f798d1ae2 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Font.h
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Font.h
@@ -59,7 +59,22 @@ private:
 
     static ErrorOr<NonnullRefPtr<Font>> try_load_from_offset(ReadonlyBytes, unsigned index = 0);
 
-    Font(ReadonlyBytes bytes, Head&& head, Name&& name, Hhea&& hhea, Maxp&& maxp, Hmtx&& hmtx, Cmap&& cmap, Optional<Loca>&& loca, Optional<Glyf>&& glyf, Optional<OS2> os2, Optional<Kern>&& kern, Optional<Fpgm> fpgm, Optional<Prep> prep)
+    Font(
+        ReadonlyBytes bytes,
+        Head&& head,
+        Name&& name,
+        Hhea&& hhea,
+        Maxp&& maxp,
+        Hmtx&& hmtx,
+        Cmap&& cmap,
+        Optional<Loca>&& loca,
+        Optional<Glyf>&& glyf,
+        Optional<OS2> os2,
+        Optional<Kern>&& kern,
+        Optional<Fpgm> fpgm,
+        Optional<Prep> prep,
+        Optional<CBLC> cblc,
+        Optional<CBDT> cbdt)
         : m_buffer(move(bytes))
         , m_head(move(head))
         , m_name(move(name))
@@ -73,6 +88,8 @@ private:
         , m_kern(move(kern))
         , m_fpgm(move(fpgm))
         , m_prep(move(prep))
+        , m_cblc(move(cblc))
+        , m_cbdt(move(cbdt))
     {
     }
 
@@ -93,6 +110,8 @@ private:
     Optional<Kern> m_kern;
     Optional<Fpgm> m_fpgm;
     Optional<Prep> m_prep;
+    Optional<CBLC> m_cblc;
+    Optional<CBDT> m_cbdt;
 
     // This cache stores information per code point.
     // It's segmented into pages with data about 256 code points each.
diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Tables.h b/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
index 8d26665f6a..8cc69fc7bc 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Tables.h
@@ -37,6 +37,7 @@ using FWord = BigEndian<i16>;
 using UFWord = BigEndian<u16>;
 using Tag = BigEndian<u32>;
 using Offset16 = BigEndian<u16>;
+using Offset32 = BigEndian<u32>;
 
 // https://learn.microsoft.com/en-us/typography/opentype/spec/head
 // head: Font Header Table
@@ -399,4 +400,137 @@ private:
     FixedArray<size_t> m_subtable_offsets;
 };
 
+// https://learn.microsoft.com/en-us/typography/opentype/spec/eblc
+// EBLC — Embedded Bitmap Location Table
+class EBLC {
+public:
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/eblc#sbitlinemetrics-record
+    struct SbitLineMetrics {
+        i8 ascender {};
+        i8 descender {};
+        u8 width_max {};
+        i8 caret_slope_numerator {};
+        i8 caret_slope_denominator {};
+        i8 caret_offset {};
+        i8 min_origin_sb {};
+        i8 min_advance_sb {};
+        i8 max_before_bl {};
+        i8 min_after_bl {};
+        i8 pad1 {};
+        i8 pad2 {};
+    };
+
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/eblc#indexsubtablearray
+    struct IndexSubTableArray {
+        BigEndian<u16> first_glyph_index;
+        BigEndian<u16> last_glyph_index;
+        Offset32 additional_offset_to_index_subtable;
+    };
+
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/eblc#indexsubheader
+    struct IndexSubHeader {
+        BigEndian<u16> index_format;
+        BigEndian<u16> image_format;
+        Offset32 image_data_offset;
+    };
+
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/eblc#indexsubtable1-variable-metrics-glyphs-with-4-byte-offsets
+    // IndexSubTable1: variable-metrics glyphs with 4-byte offsets
+    struct IndexSubTable1 {
+        IndexSubHeader header;
+        Offset32 sbit_offsets[];
+    };
+};
+
+// https://learn.microsoft.com/en-us/typography/opentype/spec/cblc
+// CBLC — Color Bitmap Location Table
+class CBLC {
+public:
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/cblc#bitmapsize-record
+    struct BitmapSize {
+        Offset32 index_subtable_array_offset;
+        BigEndian<u32> index_tables_size;
+        BigEndian<u32> number_of_index_subtables;
+        BigEndian<u32> color_ref;
+        EBLC::SbitLineMetrics hori;
+        EBLC::SbitLineMetrics vert;
+        BigEndian<u16> start_glyph_index;
+        BigEndian<u16> end_glyph_index;
+        u8 ppem_x {};
+        u8 ppem_y {};
+        u8 bit_depth {};
+        i8 flags {};
+    };
+
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/cblc#cblcheader
+    struct CblcHeader {
+        BigEndian<u16> major_version;
+        BigEndian<u16> minor_version;
+        BigEndian<u32> num_sizes;
+        BitmapSize bitmap_sizes[];
+    };
+
+    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<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)
+        : m_slice(slice)
+    {
+    }
+
+    ReadonlyBytes m_slice;
+};
+
+// https://learn.microsoft.com/en-us/typography/opentype/spec/ebdt
+// EBDT — Embedded Bitmap Data Table
+class EBDT {
+public:
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/ebdt#smallglyphmetrics
+    struct SmallGlyphMetrics {
+        u8 height {};
+        u8 width {};
+        i8 bearing_x {};
+        i8 bearing_y {};
+        u8 advance {};
+    };
+};
+
+// https://learn.microsoft.com/en-us/typography/opentype/spec/cbdt
+// CBDT — Color Bitmap Data Table
+class CBDT {
+public:
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/cbdt#table-structure
+    struct CbdtHeader {
+        BigEndian<u16> major_version;
+        BigEndian<u16> minor_version;
+    };
+
+    // https://learn.microsoft.com/en-us/typography/opentype/spec/cbdt#format-17-small-metrics-png-image-data
+    struct Format17 {
+        EBDT::SmallGlyphMetrics glyph_metrics;
+        BigEndian<u32> data_len;
+        u8 data[];
+    };
+
+    static ErrorOr<CBDT> from_slice(ReadonlyBytes);
+    ReadonlyBytes bytes() const { return m_slice; }
+
+    CbdtHeader const& header() const { return *bit_cast<CbdtHeader const*>(m_slice.data()); }
+
+private:
+    explicit CBDT(ReadonlyBytes slice)
+        : m_slice(slice)
+    {
+    }
+
+    ReadonlyBytes m_slice;
+};
+
 }