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).
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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
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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
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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)
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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..
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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..
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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".
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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..
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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);
}
