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<h1>FreeType 2.0 Build System</h1></center>
<center>
<h3>
© 2000 David Turner (<a href="fichier :///[email protected]">[email protected]</a>)<br>
© 2000 The FreeType Development Team
(<a href="mailto:[email protected]">[email protected]</a>)
</h3></center>
<center><table width=650><tr><td>
<p><hr WIDTH="100%"></p>
<h2>Table of Content</h2>
<center><table><tr><td>
<p><font size="+1"><a href="#introduction">Introduction</a></font></p>
<p><font size="+1"><a href="#features">I. Features & Background</a></font></p>
<ul>
<li><a href="#features-1">1. Convenience, not Requirement</a>
<li><a href="#features-2">2. Compiler and platform independence</a>
<li><a href="#features-3">3. Uses GNU Make</a>
<li><a href="#features-4">4. Automatic host platform detection</a>
<li><a href="#features-5">5. User-selectable builds</a>
<li><a href="#features-6">6. Robustness</a>
<li><a href="#features-7">7. Simple modules management</a>
</ul>
<p><font size="+1"><a href="#overview">II. Overview of the build process</a></font></p>
<ul>
<p><li><a href="#overview-1">1. Build setup</a>
<ul>
<li><a href="#overview-1-a">a. Default build setup</a>
<li><a href="#overview-1-b">b. Selecting another build configuration</a>
</ul>
</p>
<li><a href="#overview-2">2. Library compilation</a>
</ul>
<p><font size="+1"><a href="#setup">III. Build setup details</a></font></p>
<p><font size="+1"><a href="#compilation">IV. Library compilation details</a></font></p>
<ul>
<li><a href="#compilation-1">a. Compiling the <tt>ftsystem</tt> component</a>
<li><a href="#compilation-2">b. Compiling the base layer and optional components</a>
<li><a href="#compilation-3">c. Compiling the modules</a>
<li><a href="#compilation-4">d. Compiling the <tt>ftinit</tt> component</a>
</ul>
</ul>
</td></tr></table></center>
<hr><a name="introduction">
<h2>Introduction:</h2>
<p>This document describes the new build system that was introduced
with FreeType 2.</p>
<p><hr></p>
<a name="features">
<h2>I. Features and Background:</h2>
<p>The FreeType 2 build system is a set of Makefiles and sub-Makefiles that
are used to build the library on a very large variety of systems easily.
One of its main features are the following:</p>
<a name="features-1">
<h3>1. Convenience, not Requirement</h3>
<ul>
<p>Even though the build system is rather sophisticated, it simply is a
convenience that was written simply to allow the compilation of the
FreeType 2 library on as many platforms as possible, as easily as
possible. However, it is not a requirement and the library can be
compiled manually or in a graphical IDE without using it, with minimal
efforts</p>
<p>(for more information on this topic, see the <tt>BUILD</tt>
document that comes with your release of FreeType, in its <em>Detailed
Compilation Guide</em> section).</p>
</ul>
<a name="features-2">
<h3>2. Compiler and platform independence</h3>
<ul>
<p>The FreeType 2 build system can be used with any compiler, on any platform.
It is independent of object file suffix, executable file suffix, directory
separator convention (i.e. "/" or "\"), and compiler flags for path
inclusion, macro definition, output naming, ansi compliance, etc..</p>
<p>Supporting a new compiler is trivial and only requires writing a minimal
configuration sub-makefile that contains several Makefile variables
definitions that are later used by the rest of the build system. This is
described in details later in the document.</p>
</ul>
<a name="features-3">
<h3>3. Uses GNU Make</h3>
<ul>
<p>The build system works <em>exclusively</em> with <b>GNU Make</b>. Reason
is that it is the only make utility that has all the features required to
implement the build system as described below. Moreover, it is already
ported to hundreds of various distinct platforms and is widely and
freely available.</p>
<p>It also uses the native command line shell. <em>You thus
don't need a Unix-like shell on your platform</em>.
For example, FreeType 2 already compiles on Unix, Dos, Windows
and OS/2 right "out of the box" (assuming you have GNU Make
installed).</p>
<p>Finally, note that the build system is <em>specifically</em> designed
for gnu make and will <em>fail</em> with any other make tool. We have
<em>no plans</em> to support a different tools, as you'll rapidly
understand by reading this document or looking at the sub-makefiles
themselves.</p>
</ul>
<a name="features-4">
<h3>4. Automatic host platform detection</h3>
<ul>
<p>When you launch the build system for the first time, by simply invoking
GNU make in the top-level directory, it automatically tries to detect
your current platform in order to choose the best configuration
sub-makefile available. It then displays what it found. If everything
is ok, you can then launch compilation of the library, by invoking make
a second time.</p>
<p>The following platforms are currently automatically detected:</p>
<ul>
<li>Dos (plain-dos, windows in Dos mode, or Dos session under OS/2)
<li>Windows 95, 98 + Windows NT (a.k.a win32)
<li>OS/2
<li>Unix (uses Autoconf/Automake)
</ul>
<p>Note that adding support for a new platform requires writing a minimal
number of very small files, and simply putting them in a new sub-directory
of <tt>freetype2/config</tt>.</p>
</ul>
<a name="features-5">
<h3>5. User-selectable builds</h3>
<ul>
<p>The platform auto-detection rules try to setup the build for a default
compiler (<em>gcc</em> for most platforms), with default build options
for the library (which normally is
<em>"all features enable, no debugging"</em>), as well as the default
list of modules (which is <em>"all modules in <tt>freetype2/src</tt>"</em>)</p>
<p>There are cases where it is important to specify a different compiler,
different build options or simply a different module list. The FreeType 2
build system is designed in such a way that all of this is easily possible
from the command line, <em>without having to touch a single file</em>.
The latter is crucial when dealing with projects that need specific
builds of the library without modifying a single file from the FreeType
distribution.</p>
<p>The exact mechanism and implementation to do this is described later in
this document. It allows, for example, to compile FreeType with any of
the following compilers on Win32: gcc, Visual C++, Win32-LCC.</p>
</ul>
<a name="features-6">
<h3>6. Robustness</h3>
<ul>
<p>The build system uses a single top-level Makefile that includes
one or more sub-makefiles to build the entire library (base layer
plus all modules).
<font color="red">
To understand why this is important, we <em>strongly</em> recommend
the following article to all of our readers:</font></p>
<p>
<center>
<font size="+2"><a href="http://www.pcug.org.au/~millerp/rmch/recu-make-cons-harm.html">
Recursive Make Considered Dangerous
</a>
</font>
</center>
</p>
<p>As an example, here's a short list of files that make up the
build system. Note that each sub-makefile contains rules corresponding
to a very specific purpose, and that they all use the "<tt>.mk</tt>"
suffix:</p>
<ul>
<li><tt>freetype2/Makefile</tt>
<li><tt>freetype2/config/detect.mk</tt>
<li><tt>freetype2/config/freetype.mk</tt>
<li><tt>freetype2/config/<em><system></em>/detect.mk</tt>
<li><tt>freetype2/src/<em><module></em>/rules.mk</tt>
<li><tt>freetype2/src/<em><module></em>/module.mk</tt>
</ul>
</ul>
<a name="features-7">
<h3>7. Simple Module Management</h3>
<ul>
<p>FreeType 2 has a very modular design, and is made of a core
<em>base layer</em> that provides its high-level API as well as
generic services used by one or more <em>modules</em>.
Most modules are used to support a specific font format (like TrueType
or Type 1), and they are called <em>font drivers</em>. However, some of
them do not support font files directly, but rather provide helper
services to the font drivers.</p>
<p>FreeType 2 is designed so that adding modules at run-time is possible
and easy. Similarly, we expect many more modules to come in the near
future and wanted a build system that makes such additions to the
source package itself dead easy.
Indeed, all source code (base + modules) is located in the
<tt>freetype2/src</tt> directory hierarchy. And the build system is
capable of re-generating automatically the list of known modules
from the contents of this directory. Hence, adding a new font driver
to the FreeType sources simply requires to:</p>
<ul>
<li><p>Add a new sub-directory to <tt>freetype2/src</tt>
<li><p>Re-launch the build system</p>
</ul>
<p>There is thus no need to edit a source file</p>
</ul>
<p><hr><p>
<a name="overview">
<h2>II. Overview of the build process(es):</h2>
<p>Before describing in details how the build system works, it is essential
to give a few examples of how it's used. This section presents
what's the build process is to the typical developer:</p>
<p>Compiling the library is normally done in two steps: the first one
configures the build according to the current platform and possible
additional parameters, while the second simply compiles the library with
the information gathered in the configuration step.</p>
<a name="overview-1">
<h3>1. Build Setup</h3>
<a name="overview-1-a">
<h4>a. Default build setup</h4>
<ul>
<p>To configure the build, simply invoke gnu make from the top-level FreeType
directory. This will launch a series of rules that will detect your current
host platform, and choose a configuration file for you. It will then display
what it found. For example, here's the output of typing the command "make"
on a win32 platform (assuming this calls GNU make):</p>
<pre><font color="blue">
<font color="purple">C:\FreeType> make</font>
FreeType build system -- automatic system detection
The following settings are used:
platform win32
compiler gcc
configuration directory ./config/win32
configuration rules ./config/win32/w32-gcc.mk
If this does not correspond to your system or settings please remove the file
'config.mk' from this directory then read the INSTALL file for help.
Otherwise, simply type 'make' again to build the library.
<font color="purple">C:\FreeType></font>
</font></pre>
<p>Note that this step copies the selected configuration file (here
<tt>./config/win32/w32-gcc.mk</tt>) to <em>the current directory</em>, under
the name <tt><b>config.mk</b></tt>. This file contains data that is used
to drive the library compilation of the second step. It correspond to
the platform and compiler selected by the auto-detection phase.</p>
<p>Note that you can re-generate the <tt><b>config.mk</b></tt> file anytime
by invoking <tt>make setup</tt> whenever you need it, even when the file is
already present in the current directory.</p>
<p>Finally, if your platform is not correctly detected, the build system will
display and use configuration information for the virtual "ansi" platform.
</p>
</ul>
<a name="overview-1-b">
<h4>b. Selecting another build configuration</h4>
<ul>
<p>You may not be really satisfied by the configuration file selected by the
auto-detection routines. Typically, you might be using a compiler that is
not the default one for your platform. It is however possible to re-launch
the build setup phase with an additional argument, used to specify a
different compiler/config file. For example, you can type the following
commands on Win32 systems:</p>
<p align=center><table width="80%" cellpadding=10><tr valign=top><td>
<p><b><tt>make setup</tt></b></p>
</td><td>
<p>re-run the platform detection phase, and select the default compiler for it.
On Win32, this is <em>gcc</em>.</p>
</td></tr><tr valign=top><td>
<p><b><tt>make setup visualc</tt></b></p>
</td><td>
<p>re-run the platform detection phase, and select a config file that
corresponds to the <em>Visual C++</em> compiler</p>
</td></tr><tr valign=top><td>
<p><b><tt>make setup lcc</tt></b></p>
</td><td>
<p>re-run the platform detection phase, and select a config file that
corresponds to the <em>Win32-LCC</em> compiler</p>
</td></tr></table>
</p>
<p>Note that a specific configuration is selected with a command that
looks like : <tt><b>make setup <em>compiler</em></b></tt>,
where the <em><tt>compiler</tt></em> keywords depends on the platform.
Moreover, each one of them corresponds to a specific configuration
sub-makefile that is copied as <b><tt>config.mk</tt></b> in the current
directory.</p>
</ul>
<a name="overview-2">
<h3>2. Library compilation</h3>
<p>Once you're satisfied with the version of <b><tt>config.mk</tt></b> that
has been copied to your current directory, you can simply re-invoke
gnu make <em>with no arguments</em>. The top-level Makefile will
automatically detect the config sub-makefile in the current directory,
and use it to drive the library compilation. The latter can be seen
as a series of different steps decribed here:</p>
<ul>
<li><p><b>Compiling the <tt>ftsystem</tt> component</b><br><ul>
It encapsulates all low-level operations (memory management +
i/o access) for the library. Its default version, located in
<tt>./src/base/ftsystem.c</tt> uses the ANSI C library but
system-specific implementations are also available to
improve performance (e.g. memory-mapped files on Unix).
</ul></p>
<li><p><b>Compiling the <em>base layer</em> and optional components</b><br><ul>
They provide the library's high-level API as well as various useful
routines for client applications. Many features of the base layer can
be activated or not depending on a configuration file named
<tt>ftoption.h</tt>
</ul></p>
<li><p><b>Compiling the <em>modules</em></b><br><ul>
Each module is used to support a specific font format (it is then
called a <em>font driver</em>), or to provide helper services to
the drivers (e.g. the auto-hinter). They are all located in
sub-directories of <tt>./src</tt>, like <tt>./src/truetype</tt>,
<tt>./src/type1</tt>.
</ul></p>
<li><p><b>Compiling the <tt>ftinit</tt> component</b><br><ul>
This one is in charge of implementing <tt>FT_Init_FreeType</tt>,
the library initialisation routine. It also selects what modules
are activated when a new library instance is created.
</ul></p>
</ul>
<p><hr><p>
<a name="setup">
<h2>II. Details of the build setup.</h2>
<p>When the top-level <tt>Makefile</tt> is invoked, it looks for a
file named <b><tt>config.mk</tt></b> in the <em>current directory</em>.
If this file is found, it is used directly to build the library
(skip to <a href="library">Section III</a> for details then).</p>
<p>Otherwise, the file <b><tt>./config/detect.mk</tt></b> is included
by the top-level <tt>Makefile</tt> and parsed. Its purpose is to drive the
platform-detection phase, by:</p>
<ul>
<li><p>Defining the <tt>PLATFORM</tt> variable, which indicates
what the currently detected platform is. It is initially
set to the default value "<tt><b>ansi</b></tt>".
</p>
<li><p>Searching for a <tt>detect.mk</tt> file in <em>all
subdirectories</em> of <b><tt>./config</tt></b>.
Each such file is included and parsed. Each of these files must
try to detect if the host platform is a system it knows
about. If so, it changes the value of the <tt>PLATFORM</tt> variable
accordingly.</p>
<li><p>Copying the selected configuration submakefile to the current directory
under the name <tt><b>config.mk</b></tt>.</p>
</ul>
<p>This is illustrated by the following graphics :</p>
<p><center>
<img src="platform-detection.png" border=0>
</center></p>
<p>Each system-specific <b><tt>detect.mk</tt></b> works as follows:</p>
<ul>
<li><p>It checks that the value of <tt>PLATFORM</tt> is currently set
to <b>ansi</b>, which indicates that no platform was detected
for now. If this isn't true, it doesn't do anything</p>
<li><p>Otherwise, it runs a series of test to see wether it is on a
system it knows about. Here are a few examples of tests:</p>
<p><center><table width="80%" cellpadding=5><tr valign=top><td>
<em><b>Unix</b></em>
</td><td>
<p>checks for a file named <tt>/sbin/init</tt>, and runs, when it found
it, a 'configure' script to generate the relevant config sub-makefile</p>
</td></tr><tr valign=top><td>
<em><b>Dos</b></em>
</td><td>
<p>checks for the <tt>COMSPEC</tt> environment variable, then tries to
run the "<tt>ver</tt>" command on the current shell to check that there
is a "Dos" substring in its output; if not, it tries to find the
substring "<tt>MDOS\COMMAND</tt>" in <tt>COMSPEC</tt>, which indicates
a Dos session under OS/2.</p>
</td></tr><tr valign=top><td>
<em><b>Win32</b></em>
</td><td>
<p>if the environment variable <tt>OS</tt> is defined and has the value
<tt>Windows_NT</tt>, or if <tt>COMSPEC</tt> is defined and the
"<tt>ver</tt>" returns a string that contains <tt>Windows</tt> in it,
we're on a Win32 system.</p>
</td></tr></table></center>
</p>
<li><p>It sets the value of <tt>PLATFORM</tt> to a new value corresponding
to its platform.</p>
<li><p>It then tries to select a configuration
sub-makefile, depending on the current platform and any optional
make target (like "visualc" or "devel", etc..). Note that it can
even generate the file, as on Unix through Autoconf/Automake.</p>
<li><p>It copies the selected configuration sub-makefile to the current
directory, under the name <tt><b>config.mk</b></tt>
</ul>
<p>If one wants to support a new platform in the build system, it simply needs
to provide:</p>
<ul>
<li>A new subdirectory, in <tt>./config</tt>, with a file named
<tt>detect.mk</tt> in it, containing relevant checks for the system.
<li>One or more configuration sub-makefiles that will get copied to
<tt>config.mk</tt> at build setup time. You can use the one in
<tt>./config/ansi/config.mk</tt> as a template.
</ul>
<p>Similary, supporting a new compiler on an existing system simply means:</p>
<ul>
<li>Writing a new config sub-makefile that contains definitions used to
specify the compiler and flags for the build.
<li>Change your <tt>./config/<em>system</em>/detect.mk</tt> to recognize
a new optional build target that will copy your new config sub-makefile
instead of the default one.
</ul>
<p><hr><p>
<h2>III. Details of the library compilation.</h2>
<p>When the top-level Makefile is invoked, it looks for a file named
<tt>config.mk</tt> in the current directory. If one is found, it
defines the <tt>BUILD_FREETYPE</tt> variable, then includes and parses it.
The structure of this file is the following:
</p>
<ul>
<li><p>First, it defines a series of Make variables that describe
the host environment, like the compiler, compilation flags,
object file suffix, the directory where all object files are
placed, etc..</p>
<li><p>If <tt>BUILD_FREETYPE</tt> is defined, it includes the file
<tt><b>./config/freetype.mk</b></tt>, which is in charge of
defining all the rules used to build the library object files.
(The test is useful to use the <tt>config.mk</tt> file to
compile other projects that rely on FreeType 2, like its
demonstration programs).</p>
<li><p>Finally, it defines the rule(s) used to link FreeType 2 object files
into a library file (e.g. <tt>libfreetype.a</tt>, <tt>freetype.lib</tt>,
<tt>freetype.dll</tt>, ...). Unfortunately, the command line interface of link tools is
a <em>lot less</em> standardized than those of compilers, which
explains why this rule must be defined in the system-specific
<tt>config.mk</tt>.</p>
</ul>
<p>The following is an explanation of what <tt><b>./config/freetype.mk</b></tt>
does to build the library objects:
</p>
<h4>a. Include paths</h4>
<ul>
<p>To avoid namespace pollution, the <tt><em>freetype</em></tt> directory prefix
is used to include all public header files of the library. This means
that a client application will typically use lines like:</p>
<pre><font color="blue">
#include <freetype/freetype.h>
#include <freetype/ftglyph.h>
</font></pre>
<p>to include one the FreeType 2 public header files. <tt>freetype.mk</tt>
uses a variable named <tt><b>INCLUDES</b></tt> to hold the inclusion
paths list, and thus starts by adding <tt>./include</tt> to it. However,
nothing prevents
<p><tt>freetype.mk</tt> uses a variable named <tt><b>INCLUDES</b></tt>
to hold directory inclusion-path to be used when compiling the library.
It always add <tt>./include</tt> to this variable, which means
</ul>
<h4>b. Configuration header files:</h4>
<ul>
<p>Three header files used to configure the compilation of the
FreeType 2 library. Their default versions are all located in the
directory <tt><b>./include/freetype/config/</b></tt>, even though
project specific versions can be provided on a given build, as
described later:</p>
<ul>
<p><b><tt>#include <freetype/config/ftoption.h></tt></b><br><ul>
This file contains a set of configuration macro definitions that
can be toggled to activate or deactivate certain features of the
library. By changing one of these definitions, it is possible to
compile <em>only the features that are needed</em> for a specific
project. Note that by default, all options are enabled.
<br><br>
You might need to provide an alternative version of <tt>ftoption.h</tt>
for one of your own projects.
</ul></p>
<p><b><tt>#include <freetype/config/ftconfig.h></tt></b><br><ul>
This file includes <tt>ftoption.h</tt> but also contains some automatic
macro definitions used to indicate some important system-specific
features (e.g: word size in bytes, DLL export prefix macros, etc..).
<br><br>
You shouldn't normally need to change or provide an alternative
version of this file.
</ul></p>
<p><b><tt>#include <freetype/config/ftmodule.h></tt></b><br><ul>
This file is very special, as it is normally machine-generated, and
used by the <tt>ftinit</tt> component that is described below. To
understand it, one must reminds that FreeType 2 has an extremely
modular design and that it's possible to change, <em>at run-time</em>,
the modules it's using. The <tt>ftmodule.h</tt> file simply contains
the list of modules that are registered with each new instance of
the library.
<br><br>
Note that the file can be re-generated automatically by invoking
<tt>make setup</tt> from the top-level directory. The re-generated
list contains all the modules that were found in subdirectories of
<tt>./src</tt>.
</ul></p>
</ul>
<p>Note that we strongly advise you to avoid modifying the config files
within the FreeType 2 source directory hierarchy. Rather, it's possible
to specify alternative versions through the help of a build-specific
include path that is include before <tt>./include</tt> in the inclusion
path.</p>
<p>For example, imagine that your platform, named <em>foo</em>, needs a
specific version of <tt>ftoption.h</tt>
</ul>
<h4>a. Compiling the <b><tt>ftsystem</tt></b> component:</h4>
<ul>
<p>FreeType 2 encapsulates all low-level operations (i.e. memory management
and i/o access) within a single component called <tt><b>ftsystem</b></tt>.
Its default implementation uses the <em>ANSI C Library</em> and is located
in <tt>./src/base/ftsystem.c</tt>.</p>
<p>However, some alternate, system-specific, implementations of
<tt>ftsystem</tt> are provided with the library in order to support more
efficient and advanced features. As an example, the file
<tt>./config/unix/ftsystem.c</tt> is an implementation that
uses memory-mapped files rather than the slow ANSI <tt>fopen</tt>,
<tt>fread</tt> and <tt>fseek</tt>, boosting performance significantly.</p>
<p>The build system is thus capable of managing alternate implementations
of <tt>ftsystem</tt></p>
</ul>
<h4>b. Compiling the base layer and optional components:</h4>
<ul>
<p>The high-level API of the library is provided by a component called the
<em>base layer</em>, whose source is located in <tt>./src/base</tt>. This
directory also contains one or more components that are optional, i.e.
that are not required by the library but provide valuable routines to
client applications.</p>
<p>The features of the base library and other components are selected through
a single configuration file named
<tt><b>./include/freetype/config/ftoption.h</b></tt>. It contains a list
of commented configuration macro definitions, that can be toggled to
activate or de-activate a certain feature or component at build time.</p>
<p>For example, the code in <tt>./src/base/ftdebug.c</tt> will be compiled
only if one of these two macros are defined in <tt>ftoption.h</tt>:
<tt>FT_DEBUG_LEVEL_ERROR</tt> or <tt>FT_DEBUG_LEVEL_TRACE</tt></p>
</ul>
<h4>c. Compiling the modules:</h4>
<ul>
<p>Once the base layer is completed, the build system starts to compile each
additional module independently. These are simply defined as all source
code located in a sub-directory of <tt>./src</tt> that contains a file
named <tt><b>rules.</b></tt>, for example:
<tt>src/sfnt</tt>, <tt>src/truetype</tt>, <tt>src/type1</tt>, ...</p>
<p>The <tt><b>rules.</b></tt> file simply contains directives used by the
build system to compile the corresponding module into a single object
file.</p>
</ul>
<h4>d. Compiling the <b><tt>ftinit</tt></b> component:</h4>
<ul>
<p>The file <tt><b>./src/base/ftinit.c</b></tt> is special because it is used
to implement the library initialisation function <tt>FT_Init_FreeType</tt>.
</p>
</ul>
<p>Typically, you will end up with all object files, as well as the
corresponding library file, residing in the <tt>freetype2/obj</tt>
directory.</p>
<h3>1. Purpose of the configuration sub-makefile</h3>
<h3>2. Managing module dependencies</h3>
<h3>3. </h3>
<p><hr><p>
<a name="modules">
<h2>IV. Managing the modules list</h2>
<p><hr><p>
The build system features some important points, which are all detailed
in the following sections:<p>
<ul>
<li><b>Automatic host platform detection</b><br>
The first time the top <tt>Makefile</tt> is invoked, it will
run a series of rules to detect your platform. It will then
create a system-specific configuration sub-Makefile in the
current directory, called <b><tt>config.mk</tt></b>. You can now
invoke the top <tt>Makefile</tt> a second time to compile the
library directly.
<p>
The configuration sub-makefile can be regenerated any time
by invoking "<tt>make setup</tt>", which will re-run the
detection rules even if a <tt>config.mk</tt> is already present.
<p>
<li><b>User-selectable builds</b><br>
<p>
<li><b>Automatic detection of font drivers</b><br>
FreeType is made of a "base" layer that invokes several
separately-compiled modules. Each module is a given
font driver, in charge of supporting a given font format.
<p>
The list of font drivers is located in the file
"<tt>freetype2/config/<em>system</em>/ftmodule.h</tt>", however
it can be regenerated on-demand. Adding a new module to the
FreeType source tree is thus as easy as:<p>
<ul>
<li>create a new directory in "<tt>freetype2/src</tt>" and
put the new driver's source code and sub-makefiles there.
<p>
<li>invoke the top <tt>Makefile</tt> with target
"<tt>modules</tt>" (as in "<tt>make modules</tt>"),
as this will automatically regenerate the list of
available drivers by detecting the new directory and
its content.
</ul>
<p>
</ul>
</ul>
<p><hr><p>
<h2>II. Host Platform Detection</h2>
<ul>
When the top-level <tt>Makefile</tt> is invoked, it looks for a
file named <tt>config.mk</tt> in the current directory. If this
file is found, it is used to build the library
(see <a href="library">Section III</a>).
<p>
Otherwise, the file <tt>freetype2/config/detect.mk</tt> is included
and parsed. Its purpose is to:<p>
<ul>
<li>Define the <tt>PLATFORM</tt> variable, which indicates
what is the currently detected platform. It is initially
set to the default value "<tt>ansi</tt>".
<p>
<li>It searches for a <tt>detect.mk</tt> file in all
subdirectories of <tt>freetype2/config</tt>. Each such
file is included and parsed. Each of these files must
try to detect if the host platform is a system it knows
about. If so, it changes the value of the <tt>PLATFORM</tt>
accordingly.
</ul>
<p>
This is illustrated by the following graphics :<p>
<center>
<img src="platform-detection.png" border=0>
</center>
<p>
Note that each system-specific <tt>detect.mk</tt> is in charge
of copying a valid configuration makefile to the current directory
(i.e. the one where <tt>make</tt> was invoked), depending on the
current targets. For example, the Win32 <tt>detect.mk</tt> will
be able to detect a "<tt>visualc</tt>" or "<tt>lcc</tt>" target,
as described in section I. Similarly, the OS/2 <tt>detect.mk</tt>
can detect targets like "<tt>borlandc</tt>", "<tt>watcom</tt>"
or "<tt>visualage</tt>", etc..
</ul>
<p><hr><p>
<h2>III. Building the library</h2>
<ul>
When the top-level <tt>Makefile</tt> is invoked and that it finds
a <tt>config.mk</tt> file in the current directory, it defines
the variable <tt>BUILD_FREETYPE</tt>, then includes and parses the
configuration sub-makefile.
<p>
The latter defines a number of important variables that describe
the compilation process to the build system. Among other things:<p>
<ul>
<li>the extension to be used for object files and library files
(i.e. <tt>.o</tt> and <tt>.a</tt> on Unix, <tt>.obj</tt>
and <tt>.lib</tt> on Dos-Windows-OS/2, etc..).
<p>
<li>the directory where all object files will be stored
(usually <tt>freetype2/obj</tt>), as well as the one
containing the library file (usually the same as for
objects).
<p>
<li>the command line compiler, and its compilation flags for
indicating a new include path (usually "<tt>-I</tt>"),
a new macro declaration (usually "<tt>-D</tt>") or
the target object file (usually "<tt>-o </tt>")
</ul>
<p>
Once these variable are defined, <tt>config.mk</tt> test for the
definition of the <tt>BUILD_FREETYPE</tt> variable. If it exists,
the makefile then includes "<tt>freetype2/config/freetype.mk</tt>"
which contains the rules required to compile the library.
<p>
Note that <tt>freetype.mk</tt> also scans the subdirectories of
"<tt>freetype2/src</tt>" for a file called "<tt>rules.mk</tt>".
Each <tt>rules.mk</tt> contains, as it names suggests, the rules
required to compile a given font driver or module.
<p>
Once all this parsing is done, the library can be compiled. Usually,
each font driver is compiled as a standalone object file (e.g.
<tt>sfnt.o</tt>, <tt>truetype.o</tt> and <tt>type1.o</tt>).
<p>
This process can be illustrated by the following graphics:<p>
<center>
<img src="library-compilation.png" border=0>
</center>
<p>
</ul>
<p><hr><p>
<h2>IIV. Managing the list of modules</h2>
<ul>
The makefile <tt>freetype.mk</tt> only determines how to compile
each one of the modules that are located in the sub-directories of
<tt>freetype2/src</tt>.
<p>
However, when the function <tt>FT_Init_FreeType</tt> is invoked at
the start of an application, it must create a new <tt>FT_Library</tt>
object, and registers all <em>known</em> font drivers to it by
repeatly calling <tt>FT_Add_Driver</tt>.
<p>
The list of <em>known</em> drivers is located in the file
"<tt>freetype2/config/<em>system</em>/ftmodule.h</tt>", and is used
exclusively by the internal function <tt>FT_Default_Drivers</tt>. The
list in <tt>ftmodule.h</tt> must be re-generated each time you add
or remove a module from <tt>freetype2/src</tt>.
<p>
This is normally performed by invoking the top-level <tt>Makefile</tt>
with the <tt>modules</tt> target, as in:<p>
<ul>
<tt>make modules</tt>
</ul>
<p>
This will trigger a special rule that will re-generate
<tt>ftmodule.h</tt>. To do so, the Makefile will parse all module
directories for a file called "<tt>module.mk</tt>". Each
<tt>module.mk</tt> is a tiny sub-Makefile used to add a single
module to the driver list.
<p>
This is illustrated by the following graphics:<p>
<center>
<img src="drivers-list.png" border=0>
</center>
<p>
Note that the new list of modules is displayed in a very human-friendly
way after a "<tt>make modules</tt>". Here's an example with the current
source tree (on 11 Jan 2000):<p>
<ul><pre>
Regenerating the font drivers list in ./config/unix/ftmodule.h
* driver: sfnt ( pseudo-driver for TrueType & OpenType formats )
* driver: truetype ( Windows/Mac font files with extension *.ttf or *.ttc )
* driver: type1 ( Postscript font files with extension *.pfa or *.pfb )
-- done --
</pre></ul>
</ul>
<p><hr><p>
<h2>V. Building the demonstration programs</h2>
<ul>
Several demonstration programs are located in the
"<tt>freetype2/demos</tt>" directory hierarchy. This directory also
includes a tiny graphics sub-system that is able to blit glyphs to
a great variety of surfaces, as well as display these in various
graphics libraries or windowed environments.
<p>
This section describes how the demonstration programs are compiled,
using the configuration <tt>freetype2/config.mk</tt> and their own
<tt>freetype2/demos/Makefile</tt>.
<p>
To compile the demonstration programs, <em>after the library</em>,
simply go to <tt>freetype2/demos</tt> then invoke GNU make with no
arguments.
<p>
The top-level Makefile will detect the <tt>config.mk</tt> in the
<em>upper</em> directory and include it. Because it doesn't define
the <tt>BUILD_FREETYPE</tt> variable, this will not force the
inclusion of <tt>freetype2/config/freetype.mk</tt> as described in
the previous section.
<p>
the <tt>Makefile</tt> will then include the makefile called
"<tt>freetype2/demos/graph/rules.mk</tt>". The graphics <tt>rules.mk</tt>
defines the rules required to compile the graphics sub-system.
<p>
Because the graphics syb-system is also designed modularly, it is able
to use any number of "modules" to display surfaces on the screen.
The graphics modules are located in the subdirectories of
<tt>freetype2/demos/config</tt>. Each such directory contains a file
named <tt>rules.mk</tt> which is in charge of:<p>
<ul>
<li>detecting wether the corresponding graphics library is
available at the time of compilation.
<p>
<li>if it is, alter the compilation rules to include the graphics
module in the build of the <tt>graph</tt> library.
</ul>
<p>
When the <tt>graph</tt> library is built in <tt>demos/obj</tt>, the
demonstration programs executables are generated by the top-level
Makefile.
<p>
This is illustrated by the following graphics:<p>
<center>
<img src="demo-programs.png" border="0">
</center>
</ul>
<p><hr>
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