ref: 576403f22be42343da8e7f2c1cbc7b4aef4fc8ad
dir: /docs/CUSTOMIZE/
How to customize the compilation of the library
===============================================
FreeType is highly customizable to fit various needs, and this
document describes how it is possible to select options and
components at compilation time.
I. Configuration macros
The file `include/freetype/config/ftoption.h' contains a list of
commented configuration macros that can be toggled by developers to
indicate which features should be active while building the library.
These options range from debug level to availability of certain
features, like native TrueType hinting through a bytecode
interpreter.
We invite you to read this file for more information. You can
change the file's content to suit your needs, or override it with
one of the techniques described below.
II. Modules list
If you use GNU make please edit the top-level file `modules.cfg'.
It contains a list of available FreeType modules and extensions to
be compiled. Change it to suit your own preferences. Be aware that
certain modules depend on others, as described in the file. GNU
make uses `modules.cfg' to generate `ftmodule.h' (in the object
directory).
If you build FreeType in a directory separate from the source files,
put your customized `modules.cfg' in that directory; that way you
can keep the source files `clean'.
If you don't use GNU make you have to manually edit the file
`include/freetype/config/ftmodule.h' (which is *not* used with if
compiled with GNU make) to add or remove the drivers and components
you want to compile into the library. See `INSTALL.ANY' for more
information.
III. System interface
FreeType's default interface to the system (i.e., the parts that
deal with memory management and i/o streams) is located in
`src/base/ftsystem.c'.
The current implementation uses standard C library calls to manage
memory and to read font files. It is however possible to write
custom implementations to suit specific systems.
To tell the GNU Make-based build system to use a custom system
interface, you have to define the environment variable FTSYS_SRC to
point to the relevant implementation:
on Unix:
./configure <your options>
export FTSYS_SRC=foo/my_ftsystem.c
make
make install
on Windows:
make setup <compiler>
set FTSYS_SRC=foo/my_ftsystem.c
make
IV. Overriding default configuration and module headers
It is possible to override the default configuration and module
headers without changing the original files. There are three ways
to do that:
1. With GNU make
[This is actually a combination of method 2 and 3.]
Just put your custom `ftoption.h' file into the objects directory
(normally `<topdir>/objs' if you build in the source tree, or the
directory where you invoke configure if you build in a separate
directory), which GNU make prefers over the standard location. No
action is needed for `ftmodule.h' because it is generated
automatically in the objects directory.
2. Using the C include path
Use the C include path to ensure that your own versions of the
files are used at compile time when the lines
#include FT_CONFIG_OPTIONS_H
#include FT_CONFIG_MODULES_H
are compiled. Their default values being
<freetype/config/ftoption.h> and <freetype/config/ftmodule.h>, you
can do something like:
custom/
config/
ftoption.h => custom options header
ftmodule.h => custom modules list
include/ => normal FreeType 2 include
...
then change the C include path to always give the path to `custom'
before the FreeType 2 `include'.
3. Redefining FT_CONFIG_OPTIONS_H and FT_CONFIG_MODULES_H
Another way to do the same thing is to redefine the macros used to
name the configuration headers. To do so, you need a custom
`ft2build.h' whose content can be as simple as:
#ifndef FT2_BUILD_MY_PLATFORM_H_
#define FT2_BUILD_MY_PLATFORM_H_
#define FT_CONFIG_OPTIONS_H <custom/my-ftoption.h>
#define FT_CONFIG_MODULES_H <custom/my-ftmodule.h>
#include <freetype/config/ftheader.h>
#endif /* FT2_BUILD_MY_PLATFORM_H_ */
Place those files in a separate directory, e.g.,
custom/
ft2build.h => custom version described above
my-ftoption.h => custom options header
my-ftmodule.h => custom modules list header
and change the C include path to ensure that `custom' is always
placed before the FT2 `include' during compilation.
----------------------------------------------------------------------
Copyright (C) 2003-2020 by
David Turner, Robert Wilhelm, and Werner Lemberg.
This file is part of the FreeType project, and may only be used,
modified, and distributed under the terms of the FreeType project
license, LICENSE.TXT. By continuing to use, modify, or distribute
this file you indicate that you have read the license and understand
and accept it fully.
--- end of CUSTOMIZE ---