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+<?xml version="1.0" ?>
+<!DOCTYPE book PUBLIC "-//KDE//DTD DocBook XML V4.1.2-Based Variant V1.1//EN" "dtd/kdex.dtd" [
+ <!ENTITY % addindex "INCLUDE">
+ <!ENTITY % English "INCLUDE" > <!-- change language only here -->
+]>
+
+<book lang="&language;">
+
+<bookinfo>
+<title>KDE Architecture Overview</title>
+
+<date></date>
+<releaseinfo></releaseinfo>
+
+<authorgroup>
+<author>
+<firstname>Bernd</firstname>
+<surname>Gehrmann</surname>
+<affiliation><address><email>[email protected]</email></address></affiliation>
+</author>
+</authorgroup>
+
+<copyright>
+<year>2001</year>
+<year>2002</year>
+<holder>Bernd Gehrmann</holder>
+</copyright>
+
+<legalnotice>&FDLNotice;</legalnotice>
+
+<abstract>
+<para>This documentation gives an overview of the KDE Development Platform</para>
+</abstract>
+
+<keywordset>
+<keyword>KDE</keyword>
+<keyword>architecture</keyword>
+<keyword>development</keyword>
+<keyword>programming</keyword>
+</keywordset>
+
+</bookinfo>
+
+<chapter id="structure">
+<title>Library structure</title>
+
+<simplesect id="structure-byname">
+<title>Libraries by name</title>
+
+<variablelist>
+
+<varlistentry>
+<term><ulink url="kdeapi:kdecore/index.html">kdecore</ulink></term>
+<listitem><para>
+The kdecore library is the basic application framework for every KDE based
+program. It provides access to the configuration system, command line
+handling, icon loading and manipulation, some special kinds inter-process
+communication, file handling and various other utilities.
+</para></listitem>
+</varlistentry>
+
+<varlistentry>
+<term><ulink url="kdeapi:kdeui/index.html">kdeui</ulink></term>
+<listitem><para>
+The <literal>kdeui</literal> library provides many widgets and standard
+dialogs which Qt doesn't have or which have more features than their Qt
+counterparts. It also includes several widgets which are subclassed
+from Qt ones and are better integrated with the KDE desktop by
+respecting user preferences.
+</para></listitem>
+</varlistentry>
+
+<varlistentry>
+<term><ulink url="kdeapi:kio/index.html">kio</ulink></term>
+<listitem><para>
+The <literal>kio</literal> library contains facilities for asynchronous,
+network transparent I/O and access to mimetype handling. It also provides the
+KDE file dialog and its helper classes.
+</para></listitem>
+</varlistentry>
+
+<varlistentry>
+<term><ulink url="kdeapi:kjs/index.html">kjs</ulink></term>
+<listitem><para>
+The <literal>kjs</literal> library provides an implementation of JavaScript.
+</para></listitem>
+</varlistentry>
+
+<varlistentry>
+<term><ulink url="kdeapi:khtml/index.html">khtml</ulink></term>
+<listitem><para>
+The <literal>khtml</literal> library contains the KHTML part, a HTML browsing
+widget, DOM API and parser, including interfaces to Java and JavaScript.
+</para></listitem>
+</varlistentry>
+
+</variablelist>
+
+</simplesect>
+
+
+<simplesect id="structure-grouped">
+<title>Grouped classes</title>
+
+<para>
+Core application skeleton - classes needed by almost every application.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara>
+<title><ulink url="kdeapi:kdecore/KApplication">KApplication</ulink></title>
+<para>
+Initializes and controls a KDE application.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara>
+<title><ulink url="kdeapi:kdecore/KUniqueApplication">KUniqueApplication</ulink></title>
+<para>
+Makes sure only one instance of an application can run simultaneously.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KAboutData">KAboutData</ulink></title>
+<para>
+Holds information for the about box.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KCmdLineArgs">KCmdLineArgs</ulink></title>
+<para>
+Command line argument processing.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Configuration settings - access to KDE's hierarchical configuration
+database, global settings and application resources.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KConfig">KConfig</ulink></title>
+<para>
+Provides access to KDE's configuration database.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KSimpleConfig">KSimpleConfig</ulink></title>
+<para>
+Access to simple, non-hierarchical configuration files.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KDesktopFile">KDesktopFile</ulink></title>
+<para>
+Access to <literal>.desktop</literal> files.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KGlobalSettings">KGlobalSettings</ulink></title>
+<para>
+Convenient access to not application-specific settings.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+File and URL handling - decoding of URLs, temporary files etc.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KURL">KURL</ulink></title>
+<para>
+Represents and parses URLs.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KTempFile">KTempFile</ulink></title>
+<para>
+Creates unique files for temporary data.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KSaveFile">KSaveFile</ulink></title>
+<para>
+Allows to save files atomically.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Interprocess communication - DCOP helper classes and subprocess invocation.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KProcess">KProcess</ulink></title>
+<para>
+Invokes and controls child processes.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KShellProcess">KShellProcess</ulink></title>
+<para>
+Invokes child processes via a shell.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdesu/PtyProcess">PtyProcess</ulink></title>
+<para>
+Communication with a child processes through a pseudo terminal.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KIPC">KIPC</ulink></title>
+<para>
+Simple IPC mechanism using X11 ClientMessages.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:dcop/DCOPClient">DCOPClient</ulink></title>
+<para>
+DCOP messaging.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KDCOPPropertyProxy">KDCOPPropertyProxy</ulink></title>
+<para>
+A proxy class publishing Qt properties through DCOP.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KDCOPActionProxy">KDCOPActionProxy</ulink></title>
+<para>
+A proxy class publishing a DCOP interface for actions.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Utility classes - memory management, regular expressions, string manipulation,
+random numbers
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KRegExp">KRegExp</ulink></title>
+<para>
+POSIX regular expression matching.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KStringHandler">KStringHandler</ulink></title>
+<para>
+An extravagant interface for string manipulation.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KZoneAllocator">KZoneAllocator</ulink></title>
+<para>
+Efficient memory allocator for large groups of small objects.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KRandomSequence">KRandomSequence</ulink></title>
+<para>
+Pseudo random number generator.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Keyboard accelerators - classes helping to establish consistent key bindings
+throughout the desktop.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KAccel">KAccel</ulink></title>
+<para>
+Collection of keyboard shortcuts.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KStdAccel">KStdAccel</ulink></title>
+<para>
+Easy access to the common keyboard shortcut keys.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KGlobalAccel"></ulink></title>
+<para>
+Collection of system-wide keyboard shortcuts.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Image processing - icon loading and manipulating.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KIconLoader">KIconLoader</ulink></title>
+<para>
+Loads icons in a theme-conforming way.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KIconTheme">KIconTheme</ulink></title>
+<para>
+Helper classes for KIconLoader.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KPixmap">KPixmap</ulink></title>
+<para>
+A pixmap class with extended dithering capabilities.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KPixmapEffect">KPixmapEffect</ulink></title>
+<para>
+Pixmap effects like gradients and patterns.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KPixmapIO">KPixmapIO</ulink></title>
+<para>
+Fast <classname>QImage</classname> to <classname>QPixmap</classname> conversion.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Drag and Drop - drag objects for colors and URLs.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KURLDrag">KURLDrag</ulink></title>
+<para>
+A drag object for URLs.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KColorDrag">KColorDrag</ulink></title>
+<para>
+A drag object for colors.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KMultipleDrag">KMultipleDrag</ulink></title>
+<para>
+Allows to construct drag objects from several others.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Auto-Completion
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KCompletion">KCompletion</ulink></title>
+<para>
+Generic auto-completion of strings.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kio/KURLCompletion">KURLCompletion</ulink></title>
+<para>
+Auto-completion of URLs.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kio/KShellCompletion">KShellCompletion</ulink></title>
+<para>
+Auto-completion of executables.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Widgets - widget classes for list views, rules, color selection etc.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KListView">KListView</ulink></title>
+<para>
+A variant of <classname>QListView</classname> that honors KDE's system-wide settings.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KListView">KListBox</ulink></title>
+<para>
+A variant of <classname>QListBox</classname> that honors KDE's system-wide settings.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KListView">KIconView</ulink></title>
+<para>
+A variant of <classname>QIconView</classname> that honors KDE's system-wide settings.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KListView">KLineEdit</ulink></title>
+<para>
+A variant of <classname>QLineEdit</classname> with completion support.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KComboBox">KComboBox</ulink></title>
+<para>
+A variant of <classname>QComboBox</classname> with completion support.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KFontCombo">KFontCombo</ulink></title>
+<para>
+A combo box for selecting fonts.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KColorCombo">KColorCombo</ulink></title>
+<para>
+A combo box for selecting colors.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KColorButton">KColorButton</ulink></title>
+<para>
+A button for selecting colors.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KURLCombo">KURLCombo</ulink></title>
+<para>
+A combo box for selecting file names and URLs.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kfile/KURLRequester">KURLRequester</ulink></title>
+<para>
+A line edit for selecting file names and URLs.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KRuler">KRuler</ulink></title>
+<para>
+A ruler widget.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink
+url="kdeapi:kdeui/KAnimWidget">KAnimWidget</ulink></title>
+<para>
+animations.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KNumInput">KNumInput</ulink></title>
+<para>
+A widget for inputting numbers.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KPasswordEdit">KPasswordEdit</ulink></title>
+<para>
+A widget for inputting passwords.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Dialogs - full-featured dialogs for file, color and font selection.
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kfile/KFileDialog">KFileDialog</ulink></title>
+<para>
+A file selection dialog.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KColorDialog">KColorDialog</ulink></title>
+<para>
+A color selection dialog.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KFontDialog">KFontDialog</ulink></title>
+<para>
+A font selection dialog.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kfile/KIconDialog">KIconDialog</ulink></title>
+<para>
+An icon selection dialog.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KKeyDialog">KKeyDialog</ulink></title>
+<para>
+A dialog for editing keyboard bindings.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KEditToolBar">KEditToolBar</ulink></title>
+<para>
+A dialog for editing toolbars.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KTipDialog">KTipDialog</ulink></title>
+<para>
+A Tip-of-the-day dialog.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KAboutDialog">KAboutDialog</ulink></title>
+<para>
+An about dialog.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KLineEditDlg">KLineEditDlg</ulink></title>
+<para>
+A simple dialog for entering text.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kfile/KURLRequesterDlg">KURLRequesterDlg</ulink></title>
+<para>
+A simple dialog for entering URLs.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KMessageBox">KMessageBox</ulink></title>
+<para>
+A dialog for signaling errors and warnings.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KPasswordDialog">KPasswordDialog</ulink></title>
+<para>
+A dialog for inputting passwords.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Actions and XML GUI
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KAction">KAction</ulink></title>
+<para>
+Abstraction for an action that can be plugged into menu bars and tool bars.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KActionCollection">KActionCollection</ulink></title>
+<para>
+A set of actions.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdeui/KXMLGUIClient">KXMLGUIClient</ulink></title>
+<para>
+A GUI fragment consisting of an action collection and a DOM tree representing their location in the GUI.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kparts/KPartManager">KPartManager</ulink></title>
+<para>
+Manages the activation of XMLGUI clients.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+<para>
+Plugins and Components
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KLibrary">KLibrary</ulink></title>
+<para>
+Represents a dynamically loaded library.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KLibrary">KLibLoader</ulink></title>
+<para>
+Shared library loading.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kdecore/KLibFactory">KLibFactory</ulink></title>
+<para>
+Object factory in plugins.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kio/KServiceType">KServiceType</ulink></title>
+<para>
+Represents a service type.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kio/KService">KService</ulink></title>
+<para>
+Represents a service.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kio/KMimeType">KMimeType</ulink></title>
+<para>
+Represents a MIME type.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kio/KServiceTypeProfile">KServiceTypeProfile</ulink></title>
+<para>
+User preferences for MIME type mappings.
+</para>
+</formalpara></listitem>
+
+<listitem><formalpara><title><ulink url="kdeapi:kio/KServiceTypeProfile">KTrader</ulink></title>
+<para>
+Querying for services.
+</para>
+</formalpara></listitem>
+
+</itemizedlist>
+
+</simplesect>
+
+</chapter>
+
+
+
+<chapter id="graphics">
+<title>Graphics</title>
+
+<sect1 id="graphics-qpainter">
+<title>Low-level graphics with QPainter</title>
+
+<simplesect id="qpainter-rendering">
+<title>Rendering with QPainter</title>
+
+<para>
+Qt's low level imaging model is based on the capabilities provided by X11 and
+other windowing systems for which Qt ports exist. But it also extends these by
+implementing additional features such as arbitrary affine transformations for
+text and pixmaps.
+</para>
+
+<para>
+The central graphics class for 2D painting with Qt is
+<ulink url="kdeapi:qt/QPainter">QPainter</ulink>. It can
+draw on a
+<ulink url="kdeapi:qt/QPaintDevice">QPaintDevice</ulink>.
+There are three possible paint devices implemented: One is
+<ulink url="kdeapi:qt/QWidget">QWidget</ulink>
+which represents a widget on the screen. The second is
+<ulink url="kdeapi:qt/QPrinter">QPrinter</ulink> which
+represents a printer and produces Postscript output. The third it
+the class
+<ulink url="kdeapi:qt/QPicture">QPicture</ulink> which
+records paint commands and can save them on disk and play them back
+later. A possible storage format for paint commands is the W3C standard
+SVG.
+</para>
+
+<para>
+So, it is possible to reuse the rendering code you use for displaying a
+widget for printing, with the same features supported. Of course, in
+practice, the code is used in a slightly different context. Drawing
+on a widget is almost exclusively done in the paintEvent() method
+of a widget class.
+</para>
+
+<programlisting>
+void FooWidget::paintEvent()
+{
+ QPainter p(this);
+ // Setup painter
+ // Use painter
+}
+</programlisting>
+
+<para>
+When drawing on a printer, you have to make sure to use QPrinter::newPage()
+to finish with a page and begin a new one - something that naturally is not
+relevant for painting widgets. Also, when printing, you may want to use the
+<ulink url="kdeapi:qt/QPaintDeviceMetrics">device metrics</ulink>
+in order to compute coordinates.
+</para>
+
+</simplesect>
+
+
+<simplesect id="qpainter-transformations">
+<title>Transformations</title>
+
+<para>
+By default, when using QPainter, it draws in the natural coordinate
+system of the device used. This means, if you draw a line along the horizontal
+axis with a length of 10 units, it will be painted as a horizontal line
+on the screen with a length of 10 pixels. However, QPainter can apply arbitrary
+affine transformations before actually rendering shapes and curves. An
+affine transformation maps the x and y coordinates linearly into x' and
+y' according to
+</para>
+
+<mediaobject>
+<imageobject><imagedata fileref="affine-general.png"/></imageobject>
+</mediaobject>
+
+<para>
+The 3x3 matrix in this equation can be set with QPainter::setWorldMatrix() and
+is of type <ulink url="kdeapi:qt/QWMatrix">QWMatrix</ulink>.
+Normally, this is the identity matrix, i.e. m11 and m22 are one, and the
+other parameters are zero. There are basically three different groups of
+transformations:
+</para>
+
+<itemizedlist>
+
+<listitem><formalpara>
+<title>Translations</title>
+<para>
+These move all points of an object by a fixed amount in
+some direction. A translation matrix can be obtained by calling
+method m.translate(dx, dy) for a QWMatrix. This corresponds to the
+matrix
+</para>
+</formalpara>
+
+<mediaobject>
+<imageobject><imagedata fileref="affine-translate.png"/></imageobject>
+</mediaobject>
+
+</listitem>
+
+<listitem><formalpara>
+<title>Scaling</title>
+<para>
+These stretch or shrink the coordinates of an object, making
+it bigger or smaller without distorting it. A scaling transformation
+can be applied to a QWMatrix by calling m.scale(sx, sy). This corresponds
+to the matrix
+</para>
+</formalpara>
+
+<mediaobject>
+<imageobject><imagedata fileref="affine-scale.png"/></imageobject>
+</mediaobject>
+
+<para>
+By setting one of the parameters to a negative value, one can
+achieve a mirroring of the coordinate system.
+</para>
+
+</listitem>
+
+<listitem><formalpara>
+<title>Shearing</title>
+<para>
+A distortion of the coordinate system with two
+parameters. A shearing transformation can be applied by calling
+m.shear(sh, sv), corresponding to the matrix
+</para>
+</formalpara>
+
+<mediaobject>
+ <imageobject><imagedata fileref="affine-shear.png"/></imageobject>
+</mediaobject>
+
+</listitem>
+
+<listitem><formalpara>
+<title>Rotating</title>
+<para>
+This rotates an object. A rotation transformation can be
+applied by calling m.rotate(alpha). Note that the angle has to be given
+in degrees, not as mathematical angle! The corresponding matrix is
+</para>
+</formalpara>
+
+<mediaobject>
+<imageobject><imagedata fileref="affine-rotate.png"/></imageobject>
+</mediaobject>
+
+<para>
+Note that a rotation is equivalent with a combination of
+scaling and shearing.
+</para>
+
+</listitem>
+
+</itemizedlist>
+
+<para>
+Here are some pictures that show the effect of the elementary
+transformation to our masquot:
+</para>
+
+<informaltable frame="none">
+<tgroup cols="3">
+<tbody>
+<row>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="konqi-normal.png"/></imageobject>
+</mediaobject></entry>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="konqi-rotated.png"/></imageobject>
+</mediaobject></entry>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="konqi-sheared.png"/></imageobject>
+</mediaobject></entry>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="konqi-mirrored.png"/></imageobject>
+</mediaobject></entry>
+</row>
+<row>
+<entry>a) Normal</entry>
+<entry>b) Rotated by 30 degrees</entry>
+<entry>c) Sheared by 0.4</entry>
+<entry>d) Mirrored</entry>
+</row>
+</tbody>
+</tgroup>
+</informaltable>
+
+<para>
+Transformations can be combined by multiplying elementary matrices. Note that
+matrix operations are not commutative in general, and therefore the combined
+effect of of a concatenation depends on the order in which the matrices are
+multiplied.
+</para>
+
+</simplesect>
+
+
+<simplesect id="qpainter-strokeattributes">
+<title>Setting stroking attributes</title>
+
+<para>
+The rendering of lines, curves and outlines of polygons can be modified by
+setting a special pen with QPainter::setPen(). The argument of this function is a
+<ulink url="kdeapi:qt/QPen">QPen</ulink> object. The properties
+stored in it are a style, a color, a join style and a cap style.
+</para>
+
+<para>
+The pen style is member of the enum
+<ulink url="kdeapi:qt/Qt#PenStyle-enum">Qt::PenStyle</ulink>.
+and can take one of the following values:
+</para>
+
+<mediaobject>
+ <imageobject><imagedata fileref="penstyles.png"/></imageobject>
+</mediaobject>
+
+<para>
+The join style is a member of the enum
+<ulink url="kdeapi:qt/Qt#PenJoinStyle-enum">Qt::PenJoinStyle</ulink>.
+It specifies how the junction between multiple lines which are attached to each
+other is drawn. It takes one of the following values:
+</para>
+
+<informaltable frame="none">
+<tgroup cols="3">
+<tbody>
+<row>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="joinmiter.png"/></imageobject>
+</mediaobject></entry>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="joinbevel.png"/></imageobject>
+</mediaobject></entry>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="joinround.png"/></imageobject>
+</mediaobject></entry>
+</row>
+<row>
+<entry>a) MiterJoin</entry>
+<entry>c) BevelJoin</entry>
+<entry>b) RoundJoin</entry>
+</row>
+</tbody>
+</tgroup>
+</informaltable>
+
+<para>
+The cap style is a member of the enum
+<ulink url="kdeapi:qt/Qt#PenCapStyle-enum">Qt::PenCapStyle</ulink>and specifies how the end points of lines are drawn. It takes one of the values
+from the following table:
+</para>
+
+<informaltable frame="none">
+<tgroup cols="3">
+<tbody>
+<row>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="capflat.png"/></imageobject>
+</mediaobject></entry>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="capsquare.png"/></imageobject>
+</mediaobject></entry>
+<entry><mediaobject>
+ <imageobject><imagedata fileref="capround.png"/></imageobject>
+</mediaobject></entry>
+</row>
+<row>
+<entry>a) FlatCap</entry>
+<entry>b) SquareCap</entry>
+<entry>c) RoundCap</entry>
+</row>
+</tbody>
+</tgroup>
+</informaltable>
+
+</simplesect>
+
+
+<simplesect id="qpainter-fillattributes">
+<title>Setting fill attributes</title>
+
+<para>
+The fill style of polygons, circles or rectangles can be modified by setting
+a special brush with QPainter::setBrush(). This function takes a
+<ulink url="kdeapi:qt/QBrush">QBrush</ulink> object as argument.
+Brushes can be constructed in four different ways:
+</para>
+
+<itemizedlist>
+<listitem>
+<para>QBrush::QBrush() - This creates a brush that does not fill shapes.</para>
+</listitem>
+<listitem>
+<para>QBrush::QBrush(BrushStyle) - This creates a black brush with one of the default
+patterns shown below.</para>
+</listitem>
+<listitem>
+<para>QBrush::QBrush(const QColor &amp;, BrushStyle) - This creates a colored brush
+with one of the patterns shown below.</para>
+</listitem>
+<listitem>
+<para>QBrush::QBrush(const QColor &amp;, const QPixmap) - This creates a colored
+brush with the custom pattern you give as second parameter.</para>
+</listitem>
+</itemizedlist>
+
+<para>
+A default brush style is from the enum
+<ulink url="kdeapi:qt/Qt#BrushStyle-enum">Qt::BrushStyle</ulink>.
+Here is a picture of all predefined patterns:
+</para>
+
+<mediaobject>
+ <imageobject><imagedata fileref="brushstyles.png"/></imageobject>
+</mediaobject>
+
+<para>
+A further way to customize the brush behavior is to use the function
+QPainter::setBrushOrigin().
+</para>
+
+</simplesect>
+
+
+<simplesect id="qpainter-color">
+<title>Color</title>
+
+<para>
+Colors play a role both when stroking curves and when filling shapes. In Qt,
+colors are represented by the class
+<ulink url="kdeapi:qt/QColor">QColor</ulink>. Qt does not support
+advanced graphics features like ICC color profiles and color correction. Colors
+are usually constructed by specifying their red, green and blue components, as
+the RGB model is the way pixels are composed of on a monitor.
+</para>
+
+<para>
+It is also possible to use hue, saturation and value. This HSV representation is
+what you use in the Gtk color dialog, e.g. in GIMP. There, the hue corresponds
+to the angle on the color wheel, while the saturation corresponds to the
+distance from the center of the circle. The value can be chosen with a separate
+slider.
+</para>
+
+</simplesect>
+
+
+<simplesect id="qpainter-paintsettings">
+<title>Other settings</title>
+
+<para>
+Normally, when you paint on a paint device, the pixels you draw replace those
+that were there previously. This means, if you paint a certain region with
+a red color and paint the same region with a blue color afterwards, only
+the blue color will be visible. Qt's imaging model does not support
+transparency, i.e. a way to blend the painted foreground with the background.
+However, there is a simple way to combine background and foreground with
+boolean operators. The method QPainter::setRasterOp() sets the used operator,
+which comes from the enum
+<ulink url="kdeapi:qt/Qt#RasterOp-enum">RasterOp</ulink>.
+</para>
+
+<para>
+The default is CopyROP which ignores the background. Another popular choice is
+XorROP. If you paint a black line with this operator on a colored image, then
+the covered area will be inverted. This effect is for example used to create
+the rubberband selections in image manipulation programs known as
+"marching ants".
+</para>
+
+</simplesect>
+
+
+<simplesect id="qpainter-primitives">
+<title>Drawing graphics primitives</title>
+
+<para>
+In the following we list the elementary graphics elements supported by
+QPainter. Most of them exist in several overloaded versions which take a
+different number of arguments. For example, methods that deal with rectangles
+usually either take a
+<ulink url="kdeapi:qt/QRect">QRect</ulink> as argument or a set
+of four integers.
+</para>
+
+<itemizedlist>
+<listitem>
+<para>Drawing a single point - drawPoint().</para>
+</listitem>
+<listitem>
+<para>Drawing lines - drawLine(), drawLineSegments() and drawPolyLine().</para>
+</listitem>
+<listitem>
+<para>Drawing and filling rectangles - drawRect(), drawRoundRect(),
+fillRect() and eraseRect().</para>
+</listitem>
+<listitem>
+<para>Drawing and filling circles, ellipses and parts or them -
+drawEllipse(), drawArc(), drawPie and drawChord().</para>
+</listitem>
+<listitem>
+<para>Drawing and filling general polygons - drawPolygon().</para>
+</listitem>
+<listitem>
+<para>Drawing bezier curves - drawQuadBezier() [drawCubicBezier in Qt 3.0].</para>
+</listitem>
+</itemizedlist>
+
+</simplesect>
+
+
+<simplesect id="qpainter-pixmaps">
+<title>Drawing pixmaps and images</title>
+
+<para>
+Qt provides two very different classes to represent images.
+</para>
+
+<para>
+<ulink url="kdeapi:qt/QPixmap">QPixmap</ulink> directly corresponds
+to the pixmap objects in X11. Pixmaps are server-side objects and may - on a
+modern graphics card - even be stored directly in the card's memory. This makes
+it <emphasis>very</emphasis> efficient to transfer pixmaps to the screen. Pixmaps also act as
+an off-screen equivalent of widgets - the QPixmap class is a subclass of
+QPaintDevice, so you can draw on it with a QPainter. Elementary drawing
+operations are usually accelerated by modern graphics. Therefore, a common usage
+pattern is to use pixmaps for double buffering. This means, instead of painting
+directly on a widget, you paint on a temporary pixmap object and use the
+<ulink url="kdeapi:qt/QPaintDevice#bitBlt-1">bitBlt</ulink>
+function to transfer the pixmap to the widget. For complex repaints, this helps
+to avoid flicker.
+</para>
+
+<para>
+In contrast, <ulink url="kdeapi:qt/QImage">QImage</ulink> objects
+live on the client side. Their emphasis in on providing direct access to the
+pixels of the image. This makes them of use for image manipulation, and things
+like loading and saving to disk (QPixmap's load() method takes QImage as
+intermediate step). On the other hand, painting an image on a widget is a
+relatively expensive operation, as it implies a transfer to the X server,
+which can take some time, especially for large images and for remote servers.
+Depending on the color depth, the conversion from QImage to QPixmap may also
+require dithering.
+</para>
+
+</simplesect>
+
+
+<simplesect id="qpainter-drawingtext">
+<title>Drawing text</title>
+
+<para>
+Text can be drawn with one of the overloaded variants of the method
+QPainter::drawText(). These draw a QString either at a given point or in a given
+rectangle, using the font set by QPainter::setFont(). There is also a parameter
+which takes an ORed combination of some flags from the enums
+<ulink url="kdeapi:qt/Qt#AlignmentFlags-enum">Qt::AlignmentFlags</ulink>
+and
+<ulink url="kdeapi:qt/Qt#TextFlags-enum">Qt::TextFlags</ulink>
+</para>
+
+<para>
+Beginning with version 3.0, Qt takes care of the complete text layout even for
+languages written from right to left.
+</para>
+
+<para>
+A more advanced way to display marked up text is the
+<ulink url="kdeapi:qt/QSimpleRichText">QSimpleRichText</ulink>
+class. Objects of this class can be constructed with a piece of text using
+a subset of the HTML tags, which is quite rich and provides even tables.
+The text style can be customized by using a
+<ulink url="kdeapi/qt/QStyleSheet">QStyleSheet</ulink> (the
+documentation of the tags can also be found here). Once the rich text object has
+been constructed, it can be rendered on a widget or another paint device with
+the QSimpleRichText::draw() method.
+</para>
+
+</simplesect>
+
+</sect1>
+
+
+<sect1 id="graphics-qcanvas">
+<title>Structured graphics with QCanvas</title>
+
+<para>
+QPainter offers a powerful imaging model for painting on widgets and pixmaps.
+However, it can also be cumbersome to use. Each time your widget receives
+a paint event, it has to analyze the QPaintEvent::region() or
+QPaintEvent::rect() which has to be redrawn. Then it has to setup a
+QPainter and paint all objects which overlap with that region. For example,
+image a vector graphics program which allows to drag objects like polygons,
+circles and groups of them around. Each time those objects move a bit, the
+widget's mouse event handler triggers a paint event for the whole area covered
+by the objects in their old position and in their new position. Figuring
+out the necessary redraws and doing them in an efficient way can be difficult,
+and it may also conflict with the object-oriented structure of the program's
+source code.
+</para>
+
+<para>
+As an alternative, Qt contains the class
+<ulink url="kdeapi:qt/QCanvas">QCanvas</ulink> in which
+you put graphical objects like polygons, text, pixmaps. You may also provide
+additional items by subclassing
+<ulink url="kdeapi:qt/QCanvasItem">QCanvasItem</ulink> or
+one of its more specialized subclasses. A canvas can be shown on the screen by
+one or more widgets of the class
+<ulink url="kdeapi:qt/QCanvas">QCanvasView</ulink> which
+you have to subclass in order to handle user interactions. Qt takes care of
+all repaints of objects in the view, whether they are caused by the widget
+being exposed, new objects being created or modified or other things. By using
+double buffering, this can be done in an efficient and flicker-free way.
+</para>
+
+<para>
+Canvas items can overlap each other. In this case, the visible one depends on
+the z order which can be assigned by QCanvasItem::setZ(). Items can also be
+made visible or invisible. You can also provide a background to be drawn
+"behind" all items and a foreground. For associating mouse events with objects,
+in the canvas, there is the method QCanvas::collisions() which returns a list
+of items overlapping with a given point. Here we show a screenshot of a canvas
+view in action:
+</para>
+
+<mediaobject>
+<imageobject><imagedata fileref="canvas.png"/></imageobject>
+</mediaobject>
+
+<para>
+Here, the mesh is drawn in the background. Furthermore, there is a
+QCanvasText item and a violet QCanvasPolygon. The butterfly is a
+QCanvasPixmap. It has transparent areas, so you can see the underlying
+items through it.
+</para>
+
+<para>
+A tutorial on using QCanvas for writing sprite-based games can be
+found <ulink url="http://zez.org/article/articleview/2/1/">here</ulink>.
+</para>
+
+</sect1>
+
+
+<sect1 id="graphics-qglwidget">
+<title>3D graphics with OpenGL</title>
+
+<simplesect id="qglwidget-lowlevel">
+<title>Low-level interface</title>
+
+<para>
+The de facto standard for rendering 3D graphics today is
+<ulink url="http://www.opengl.org">OpenGL</ulink>. Implementations of this
+specification come with Microsoft Windows, Mac OS X and XFree86 and often
+support the hardware acceleration features offered by modern graphics cards.
+OpenGL itself only deals with rendering on a specified area of the framebuffer
+through a <emphasis>GL context</emphasis> and does not have any interactions
+with the toolkit of the environment
+</para>
+
+<para>
+Qt offers the widget <ulink url="kdeapi:qt/QGLWidget">QGLWidget</ulink>
+which encapsulates a window with an associated GL context. Basically, you use it
+by subclassing it and reimplementing some methods.
+</para>
+
+<itemizedlist>
+
+<listitem><para>
+Instead of reimplementing paintEvent() and using QPainter to draw the widget's
+contents, you override paintGL() and use GL commands to render a scene. QLWidget
+will take care of making its GL context the current one before paintGL() is
+called, and it will flush afterwards.
+</para></listitem>
+
+<listitem><para>
+The virtual method initializeGL() is called once before the first time resizeGL()
+or paintGL() are called. This can be used to construct display lists for objects,
+and make any initializations.
+</para></listitem>
+
+<listitem><para>
+Instead of reimplementing resizeEvent(), you override resizeGL(). This can
+be used to set the viewport appropriately.
+</para></listitem>
+
+<listitem><para>
+Instead of calling update() when the state of the scene has changed - for example
+when you animate it with a timer -, you should call updateGL(). This will trigger
+a repaint.
+</para></listitem>
+
+</itemizedlist>
+
+<para>
+In general, QGLWidget behaves just like any other widget, i.e. for example
+you can process mouse events as usual, resize the widget and combine it with
+others in a layout.
+</para>
+
+<mediaobject>
+<imageobject><imagedata fileref="opengl.png"/></imageobject>
+</mediaobject>
+
+<para>
+Qt contains some examples of QGLWidget usage in its <literal>demo</literal>
+example. A collection of tutorials can be found
+<ulink url="http://www.libsdl.org/opengl/intro.html">here</ulink>,
+and more information and a reference of OpenGL is available on the
+<ulink url="http://www.opengl.org">OpenGL homepage</ulink>.
+</para>
+
+</simplesect>
+
+
+<simplesect id="qglwidget-highlevel">
+<title>High-level interfaces</title>
+
+<para>
+OpenGL is a relatively low-level interface for drawing 3D graphics. In the same
+way QCanvas gives the programmer a higher-level interface which details with
+objects and their properties, there are also high-level interfaces for 3D graphics.
+One of the most popular is Open Inventor. Originally a technology developed by SGI,
+there is today also the open source implementation
+<ulink url="http://www.coin3d.org">Coin</ulink>, complemented by a toolkit binding to Qt
+called SoQt.
+</para>
+
+<para>
+The basic concept of Open Inventor is that of a <emphasis>scene</emphasis>.
+A scene can be loaded from disk and saved in a special format closely related
+to <ulink url="http://www.vrml.org">VRML</ulink>. A scene consists of a
+collection of objects called <emphasis>nodes</emphasis>. Inventor already
+provides a rich collection of reusable nodes, such as cubes, cylinders and
+meshes, furthermore light sources, materials, cameras etc. Nodes are
+represented by C++ classes and can be combined and subclassed.
+</para>
+
+<para>
+An introduction to Inventor can be found
+<ulink url="http://www.motifzone.com/tmd/articles/OpenInventor/OpenInventor.html">here</ulink>
+(in general, you can substitute all mentions of SoXt by SoQt in this article).
+</para>
+
+</simplesect>
+
+</sect1>
+
+</chapter>
+
+
+
+<chapter id="userinterface">
+<title>User interface</title>
+
+<sect1 id="userinterface-actionpattern">
+<title>The action pattern</title>
+
+<para></para>
+
+</sect1>
+
+
+<sect1 id="userinterface-xmlgui">
+<title>Defining menus and toolbars in XML</title>
+
+<simplesect id="xmlgui-intro">
+<title>Introduction</title>
+
+<para>
+While the <link linkend="userinterface-actionpattern">action pattern</link>
+allows to encapsulate actions triggered by the user in an object which can be
+"plugged" somewhere in the menu bars or toolbars, it does not by itself solve
+the problem of constructing the menus themselves. In particular, you have to
+build all popup menus in C++ code and explicitly insert the actions in a
+certain order, under consideration of the style guide for standard actions.
+This makes it pretty difficult to allow the user to customize the menus or
+change shortcuts to fit his needs, without changing the source code.
+</para>
+
+<para>
+This problem is solved by a set of classes called <literal>XMLGUI</literal>.
+Basically, this separates actions (coded in C++) from their appearance in menu
+bars and tool bars (coded in XML). Without modifying any source code, menus
+can be simply customized by adjusting an XML file. Furthermore, it helps
+to make sure that standard actions (such as
+<menuchoice><guimenu>File</guimenu><guimenuitem>Open</guimenuitem></menuchoice>
+or <menuchoice><guimenu>Help</guimenu><guimenuitem>About</guimenuitem></menuchoice>)
+appear in the locations suggested by the style guide. XMLGUI is especially
+important for modular programs, where the items appearing in the menu bar may
+come from many different plugins or parts.
+</para>
+
+<para>
+KDE's class for toplevel windows,
+<ulink url="kdeapi:kdeui/KMainWindow.html">KMainWindow</ulink>,
+inherits
+<ulink url="kdeapi:kdeui/KXMLGUIClient.html">KXMLGUIClient</ulink>
+and therefore supports XMLGUI out of the box. All actions created within it must
+have the client's <literal>actionCollection()</literal> as parent. A call to
+<literal>createGUI()</literal> will then build the whole set of menu and tool
+bars defined the applications XML file (conventionally with the suffix
+<literal>ui.rc</literal>).
+</para>
+
+</simplesect>
+
+
+<simplesect id="xmlgui-kviewexample">
+<title>An example: Menu in KView</title>
+
+<para>
+In the following, we take KDE's image view <application>KView</application> as
+example. It has a <literal>ui.rc</literal> file named
+<filename>kviewui.rc</filename> which is installed with the
+<filename>Makefile.am</filename> snippet
+</para>
+
+<programlisting>
+rcdir = $(kde_datadir)/kview
+rc_DATA = kviewui.rc
+</programlisting>
+
+<para>
+Here is an excerpt from the <filename>kviewui.rc</filename> file. For
+simplicity, we show only the definition of the <guimenu>View</guimenu> menu.
+</para>
+
+<programlisting>
+&lt;!DOCTYPE kpartgui&gt;
+&lt;kpartgui name="kview"&gt;
+ &lt;MenuBar&gt;
+ &lt;Menu name="view" &gt;
+ &lt;Action name="zoom50" /&gt;
+ &lt;Action name="zoom100" /&gt;
+ &lt;Action name="zoom200" /&gt;
+ &lt;Action name="zoomMaxpect" /&gt;
+ &lt;Separator/&gt;
+ &lt;Action name="fullscreen" /&gt;
+ &lt;/Menu&gt;
+ &lt;/MenuBar&gt;
+&lt;/kpartgui&gt;
+</programlisting>
+
+<para>
+The corresponding part of the setup in C++ is:
+</para>
+
+<programlisting>
+ KStdAction::zoomIn ( this, SLOT(slotZoomIn()), actionCollection() );
+ KStdAction::zoomOut ( this, SLOT(slotZoomOut()), actionCollection() );
+ KStdAction::zoom ( this, SLOT(slotZoom()), actionCollection() );
+ new KAction ( i18n("&amp;Half size"), ALT+Key_0,
+ this, SLOT(slotHalfSize()),
+ actionCollection(), "zoom50" );
+ new KAction ( i18n("&amp;Normal size"), ALT+Key_1,
+ this, SLOT(slotDoubleSize()),
+ actionCollection(), "zoom100" );
+ new KAction ( i18n("&amp;Double size"), ALT+Key_2,
+ this, SLOT(slotDoubleSize()),
+ actionCollection(), "zoom200" );
+ new KAction ( i18n("&amp;Fill Screen"), ALT+Key_3,
+ this, SLOT(slotFillScreen()),
+ actionCollection(), "zoomMaxpect" );
+ new KAction ( i18n("Fullscreen &amp;Mode"), CTRL+SHIFT+Key_F,
+ this, SLOT(slotFullScreen()),
+ actionCollection(), "fullscreen" );
+</programlisting>
+
+<para>
+The <guimenu>View</guimenu> menu resulting from this GUI definition looks like
+in this screenshot:
+</para>
+
+<mediaobject>
+<imageobject><imagedata fileref="kview-menu.png"/></imageobject>
+</mediaobject>
+
+<para>
+The XML file begins with a document type declaration. The DTD for kpartgui can
+be found in the kdelibs sources in <filename>kdeui/kpartgui.dtd</filename>. The
+outermost element of the file contains the instance name of the application as
+attribute. It can also contain a version number in the form "version=2". This
+is useful when you release new versions of an application with a changed menu
+structure, e.g. with more features. If you bump up the version number of the
+<literal>ui.rc</literal> file, KDE makes sure that any customized version of
+the file is discarded and the new file is used instead.
+</para>
+
+<para>
+The next line, <literal>&lt;MenuBar&gt;</literal>, contains a declaration of a
+menu bar. You can also insert any number of <literal>&lt;ToolBar&gt;</literal>
+declarations in order to create some tool bars. The menu contains a submenu
+with the name "view". This name is already predefined, and thus you see a
+translated version of the word "View" in the screenshot. If you declare your
+own submenus, you have to add the title explicitly. For example,
+<application>KView</application> has a submenu with the title "Image" which is
+declared as follows:
+</para>
+
+<programlisting>
+&lt;Menu name="image" &gt;
+ &lt;text&gt;&amp;amp;Image&lt;/text&gt;
+ ...
+&lt;/Menu&gt;
+</programlisting>
+
+<para>
+In KDE's automake framework, such titles are automatically extracted and put
+into the application's <ulink url="kde-i18n-howto.html"><literal>.po</literal></ulink>
+file , so it is considered by translators. Note that you have to write the
+accelerator marker "&amp;" in the form XML compliant form "&amp;amp;".
+</para>
+
+<para>
+Let us come back to the example. <application>KView</application>'s
+<guimenu>View</guimenu> menu contains a couple of custom actions:
+<literal>zoom50</literal>, <literal>zoom100</literal>,
+<literal>zoom200</literal>, <literal>zoomMaxpect</literal> and
+<literal>fullscreen</literal>, declared with a
+<literal>&lt;Action&gt;</literal> element. The separator in the
+screenshots corresponds to the <literal>&lt;Separator&gt;</literal> element.
+</para>
+
+<para>
+You will note that some menu items do not not have a corresponding element in
+the XML file. These are <emphasis>standard actions</emphasis>. Standard
+actions are created by the class
+<ulink url="kdeapi:kdeui/KStdAction.html">KStdAction</ulink>.
+When you create such actions in your application (such as in the C++ example
+above), they will automatically be inserted in a prescribed position, and
+possibly with an icon and a shortcut key. You can look up these locations in
+the file <filename>kdeui/ui_standards.rc</filename> in the kdelibs sources.
+</para>
+
+</simplesect>
+
+
+<simplesect id="xmlgui-konqexample">
+<title>An example: Toolbars in Konqueror</title>
+
+<para>
+For the discussion of toolbars, we switch to
+<application>Konqueror</application>'s GUI definition. This excerpt defines
+the location bar, which contains the input field for URLs.
+</para>
+
+<programlisting>
+&lt;ToolBar name="locationToolBar" fullWidth="true" newline="true" &gt;
+ &lt;text&gt;Location Toolbar&lt;/text&gt;
+ &lt;Action name="clear_location" /&gt;
+ &lt;Action name="location_label" /&gt;
+ &lt;Action name="toolbar_url_combo" /&gt;
+ &lt;Action name="go_url" /&gt;
+&lt;/ToolBar&gt;
+</programlisting>
+
+<para>
+The first thing we notice is that there are a lot more attributes than for
+menu bars. These include:
+</para>
+
+<itemizedlist>
+
+<listitem><para>
+<literal>fullWidth</literal>: Tells XMLGUI that the toolbar has the same width as the
+ toplevel window. Af this is "false", the toolbar only takes as much space as
+ necessary, and further toolbars are put in the same row.
+</para></listitem>
+
+<listitem><para>
+<literal>newline</literal>: This is related to the option above. If newline is "true",
+the toolbar starts a new row. Otherwise it may be put in the row together
+with the previous toolbar.
+</para></listitem>
+
+<listitem><para>
+<literal>noEdit</literal>: Normally toolbars can be customized by the user,
+e.g. in <menuchoice><guimenu>Settings</guimenu><guimenuitem>Configure
+Toolbars</guimenuitem></menuchoice> in
+<application>Konqueror</application>. Setting this option to "true" marks this
+toolbar as not editable. This is important for toolbars which are filled with
+items at runtime, e.g. <application>Konqueror</application>'s bookmark toolbar.
+</para></listitem>
+
+<listitem><para>
+<literal>iconText</literal>: Tells XMLGUI to show the text of the action next to the
+icon. Normally, the text is only shown as a tooltip when the mouse cursor
+remains over the icon for a while. Possible values for this attribute are
+"icononly" (shows only the icon), "textonly" (shows only the text),
+"icontextright" (shows the text on the right side of the icon) and
+"icontextbottom" (shows the text beneath the icon).
+</para></listitem>
+
+
+<listitem><para>
+<literal>hidden</literal>: If this is "true", the toolbar is not visible initially
+and must be activated by some menu item.
+</para></listitem>
+
+
+<listitem><para>
+<literal>position</literal>: The default for this attribute is "top", meaning that the
+toolbar is positioned under the menu bar. For programs with many tools,
+such as graphics programs, it may be interesting to replace this with
+"left", "right" or "bottom".
+</para></listitem>
+
+</itemizedlist>
+
+</simplesect>
+
+
+<simplesect id="xmlgui-dynamical">
+<title>Dynamical menus</title>
+
+<para>
+Obviously, an XML can only contain a static description of a user interface.
+Often, there are menus which change at runtime. For example,
+<application>Konqueror</application>'s <guimenu>Location</guimenu> menu
+contains a set of items <guimenuitem>Open with Foo</guimenuitem> with the
+applications able to load a file with a given MIME type. Each time the
+document shown changes, the list of menu items is updated. XMLGUI is prepared
+to handle such cases with the notion of <emphasis>action lists</emphasis>.
+An action list is declared as one item in the XML file, but consists of
+several actions which are plugged into the menu at runtime. The above example
+is implemented with the following declaration in
+<application>Konqueror</application>'s XML file:
+</para>
+
+<programlisting>
+&lt;Menu name="file"&gt;
+ &lt;text&gt;&amp;amp;Location&lt;/text&gt;
+ ...
+ &lt;ActionList name="openwith"&gt;
+ ...
+&lt;/Menu&gt;
+</programlisting>
+
+<para>
+The function <function>KXMLGUIClient::plugActionList()</function> is then used
+to add actions to be displayed, whereas the function
+<function>KXMLGuiClient::unplugActionList()</function> removes all
+plugged actions. The routine responsible for updating looks as follows:
+</para>
+
+<programlisting>
+void MainWindow::updateOpenWithActions()
+{
+ unplugActionList("openwith");
+ openWithActions.clear();
+ for ( /* iterate over the relevant services */ ) {
+ KAction *action = new KAction( ...);
+ openWithActions.append(action);
+ }
+ plugActionList("openwith", openWithActions);
+}
+</programlisting>
+
+<para>
+Note that in contrast to the static actions, the ones created here are
+<emphasis>not</emphasis> constructed with the action collection as parent, and
+you are responsible for deleting them for yourself. The simplest way to achievethis
+is by using <literal>openWithActions.setAutoDelete(true)</literal> in the above
+example.
+</para>
+
+</simplesect>
+
+
+<simplesect id="xmlgui-contextmenus">
+<title>Context menus</title>
+
+<para>
+The examples above only contained cases where a main window's menubar and
+toolbars were created. In the cases, the processes of constructing these
+containers is completely hidden from you behind the
+<function>createGUI()</function> call (except if you have custom containers).
+However, there are cases, where you want to construct other containers and
+populate them with GUI definitions from the XML file. One such example are
+context menus. In order to get a pointer to a context menu, you have to
+ask the client's factory for it:
+</para>
+
+<programlisting>
+void MainWindow::popupRequested()
+{
+ QWidget *w = factory()->container("context_popup", this);
+ QPopupMenu *popup = static_cast&lt;QPopupMenu *&gt;(w);
+ popup->exec(QCursor::pos());
+}
+</programlisting>
+
+<para>
+The method <function>KXMLGUIFactory::container()</function> used above looks
+whether it finds a container in the XML file with the given name. Thus, a
+possible definition could look as follows:
+</para>
+
+<programlisting>
+...
+&lt;Menu name="context_popup"&gt;
+ &lt;Action name="file_add"/&gt;
+ &lt;Action name="file_remove"/&gt;
+&lt;/Menu&gt;
+...
+</programlisting>
+
+</simplesect>
+
+</sect1>
+
+
+<sect1 id="help">
+<title>Providing online help</title>
+
+<para>
+Making a program easy and intuitive to use involves a wide range of
+facilities which are usually called online help. Online help has several,
+partially conflicting goals: on the one, it should give the user answers
+to the question "How can I do a certain task?", on the other hand it
+should help the user exploring the application and finding features he
+doesn't yet know about. It is important to recognize that this can only
+be achieved by offering several levels of help:
+</para>
+
+<itemizedlist>
+
+<listitem><para>
+Tooltips are tiny labels that pop up over user interface elements when
+the mouse remains there longer. They are especially important for tool-
+bars, where icons are not always sufficient to explain the purpose of
+a button.
+</para></listitem>
+
+<listitem><para>
+"What's this?" help is usually a longer and richer explanation of a widget
+or a menu item. It is also more clunky to use: In dialogs, it can be invoked
+in two ways: either by pressing
+<keycombo><keycap>Shift</keycap><keycap>F1</keycap></keycombo> or by clicking
+on the question mark in the title bar (where the support of the latter depends
+on the window manager). The mouse pointer then turns into an arrow with a
+question mark, and the help window appears when a user interfact element has
+been clicked. "What's this?" help for menu items is usually activated by a
+button in the toolbar which contains an arrow and a question mark.
+</para></listitem>
+
+<listitem><para>
+The problem with this approach is that the user can't see whether a widget
+provides help or not. When the user activates the question mark button and
+doesn't get any help window when clicking on a user interface element, he
+will get frustrated very quickly.
+</para>
+
+<para>
+The advantage of "What's this?" help windows as provided by Qt and KDE is that
+they can contain <ulink url="kdeapi:qt/QStyleSheet">rich text</ulink>,
+i.e. the may contain different fonts, bold and italic text and even images and tables.
+</para>
+
+<para>
+An example of "What's this?" help:
+</para>
+
+<mediaobject>
+<imageobject><imagedata fileref="whatsthis.png"/></imageobject>
+</mediaobject>
+
+</listitem>
+
+<listitem><para>
+Finally, every program should have a manual. A manual is normally viewed in
+<application>KHelpCenter</application> by activating the
+<guimenu>Help</guimenu> menu. That means, a complete additional application
+pops up and diverts the user from his work. Consequently, consulting the
+manual should only be necessary if other facilities like tooltips and what's
+this help are not sufficient. Of course, a manual has the advantage that it
+does not explain single, isolated aspects of the user interface. Instead, it
+can explain aspects of the application in a greater context. Manuals for KDE
+are written using the <ulink url="http://i18n.kde.org">DocBook</ulink> markup
+language.
+</para></listitem>
+
+</itemizedlist>
+
+<para>
+From the programmer's point of view, Qt provides an easy to use API for online
+help. To assign a tooltip to widget, use the
+<ulink url="kdeapi:qt/QToolTip">QToolTip</ulink> class.
+</para>
+
+<programlisting>
+QToolTip::add(w, i18n("This widget does something."))
+</programlisting>
+
+<para>
+If the menu bars and tool bars are created using the <ulink url="actionpattern.html">
+action pattern</ulink>, the string used as tooltip is derived from the first argument
+of the <ulink url="kdeapi:kdeui/KAction.html">KAction</ulink> constructor:
+</para>
+
+<programlisting>
+action = new KAction(i18n("&amp;Delete"), "editdelete",
+ SHIFT+Key_Delete, actionCollection(), "del")
+</programlisting>
+
+<para>
+Here it is also possible to assign a text which is shown in the status bar when the
+respective menu item is highlighted:
+</para>
+
+<programlisting>
+action->setStatusText(i18n("Deletes the marked file"))
+</programlisting>
+
+<para>
+The API for "What's this?' help is very similar. In dialogs, use the following
+code:
+</para>
+
+<programlisting>
+QWhatsThis::add(w, i18n("&lt;qt&gt;This demonstrates &lt;b&gt;Qt&lt;/b&gt;'s"
+ " rich text engine.&lt;ul&gt;"
+ "&lt;li&gt;Foo&lt;/li&gt;"
+ "&lt;li&gt;Bar&lt;/li&gt;"
+ "&lt;/ul&gt;&lt;/qt&gt;"))
+</programlisting>
+
+<para>
+For menu items, use
+</para>
+
+<programlisting>
+action->setWhatsThis(i18n("Deletes the marked file"))
+</programlisting>
+
+<para>
+The invocation of <application>KHelpCenter</application> is encapsulated in the
+<ulink url="kdeapi:kdecore/KApplication">KApplication</ulink>
+class. In order to show the manual of your application, just use
+</para>
+
+<programlisting>
+kapp->invokeHelp()
+</programlisting>
+
+<para>
+This displays the first page with the table of contents. When you want to
+display only a certain section of the manual, you can give an additional
+argument to <function>invokeHelp()</function> determining the anchor which
+the browser jumps to.
+</para>
+
+</sect1>
+
+</chapter>
+
+
+
+<chapter id="components">
+<title>Components and services</title>
+
+<sect1 id="components-services">
+<title>KDE services</title>
+
+<simplesect id="services-whatarekdeservices">
+<title>What are KDE services?</title>
+
+<para>
+The notion of a <emphasis>service</emphasis> is a central concept in KDE's
+modular architecture. There is no strict technical implementation connected
+with this term - services can be plugins in the form of shared libraries,
+or they can be programs controlled via <ulink url="dcop.html">DCOP</ulink>.
+By claiming to be of a certain <emphasis>service type</emphasis>, a service
+promises to implement certain APIs or features. In C++ terms, one can think
+of a service type as an abstract class, and a service as an implementation
+of that interface.
+</para>
+
+<para>
+The advantage of this separation is clear: An application utilizing a service
+type does not have to know about possible implementations of it. It just uses
+the APIs associated with the service type. In this way, the used service can be
+changed without affecting the application. Also, the user can configure which
+services he prefers for certain features.
+</para>
+
+<para>
+Some examples:
+</para>
+
+<itemizedlist>
+
+<listitem><para>
+The HTML rendering engine used in <application>Konqueror</application> is an
+embedable component that implements the service types
+<literal>KParts/ReadOnlyPart</literal> and <literal>Browser/View</literal>.
+</para></listitem>
+<listitem><para>
+In <application>KDevelop</application> HEAD, most functionality is packaged in
+plugins with the service type <literal>KDevelop/Part</literal>. At startup,
+all services with this type are loaded, such that you can extend the IDE in a
+very flexible way.
+</para></listitem>
+<listitem><para>
+In the icon view, <application>Konqueror</application> displays - if enabled -
+thumbnail pictures of images, HTML pages, PDF and text files. This ability can
+be extended. If you want it to display preview pictures of your own data files
+with some MIME type, you can implement a service with service type
+<classname>ThumbCreator</classname>.
+</para></listitem>
+
+</itemizedlist>
+
+<para>
+Obviously, a service is not only characterized by the service types it
+implements, but also by some <emphasis>properties</emphasis>. For example, a
+ThumbCreator does not only claim to implement the C++ class with the type
+<classname>ThumbCreator</classname>, it also has a list of MIME types it is
+responsible for. Similarly, KDevelop parts have the programming language they
+support as a property. When an application requests a service type, it can
+also list constraints on the properties of the service. In the above example,
+when KDevelop loads the plugins for a Java project, it asks only for the
+plugins which have Java as the programming language property. For this
+purpose, KDE contains a full-blown CORBA-like <emphasis>trader</emphasis> with
+a complex query language.
+</para>
+
+</simplesect>
+
+
+<simplesect id="services-definingservicetypes">
+<title>Defining service types</title>
+
+<para>
+New service types are added by installing a description of them into the
+directory <filename>KDEDIR/share/servicetypes</filename>. In an automake
+framework, this can be done with this <filename>Makefile.am</filename>
+snippet:
+</para>
+
+<programlisting>
+kde_servicetypesdir_DATA = kdeveloppart.desktop
+EXTRA_DIST = $(kde_servicetypesdir_DATA)
+</programlisting>
+
+<para>
+The definition <filename>kdeveloppart.desktop</filename> of a
+<application>KDevelop</application> part looks as follows:
+</para>
+
+<programlisting>
+[Desktop Entry]
+Type=ServiceType
+X-KDE-ServiceType=KDevelop/Part
+Name=KDevelop Part
+
+[PropertyDef::X-KDevelop-Scope]
+Type=QString
+
+[PropertyDef::X-KDevelop-ProgrammingLanguages]
+Type=QStringList
+
+[PropertyDef::X-KDevelop-Args]
+Type=QString
+</programlisting>
+
+<para>
+In addition to the usual entries, this example demonstrates how you declare
+that a service has some properties. Each property definition corresponds
+to a group <literal>[PropertyDef::name]</literal> in the configuration file. In
+this group, the <literal>Type</literal> entry declares the type of the property.
+Possible types are everything that can be stored in a
+<ulink url="kdeapi:qt/QVariant">QVariant</ulink>.
+</para>
+
+</simplesect>
+
+
+<simplesect id="services-defininglibraryservices">
+<title>Defining shared library services</title>
+
+<para>
+Service definitions are stored in the directory
+<filename>KDEDIR/share/services</filename>:
+</para>
+
+<programlisting>
+kde_servicesdir_DATA = kdevdoxygen.desktop
+EXTRA_DIST = $(kde_servicesdir_DATA)
+</programlisting>
+
+<para>
+The content of the following example file
+<filename>kdevdoxygen.desktop</filename> defines the
+<literal>KDevDoxygen</literal> plugin with the service type
+<literal>KDevelop/Part</literal>:
+</para>
+
+<programlisting>
+[Desktop Entry]
+Type=Service
+Comment=Doxygen
+Name=KDevDoxygen
+ServiceTypes=KDevelop/Part
+X-KDE-Library=libkdevdoxygen
+X-KDevelop-ProgrammingLanguages=C,C++,Java
+X-KDevelop-Scope=Project
+</programlisting>
+
+<para>
+In addition to the usual declarations, an important entry is
+<literal>X-KDE-Library</literal>. This contains the name of the libtool
+library (without the <literal>.la</literal> extension). It also fixes
+(with the prefix <literal>init_</literal> prepended) the name of the exported
+symbol in the library which returns an object factory. For the above example,
+the library must contain the following function:
+</para>
+
+<programlisting>
+extern "C" {
+ void *init_libkdevdoxygen()
+ {
+ return new DoxygenFactory;
+ }
+};
+</programlisting>
+
+<para>
+The type of the factory class <classname>DoxygenFactory</classname> depends on
+the specific service type the service implements. In our example of a KDevelop
+plugin, the factory must be a <classname>KDevFactory</classname> (which
+inherits <classname>KLibFactory</classname>). More common examples are
+<ulink url="kdeapi:kparts/KParts::Factory">KParts::Factory</ulink>
+which is supposed to produce
+<ulink url="kdeapi:kparts/KParts::ReadOnlyPart">KParts::ReadOnlyPart</ulink>
+objects or in most cases the generic
+<ulink url="kdeapi:kdecore/KLibFactory">KLibFactory</ulink>.
+</para>
+
+</simplesect>
+
+
+<simplesect id="services-usinglibraryservices">
+<title>Using shared library services</title>
+
+<para>
+In order to use a shared library service in an application, you need to obtain a
+<ulink url="kdeapi:kio/KService.html">KService</ulink> object
+representing it. This is discussed in the
+<ulink url="mime.html">section about MIME types</ulink> (and in a section about the
+trader to be written :-)
+</para>
+
+<para>
+With the <classname>KService</classname> object at hand, you can very simply
+load the library and get a pointer to its factory object:
+</para>
+
+<programlisting>
+KService *service = ...
+QString libName = QFile::encodeName(service->library());
+KLibFactory *factory = KLibLoader::self()->factory(libName);
+if (!factory) {
+ QString name = service->name();
+ QString errorMessage = KLibLoader::self()->lastErrorMessage();
+ KMessageBox::error(0, i18n("There was an error loading service %1.\n"
+ "The diagnostics from libtool is:\n%2")
+ .arg(name).arg(errorMessage);
+}
+</programlisting>
+
+<para>
+From this point, the further proceeding depends again on the service type. For
+generic plugins, you create objects with the method
+<ulink url="kdeapi:kdecore/KLibFactory.html#ref3">KLibFactory::create()</ulink>.
+For KParts, you must cast the factory pointer to the more specific KParts::Factory and use
+its create() method:
+</para>
+
+<programlisting>
+if (factory->inherits("KParts::Factory")) {
+ KParts::Factory *partFactory = static_cast&lt;KParts::Factory*&gt;(factory);
+ QObject *obj = partFactory->createPart(parentWidget, widgetName,
+ parent, name, "KParts::ReadOnlyPart");
+ ...
+} else {
+ cout &lt;&lt; "Service does not implement the right factory" &lt;&lt; endl;
+}
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="services-definingdcopservices">
+<title>Defining DCOP services</title>
+
+<para>
+A DCOP service is usually implemented as a program that is started up when it is
+needed. It then goes into a loop and listens for DCOP connections. The program
+may be an interactive one, but it may also run completely or for a part of its
+lifetime as a daemon in the background without the user noticing it. An example
+for such a daemon is <literal>kio_uiserver</literal>, which implements user interaction
+such as progress dialog for the KIO library. The advantage of such a centralized
+daemon in this context is that e.g. the download progress for several different
+files can be shown in one window, even if those downloads were initiated from
+different applications.
+</para>
+
+<para>
+A DCOP service is defined differently from a shared library service. Of course,
+it doesn't specify a library, but instead an executable. Also, DCOP services
+do not specify a ServiceType line, because usually they are started by their
+name. As additional properties, it contains two lines:
+</para>
+
+<para>
+<literal>X-DCOP-ServiceType</literal> specifies the way the service is
+started. The value <literal>Unique</literal> says that the service must not be
+started more than once. This means, if you try to start this service (e.g. via
+<ulink url="kdeapi:kdecore/KApplication.html#startServiceByName">
+KApplication::startServiceByName()</ulink>, KDE looks whether it is already
+registered with DCOP and uses the running service. If it is not registered yet,
+KDE will start it up and wait until is registered. Thus, you can immediately
+send DCOP calls to the service. In such a case, the service should be implemented
+as a
+<ulink url="kdeapi:kdecore/KUniqueApplication.html">KUniqueApplication</ulink>.
+</para>
+
+<para>
+The value <literal>Multi</literal> for <literal>X-DCOP-ServiceType</literal> says that multiple
+instances of the service can coexist, so every attempt to start the service
+will create another process. As a last possibility the value <literal>None</literal>
+can be used. In this case, a start of the service will not wait until it
+is registered with DCOP.
+</para>
+
+<para>
+<literal>X-KDE-StartupNotify</literal> should normally be set to false. Otherwise, when
+the program is started, the task bar will show a startup notification, or, depending
+on the user's settings, the cursor will be changed.
+</para>
+
+<para>
+Here is the definition of <literal>kio_uiserver</literal>:
+</para>
+
+<programlisting>
+[Desktop Entry]
+Type=Service
+Name=kio_uiserver
+Exec=kio_uiserver
+X-DCOP-ServiceType=Unique
+X-KDE-StartupNotify=false
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="services-usingdcopservices">
+<title>Using DCOP services</title>
+
+<para>
+A DCOP service is started with one of several methods in the KApplication
+class:
+</para>
+
+<programlisting>
+DCOPClient *client = kapp->dcopClient();
+client->attach();
+if (!client->isApplicationRegistered("kio_uiserver")) {
+ QString error;
+ if (KApplication::startServiceByName("kio_uiserver", QStringList(), &amp;error))
+ cout &lt;&lt; "Starting kioserver failed with message " &lt;&lt; error &lt;&lt; endl;
+}
+...
+QByteArray data, replyData;
+QCString replyType;
+QDataStream arg(data, IO_WriteOnly);
+arg &lt;&lt; true;
+if (!client->call("kio_uiserver", "UIServer", "setListMode(bool)",
+ data, replyType, replyData))
+ cout &lt;&lt; "Call to kio_uiserver failed" &lt;&lt; endl;
+...
+</programlisting>
+
+<para>
+Note that the example of a DCOP call given here uses explicit marshalling
+of arguments. Often you will want to use a stub generated by dcopidl2cpp
+instead, because it is much simpler and less error prone.
+</para>
+
+<para>
+In the example given here, the service was started "by name", i.e. the
+first argument to <function>KApplication::startServiceByName()</function> is
+the name is appearing in the <literal>Name</literal> line of the desktop
+file. An alternative is to use
+<function>KApplication::startServiceByDesktopName()</function>, which takes
+the file name of its desktop file as argument, i.e. in this case
+<literal>"kio_uiserver.desktop"</literal>.
+</para>
+
+<para>
+All these calls take a list of URLs as a second argument, which is given
+to the service on the command line. The third argument is a pointer to a
+<classname>QString</classname>. If starting the service fails, this argument
+is set to a translated error message.
+</para>
+
+</simplesect>
+
+</sect1>
+
+
+<sect1 id="components-mime">
+<title>MIME types</title>
+
+<simplesect id="mime-whataremimetypes">
+<title>What are MIME types?</title>
+
+<para>
+MIME types are used to describe the content type of files or data
+chunks. Originally they were introduced in order to allow sending around image
+or sound files etc. by e-mail (MIME stands for "Multipurpose Internet Mail
+Extensions"). Later this system was also used by web browsers to determine how
+to present data sent by a web server to the user. For example, an HTML page
+has a MIME type "text/html", a postscript file "application/postscript". In
+KDE, this concept is used at a variety of places:
+</para>
+
+<itemizedlist>
+
+<listitem><para>
+In <application>Konqueror</application>'s icon view, files are represented by
+icons. Each MIME type has a certain associated icon shown here.
+</para></listitem>
+
+<listitem><para>
+When you click onto a file icon or a file name in
+<application>Konqueror</application>, either the file is shown in an embedded
+view, or an application associated with the file type is opened.
+</para></listitem>
+
+<listitem><para>
+When you drag and drop some data from one application to another (or
+within the same application), the drop target may choose to accept only
+certain data types. Furthermore, it will handle image data different
+from textual data.
+</para></listitem>
+
+<listitem><para>
+Clipboard data has a MIME type. Traditionally, X programs only handle
+pixmaps or texts, but with Qt, there are no restrictions on the data type.
+</para></listitem>
+
+</itemizedlist>
+
+<para>
+From the above examples, it is clear that MIME handling is a complex issue.
+First, it is necessary to establish a mapping from file names to MIME types.
+KDE goes one step further in allowing even file contents to be mapped to
+MIME types, for cases in which the file name is not available. Second, it
+is necessary to map MIME types to applications or libraries which can view
+or edit a file with a certain type, or create a thumbnail picture for it.
+</para>
+
+<para>
+There is a variety of APIs to figure out the MIME type of data or files. In
+general, there is a certain speed/reliability trade-off you have to make. You
+can find out the type of a file by examining only its file name (i.e. in most
+cases the file name extension). For example, a file
+<filename>foo.jpg</filename> is normally "image/jpeg". In cases where the
+extension is stripped off this is not safe, and you actually have to look at
+the contents of the file. This is of course slower, in particular for files
+that have to be downloaded via HTTP first. The content-based method is based
+on the file <filename>KDEDIR/share/mimelnk/magic</filename> and therefore
+difficult to extend. But in general, MIME type information can easily be made
+available to the system by installing a <literal>.desktop</literal> file, and
+it is efficiently and conveniently available through the KDE libraries.
+</para>
+
+</simplesect>
+
+
+<simplesect id="mime-definingmimetypes">
+<title>Defining MIME types</title>
+
+<para>
+Let us define a type <literal>"application/x-foo"</literal> for our new
+<application>foobar</application> program. To this end, you have to write a
+file <filename>foo.desktop</filename> and install it into
+<filename>KDEDIR/share/mimelnk/application</filename>. (This is the usual
+location, which may differ between distributions). This can be done by adding
+this to the <filename>Makefile.am</filename>:
+</para>
+
+<programlisting>
+mimedir = $(kde_mimedir)/application
+mime_DATA = foo.desktop
+EXTRA_DIST = $(mime_DATA)
+</programlisting>
+
+<para>
+The file <filename>foo.desktop</filename> should look as follows:
+</para>
+
+<programlisting>
+[Desktop Entry]
+Type=MimeType
+MimeType=application/x-foo
+Icon=fooicon
+Patterns=*.foo;
+DefaultApp=foobar
+Comment=Foo Data File
+Comment[de]=Foo Datei
+</programlisting>
+
+<para>
+The <literal>"Comment"</literal> entry is supposed to be translated. Since the
+<filename>.desktop</filename> file specifies an icon, you should also install
+an icon <filename>fooicon.png</filename>, which represents the file e.g. in
+<application>Konqueror</application>.
+</para>
+
+<para>
+In the KDE libraries, such a type definition is mapped to an instance of the
+class <ulink url="kdeapi:kio/KMimeType.html">KMimeType</ulink>.
+Use this like in the following example:
+</para>
+
+<programlisting>
+KMimeType::Ptr type = KMimeType::mimeType("application/x-foo");
+cout &lt;&lt; "Type: " &lt;&lt; type->name() &lt; endl;
+cout &lt;&lt; "Icon: " &lt;&lt; type->icon() &lt; endl;
+cout &lt;&lt; "Comment: " &lt;&lt; type->icon() &lt; endl;
+QStringList patterns = type->patterns();
+QStringList::ConstIterator it;
+for (it = patterns.begin(); it != patterns.end(); ++it)
+ cout &lt;&lt; "Pattern: " &lt;&lt; (*it) &lt;&lt; endl;
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="mime-determiningmimetypes">
+<title>Determining the MIME type of data</title>
+
+<para>
+The fast method for determining the type of a file is
+<function>KMimeType::findByURL()</function>. This looks for the URL string and
+in most cases determines the type from the extension. For certain protocols
+(e.g. http, man, info), this mechanism is not used. For example, CGI scripts
+on web servers written in Perl often have the extension
+<literal>.pl</literal>, which would indicate a
+<literal>"text/x-perl"</literal> type. However, we file delivered by the
+server is the output of this script, which is normally HTML. For such a case,
+<function>KMimeType::findByURL()</function> returns the MIME type
+<literal>"application/octet-stream"</literal> (available through
+<function>KMimeType::defaultMimeType()</function>), which indicates a failure
+to find out the type.
+</para>
+
+<programlisting>
+KMimeType::Ptr type = KMimeType::findByURL("/home/bernd/foobar.jpg");
+if (type->name() == KMimeType::defaultMimeType())
+ cout &lt;&lt; "Could not find out type" &lt;&lt; endl;
+else
+ cout &lt;&lt; "Type: " &lt;&lt; type->name() &lt;&lt; endl;
+</programlisting>
+
+<para>
+(this method has some more arguments, but these are undocumented, so simply
+forget about them.)
+</para>
+
+<para>
+You may want to find out a MIME from the contents of file instead of
+the file name. This is more reliable, but also slower, as it requires
+reading a part of the file. This is done with the
+<ulink url="kdeapi:kio/KMimeMagic.html">KMimeMagic</ulink>
+class, which has different error handling:
+</para>
+
+<programlisting>
+KMimeMagicResult *result = KMimeMagic::self()->findFileType("/home/bernd/foobar.jpg");
+if (!result || !result->isValid())
+ cout &lt;&lt; "Could not find out type" &lt;&lt; endl;
+else
+ cout &lt;&lt; "Type: " &lt;&lt; result->mimeType() &lt;&lt; endl;
+</programlisting>
+
+<para>
+As a variant of this function, you can also determine the type of a memory
+chunk. This is e.g. used in <application>Kate</application> in order to find
+out the highlighting mode:
+</para>
+
+<programlisting>
+QByteArray array;
+...
+KMimeMagicResult *result = KMimeMagic::self()->findBufferType(array);
+if (!result || !result->isValid())
+ cout &lt;&lt; "Could not find out type" &lt;&lt; endl;
+else
+ cout &lt;&lt; "Type: " &lt;&lt; result->mimeType() &lt;&lt; endl;
+</programlisting>
+
+<para>
+Of course, even KMimeMagic is only able to determine a file type from the
+contents of a local file. For remote files, there is a further possibility:
+</para>
+
+<programlisting>
+KURL url("http://developer.kde.org/favicon.ico");
+QString type = KIO::NetAccess::mimetype(url);
+if (type == KMimeType::defaultMimeType())
+ cout &lt;&lt; "Could not find out type" &lt;&lt; endl;
+else
+ cout &lt;&lt; "Type: " &lt;&lt; type &lt;&lt; endl;
+</programlisting>
+
+<para>
+This starts a KIO job to download a part of the file and check this.
+Note that this function is perhaps quite slow and blocks the program. Normally
+you will only want to use this if <function>KMimeType::findByURL()</function>
+has returned <literal>"application/octet-stream"</literal>.
+</para>
+
+<para>
+On the other hand, if you do not want to block your application, you can also
+explicitly start the KIO job and connect to some of its signals:
+</para>
+
+<programlisting>
+void FooClass::findType()
+{
+ KURL url("http://developer.kde.org/favicon.ico");
+ KIO::MimetypeJob *job = KIO::mimetype(url);
+ connect( job, SIGNAL(result(KIO::Job*)),
+ this, SLOT(mimeResult(KIO::Job*)) );
+}
+
+void FooClass::mimeResult(KIO::Job *job)
+{
+ if (job->error())
+ job->showErrorDialog();
+ else
+ cout &lt;&lt; "MIME type: " &lt;&lt; ((KIO::MimetypeJob *)job)->mimetype() &lt;&lt; endl;
+}
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="mime-mappingmimetypes">
+<title>Mapping a MIME type to an application or service</title>
+
+<para>
+When an application is installed, it installs a <literal>.desktop</literal>
+file which contains a list of MIME types this application can load. Similarly,
+components like KParts make this information available by their service
+<literal>.desktop</literal> files. So in general, there are several programs
+and components which can process a given MIME type. You can obtain such a list
+from the class <classname>KServiceTypeProfile</classname>:
+</para>
+
+<programlisting>
+KService::OfferList offers = KServiceTypeProfile::offers("text/html", "Application");
+KService::OfferList::ConstIterator it;
+for (it = offers.begin(); it != offers.end(); ++it) {
+ KService::Ptr service = (*it);
+ cout &lt;&lt; "Name: " &lt;&lt; service->name() &lt;&lt; endl;
+}
+</programlisting>
+
+<para>
+The return value of this function is a list of service offers. A
+<classname>KServiceOffer</classname> object packages a KService::Ptr together
+with a preference number. The list returned by
+<function>KServiceTypeProfile::offers()</function> is ordered by the user's
+preference. The user can change this by calling <command>"keditfiletype
+text/html"</command> or choosing <guimenuitem>Edit File Type</guimenuitem> on
+<application>Konqueror</application>'s context menu on a HTML file.
+</para>
+
+<para>
+In the above example, an offer list of the applications supporting
+<literal>text/html</literal> was requested. This will - among others - contain
+HTML editors like <application>Quanta Plus</application>. You can also replace
+the second argument <literal>"Application"</literal> by
+<literal>"KParts::ReadOnlyPart"</literal>. In that case, you get a list of
+embedable components for presenting HTML content, for example KHTML.
+</para>
+
+<para>
+In most cases, you are not interested in the list of all service offers
+for a combination of MIME type and service type. There is a convenience
+function which gives you only the service offer with the highest preference:
+</para>
+
+<programlisting>
+KService::Ptr offer = KServiceTypeProfile::preferredService("text/html", "Application");
+if (offer)
+ cout &lt;&lt; "Name: " &lt;&lt; service->name() &lt;&lt; endl;
+else
+ cout &lt;&lt; "No appropriate service found" &lt;&lt; endl;
+</programlisting>
+
+<para>
+For even more complex queries, there is a full-blown CORBA-like
+<ulink url="kdeapi:kio/KTrader.html">trader</ulink>.
+</para>
+
+<para>
+In order to run an application service with some URLs, use
+<ulink url="kdeapi:kio/KRun.html">KRun</ulink>:
+</para>
+
+<programlisting>
+KURL::List urlList;
+urlList &lt;&lt; "http://www.ietf.org/rfc/rfc1341.txt?number=1341";
+urlList &lt;&lt; "http://www.ietf.org/rfc/rfc2046.txt?number=2046";
+KRun::run(offer.service(), urlList);
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="mime-misc">
+<title>Miscellaneous</title>
+
+<para>
+In this section, we want to list some APIs which are loosely related
+to the previous discussion.
+</para>
+
+<para>
+Getting an icon for a URL. This looks for the type of the URL
+and returns the associated icon.
+</para>
+
+<programlisting>
+KURL url("ftp://ftp.kde.org/pub/incoming/wibble.c");
+QString icon = KMimeType::iconForURL(url);
+</programlisting>
+
+<para>
+Running a URL. This looks for the type of the URL and starts the
+user's preferred program associated with this type.
+</para>
+
+<programlisting>
+KURL url("http://dot.kde.org");
+new KRun(url);
+</programlisting>
+
+</simplesect>
+
+</sect1>
+
+
+<sect1 id="nettransparency">
+<title>Network transparency</title>
+
+<simplesect id="nettransparency-intro">
+<title>Introduction</title>
+
+<para>
+In the age of the world wide web, it is of essential importance that desktop
+applications can access resources over the internet: they should be able to
+download files from a web server, write files to an ftp server or read mails
+from a web server. Often, the ability to access files regardless of their
+location is called <emphasis>network transparency</emphasis>.
+</para>
+
+<para>
+In the past, different approaches to this goals were implemented. The old NFS
+file system is an attempt to implement network transparency on the level of
+the POSIX API. While this approach works quite well in local, closely coupled
+networks, it does not scale for resources to which access is unreliable and
+possibly slow. Here, <emphasis>asynchronicity</emphasis> is important. While
+you are waiting for your web browser to download a page, the user interface
+should not block. Also, the page rendering should not begin when the page is
+completely available, but should updated regularly as data comes in.
+</para>
+
+<para>
+In the KDE libraries, network transparency is implemented in the KIO API. The
+central concept of this architecture is an IO <emphasis>job</emphasis>. A job
+may copy, or delete files or similar things. Once a job is started, it works
+in the background and does not block the application. Any communication from
+the job back to the application - like delivering data or progress information
+- is done integrated with the Qt event loop.
+</para>
+
+<para>
+Background operation is achieved by starting <emphasis>ioslaves</emphasis> to
+perform certain tasks. ioslaves are started as separate processes and are
+communicated with through UNIX domain sockets. In this way, no multi-threading
+is necessary and unstable slaves can not crash the application that uses them.
+</para>
+
+<para>
+File locations are expressed by the widely used URLs. But in KDE, URLs do not
+only expand the range of addressable files beyond the local file system. It
+also goes in the opposite direction - e.g. you can browse into tar archives.
+This is achieved by nesting URLs. For example, a file in a tar archive on
+a http server could have the URL
+</para>
+
+<programlisting>
+http://www-com.physik.hu-berlin.de/~bernd/article.tgz#tar:/paper.tex
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-usingkio">
+<title>Using KIO</title>
+
+<para>
+In most cases, jobs are created by calling functions in the KIO namespace.
+These functions take one or two URLs as arguments, and possible other
+necessary parameters. When the job is finished, it emits the signal
+<literal>result(KIO::Job*)</literal>. After this signal has been emitted, the job
+deletes itself. Thus, a typical use case will look like this:
+</para>
+
+<programlisting>
+void FooClass::makeDirectory()
+{
+ SimpleJob *job = KIO::mkdir(KURL("file:/home/bernd/kiodir"));
+ connect( job, SIGNAL(result(KIO::Job*)),
+ this, SLOT(mkdirResult(KIO::Job*)) );
+}
+
+void FooClass::mkdirResult(KIO::Job *job)
+{
+ if (job->error())
+ job->showErrorDialog();
+ else
+ cout &lt;&lt; "mkdir went fine" &lt;&lt; endl;
+}
+</programlisting>
+
+<para>
+Depending on the type of the job, you may connect also to other
+signals.
+</para>
+
+<para>
+Here is an overview over the possible functions:
+</para>
+
+<variablelist>
+
+<varlistentry><term>KIO::mkdir(const KURL &amp;url, int permission)</term>
+<listitem><para>
+Creates a directory, optionally with certain permissions.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::rmdir(const KURL &amp;url)</term>
+<listitem><para>
+Removes a directory.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::chmod(const KURL &amp;url, int permissions)</term>
+<listitem><para>
+Changes the permissions of a file.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::rename(const KURL &amp;src, const KURL &amp;dest,
+ bool overwrite)</term>
+<listitem><para>
+Renames a file.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::symlink(const QString &amp;target, const KURL &amp;dest,
+ bool overwrite, bool showProgressInfo)</term>
+<listitem><para>
+Creates a symbolic link.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::stat(const KURL &amp;url, bool showProgressInfo)</term>
+<listitem><para>
+Finds out certain information about the file, such as size, modification
+time and permissions. The information can be obtained from
+KIO::StatJob::statResult() after the job has finished.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::get(const KURL &amp;url, bool reload, bool showProgressInfo)</term>
+<listitem><para>
+Transfers data from a URL.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::put(const KURL &amp;url, int permissions, bool overwrite,
+ bool resume, bool showProgressInfo)</term>
+<listitem><para>
+Transfers data to a URL.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::http_post(const KURL &amp;url, const QByteArray &amp;data,
+ bool showProgressInfo)</term>
+<listitem><para>Posts data. Special for HTTP.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::mimetype(const KURL &amp;url, bool showProgressInfo)</term>
+<listitem><para>
+Tries to find the MIME type of the URL. The type can be obtained from
+KIO::MimetypeJob::mimetype() after the job has finished.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::file_copy(const KURL &amp;src, const KURL &amp;dest, int permissions,
+ bool overwrite, bool resume, bool showProgressInfo)</term>
+<listitem><para>
+Copies a single file.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::file_move(const KURL &amp;src, const KURL &amp;dest, int permissions,
+ bool overwrite, bool resume, bool showProgressInfo)</term>
+<listitem><para>
+Renames or moves a single file.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::file_delete(const KURL &amp;url, bool showProgressInfo)</term>
+<listitem><para>
+Deletes a single file.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::listDir(const KURL &amp;url, bool showProgressInfo)</term>
+<listitem><para>
+Lists the contents of a directory. Each time some new entries are known, the
+signal KIO::ListJob::entries() is emitted.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::listRecursive(const KURL &amp;url, bool showProgressInfo)</term>
+<listitem><para>
+Similar to the listDir() function, but this one is recursive.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::copy(const KURL &amp;src, const KURL &amp;dest, bool showProgressInfo)</term>
+<listitem><para>
+Copies a file or directory. Directories are copied recursively.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::move(const KURL &amp;src, const KURL &amp;dest, bool showProgressInfo)</term>
+<listitem><para>
+Moves or renames a file or directory.
+</para></listitem>
+</varlistentry>
+
+<varlistentry><term>KIO::del(const KURL &amp;src, bool shred, bool showProgressInfo)</term>
+<listitem><para>
+Deletes a file or directory.
+</para></listitem>
+</varlistentry>
+
+</variablelist>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-direntries">
+<title>Directory entries</title>
+
+<para>
+Both the KIO::stat() and KIO::listDir() jobs return their results as a type
+UDSEntry, UDSEntryList resp. The latter is defined as QValueList&lt;UDSEntry&gt;.
+The acronym UDS stands for "Universal directory service". The principle behind
+it is that the a directory entry only carries the information which an ioslave
+can provide, not more. For example, the http slave does not provide any
+information about access permissions or file owners.
+Instead, a UDSEntry is a list of UDSAtoms. Each atom provides a specific piece
+of information. It consists of a type stored in m_uds and either an integer
+value in m_long or a string value in m_str, depending on the type.
+</para>
+
+<para>
+The following types are currently defined:
+</para>
+
+<itemizedlist>
+
+<listitem><para>
+UDS_SIZE (integer) - Size of the file.
+</para></listitem>
+
+<listitem><para>
+UDS_USER (string) - User owning the file.
+</para></listitem>
+
+<listitem><para>
+UDS_GROUP (string) - Group owning the file.
+</para></listitem>
+
+<listitem><para>
+UDS_NAME (string) - File name.
+</para></listitem>
+
+<listitem><para>
+UDS_ACCESS (integer) - Permission rights of the file, as e.g. stored
+by the libc function stat() in the st_mode field.
+</para></listitem>
+
+<listitem><para>
+UDS_FILE_TYPE (integer) - The file type, as e.g. stored by stat() in the
+st_mode field. Therefore you can use the usual libc macros like S_ISDIR to
+test this value. Note that the data provided by ioslaves corresponds to
+stat(), not lstat(), i.e. in case of symbolic links, the file type here is
+the type of the file pointed to by the link, not the link itself.
+</para></listitem>
+
+<listitem><para>
+UDS_LINK_DEST (string) - In case of a symbolic link, the name of the file
+pointed to.
+</para></listitem>
+
+<listitem><para>
+UDS_MODIFICATION_TIME (integer) - The time (as in the type time_t) when the
+file was last modified, as e.g. stored by stat() in the st_mtime field.
+</para></listitem>
+
+<listitem><para>
+UDS_ACCESS_TIME (integer) - The time when the file was last accessed, as
+e.g. stored by stat() in the st_atime field.
+</para></listitem>
+
+<listitem><para>
+UDS_CREATION_TIME (integer) - The time when the file was created, as e.g.
+stored by stat() in the st_ctime field.
+</para></listitem>
+
+<listitem><para>
+UDS_URL (string) - Provides a URL of a file, if it is not simply the
+the concatenation of directory URL and file name.
+</para></listitem>
+
+<listitem><para>
+UDS_MIME_TYPE (string) - MIME type of the file
+</para></listitem>
+
+<listitem><para>
+UDS_GUESSED_MIME_TYPE (string) - MIME type of the file as guessed by the
+slave. The difference to the previous type is that the one provided here
+should not be taken as reliable (because determining it in a reliable way
+would be too expensive). For example, the KRun class explicitly checks the
+MIME type if it does not have reliable information.
+</para></listitem>
+
+</itemizedlist>
+
+<para>
+Although the way of storing information about files in a
+<classname>UDSEntry</classname> is flexible and practical from the ioslave
+point of view, it is a mess to use for the application programmer. For
+example, in order to find out the MIME type of the file, you have to iterate
+over all atoms and test whether <literal>m_uds</literal> is
+<literal>UDS_MIME_TYPE</literal>. Fortunately, there is an API which is a lot
+easier to use: the class <classname>KFileItem</classname>.
+</para>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-syncuse">
+<title>Synchronous usage</title>
+
+<para>
+Often, the asynchronous API of KIO is too complex to use and therefore
+implementing full asynchronicity is not a priority. For example, in a program
+that can only handle one document file at a time, there is little that can be
+done while the program is downloading a file anyway. For these simple cases,
+there is a mucher simpler API in the form of a set of static functions in
+KIO::NetAccess. For example, in order to copy a file, use
+</para>
+
+<programlisting>
+KURL source, target;
+source = ...;
+target = ...
+KIO::NetAccess::copy(source, target);
+</programlisting>
+
+<para>
+The function will return after the complete copying process has finished. Still,
+this method provides a progress dialog, and it makes sure that the application
+processes repaint events.
+</para>
+
+<para>
+A particularly interesting combination of functions is
+<function>download()</function> in combination with
+<function>removeTempFile()</function>. The former downloads a file from given
+URL and stores it in a temporary file with a unique name. The name is stored
+in the second argument. <emphasis>If</emphasis> the URL is local, the file is
+not downloaded, and instead the second argument is set to the local file
+name. The function <function>removeTempFile()</function> deletes the file
+given by its argument if the file is the result of a former download. If that
+is not the case, it does nothing. Thus, a very easy to use way of loading
+files regardless of their location is the following code snippet:
+</para>
+
+<programlisting>
+KURL url;
+url = ...;
+QString tempFile;
+if (KIO::NetAccess::download(url, tempFile) {
+ // load the file with the name tempFile
+ KIO::NetAccess::removeTempFile(tempFile);
+}
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-metadata">
+<title>Meta data</title>
+
+<para>
+As can be seen above, the interface to IO jobs is quite abstract and does not
+consider any exchange of information between application and IO slave that
+is protocol specific. This is not always appropriate. For example, you may give
+certain parameters to the HTTP slave to control its caching behavior or
+send a bunch of cookies with the request. For this need, the concept of meta
+data has been introduced. When a job is created, you can configure it by adding
+meta data to it. Each item of meta data consists of a key/value pair. For
+example, in order to prevent the HTTP slave from loading a web page from its
+cache, you can use:
+</para>
+
+<programlisting>
+void FooClass::reloadPage()
+{
+ KURL url("http://www.kdevelop.org/index.html");
+ KIO::TransferJob *job = KIO::get(url, true, false);
+ job->addMetaData("cache", "reload");
+ ...
+}
+</programlisting>
+
+<para>
+The same technique is used in the other direction, i.e. for communication from
+the slave to the application. The method
+<function>Job::queryMetaData()</function> asks for the value of the certain
+key delivered by the slave. For the HTTP slave, one such example is the key
+<literal>"modified"</literal>, which contains a (stringified representation of)
+the date when the web page was last modified. An example how you can use this
+is the following:
+</para>
+
+<programlisting>
+void FooClass::printModifiedDate()
+{
+ KURL url("http://developer.kde.org/documentation/kde2arch/index.html");
+ KIO::TransferJob *job = KIO::get(url, true, false);
+ connect( job, SIGNAL(result(KIO::Job*)),
+ this, SLOT(transferResult(KIO::Job*)) );
+}
+
+void FooClass::transferResult(KIO::Job *job)
+{
+ QString mimetype;
+ if (job->error())
+ job->showErrorDialog();
+ else {
+ KIO::TransferJob *transferJob = (KIO::TransferJob*) job;
+ QString modified = transferJob->queryMetaData("modified");
+ cout &lt;&lt; "Last modified: " &lt;&lt; modified &lt;&lt; endl;
+}
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-scheduling">
+<title>Scheduling</title>
+
+<para>
+When using the KIO API, you usually do not have to cope with the details of
+starting IO slaves and communicating with them. The normal use case is to
+start a job and with some parameters and handle the signals the jobs emits.
+</para>
+
+<para>
+Behind the curtains, the scenario is a lot more complicated. When you create a
+job, it is put in a queue. When the application goes back to the event loop,
+KIO allocates slave processes for the jobs in the queue. For the first jobs
+started, this is trivial: an IO slave for the appropriate protocol is started.
+However, after the job (like a download from an http server) has finished, it
+is not immediately killed. Instead, it is put in a pool of idle slaves and
+killed after a certain time of inactivity (current 3 minutes). If a new request
+for the same protocol and host arrives, the slave is reused. The obvious
+advantage is that for a series of jobs for the same host, the cost for creating
+new processes and possibly going through an authentication handshake is saved.
+</para>
+
+<para>
+Of course, reusing is only possible when the existing slave has already finished
+its previous job. when a new request arrives while an existing slave process is
+still running, a new process must be started and used. In the API usage in the
+examples above, there are no limitation for creating new slave processes: if you
+start a consecutive series of downloads for 20 different files, then KIO will
+start 20 slave processes. This scheme of assigning slaves to jobs is called
+<emphasis>direct</emphasis>. It not always the most appropriate scheme, as it
+may need much memory and put a high load on both the client and server machines.
+</para>
+
+<para>
+So there is a different way. You can <emphasis>schedule</emphasis> jobs. If
+you do this, only a limited number (currently 3) of slave processes for a
+protocol will be created. If you create more jobs than that, they are put in a
+queue and are processed when a slave process becomes idle. This is done as
+follows:
+</para>
+
+<programlisting>
+KURL url("http://developer.kde.org/documentation/kde2arch/index.html");
+KIO::TransferJob *job = KIO::get(url, true, false);
+KIO::Scheduler::scheduleJob(job);
+</programlisting>
+
+<para>
+A third possibility is <emphasis>connection oriented</emphasis>. For example,
+for the IMAP slave, it does not make any sense to start multiple processes for
+the same server. Only one IMAP connection at a time should be enforced. In
+this case, the application must explicitly deal with the notion of a slave. It
+has to deallocate a slave for a certain connection and then assign all jobs
+which should go through the same connection to the same slave. This can again
+be easily achieved by using the KIO::Scheduler:
+</para>
+
+<programlisting>
+KURL baseUrl("imap://[email protected]");
+KIO::Slave *slave = KIO::Scheduler::getConnectedSlave(baseUrl);
+
+KIO::TransferJob *job1 = KIO::get(KURL(baseUrl, "/INBOX;UID=79374"));
+KIO::Scheduler::assignJobToSlave(slave, job1);
+
+KIO::TransferJob *job2 = KIO::get(KURL(baseUrl, "/INBOX;UID=86793"));
+KIO::Scheduler::assignJobToSlave(slave, job2);
+
+...
+
+KIO::Scheduler::disconnectSlave(slave);
+</programlisting>
+
+<para>
+You may only disconnect the slave after all jobs assigned to it are guaranteed
+to be finished.
+</para>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-definingslaves">
+<title>Defining an ioslave</title>
+
+<para>
+In the following we discuss how you can add a new ioslave to the system.
+In analogy to services, new ioslaves are advertised to the system by
+installing a little configuration file. The following Makefile.am
+snippet installs the ftp protocol:
+</para>
+
+<programlisting>
+protocoldir = $(kde_servicesdir)
+protocol_DATA = ftp.protocol
+EXTRA_DIST = $(mime_DATA)
+</programlisting>
+
+<para>
+The contents of the file ftp.protocol is as follows:
+</para>
+
+<programlisting>
+[Protocol]
+exec=kio_ftp
+protocol=ftp
+input=none
+output=filesystem
+listing=Name,Type,Size,Date,Access,Owner,Group,Link,
+reading=true
+writing=true
+makedir=true
+deleting=true
+Icon=ftp
+</programlisting>
+
+<para>
+The <literal>"protocol"</literal> entry defines for which protocol this slave
+is responsible. <literal>"exec"</literal> is (in contrast what you would
+expect naively) the name of the library that implements the slave. When the
+slave is supposed to start, the <command>"kdeinit"</command> executable is
+started which in turn loads this library into its address space. So in
+practice, you can think of the running slave as a separate process although it
+is implemented as library. The advantage of this mechanism is that it saves a
+lot of memory and reduces the time needed by the runtime linker.
+</para>
+
+<para>
+The "input" and "output" lines are not used currently.
+</para>
+
+<para>
+The remaining lines in the <literal>.protocol</literal> file define which
+abilities the slave has. In general, the features a slave must implement are
+much simpler than the features the KIO API provides for the application. The
+reason for this is that complex jobs are scheduled to a couple of subjobs. For
+example, in order to list a directory recursively, one job will be started for
+the toplevel directory. Then for each subdirectory reported back, new subjobs
+are started. A scheduler in KIO makes sure that not too many jobs are active
+at the same time. Similarly, in order to copy a file within a protocol that
+does not support copying directly (like the <literal>ftp:</literal> protocol),
+KIO can read the source file and then write the data to the destination
+file. For this to work, the <literal>.protocol</literal> must advertise the
+actions its slave supports.
+</para>
+
+<para>
+Since slaves are loaded as shared libraries, but constitute standalone programs,
+their code framework looks a bit different from normal shared library plugins.
+The function which is called to start the slave is called
+<function>kdemain()</function>. This function does some initializations and
+then goes into an event loop and waits for requests by the application using
+it. This looks as follows:
+</para>
+
+<programlisting>
+extern "C" { int kdemain(int argc, char **argv); }
+
+int kdemain(int argc, char **argv)
+{
+ KLocale::setMainCatalogue("kdelibs");
+ KInstance instance("kio_ftp");
+ (void) KGlobal::locale();
+
+ if (argc != 4) {
+ fprintf(stderr, "Usage: kio_ftp protocol "
+ "domain-socket1 domain-socket2\n");
+ exit(-1);
+ }
+
+ FtpSlave slave(argv[2], argv[3]);
+ slave.dispatchLoop();
+ return 0;
+}
+</programlisting>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-implementingslaves">
+<title>Implementing an ioslave</title>
+
+<para>
+Slaves are implemented as subclasses of <classname>KIO::SlaveBase</classname>
+(FtpSlave in the above example). Thus, the actions listed in the
+<literal>.protocol</literal> correspond to certain virtual functions in
+<classname>KIO::SlaveBase</classname> the slave implementation must
+reimplement. Here is a list of possible actions and the corresponding virtual
+functions:
+</para>
+
+<variablelist>
+
+<varlistentry><term>reading - Reads data from a URL</term>
+<listitem><para>void get(const KURL &amp;url)</para></listitem></varlistentry>
+
+<varlistentry><term>writing - Writes data to a URL and create the file if it does not exist yet.</term>
+<listitem><para>void put(const KURL &amp;url, int permissions, bool overwrite, bool resume)</para></listitem></varlistentry>
+
+<varlistentry><term>moving - Renames a file.</term>
+<listitem><para>void rename(const KURL &amp;src, const KURL &amp;dest, bool overwrite)</para></listitem></varlistentry>
+
+<varlistentry><term>deleting - Deletes a file or directory.</term>
+<listitem><para>void del(const KURL &amp;url, bool isFile)</para></listitem></varlistentry>
+
+<varlistentry><term>listing - Lists the contents of a directory.</term>
+<listitem><para>void listDir(const KURL &amp;url)</para></listitem></varlistentry>
+
+<varlistentry><term>makedir - Creates a directory.</term>
+<listitem><para>void mkdir(const KURL &amp;url, int permissions)</para></listitem></varlistentry>
+
+</variablelist>
+
+<para>
+Additionally, there are reimplementable functions not listed in the <literal>.protocol</literal>
+file. For these operations, KIO automatically determines whether they are supported
+or not (i.e. the default implementation returns an error).
+</para>
+
+<variablelist>
+
+<varlistentry><term>Delivers information about a file, similar to the C function stat().</term>
+<listitem><para>void stat(const KURL &amp;url)</para></listitem></varlistentry>
+
+<varlistentry><term>Changes the access permissions of a file.</term>
+<listitem><para>void chmod(const KURL &amp;url, int permissions)</para></listitem></varlistentry>
+
+<varlistentry><term>Determines the MIME type of a file.</term>
+<listitem><para>void mimetype(const KURL &amp;url)</para></listitem></varlistentry>
+
+<varlistentry><term>Copies a file.</term>
+<listitem><para>copy(const KURL &amp;url, const KURL &amp;dest, int permissions, bool overwrite)</para></listitem></varlistentry>
+
+<varlistentry><term>Creates a symbolic link.</term>
+<listitem><para>void symlink(const QString &amp;target, const KURL &amp;dest, bool overwrite)</para></listitem></varlistentry>
+
+</variablelist>
+
+<para>
+All these implementation should end with one of two calls: If the operation
+was successful, they should call <literal>finished()</literal>. If an error has occurred,
+<literal>error()</literal> should be called with an error code as first argument and a
+string in the second. Possible error codes are listed as enum
+<type>KIO::Error</type>. The second argument is usually the URL in
+question. It is used e.g. in <function>KIO::Job::showErrorDialog()</function>
+in order to parameterize the human-readable error message.
+</para>
+
+<para>
+For slaves that correspond to network protocols, it might be interesting to
+reimplement the method <function>SlaveBase::setHost()</function>. This is
+called to tell the slave process about the host and port, and the user name
+and password to log in. In general, meta data set by the application can be
+queried by <function>SlaveBase::metaData()</function>. You can check for the
+existence of meta data of a certain key with
+<function>SlaveBase::hasMetaData()</function>.
+</para>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-communication">
+<title>Communicating back to the application</title>
+
+<para>
+Various actions implemented in a slave need some way to communicate data back
+to the application using the slave process:
+</para>
+
+<itemizedlist>
+
+<listitem><para>
+<function>get()</function> sends blocks of data. This is done with
+<function>data()</function>, which takes a <classname>QByteArray</classname>
+as argument. Of course, you do not need to send all data at once. If you send
+a large file, call <function>data()</function> with smaller data blocks, so
+the application can process them. Call <function>finished()</function> when
+the transfer is finished.
+</para></listitem>
+
+<listitem><para>
+<function>listDir()</function> reports information about the entries of a
+directory. For this purpose, call <function>listEntries()</function> with a
+<classname>KIO::UDSEntryList</classname> as argument. Analogously to
+<function>data()</function>, you can call this several times. When you are
+finished, call <function>listEntry()</function> with the second argument set
+to true. You may also call <function>totalSize()</function> to report the
+total number of directory entries, if known.
+</para></listitem>
+
+<listitem><para>
+<function>stat()</function> reports information about a file like size, MIME
+type, etc. Such information is packaged in a
+<classname>KIO::UDSEntry</classname>, which will be discussed below. Use
+<function>statEntry()</function> to send such an item to the application.
+</para></listitem>
+
+<listitem><para>
+<function>mimetype()</function> calls <function>mimeType()</function> with a
+string argument.
+</para></listitem>
+
+<listitem><para>
+<function>get()</function> and <function>copy()</function> may want to provide
+progress information. This is done with the methods
+<function>totalSize()</function>, <function>processedSize()</function>,
+<function>speed()</function>. The total size and processed size are reported
+as bytes, the speed as bytes per second.
+</para></listitem>
+
+<listitem><para>
+You can send arbitrary key/value pairs of meta data with
+<function>setMetaData()</function>.
+</para></listitem>
+
+</itemizedlist>
+
+</simplesect>
+
+
+<simplesect id="nettransparency-interacting">
+<title>Interacting with the user</title>
+
+<para>
+Sometimes a slave has to interact with the user. Examples include informational
+messages, authentication dialogs and confirmation dialogs when a file is about
+to be overwritten.
+</para>
+
+<itemizedlist>
+
+<listitem><para>
+<function>infoMessage()</function> - This is for informational feedback, such
+as the message "Retrieving data from &lt;host&gt;" from the http slave, which
+is often displayed in the status bar of the program. On the application side,
+this method corresponds to the signal
+<function>KIO::Job::infoMessage()</function>.
+</para></listitem>
+
+<listitem><para>
+<function>warning()</function> - Displays a warning in a message box with
+<function>KMessageBox::information()</function>. If a message box is still
+open from a former call of warning() from the same slave process, nothing
+happens.
+</para></listitem>
+
+<listitem><para>
+<function>messageBox()</function> - This is richer than the previous
+method. It allows to open a message box with text and caption and some
+buttons. See the enum <type>SlaveBase::MessageBoxType</type> for reference.
+</para></listitem>
+
+<listitem><para>
+<function>openPassDlg()</function> - Opens a dialog for the input of user name
+and password.
+</para></listitem>
+
+</itemizedlist>
+
+</simplesect>
+
+</sect1>
+
+</chapter>
+
+
+
+<appendix id="misc">
+<title>Licensing</title>
+
+&underFDL;
+&underGPL;
+
+</appendix>
+
+</book>