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| author | toma <toma@283d02a7-25f6-0310-bc7c-ecb5cbfe19da> | 2009-11-25 17:56:58 +0000 |
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| committer | toma <toma@283d02a7-25f6-0310-bc7c-ecb5cbfe19da> | 2009-11-25 17:56:58 +0000 |
| commit | 114a878c64ce6f8223cfd22d76a20eb16d177e5e (patch) | |
| tree | acaf47eb0fa12142d3896416a69e74cbf5a72242 /doc/kdearch/index.docbook | |
| download | tdevelop-114a878c64ce6f8223cfd22d76a20eb16d177e5e.tar.gz tdevelop-114a878c64ce6f8223cfd22d76a20eb16d177e5e.zip | |
Copy the KDE 3.5 branch to branches/trinity for new KDE 3.5 features.
BUG:215923
git-svn-id: svn://anonsvn.kde.org/home/kde/branches/trinity/kdevelop@1054174 283d02a7-25f6-0310-bc7c-ecb5cbfe19da
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1 files changed, 3337 insertions, 0 deletions
diff --git a/doc/kdearch/index.docbook b/doc/kdearch/index.docbook new file mode 100644 index 00000000..b1a40091 --- /dev/null +++ b/doc/kdearch/index.docbook @@ -0,0 +1,3337 @@ +<?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>bernd@kdevelop.org</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 &, BrushStyle) - This creates a colored brush +with one of the patterns shown below.</para> +</listitem> +<listitem> +<para>QBrush::QBrush(const QColor &, 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> +<!DOCTYPE kpartgui> +<kpartgui name="kview"> + <MenuBar> + <Menu name="view" > + <Action name="zoom50" /> + <Action name="zoom100" /> + <Action name="zoom200" /> + <Action name="zoomMaxpect" /> + <Separator/> + <Action name="fullscreen" /> + </Menu> + </MenuBar> +</kpartgui> +</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("&Half size"), ALT+Key_0, + this, SLOT(slotHalfSize()), + actionCollection(), "zoom50" ); + new KAction ( i18n("&Normal size"), ALT+Key_1, + this, SLOT(slotDoubleSize()), + actionCollection(), "zoom100" ); + new KAction ( i18n("&Double size"), ALT+Key_2, + this, SLOT(slotDoubleSize()), + actionCollection(), "zoom200" ); + new KAction ( i18n("&Fill Screen"), ALT+Key_3, + this, SLOT(slotFillScreen()), + actionCollection(), "zoomMaxpect" ); + new KAction ( i18n("Fullscreen &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><MenuBar></literal>, contains a declaration of a +menu bar. You can also insert any number of <literal><ToolBar></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> +<Menu name="image" > + <text>&amp;Image</text> + ... +</Menu> +</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 "&" in the form XML compliant form "&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><Action></literal> element. The separator in the +screenshots corresponds to the <literal><Separator></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> +<ToolBar name="locationToolBar" fullWidth="true" newline="true" > + <text>Location Toolbar</text> + <Action name="clear_location" /> + <Action name="location_label" /> + <Action name="toolbar_url_combo" /> + <Action name="go_url" /> +</ToolBar> +</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> +<Menu name="file"> + <text>&amp;Location</text> + ... + <ActionList name="openwith"> + ... +</Menu> +</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<QPopupMenu *>(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> +... +<Menu name="context_popup"> + <Action name="file_add"/> + <Action name="file_remove"/> +</Menu> +... +</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("&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("<qt>This demonstrates <b>Qt</b>'s" + " rich text engine.<ul>" + "<li>Foo</li>" + "<li>Bar</li>" + "</ul></qt>")) +</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<KParts::Factory*>(factory); + QObject *obj = partFactory->createPart(parentWidget, widgetName, + parent, name, "KParts::ReadOnlyPart"); + ... +} else { + cout << "Service does not implement the right factory" << 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(), &error)) + cout << "Starting kioserver failed with message " << error << endl; +} +... +QByteArray data, replyData; +QCString replyType; +QDataStream arg(data, IO_WriteOnly); +arg << true; +if (!client->call("kio_uiserver", "UIServer", "setListMode(bool)", + data, replyType, replyData)) + cout << "Call to kio_uiserver failed" << 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 << "Type: " << type->name() < endl; +cout << "Icon: " << type->icon() < endl; +cout << "Comment: " << type->icon() < endl; +QStringList patterns = type->patterns(); +QStringList::ConstIterator it; +for (it = patterns.begin(); it != patterns.end(); ++it) + cout << "Pattern: " << (*it) << 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 << "Could not find out type" << endl; +else + cout << "Type: " << type->name() << 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 << "Could not find out type" << endl; +else + cout << "Type: " << result->mimeType() << 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 << "Could not find out type" << endl; +else + cout << "Type: " << result->mimeType() << 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 << "Could not find out type" << endl; +else + cout << "Type: " << type << 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 << "MIME type: " << ((KIO::MimetypeJob *)job)->mimetype() << 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 << "Name: " << service->name() << 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 << "Name: " << service->name() << endl; +else + cout << "No appropriate service found" << 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 << "http://www.ietf.org/rfc/rfc1341.txt?number=1341"; +urlList << "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 << "mkdir went fine" << 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 &url, int permission)</term> +<listitem><para> +Creates a directory, optionally with certain permissions. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::rmdir(const KURL &url)</term> +<listitem><para> +Removes a directory. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::chmod(const KURL &url, int permissions)</term> +<listitem><para> +Changes the permissions of a file. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::rename(const KURL &src, const KURL &dest, + bool overwrite)</term> +<listitem><para> +Renames a file. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::symlink(const QString &target, const KURL &dest, + bool overwrite, bool showProgressInfo)</term> +<listitem><para> +Creates a symbolic link. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::stat(const KURL &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 &url, bool reload, bool showProgressInfo)</term> +<listitem><para> +Transfers data from a URL. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::put(const KURL &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 &url, const QByteArray &data, + bool showProgressInfo)</term> +<listitem><para>Posts data. Special for HTTP. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::mimetype(const KURL &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 &src, const KURL &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 &src, const KURL &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 &url, bool showProgressInfo)</term> +<listitem><para> +Deletes a single file. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::listDir(const KURL &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 &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 &src, const KURL &dest, bool showProgressInfo)</term> +<listitem><para> +Copies a file or directory. Directories are copied recursively. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::move(const KURL &src, const KURL &dest, bool showProgressInfo)</term> +<listitem><para> +Moves or renames a file or directory. +</para></listitem> +</varlistentry> + +<varlistentry><term>KIO::del(const KURL &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<UDSEntry>. +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 << "Last modified: " << modified << 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://bernd@albert.physik.hu-berlin.de"); +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 &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 &url, int permissions, bool overwrite, bool resume)</para></listitem></varlistentry> + +<varlistentry><term>moving - Renames a file.</term> +<listitem><para>void rename(const KURL &src, const KURL &dest, bool overwrite)</para></listitem></varlistentry> + +<varlistentry><term>deleting - Deletes a file or directory.</term> +<listitem><para>void del(const KURL &url, bool isFile)</para></listitem></varlistentry> + +<varlistentry><term>listing - Lists the contents of a directory.</term> +<listitem><para>void listDir(const KURL &url)</para></listitem></varlistentry> + +<varlistentry><term>makedir - Creates a directory.</term> +<listitem><para>void mkdir(const KURL &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 &url)</para></listitem></varlistentry> + +<varlistentry><term>Changes the access permissions of a file.</term> +<listitem><para>void chmod(const KURL &url, int permissions)</para></listitem></varlistentry> + +<varlistentry><term>Determines the MIME type of a file.</term> +<listitem><para>void mimetype(const KURL &url)</para></listitem></varlistentry> + +<varlistentry><term>Copies a file.</term> +<listitem><para>copy(const KURL &url, const KURL &dest, int permissions, bool overwrite)</para></listitem></varlistentry> + +<varlistentry><term>Creates a symbolic link.</term> +<listitem><para>void symlink(const QString &target, const KURL &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 <host>" 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> |