gtk2/docs/gtk-config.txt

CONFIGURING PACKAGES TO WORK WITH GTK
-------------------------------------

Compiling a program successfully against the GTK, GDK, and GLIB
libraries can require a large number of command line options
to your compiler and linker that are hard to guess correctly.
The additional libraries required may, for example, depend on the
manner which GTK was configured

Several tools are included in this package to make process
easier.

First, there is the shell script 'gtk-config' (installed in
$exec_prefix/bin):

Invoking gtk-config
-------------------

gtk-config takes the following flags:

  --version
     Prints out the version of GTK installed

  --cflags
     Prints '-I' flags pointing to the installed header files.

  --libs
     Prints out the linker flags necessary to link a program against GTK
   
  --prefix[=PREFIX]
     If PREFIX is specified, overrides the configured value of $prefix.
     (And of exec-prefix, unless --exec-prefix is also specified)
     Otherwise, prints out the configured value of $prefix

  --exec-prefix[=PREFIX]
     If PREFIX is specified, overrides the configured value of $exec_prefix.
     Otherwise, prints out the configured value of $exec_prefix
 
You may also add to the command line a list of additional
libraries that gtk-config should supply the CFLAGS and LIBS
for. The only currently supported library is 'gthread'.

As an example of this latter usage, you can get the
appropriate cflags for a threaded program with:

 gtk-config --cflags gthread


Example of using gtk-config
---------------------------

Typically, gtk-config will be used within a configure script,
as described below. It, however, can also be used directly
from the command line to compile a simple program. For example:

  cc -o simple `gtk-config --cflags` simple.c `gtk-config --libs`

This command line might expand to (for example):

  cc -o simple -I/usr/local/lib/glib/include -I/usr/local/include \
    -I/usr/X11R6/include simple.c -L/usr/local/lib -L/usr/X11R6/lib \
    -lgtk -lgdk -lglib -lXi -lXext -lX11 -lm

Not only is the form using gtk-config easier to type, it will
work on any system, no matter how GTK was configured.


AM_PATH_GTK
-----------

For packages configured using GNU automake, GTK also provides
a macro to automate the process of running GTK.

 AM_PATH_GTK([MINIMUM-VERSION, [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]]])

This macro:

 * Determines the location of GTK using gtk-config, which is either
   found in the user's path, or from the environment variable
   GTK_CONFIG

 * Tests the installed libraries to make sure that there version
   is later than MINIMUM-VERSION. (A default version will be used
   if not specified)

 * If the required version was found, sets the GTK_CFLAGS variable to
   the output of `gtk-config --cflags` and the GTK_LIBS variable to
   the output of `gtk-config --libs`, and calls AC_SUBST() for these
   variables so they can be used in generated makefiles, and then
   executes ACTION-IF-FOUND.

 * If the required version was not found, sets GTK_CFLAGS and GTK_LIBS
   to empty strings, and executes ACTION-IF-NOT-FOUND.

This macro is in file 'gtk.m4' which is installed in $datadir/aclocal.
Note that if automake was installed with a different --prefix than
GTK, you will either have to manually move gtk.m4 to automake's
$datadir/aclocal, or give aclocal the -I option when running it.


Configuring a package that uses AM_PATH_GTK
-------------------------------------------

Simply make sure that gtk-config is in your path, and run
the configure script.

Notes:

* The directory where the GTK libraries are installed needs
  to be found by your system's dynamic linker.
  
  This is generally done by

    editing /etc/ld.so.conf and running ldconfig

  Or by:
   
    setting the environment variable LD_LIBRARY_PATH, 

  or, as a last resort, 
 
    Giving a -R or -rpath flag (depending on your linker) when
    running configure, for instance:

      LDFLAGS=-R/usr/home/owen/lib ./configure

* You can also specify a gtk-config not in your path by
  setting the GTK_CONFIG environment variable to the
  name of the executable

* If you move the GTK package from its installed location,
  you will need either need to modify gtk-config script
  manually to point to the new location or rebuild GTK.

Advanced note:

* configure flags
  
  --with-gtk-prefix=PREFIX
  --with-gtk-exec-prefix=PREFIX 

  are provided to override the prefix and exec-prefix that were stored
  in the gtk-config shell script by GTK's configure. You are generally
  better off configuring GTK with the right path to begin with.

Example of a package using AM_PATH_GTK
--------------------------------------

The following shows how to build a simple package using automake
and the AM_PATH_GTK macro. The program used here is the testinput.c

You should first read the introductory portions of the automake
Manual, if you are not already familiar with it.

Two files are needed, 'configure.ac', which is used to build the
configure script:

==configure.ac===
dnl Process this file with autoconf to produce a configure script.
AC_INIT(testinput.c)

AM_INIT_AUTOMAKE(testinput.c, 1.0.0)

AC_PROG_CC
AM_PROG_CC_STDC
AC_PROG_INSTALL

AM_PATH_GTK(0.99.5,
          [LIBS="$LIBS $GTK_LIBS"
           CFLAGS="$CFLAGS $GTK_CFLAGS"],
 	  AC_MSG_ERROR(Cannot find GTK: Is gtk-config in path?))

AC_OUTPUT(Makefile)
=================

The only command in this which is not standard for automake
is the AM_PATH_GTK() macro.

That command does the following:

 If a GTK version greater than 0.99.5 is found, adds $GTK_LIBS to 
 $LIBS and $GTK_CFLAGS to $CFLAGS. Otherwise, dies with the error
 message "Cannot find GTK: Is gtk-config in path?"

And the 'Makefile.am', which will be used to build the Makefile.

== Makefile.am ==
bin_PROGRAMS = testinput
testinput_SOURCES = testinput.c
=================

This Makefile.am, says that we are building a single executable,
from a single sourcefile 'testinput.c'. Since every program
we are building uses GTK we simply added the GTK options
to $LIBS and $CFLAGS, but in other circumstances, we might
want to specify them on a per-program basis: for instance by
adding the lines:

  testinput_LDADD = $(GTK_LIBS)
  INCLUDES = $(GTK_CFLAGS)

to the Makefile.am.

To try this example out, create a new directory, add the two
files above two it, and copy the testinput.c file from 
the gtk/ subdirectory to the new directory. Edit the line:

  #include "gtk.h"

in testgtk.c, to read:

  #include <gtk/gtk.h>


Now execute the following commands:

  automake --add-missing
  aclocal
  autoconf
  
You now have a package that can be built in the normal fashion

  ./configure
  make
  make install


Notes:

* If you are converting a package that used a pre-1.0 version of
  GTK, you should remove the autoconf tests for X. The results
  of these tests are included in gtk-config and will be added
  to GTK_LIBS and GTK_CFLAGS by the AM_PATH_GTK macro.

                                        Owen Taylor
                                        14 Mar 1997