248 lines
9.7 KiB
Plaintext
248 lines
9.7 KiB
Plaintext
This file summarizes the changes that occured since the last "beta" of FreeType 2.
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Because the list is important, it has been divided into separate sections:
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Table Of Contents:
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I High-Level Interface (easier !)
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II Directory Structure
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III Glyph Image Formats
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IV Build System
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V Portability
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VI Font Drivers
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-----------------------------------------------------------------------------------------
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High-Level Interface :
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The high-level API has been considerably simplified. Here is how :
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- resource objects have disappeared. this means that face objects can
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now be created with a single function call (see FT_New_Face and
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FT_Open_Face)
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- when calling either FT_New_Face & FT_Open_Face, a size object and a
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glyph slot object are automatically created for the face, and can be
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accessed through "face->glyph" and "face->size" if one really needs to.
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In most cases, there's no need to call FT_New_Size or FT_New_Glyph.
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- similarly, FT_Load_Glyph now only takes a "face" argument (instead of
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a glyph slot and a size). Also, it's "result" parameter is gone, as
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the glyph image type is returned in the field "face->glyph.format"
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- the list of available charmaps is directly accessible through
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"face->charmaps", counting "face->num_charmaps" elements. Each
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charmap has an 'encoding' field which specifies which known encoding
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it deals with. Valid values are, for example :
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ft_encoding_unicode (for ASCII, Latin-1 and Unicode)
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ft_encoding_apple_roman
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ft_encoding_sjis
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ft_encoding_adobe_standard
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ft_encoding_adobe_expert
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other values may be added in the future. Each charmap still holds its
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"platform_id" and "encoding_id" values in case the encoding is too
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exotic for the current library
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-----------------------------------------------------------------------------------------
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Directory Structure:
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Should seem obvious to most of you:
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freetype/
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config/ -- configuration sub-makefiles
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ansi/
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unix/ -- platform-specific configuration files
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win32/
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os2/
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msdos/
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include/ -- public header files, those to be included directly
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by client apps
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src/ -- sources of the library
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base/ -- the base layer
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sfnt/ -- the sfnt "driver" (see the drivers section below)
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truetype/ -- the truetype driver
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type1/ -- the type1 driver
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shared/ -- some header files shared between drivers
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demos/ -- demos/tools
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docs/ -- documentation (a bit empty for now)
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-----------------------------------------------------------------------------------------
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Glyph Image Formats :
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Drivers are now able to register new glyph image formats within the library.
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For now, the base layer supports of course bitmaps and vector outlines, but
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one could imagine something different like colored bitmaps, bi-color
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vectors or wathever else (Metafonts anyone ??).
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See the file `include/ftimage.h'. Note also that the type FT_Raster_Map is
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gone, and is now replaced by FT_Bitmap, which should encompass all known
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bitmap types.
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Each new image format must provide at least one "raster", i.e. a module
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capable of transforming the glyph image into a bitmap. It's also possible
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to change the default raster used for a given glyph image format.
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The default outline scan-converter now uses 128 levels of grays by default,
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which tends to smooth many things. Note that the demo programs have been
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updated significantly in order to display these..
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-----------------------------------------------------------------------------------------
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Build system :
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You still need GNU Make to build the library. The build system has been
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very seriously re-vamped in order to provide things like :
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- automatic host platform detection (reverting to 'config/ansi'
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if it is not detected, with pseudo-standard compilation flags)
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- the ability to compile from the Makefiles with very different and
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exotic compilers. Note that linking the library can be difficult for
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some platforms.
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For example, the file `config/win32/lcclib.bat' is invoked by the
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build system to create the ".lib" file with LCC-Win32 because its
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librarian has too many flaws to be invoked directly from the Makefile.
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Here's how it works :
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- the first time you type `make', the build system runs a series of
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sub-makefiles in order to detect your host platform. It then dumps
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what it found, and creates a file called `config.mk' in the current
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directory. This is a sub-Makefile used to define many important Make
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variables used to build the library.
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- the second time, the build system detects the `config.mk' then use it
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to build the library. All object files go into 'obj' by default, as
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well as the library file, but this can easily be changed.
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Note that you can run "make setup" to force another host platform detection
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even if a `config.mk' is present in the current directory. Another solution
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is simply to delete the file, then re-run make.
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Finally, the default compiler for all platforms is gcc (for now, this will
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hopefully changed in the future). You can however specify a different
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compiler by specifying it after the 'setup' target as in :
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gnumake setup lcc on Win32 to use the LCC compiler
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gnumake setup visualc on Win32 to use Visual C++
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See the file `config/<system>/detect.mk' for a list of supported compilers
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for your platforms.
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It should be relatively easy to write new detection rules files and
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config.mk..
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Finally, to build the demo programs, go to `demos' and launch GNU Make,
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it will use the `config.mk' in the top directory to build the test
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programs..
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-----------------------------------------------------------------------------------------
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Portability :
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In the previous beta, a single FT_System object was used to encompass
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all low-level operations like thread synchronisation, memory management
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and i/o access. This has been greatly simplified :
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- thread synchronisation has been dropped, for the simple reason that
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the library is already re-entrant, and that if you really need two
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threads accessing the same FT_Library, you should really synchronize
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access to it yourself with a simple mutex.
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- memory management is performed through a very simple object called
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"FT_Memory", which really is a table containing a table of pointers
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to functions like malloc, realloc and free as well as some user data
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(closure).
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- resources have disappeared (they created more problems than they
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solved), and i/o management have been simplified greatly as a
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result. Streams are defined through FT_Stream objects, which can
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be either memory-based or disk-based.
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Note that each face has its own stream, which is closed only when
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the face object is destroyed. Hence, a function like TT_Flush_Face
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in 1.x cannot be directly supported. However, if you really need
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something like this, you can easily tailor your own streams to achieve
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the same feature at a lower level (and use FT_Open_Face instead of
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FT_New_Face to create the face).
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See the file "include/ftsystem.h" for more details, as well as the
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implementations found in "config/unix" and "config/ansi".
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-----------------------------------------------------------------------------------------
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Font Drivers :
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The Font Driver interface has been modified in order to support
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extensions & versioning.
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The list of the font drivers that are statically linked to the
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library at compile time is managed through a new configuration file
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called `config/<platform>/ftmodule.h'.
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This file is autogenerated when invoking `make modules'. This target
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will parse all sub-directories of 'src', looking for a "module.mk"
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rules file, used to describe the driver to the build system.
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Hence, one should call `make modules' each time a font driver is added
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or removed from the `src' directory.
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Finally, this version provides a "pseudo-driver" in `src/sfnt'. This
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driver doesn't support font files directly, but provides services used
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by all TrueType-like font drivers. Hence, its code is shared between
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the TrueType & OpenType font formats, and possibly more formats to
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come if we're lucky..
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-----------------------------------------------------------------------------------------
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Extensions support :
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The extensions support is inspired by the one found in 1.x.
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Now, each font driver has its own "extension registry", which lists
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which extensions are available for the font faces managed by the driver.
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Extension ids are now strings, rather than 4-byte tags, as this is
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usually more readable..
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Each extension has:
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- some data, associated to each face object
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- an interface (table of function pointers)
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An extension that is format-specific should simply register itself
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to the correct font driver. Here is some example code:
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// Registering an extensions
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//
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FT_Error FT_Init_XXXX_Extension( FT_Library library )
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{
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FT_DriverInterface* tt_driver;
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driver = FT_Get_Driver( library, "truetype" );
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if (!driver) return FT_Err_Unimplemented_Feature;
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return FT_Register_Extension( driver, &extension_class );
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}
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// Implementing the extensions
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//
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FT_Error FT_Proceed_Extension_XXX( FT_Face face )
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{
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FT_XXX_Extension ext;
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FT_XXX_Extension_Interface ext_interface;
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ext = FT_Get_Extension( face, "extensionid", &ext_interface );
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if (!ext) return error;
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return ext_interface->do_it(ext);
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}
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