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<h1>
FreeType 2.0 Build System</h1></center>

<center>
<h3>
&copy; 2000 David Turner (<a href="fichier :///david@freetype.org">david@freetype.org</a>)<br>
&copy; 2000 The FreeType Development Team
(<a href="mailto:devel@freetype.org">devel@freetype.org</a>)
</h3></center>

<p><br>
<hr WIDTH="100%">
<br>&nbsp;
<h2>Introduction:</h2>
<ul>
	This document describes the new build system that was introduced
    with FreeType 2.
</ul>

<p><hr><p>

<h2>I. Features and Background:</h2>
<ul>
	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. To
	understand it properly, it must be noticed that:<p>
	<ul>
		<li>The build system is made of a <em>single Makefile</em>,
			dispatched over several directories with the help of the
			<tt>include</tt> directive. Technically speaking, it is
			composed of the top-level "<tt>freetype2/Makefile</tt>"
			which includes several other sub-Makefiles, whose extension
			is always "<tt>.mk</tt>". Examples are:<p>
			<ul>
				<tt>freetype2/config/freetype.mk</tt><br>
				<tt>freetype2/config/<em>system</em>/detect.mk</tt><br>
				<tt>freetype2/src/<em>module</em>/rules.mk</tt><br>
				etc..
			</ul>
			<p>
			<font size="+2" color="red">
			We <em>strongly</em> recommend the following article:<p>
			<center>
			  <a href="http://www.pcug.org.au/~millerp/rmch/recu-make-cons-harm.html">
			  Recursive Make Considered Dangerous
			  </a>
			</center>
			</font>
			<p>
			To understand why such a layout was chosen.
			<p>

		<li>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>
			<em>You 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>
			Note that we have <em>no plans</em> to support a different
			make tool, as you'll rapidly understand by reading this
			document or looking at the Makefiles themselves.
			<p>
	</ul>
	<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>
			The system-specific <b><tt>config.mk</tt></b> created when
			running <tt>make</tt> for the first time contains various
			definitions, including compiler, compiler flags, object files
			directories, etc.. However, a given platform has often several
			compilers available, each with a different name and flags to be
			used. Rather than trying to detect the compiler in the build
			system, users can also specify which compiler they use when
			running <tt>make</tt>.
			<p>
			For example, on Win32 platforms:<p>
			<ul>
				<table>
					<tr valign="top">
					<td><b><tt>make&nbsp;setup</tt></b>
					<td>Will generate a <tt>config.mk</tt> that
					    can be used to compile the library with
						<b><tt>gcc</tt></b> (<em>which is the default
						compiler for most supported platforms</em>).

					<tr valign="top">
					<td><b><tt>make&nbsp;setup&nbsp;visualc</tt></b>
					<td>Will generate a different <tt>config.mk</tt>
					    that can be used to compile the library
						with the Visual C++ command-line compiler.

					<tr valign="top">
					<td><b><tt>make&nbsp;setup&nbsp;lcc</tt></b>
					<td>Will generate a different <tt>config.mk</tt>
						that can be used to compile the library
						with the Win32-LCC compiler.
				</table>
			</ul>
			<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&nbsp;</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>

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