freetype/CHANGES

LATEST CHANGES - 27-jan-2000

  - updated the "sfnt" module interface to allow several SFNT-based
    drivers to co-exist peacefully
    
  - updated the "T1_Face" type to better separate Postscript font content
    from the rest of the FT_Face structure. Might be used later by the
    CFF/Type2 driver..
    
  - added an experimental replacement Type 1 driver featuring advanced
    (and speedy) pattern matching to retrieve the data from postscript
    fonts.

  - very minor changes in the implementation of FT_Set_Char_Size and
    FT_Set_Pixel_Sizes (they now implement default to ligthen the
    font driver's code).


=============================================================================
OLD MESSAGE

This file summarizes the changes that occured since the last "beta" of FreeType 2.
Because the list is important, it has been divided into separate sections:

Table Of Contents:

    I   High-Level Interface (easier !)
   II   Directory Structure
  III   Glyph Image Formats
   IV   Build System
    V   Portability
   VI   Font Drivers

-----------------------------------------------------------------------------------------
High-Level Interface :

  The high-level API has been considerably simplified. Here is how :

    - resource objects have disappeared. this means that face objects can
      now be created with a single function call (see FT_New_Face and
      FT_Open_Face)
    
    - when calling either FT_New_Face & FT_Open_Face, a size object and a
      glyph slot object are automatically created for the face, and can be
      accessed through "face->glyph" and "face->size" if one really needs to.
      In most cases, there's no need to call FT_New_Size or FT_New_Glyph.
    
    - similarly, FT_Load_Glyph now only takes a "face" argument (instead of
      a glyph slot and a size). Also, it's "result" parameter is gone, as
      the glyph image type is returned in the field "face->glyph.format"
    
    - the list of available charmaps is directly accessible through
      "face->charmaps", counting "face->num_charmaps" elements. Each
      charmap has an 'encoding' field which specifies which known encoding
      it deals with. Valid values are, for example :
    
          ft_encoding_unicode      (for ASCII, Latin-1 and Unicode)
          ft_encoding_apple_roman
          ft_encoding_sjis
          ft_encoding_adobe_standard
          ft_encoding_adobe_expert
    
      other values may be added in the future. Each charmap still holds its
      "platform_id" and "encoding_id" values in case the encoding is too
      exotic for the current library


-----------------------------------------------------------------------------------------
Directory Structure:

  Should seem obvious to most of you:

     freetype/
         config/        -- configuration sub-makefiles
            ansi/
            unix/       -- platform-specific configuration files
            win32/
            os2/
            msdos/

         include/       -- public header files, those to be included directly
                           by client apps

         src/           -- sources of the library
           base/        -- the base layer
           sfnt/        -- the sfnt "driver" (see the drivers section below)
           truetype/    -- the truetype driver
           type1/       -- the type1 driver
           shared/      -- some header files shared between drivers

         demos/         -- demos/tools

         docs/          -- documentation (a bit empty for now)

-----------------------------------------------------------------------------------------
Glyph Image Formats :

  Drivers are now able to register new glyph image formats within the library.
  For now, the base layer supports of course bitmaps and vector outlines, but
  one could imagine something different like colored bitmaps, bi-color
  vectors or wathever else (Metafonts anyone ??).

  See the file `include/ftimage.h'. Note also that the type FT_Raster_Map is
  gone, and is now replaced by FT_Bitmap, which should encompass all known
  bitmap types.

  Each new image format must provide at least one "raster", i.e. a module
  capable of transforming the glyph image into a bitmap. It's also possible
  to change the default raster used for a given glyph image format.

  The default outline scan-converter now uses 128 levels of grays by default,
  which tends to smooth many things. Note that the demo programs have been
  updated significantly in order to display these..


-----------------------------------------------------------------------------------------
Build system :

  You still need GNU Make to build the library. The build system has been
  very seriously re-vamped in order to provide things like :

   - automatic host platform detection (reverting to 'config/ansi'
     if it is not detected, with pseudo-standard compilation flags)

   - the ability to compile from the Makefiles with very different and
     exotic compilers. Note that linking the library can be difficult for
     some platforms.

     For example, the file `config/win32/lcclib.bat' is invoked by the
     build system to create the ".lib" file with LCC-Win32 because its
     librarian has too many flaws to be invoked directly from the Makefile.

  Here's how it works :

  - the first time you type `make', the build system runs a series of
    sub-makefiles in order to detect your host platform. It then dumps
    what it found, and creates a file called `config.mk' in the current
    directory. This is a sub-Makefile used to define many important Make
    variables used to build the library.

  - the second time, the build system detects the `config.mk' then use it
    to build the library. All object files go into 'obj' by default, as
    well as the library file, but  this can easily be changed.

  Note that you can run "make setup" to force another host platform detection
  even if a `config.mk' is present in the current directory. Another solution
  is simply to delete the file, then re-run make.

  Finally, the default compiler for all platforms is gcc (for now, this will
  hopefully changed in the future). You can however specify a different
  compiler by specifying it after the 'setup' target as in :

      gnumake setup lcc         on Win32 to use the LCC compiler
      gnumake setup visualc     on Win32 to use Visual C++

  See the file `config/<system>/detect.mk' for a list of supported compilers
  for your platforms.

  It should be relatively easy to write new detection rules files and
  config.mk..

  Finally, to build the demo programs, go to `demos' and launch GNU Make,
  it will use the `config.mk' in the top directory to build the test
  programs..

-----------------------------------------------------------------------------------------
Portability :

  In the previous beta, a single FT_System object was used to encompass
  all low-level operations like thread synchronisation, memory management
  and i/o access. This has been greatly simplified :

    - thread synchronisation has been dropped, for the simple reason that
      the library is already re-entrant, and that if you really need two
      threads accessing the same FT_Library, you should really synchronize
      access to it yourself with a simple mutex.

    - memory management is performed through a very simple object called
      "FT_Memory", which really is a table containing a table of pointers
      to functions like malloc, realloc and free as well as some user data
      (closure).

    - resources have disappeared (they created more problems than they
      solved), and i/o management have been simplified greatly as a
      result. Streams are defined through FT_Stream objects, which can
      be either memory-based or disk-based.

      Note that each face has its own stream, which is closed only when
      the face object is destroyed. Hence, a function like TT_Flush_Face
      in 1.x cannot be directly supported. However, if you really need
      something like this, you can easily tailor your own streams to achieve
      the same feature at a lower level (and use FT_Open_Face instead of
      FT_New_Face to create the face).

  See the file "include/ftsystem.h" for more details, as well as the
  implementations found in "config/unix" and "config/ansi".


-----------------------------------------------------------------------------------------
Font Drivers :
  

  The Font Driver interface has been modified in order to support
  extensions & versioning.


  The list of the font drivers that are statically linked to the
  library at compile time is managed through a new configuration file
  called `config/<platform>/ftmodule.h'.

  This file is autogenerated when invoking `make modules'. This target
  will parse all sub-directories of 'src', looking for a "module.mk"
  rules file, used to describe the driver to the build system.

  Hence, one should call `make modules' each time a font driver is added
  or removed from the `src' directory.


  Finally, this version provides a "pseudo-driver" in `src/sfnt'. This
  driver doesn't support font files directly, but provides services used
  by all TrueType-like font drivers. Hence, its code is shared between
  the TrueType & OpenType font formats, and possibly more formats to
  come if we're lucky..

-----------------------------------------------------------------------------------------
Extensions support :

  The extensions support is inspired by the one found in 1.x.

  Now, each font driver has its own "extension registry", which lists
  which extensions are available for the font faces managed by the driver.

  Extension ids are now strings, rather than 4-byte tags, as this is
  usually more readable..

  Each extension has:
    - some data, associated to each face object
    - an interface (table of function pointers)

  An extension that is format-specific should simply register itself
  to the correct font driver. Here is some example code:

   // Registering an extensions
   //
   FT_Error  FT_Init_XXXX_Extension( FT_Library  library )
   {
     FT_DriverInterface*  tt_driver;

     driver = FT_Get_Driver( library, "truetype" );
     if (!driver) return FT_Err_Unimplemented_Feature;

     return FT_Register_Extension( driver, &extension_class );   
   }

   
   // Implementing the extensions
   //
   FT_Error  FT_Proceed_Extension_XXX( FT_Face  face )
   {
     FT_XXX_Extension            ext;
     FT_XXX_Extension_Interface  ext_interface;

     ext = FT_Get_Extension( face, "extensionid", &ext_interface );
     if (!ext) return error;

     return ext_interface->do_it(ext);
   }