Development/Tutorials/Kate/KatePluginTutorial

Creating your first Kate Plugin

Tutorial Series	Kate Plugin Tutorial
Previous	C++, Qt, KDE4 development environment
What's Next	Add a configuration dialog for it (Work in progress)
Further Reading	CMake, The actual plugin code

Abstract

We are going to create a dummy plugin for Kate in this tutorial. Our plugin will be able to insert current Date & Time. For now, our plugin will add on the cursor position on the active document the next information:

• MM-DD-YYYY HH:MM (something like "08-22-2007 23:45")

On the next chapter we will learn how to customize this output string creating a configuration dialog for this plugin.

The Code

The .desktop file

Every plugin needs a .desktop file that describes it.

ktexteditor_timedate.desktop

[Desktop Entry]
Encoding=UTF-8
X-KDE-Library=ktexteditor_timedate
X-KDE-PluginInfo-Author=Konqui the Dragon
X-KDE-PluginInfo-Email=[email protected]
X-KDE-PluginInfo-Name=ktexteditortimedate
X-KDE-PluginInfo-Version=0.1
X-KDE-PluginInfo-Website=http://kate.kde.org
X-KDE-PluginInfo-Category=Editor
X-KDE-PluginInfo-Depends=
X-KDE-PluginInfo-License=GPL
X-KDE-PluginInfo-EnabledByDefault=false
X-KDE-ParentApp=kate
ServiceTypes=KTextEditor/Plugin
Type=Service
Icon=korganizer
Name=Time & Date
Comment=Insert current Time & Date

There are important parts on this file:

• X-KDE-Library: will define the library that provides this plugin. It is _really_ important that this variable matches exactly the same with the actual name of the library being built. You will understand this better when getting to the finish of this tutorial on the part "Building it all, the CMakeLists.txt".
• X-KDE-PluginInfo-Name: no special characters. The name of the plugin.
• X-KDE-PluginInfo-Category: important when the plugin selector loads it. Usually here you want always to put "Editor".
• X-KDE-PluginInfo-Depends: if your plugin depends on another, write here the corresponding X-KDE-PluginInfo-Name that is needed to be loaded too when loading this plugin.
• X-KDE-PluginInfo-EnabledByDefault: whether the plugin is enabled by default. Applied when clicking on "Defaults" button on the plugin selector.
• X-KDE-ParentApp: you want here always "kate".
• ServiceTypes: you will always need here "KTextEditor/Plugin".
• Type: in order to load it properly this is needed as "Service".

The resource contents file

This file is the one that will let our plugin merge with the Kate environment (toolbars and/or menubars). In this case when our plugin is loaded this file tells the KDE XML classes that it will add a separator, and that there is an action named "tools_insert_timedate". We will need to interact with this action later.

timedateui.rc

<!DOCTYPE kpartgui>
<kpartplugin name="ktexteditor_timedate" library="ktexteditor_timedate" version="2">
<MenuBar>
 <Menu name="tools"><Text>&amp;Tools</Text>
    <separator group="tools_operations" />
    <Action name="tools_insert_timedate" group="tools_operations"/>
 </Menu>
</MenuBar>
</kpartplugin>

The header file

timedate.h

// Avoid multiple header inclusion
#ifndef TIMEDATE_H
#define TIMEDATE_H

// Include the basics
#include <ktexteditor/plugin.h>
#include <ktexteditor/view.h>
#include <kxmlguiclient.h>
#include <klocalizedstring.h>

#include <QtCore/QEvent>
#include <QtCore/QObject>
#include <QtCore/QList>

// This is the default string that will be printed out. As not everybody prints
// it by default as: MM-DD-YYYY HH:MM, but for example, on other cultures we can
// find DD-MM-YYYY HH:MM, we mark this default string for translators to translate
// it. With this macro I18N_NOOP2 we are able to add comments for making the translation
// easier and in context. If a translator sees "%m-%e-%Y %H:%M" can think: "what is this
// guy talking about?". So we add the explanation on the first parameter.
// Anyway, this is not important, do not get stucked here. If you do not understand
// this declaration, think of it as:
//
// static QString localizedTimeDate = "%m-%e-%Y %H:%M";

static QString localizedTimeDate =
    I18N_NOOP2("This is a localized string for default time & date printing on kate document."
               "%e means day in XX format."
               "%m means month in XX format."
               "%Y means year in XXXX format."
               "%H means hours in XX format."
               "%M means minutes in XX format."
               "Please, if in your language time or date is written in a different order, change it here",
               "%m-%e-%Y %H:%M");


/**
  * This is the plugin class. There will be only one instance of this class.
  * We always want to inherit KTextEditor::Plugin here.
  */
class TimeDatePlugin
  : public KTextEditor::Plugin
{
  public:
    // Constructor
    explicit TimeDatePlugin(QObject *parent = 0,
                            const QStringList &args = QStringList());
    // Destructor
    virtual ~TimeDatePlugin();

    // Overriden methods
    // This method is called when a plugin has to be added to a view. As there
    // is only one instance of this plugin, but it is possible for plugins to
    // behave in different ways in different opened views where it is loaded, in
    // Kate plugins are added to views. For that reason we have the plugin itself
    // (this class) and then the plugin view class.
    // In this methods we have to create/remove TimeDatePluginView classes.
    void addView (KTextEditor::View *view);
    void removeView (KTextEditor::View *view);

    void readConfig();
    void writeConfig();

    virtual void readConfig (KConfig *) {}
    virtual void writeConfig (KConfig *) {}

  private:
    QList<class TimeDatePluginView*> m_views;
};

/**
  * This is the plugin view class. There can be as much instances as views exist.
  */
class TimeDatePluginView
   : public QObject, public KXMLGUIClient
{
  Q_OBJECT

  public:
    explicit TimeDatePluginView(KTextEditor::View *view = 0);
    ~TimeDatePluginView();

  private Q_SLOTS:
    void slotInsertTimeDate();

  private:
    KTextEditor::View *m_view;
};

#endif // TIMEDATE_H

The source file

timedate.cpp

// Own includes
#include "timedate.h"

// Include the basics
#include <ktexteditor/document.h>

#include <kgenericfactory.h>
#include <klocale.h>
#include <kaction.h>
#include <kactioncollection.h>
#include <kdatetime.h>

// Without this macro call, the library loader won't find our plugin when trying
// to load it. This macro adds code automagically that will let our plugin
// be loaded on runtime.
// The first parameter is the X-KDE-FactoryName on the .desktop file.
// As we haven't provided such parameter, in this case (because our library is only
// exporting one symbol, this plugin), we put here the X-KDE-LibraryName.
// The second parameter will determine which type is our class, in this case it is
// a TimeDatePlugin and the name of the X-KDE-FactoryName again. Same as before,
// as we do not have X-KDE-FactoryName, we put there the X-KDE-LibraryName.
// Is important to provide as last parameter "ktexteditor_plugins".
K_EXPORT_COMPONENT_FACTORY(ktexteditor_timedate, KGenericFactory<TimeDatePlugin>("ktexteditor_timedate", "ktexteditor_plugins"))

// Constructor
TimeDatePlugin::TimeDatePlugin(QObject *parent, const QStringList &args)
    : KTextEditor::Plugin(parent)
{
    // Avoid warning on compile time because of unused argument
    Q_UNUSED(args);
}

// Destructor
TimeDatePlugin::~TimeDatePlugin()
{
}

// Create the plugin view class and add it to the views list
void TimeDatePlugin::addView(KTextEditor::View *view)
{
    TimeDatePluginView *nview = new TimeDatePluginView(view);
    m_views.append(nview);
}

// Find the view where we want to remove the plugin from, and remove it.
// Do not forget to free the memory.
void TimeDatePlugin::removeView(KTextEditor::View *view)
{
    for (int z = 0; z < m_views.size(); z++)
    {
        if (m_views.at(z)->parentClient() == view)
        {
            TimeDatePluginView *nview = m_views.at(z);
            m_views.removeAll(nview);
            delete nview;
        }
    }
}

// We do nothing on this methods since our plugin is not configurable yet
void TimeDatePlugin::readConfig()
{
}

void TimeDatePlugin::writeConfig()
{
}

// Plugin view class
TimeDatePluginView::TimeDatePluginView(KTextEditor::View *view)
  : QObject(view)
  , KXMLGUIClient(view)
  , m_view(view)
{
    // Insert the plugin
    view->insertChildClient(this);
    setComponentData(KGenericFactory<TimeDatePlugin>::componentData());

    KAction *action = new KAction(i18n("Insert Time && Date"), this);
    // Here we need as first parameter the same we declared at the resource
    // contents file (timedateui.rc). We named the action "tools_insert_timedate".
    // Here is where we connect it to an actual KDE action.
    actionCollection()->addAction("tools_insert_timedate", action);
    action->setShortcut(Qt::CTRL + Qt::Key_D);
    // As usual, we connect the signal triggered() to a slot here. When the menu
    // element is clicked, we go to the slot slotInsertTimeDate().
    connect(action, SIGNAL(triggered()), this, SLOT(slotInsertTimeDate()));

    // This is always needed, tell the KDE XML GUI client that we are using
    // that file for reading actions from.
    setXMLFile("timedateui.rc");
}

// Destructor
TimeDatePluginView::~TimeDatePluginView()
{
}

// The slot that will be called when the menu element "Insert Time & Date" is
// clicked.
void TimeDatePluginView::slotInsertTimeDate()
{
    // We create a KDateTime object with the current time & date.
    KDateTime dt(QDateTime::currentDateTime());
    // We insert the information in the document at the current cursor position
    // with the default string declared on the header.
    m_view->document()->insertText(m_view->cursorPosition(), dt.toString(localizedTimeDate));
}

// We need to include the moc file since we have declared slots and we are using
// the Q_OBJECT macro on the TimeDatePluginView class.
#include "timedate.moc"

Building it all, the CMakeLists.txt

Finally, to put everything together you need to build everything, to tell cmake what needs to go where there is the CMakeLists.txt file.

For more details on CMake please read Development/Tutorials/CMake

# We are calling our plugin "ktexteditor_timedate", and it contains only
# one source file: timedate.cpp.
kde4_add_plugin(ktexteditor_timedate timedate.cpp)

# We need to link our plugin against kdecore libs, as well as ktexteditor
target_link_libraries(ktexteditor_timedate ${KDE4_KDECORE_LIBS} ktexteditor)

# Well, we want to install our plugin on the plugin directory
install(TARGETS ktexteditor_timedate DESTINATION ${PLUGIN_INSTALL_DIR})

# We also want to install the resource contents file on the data directory, at
# the subdirectory of our plugin name, so it does not mix up with other resource
# contents files.
install(FILES timedateui.rc DESTINATION ${DATA_INSTALL_DIR}/ktexteditor_timedate)

# We want to install the desktop file that describes our plugin too. It will go
# on the services directory.
install(FILES ktexteditor_timedate.desktop DESTINATION ${SERVICES_INSTALL_DIR})

The next part

Now you are ready for adding to this plugin a configuration dialog that lets the user customize the way the string is printed out on the screen.