C/C++ Architectural Changes: develop → addfeatures

March 23, 2026 · View on GitHub

This is an AI summary of the changes to our C/C++ code, for reference.

Summary Statistics

Overall Code Metrics

  • Total source files: 177 → 150 (-27 files, -15%)
  • C files (.c): 170 → 76 (-94 files, -55%)
  • C++ files (.cpp): 7 → 74 (+67 files, +957%)
  • Language ratio change: 96% C / 4% C++ → 51% C / 49% C++

By Component

  • makeotf → addfeatures: 52 files → 32 files (-20 files, -38% reduction)
  • spot: 61 files → 56 files (-5 files, -8% reduction)
  • shared library: Flattened structure, major C→C++ conversions
  • NEW: c/afdko/: Unified binary dispatcher (2 files)
  • NO LONGER SEPARATE: tx/: Integrated into unified binary

Major Architectural Changes

1. Unified Binary (c/afdko/)

NEW component providing single entry point for all C++ tools

Files:

  • afdko_main.cpp - Fast dispatcher for C++ commands
  • Embeds Python interpreter for Python commands and help

Design:

  • Fast path: C++ commands dispatched directly without Python overhead
  • Python fallback: Help, Python commands, unknown commands → invoke Python
  • Links to 9 C++ tool entry points: tx, sfntedit, spot, addfeatures, detype1, type1, sfntdiff, mergefonts, rotatefont
  • Abbreviation support built-in (e.g., se → sfntedit, af → addfeatures)

2. makeotf → addfeatures Transformation

Major refactoring and renaming:

  • 52 source files → 32 source files (-38%)
  • Extensive C → C++ conversion in hotconv/ subsystem
  • Removed Type 1 → CFF conversion logic (now handled by tx)
  • Added CFF2 variable font support
  • Cleaner separation of concerns

File structure changes:

develop: c/makeotf/
  source/
    cbpriv.c, cb.c, mac.c, c_main.c, file.c, fcdb.c, main.cpp
  lib/
    typecomp/    (14 files)
    cffread/     (2 files)
    hotconv/     (26+ files - feature compilation)
    api/         (headers)

addfeatures: c/addfeatures/
  cb.cpp, fcdb.cpp, main.cpp    (C→C++ conversions)
  hotconv/     (30 files, many C→C++ conversions)
    - BASE.cpp, GDEF.cpp, GPOS.cpp, GSUB.cpp
    - MVAR.cpp, STAT.cpp (new variable font support)
    - OS_2.cpp, head.cpp, hmtx.cpp, vmtx.cpp
    - FeatParser.cpp, FeatLexer.cpp, FeatVisitor.cpp
    - cmap.cpp, name.cpp, post.cpp, maxp.cpp
    - hot.cpp, otl.cpp, sfnt.cpp
  pstoken/     (parser component)
  include/
  utils/

Eliminated components (moved to shared or removed):

  • typecomp/ library (Type 1 compilation - now in tx/shared)
  • cffread/ library (CFF reading - now in shared)
  • File I/O abstractions consolidated

3. Shared Library Restructuring

Structure flattening:

develop: c/shared/source/
  tx_shared/tx_shared.c
  uforead/uforead.c
  ufowrite/ufowrite.c
  t1read/t1read.c
  t1cstr/t1cstr.c
  t2cstr/t2cstr.c
  svgwrite/svgwrite.c
  pdfwrite/pdfwrite.c
  ... (many subdirectories)

addfeatures: c/shared/
  tx_shared.cpp       (C→C++)
  uforead.cpp         (C→C++)
  ufowrite.cpp        (C→C++)
  t1read.cpp          (C→C++)
  t1cstr.cpp          (C→C++)
  t2cstr.cpp          (C→C++)
  svgwrite.cpp        (C→C++)
  pdfwrite.cpp        (C→C++)
  sfntread.cpp        (C→C++)
  sfntwrite.cpp       (C→C++)
  ttread.cpp          (C→C++)
  goadb.cpp           (NEW - GOADB support from makeotfexe)
  designspace.cpp     (NEW - designspace parsing)
  varsupport.cpp      (NEW - variable font support)
  ... (flat structure, many more .cpp files)

Key changes:

  • Eliminated deeply nested directory structure
  • Major C → C++ conversions throughout
  • Consolidated font reading/writing code
  • Added new support libraries (GOADB, designspace, variable fonts)

4. C → C++ Conversions

Major files converted:

  • tx_shared.c → tx_shared.cpp (226KB, core tx functionality)
  • uforead.c → uforead.cpp (120KB)
  • ufowrite.c → ufowrite.cpp (47KB)
  • t1read.c → t1read.cpp (107KB)
  • t1cstr.c → t1cstr.cpp (52KB)
  • t2cstr.c → t2cstr.cpp (72KB)
  • ttread.c → ttread.cpp (112KB)
  • svgwrite.c → svgwrite.cpp (21KB)
  • pdfwrite.c → pdfwrite.cpp (50KB)
  • sfntread.c → sfntread.cpp (10KB)
  • sfntwrite.c → sfntwrite.cpp (16KB)
  • cffread_abs.c → cffread_abs.cpp (112KB)
  • Many hotconv/ files (GSUB.c → GSUB.cpp, GPOS.c → GPOS.cpp, etc.)

Total converted: ~94 .c files eliminated, ~67 new .cpp files created

5. Integration Points

tx integration:

  • No longer separate c/tx/ directory
  • Core tx code in shared library (tx_shared.cpp)
  • Thin main() in c/afdko/afdko_main.cpp dispatcher
  • Same functionality, better code reuse

Version integration:

  • NEW: c/shared/version.h.in, version.cpp.in (CMake templates)
  • FDK_VERSION now generated at build time
  • Flows from setuptools_scm → CMake → all tools
  • Constructor-based initialization for Cython compatibility

6. What Was Kept as C

Still .c files (76 total):

  • Low-level font manipulation code (ctutil.c, da.c, dynarr.c, sha1.c, smem.c)
  • Legacy Type 1 support files (t13fail.c, t13supp.c)
  • Core CFF reading (cffread.c)
  • Parser token handling (pstoken.c in addfeatures/)
  • Some spot/ proof generation code
  • Platform-specific code in some cases

Benefits of These Changes

  1. Code Reduction: 15% fewer source files overall
  2. Modern C++: Better type safety, RAII, standard library usage
  3. Unified Architecture: Single binary entry point, better code sharing
  4. Flatter Structure: Easier navigation, reduced directory nesting
  5. Better Separation: Clear boundaries between font I/O, feature compilation, proof generation
  6. Variable Font Support: New capabilities enabled by cleaner architecture
  7. Build Integration: Proper version flow, better CMake integration
  8. Performance: Fast dispatch for C++ commands, Python fallback for flexibility

Migration Impact

For users: Transparent - same functionality, different implementation For developers:

  • Much cleaner codebase to work with
  • Modern C++ patterns throughout
  • Better organized shared library
  • Single unified entry point simplifies debugging
  • Flatter structure easier to navigate

Technical Debt Addressed

  1. Eliminated deeply nested directory structures
  2. Consolidated redundant font reading/writing code
  3. Removed obsolete Type 1 → CFF conversion from addfeatures
  4. Unified command dispatch architecture
  5. Modernized C → C++ for better maintainability
  6. Integrated version string generation properly

Future Path

This architectural foundation supports:

  • Further C → C++ conversions as needed
  • Additional variable font features
  • Better testing and code coverage
  • Potential for shared library distribution
  • Cleaner plugin/extension architecture