path: root/docbook/edg_src/EDG_chapter_userinterface.xml

<!-- EDG Chapter User Interface -->
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<chapter id="ChapterUserInterface">
  <title>User Interface</title>
  
  <section id="ChUIIntro">
	<title>Introduction</title>
	<para>
	Ethereal can be "logically" seperated into the backend (dissecting of
	protocols, file load/save, capturing, ...) and the frontend (the user
	interface). However, there's currently no clear seperation between
	these two parts (no clear API definition), but this might change in the
	future.
	</para>
	<para>
	The following frontends are currently maintained by the Ethereal
	development team:
	<itemizedlist>
	  <listitem><para>
	  Ethereal, GTK1.x based
	  </para></listitem>
	  <listitem><para>
	  Ethereal, GTK 2.x based
	  </para></listitem>
	  <listitem><para>
	  Tethereal, console based
	  </para></listitem>
	</itemizedlist>
	There are other Ethereal frontends existing, not developped nor
	maintained by the Ethereal development team:
	<itemizedlist>
	  <listitem><para>
	  Packetyzer (Win32 native interface, written in Delphi and released
	  under the GPL, see: 
	  <ulink url="http://www.networkchemistry.com/products/packetyzer/"/>)
	  </para></listitem>
	  <listitem><para>
	  hethereal (web based frontend, not actively maintained and not
	  finished)
	  </para></listitem>
	</itemizedlist>
	This chapter is focussed on the Ethereal frontend, and especially on
	the GTK specific things.
	</para>
  </section>
  
	<section id="ChUIGTK">
	<title>The GTK library</title>
	<para>
	Ethereal is based on the GTK toolkit, see: <ulink url="http://www.gtk.org"/>
	for
	details. GTK is designed to hide the details of the underlying GUI in
	a platform independant way. As this is appreciated for a
	multiplatform tool, this has some drawbacks, as it will result in a
	somewhat "non native" look and feel. For example: on win32, the "File
	open" dialog of Ethereal looks very different compared to the native
	win32 dialog the win32 users are used to see.
	</para>
	<para>
	GTK is available for a lot of different platforms including, but not
	limitted, to: unix/linux, mac os x and win32. It's the foundation of
	the famous GNOME desktop, so the future development of GTK should be
	certain.
	GTK is implemented in plain C (as Ethereal itself), and available under
	the LGPL (Lesser General Public License), being free to used by
	commercial and noncommercial applications.
	</para>
	<para>
	There are other similar toolkits like Qt, wxwidgets, ..., which could
	also
	be used for Ethereal. There's no "one and only" reason for or against
	any of these toolkits. However, the decision towards GTK was made a
	long time ago :-)
	</para>
	<para>
	At the time this document is written there are two major GTK versions
	available:
	</para>
	
	
	<section id="ChUIGTK1x">
	<title>GTK Version 1.x</title>
	<para>
	GTK 1.x was the first major release. Today there are 1.2.x and 1.3.x
	versions "in the wild", with only very limitted differences in the API.
	</para>
	<para>
	Advantages (compared to GTK 2.x):
	<itemizedlist>
	  <listitem><para>
	  available on a lot of different platforms
	  </para></listitem>
	  <listitem><para>
	  very stable as it's matured for quite a while now
	  </para></listitem>
	</itemizedlist>
	Disadvantages:
	<itemizedlist>
	  <listitem><para>
	  the look and feel is a bit oldfashioned
	  </para></listitem>
	  <listitem><para>
	  not recommended for future developments
	  </para></listitem>
	</itemizedlist>
	GTK 1.x depends on the following libraries:
	<itemizedlist>
	  <listitem><para>
	  GDK (GDK is the abstraction layer
	  that allows GTK+ to support multiple
	  windowing systems. GDK provides drawing and window system facilities
	  on X11, Windows, and the Linux framebuffer device.)
	  </para></listitem>
	  <listitem><para>
	  GLib (A general-purpose utility
	  library, not specific to graphical user interfaces.
	  GLib provides many useful data types, macros, type conversions,
	  string utilities, file utilities, a main loop abstraction, and so on.)
	  </para></listitem>
	</itemizedlist>
	GTK 1.x is working on GLib 1.x (typical for Unix like systems) or 2.x
	(typical for Win32 like systems).
	</para>
	<para>
	XXX: include Ethereal GTK1 screenshot
	</para>
	</section>


	<section id="ChUIGTK2x">
	<title>GTK Version 2.x</title>
	<para>
	Advantages (compared to GTK 1.x):
	<itemizedlist>
	  <listitem><para>
	  nice look and feel (compared to version 1.x)
	  </para></listitem>
	  <listitem><para>
	  recommended for future developments
	  </para></listitem>
	</itemizedlist>
	Disadvantages:
	<itemizedlist>
	  <listitem><para>
	  not available on all platforms (compared to version 1.x)
	  </para></listitem>
	  <listitem><para>
	  maybe a bit less stable compared to version 1.x (but should be
	  production stable too)
	  </para></listitem>
	  <listitem><para>
	  more dependencies compared to 1.x, see below
	  </para></listitem>
	</itemizedlist>
	GTK 2.x depends on the following libraries:
	<itemizedlist>
	  <listitem><para>
	  GObject (Object library. Basis for GTK and others)
	  </para></listitem>
	  <listitem><para>
	  GLib (A general-purpose utility
	  library, not specific to graphical user interfaces.
	  GLib provides many useful data types, macros, type conversions,
	  string utilities, file utilities, a main loop abstraction, and so on.)
	  </para></listitem>
	  <listitem><para>
	  Pango (Pango is a library for internationalized text handling. It centers
	  around the #PangoLayout object, representing a paragraph of text.
	  Pango provides the engine for #GtkTextView, #GtkLabel, #GtkEntry, and
	  other widgets that display text.)
	  </para></listitem>
	  <listitem><para>
	  ATK (ATK is the Accessibility Toolkit. It provides a set of generic
	  interfaces allowing accessibility technologies to interact with a
	  graphical user interface. For example, a screen reader uses ATK to
	  discover the text in an interface and read it to blind users. GTK+
	  widgets have built-in support for accessibility using the ATK
	  framework.)
	  </para></listitem>
	  <listitem><para>
	  GdkPixbuf (This is a small library which allows you to create #GdkPixbuf
	  ("pixel buffer") objects from image data or image files. Use a
	  #GdkPixbuf in combination with #GtkImage to display images.)
	  </para></listitem>
	  <listitem><para>
	  GDK (GDK is the abstraction layer that allows GTK+ to support multiple
	  windowing systems. GDK provides drawing and window system facilities
	  on X11, Windows, and the Linux framebuffer device.)
	  </para></listitem>
	</itemizedlist>
	XXX: include Ethereal GTK2 screenshot
	</para>
	</section>

	<section id="ChUIGTKCompat">
	<title>Compatibility between 1.x and 2.x</title>
	<para>
	The GTK library itself defines some values which makes it easy to
	distinguish between the versions, e.g.:
	GTK_MAJOR_VERSION GTK_MINOR_VERSION
	will be set to the GTK version at compile time somewhere inside the
	gtk.h headers.
	</para>
	<para>
	There are some common compatibility issues in Ethereal between the two
	versions. 
	</para>
	<para>
	Most of them (the more simple ones) are collected in
	gtk/compat_macros.h and can be used in an version independant manner.
	</para>
	<para>
	However, there are major differences between the two versions, making
	it necessary to distinct between them, like:
	<programlisting>
<![CDATA[
#if GTK_MAJOR_VERSION >= 2
   ...
#else
   ...
#endif]]>
</programlisting>
	</para>
	</section>

	</section>

	<section id="ChUIGUIDocs">
	<title>GUI Reference documents</title>
	<para>
	Although the GUI development of Ethereal is platform independant, the 
	Ethereal development team tries to
	follow the GNOME Human Interface Guidelines (HIG) where appropriate. 
	This is the case, because both GNOME and Ethereal are based on the GTK+ 
	toolkit and the GNOME HIG is excellently written and easy to understand.
	</para>
	<para>
	For further reference, see the following documents:
	<itemizedlist>
	  <listitem><para>
	  GNOME Human Interface Guidelines at:
	  <ulink url="http://developer.gnome.org/projects/gup/hig/"/>
	  </para></listitem>
	  <listitem><para>
	  KDE user interface related documents at:
	  <ulink url="http://developer.kde.org/documentation/library/ui.html"/>
	  </para></listitem>
	  <listitem><para>
	  Win32 XXX - where are good win32 styleguides available?
	  </para></listitem>
	</itemizedlist>
	</para>
	</section>
	
  <section id="ChUIGTKDialogs">
	<title>Adding/Extending Dialogs</title>
	<para>
	This is usually the main area for contributing new user interface features.
	</para>
	<para>
	XXX: add the various functions from gtk/dlg_utils.h
	</para>
  </section>

  <section id="ChUIGTKWidgetNamings">
	<title>Widget naming</title>
	<para>
	It seems to become common sense, to name the widgets with some
	descriptive trailing, like:
	<itemizedlist>
	  <listitem><para>
	  xy_lb = gtk_label_new();
	  </para></listitem>
	  <listitem><para>
	  xy_cb = gtk_checkbox_new();
	  </para></listitem>
	  <listitem><para>
	  XXX: add more examples
	  </para></listitem>
	</itemizedlist>
	However, this schema isn't used at all places inside the code.
	</para>
  </section>


  <section id="ChUIGTKPitfalls">
	<title>Common GTK programming pitfalls</title>
	<para>
	There are some common pitfalls in GTK programming.
	</para>

	<section id="ChUIGTKShowAll">
	<title>Usage of gtk_widget_show() / gtk_widget_show_all()</title>
	<para>
	When a GTK widget is created it will be hidden by default. In order to
	show it, a call to gtk_widget_show() has to be done.
	</para>
	<para>
	It isn't necessary to do this for each and every widget created. A call
	to
	gtk_widget_show_all() on the parent of all the widgets in question
	(e.g. a dialog window) can be done, so all of it's child widgets will
	be shown too.
	</para>
	</section>
	
  </section>

</chapter>
<!-- End of EUG Chapter User Interface -->