afdko

C/C++ Architectural Changes: develop → addfeatures

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

This site is open source. Improve this page.