gtk-faq.sgml

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it. There is the GTK+ Tutorial <ulink
url="http://www.gtk.org/tutorial/">
http://www.gtk.org/tutorial/</ulink>, which is undergoing
development. This will introduce you to writing applications
using C.</para>

<para>The GTK+ Tutorial doesn't contain information on all of
the widgets that are in GTK+. For example code on how to use
the basics of all the GTK+ widgets you should look in the
directory 'tests' (and associated source files) within the GTK+
distribution. Looking at these examples will give you a good
grounding on what the widgets can do.</para>

</sect1>

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<sect1>
<title>How do I use the Glade GUI builder with GTK+? <emphasis>[GTK 2.x]</emphasis></title>

<para>There are two ways to use Glade. The first way is to use
Glade's facilities for generating code; the second
way is to use the libglade library which directly loads
the XML user interface description files that Glade
generates into a running program.</para>

<para>Experienced GTK+ programmers generally strongly recommend
using libglade; you don't have to worry about the interaction
between Glade generating the source and you editing it,
and its been shown to be a method that works better
for large projects, so there is a lot of example code
out there you can look at.</para>

<para>An introduction to using libglade can be found in the 
libglade API docs
(<ulink url="http://developer.gnome.org/doc/API/2.0/libglade/libglade-notes.html#libglade-basics">
http://developer.gnome.org/doc/API/2.0/libglade/libglade-notes.html#libglade-basics</ulink>)
.</para>

</sect1>

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<sect1>
<title>How do I write security sensitive/SUID/SGID programs with GTK+?
Is GTK+ secure? What's this GTK_MODULES security hole I heard about?
<emphasis>[GTK 2.x]</emphasis></title>

<para>The short answer to this question is: you can't, so don't write SUID/SGID
programs with GTK+</para>

<para>GTK+ will refuse to run with elevated privileges, as it is not designed
to be used in this manner. The only correct way to write a setuid program with
a graphical user interface is to have a setuid backend that communicates with
the non-setuid graphical user interface via a mechanism such as a pipe and that
considers the input it receives to be untrusted.</para>

<para>For a more thorough explanation of the GTK+ Developers position on
this issue see <ulink
url="http://www.gtk.org/setuid.html">http://www.gtk.org/setuid.html</ulink>.</para>

</sect1>

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<sect1>
<title>I tried to compile a small <command>Hello World</command> of mine,
but it failed. Any clue? <emphasis>[GTK 2.x]</emphasis></title>

<para>Since you are good at coding, we will not deal with
compile time errors here :)</para>

<para>The classic command line to compile a GTK+ based program is</para>
<para><literallayout>
<literal>gcc -o myprog [c files] `pkg-config gtk+-2.0 --cflags --libs`</literal>
</literallayout></para>

<para>You should notice the backquote character which is used
in this command line. A common mistake when you start a GTK+
based development is to use quotes instead of backquotes. If
you do so, the compiler will complain about an unknown file
called <filename>pkg-config gtk+-2.0 --cflags --libs</filename>. The
text in backquotes is an instruction to your shell to
substitute the output of executing this command into the
commandline.</para>

<para>The command line above ensures that:</para>

<itemizedlist>
<listitem><simpara>the correct C compiler flags will be used
to compile the program (including the complete C header
directory list)</simpara>
</listitem>

<listitem><simpara>your program will be linked with the
needed libraries.</simpara>
</listitem>
</itemizedlist>

</sect1>

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<sect1>
<title>What about using the <command>make</command>
utility? <emphasis>[GTK 2.x]</emphasis></title>

<para>This is a sample makefile which compiles a GTK+ based
program:</para>

<programlisting role="C">
# basic GTK+ app makefile
SOURCES = myprg.c foo.c bar.c
OBJS    = ${SOURCES:.c=.o}
CFLAGS  = `pkg-config gtk+-2.0 --cflags`
LDADD   = `pkg-config gtk+-2.0 --libs`
CC      = gcc
PACKAGE = myprg

all : ${OBJS}
  ${CC} -o ${PACKAGE} ${OBJS} ${LDADD}

.c.o:
  ${CC} ${CFLAGS} -c $<

# end of file
</programlisting>

<para>For more information about the <command>make</command> utility, you
should read either the related man page or the relevant info file.</para>

</sect1>

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<sect1>
<title>I use the backquote stuff in my makefiles, but my make
process failed. <emphasis>[GTK 2.x]</emphasis></title>

<para>The backquote construction seems to not be accepted by
some old <command>make</command> utilities. If you use one of these, the
make process will probably fail. In order to have the
backquote syntax working again, you should use the GNU make
utility (get it on the GNU ftp server at <ulink
url="ftp://ftp.gnu.org/gnu/make/">ftp://ftp.gnu.org/gnu/make/</ulink>).</para>

</sect1>

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<sect1>
<title>I want to add some configure stuff, how could I do
this? <emphasis>[GTK 2.x]</emphasis></title>

<para>To use autoconf/automake, you must first install the
relevant packages. These are:</para>

<itemizedlist spacing=Compact>
<listitem><simpara>the m4 preprocessor v1.4 or better</simpara>
</listitem>

<listitem><simpara>autoconf v2.54 or better</simpara>
</listitem>

<listitem><simpara>automake v1.7 or better suggested</simpara>
</listitem>
</itemizedlist>

<para>You'll find these packages on the main GNU ftp server
(<ulink url="ftp://ftp.gnu.org/">ftp://ftp.gnu.org/</ulink>)
or on any GNU mirror.</para>

<para>In order to use the powerful autoconf/automake scheme,
you must create a configure.in which may look like:</para>

<programlisting role="C">
dnl Process this file with autoconf to produce a configure script.
dnl configure.in for a GTK+ based program

AC_INIT(myprg.c)
AM_INIT_AUTOMAKE(mypkgname, 0.0.1)
AM_CONFIG_HEADER(config.h)

dnl Checks for programs.
AC_PROG_CC dnl check for the c compiler
dnl you should add CFLAGS="" here, 'cos it is set to -g by PROG_CC

dnl Checks for libraries.
AM_PATH_GTK_2_0(2.2.0,,AC_MSG_ERROR(mypkgname 0.1 needs GTK+ 2.2.0))

AC_OUTPUT(
	Makefile
)
</programlisting>

<para>You must add a Makefile.am file:</para>

<programlisting role="C">
bin_PROGRAMS    = myprg
myprg_SOURCES   = myprg.c foo.c bar.c
INCLUDES        = @GTK_CFLAGS@
LDADD           = @GTK_LIBS@
CLEANFILES      = *~
DISTCLEANFILES  = .deps/*.P
</programlisting>

<para>If your project contains more than one subdirectory,
you'll have to create one Makefile.am in each directory plus a
master Makefile.am which will look like:</para>

<programlisting role="C">
SUBDIRS         = mydir1 mydir2 mydir3
</programlisting>

<para>then, to use these, simply type the following
commands:</para>

<programlisting role="C">
aclocal
autoheader
autoconf
automake --add-missing --include-deps --foreign 
</programlisting>

<para>For further information, you should look at the autoconf
and the automake documentation (the shipped info files are
really easy to understand, and there are plenty of web
resources that deal with autoconf and automake).</para>

</sect1>

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<sect1>
<title>I try to debug my GTK+ application with gdb, but it
hangs my X server when I hit some breakpoint. Any
Idea? <emphasis>[GTK 2.x]</emphasis></title>

<para>From Federico Mena Quintero:</para>

<para><quote>X is not locked up.  It is likely that you are hitting a
breakpoint inside a callback that is called from a place in Gtk that has
a mouse grab.</quote></para>

<para><quote>Run your program with the <literal>--sync</literal>
option; it will make it easier to debug. Also, you may want to
use the console for running the debugger, and just let the
program run in another console with the X server.</quote></para>

<para>Eric Mouw had another solution:</para>

<para><quote>An old terminal connected to an otherwise unused serial
port is also great for debugging X programs. Old vt100/vt220
terminals are dirt cheap but a bit hard to get (here in The
Netherlands, YMMV).</quote></para>

<para>
Another option is to run your application on Xnest. Xnest is an X server
which displays its root window in a regular window of another X server.  
A pointer grab on the Xnest display will not affect the GUI of your debugger
running on your regular X server.
<programlisting>
Xnest :1
twm -display :1
myapp --display=:1
</programlisting>
</para>
</sect1>
</chapter>

<!-- ***************************************************************** -->
<chapter>
<title>Development with GTK+: general questions</title>

<!-- ----------------------------------------------------------------- -->

<sect1>
<title>What widgets are in GTK?</title>

<para>The GTK+ Tutorial lists the following widgets:</para>

<programlisting role="C">
  GtkObject
   +GtkData
   | +GtkAdjustment
   | `GtkTooltips
   `GtkWidget
     +GtkContainer
     | +GtkBin
     | | +GtkAlignment
     | | +GtkEventBox
     | | +GtkFrame
     | | | `GtkAspectFrame
     | | +GtkHandleBox
     | | +GtkItem
     | | | +GtkListItem
     | | | +GtkMenuItem
     | | | | `GtkCheckMenuItem
     | | | |   `GtkRadioMenuItem
     | | | `GtkTreeItem
     | | +GtkViewport
     | | `GtkWindow
     | |   +GtkColorSelectionDialog
     | |   +GtkDialog
     | |   | `GtkInputDialog
     | |   `GtkFileSelection
     | +GtkBox
     | | +GtkButtonBox
     | | | +GtkHButtonBox
     | | | `GtkVButtonBox
     | | +GtkHBox
     | | | +GtkCombo
     | | | `GtkStatusbar
     | | `GtkVBox
     | |   +GtkColorSelection
     | |   `GtkGammaCurve
     | +GtkButton
     | | +GtkOptionMenu
     | | `GtkToggleButton
     | |   `GtkCheckButton
     | |     `GtkRadioButton
     | +GtkCList
     |   `GtkCTree
     | +GtkFixed
     | +GtkList
     | +GtkMenuShell
     | | +GtkMenuBar
     | | `GtkMenu
     | +GtkNotebook
     | +GtkPaned
     | | +GtkHPaned
     | | `GtkVPaned
     | +GtkScrolledWindow
     | +GtkTable
     | +GtkToolbar
     | `GtkTree
     +GtkDrawingArea
     | `GtkCurve
     +GtkEditable
     | +GtkEntry
     | | `GtkSpinButton
     | `GtkText
     +GtkMisc
     | +GtkArrow
     | +GtkImage
     | +GtkLabel
     | | `GtkTipsQuery
     | `GtkPixmap
     +GtkPreview
     +GtkProgressBar
     +GtkRange
     | +GtkScale
     | | +GtkHScale
     | | `GtkVScale
     | `GtkScrollbar
     |   +GtkHScrollbar
     |   `GtkVScrollbar
     +GtkRuler
     | +GtkHRuler
     | `GtkVRuler
     `GtkSeparator
       +GtkHSeparator
       `GtkVSeparator
</programlisting>
</sect1>

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<sect1>
<title>Is GTK+ thread safe? How do I write multi-threaded GTK+
applications? <emphasis>[GTK 2.x]</emphasis></title>

<para>The GLib library can be used in a thread-safe mode by
calling g_thread_init() before making any other GLib
calls. In this mode GLib automatically locks all internal
data structures as needed.  This does not mean that two
threads can simultaneously access, for example, a single hash
table, but they can access two different hash tables
simultaneously. If two different threads need to access the
same hash table, the application is responsible for locking
itself.</para>

<para>In order to make GDK thread aware, you also need to
call gdk_threads_init() in conjunction with the above call.
There is a single global
lock that you must acquire with gdk_threads_enter() before
making any GDK calls, and release with gdk_threads_leave()
afterwards throughout your code.</para>

<para>A minimal main program for a threaded GTK+ application
looks like:</para>

<programlisting role="C">
int
main (int argc, char *argv[])
{
  GtkWidget *window;

  /* init threads */	
  g_thread_init(NULL);
  gdk_threads_init();
  
  /* init gtk */
  gtk_init(&amp;argc, &amp;argv);

  window = create_window();
  gtk_widget_show(window);

  gdk_threads_enter();
  gtk_main();
  gdk_threads_leave();

  return 0;