Difference between revisions of "Development/Tutorials/Using KActions"

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{{TutorialBrowser|
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series=Beginner Tutorial|
 +
 +
name=How To Use KActions and XMLGUI|
 +
 +
pre=[[Development/Tutorials/Using_KXmlGuiWindow|Tutorial 2 - KXmlGuiWindow]], Basic XML knowledge|
 +
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next=[[Development/Tutorials/Saving_and_loading|Tutorial 4 - Saving and loading]]|
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reading=None
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}}
 +
 
==Abstract==
 
==Abstract==
We're going to introduce the concept of actions. Actions are a unified way of supplying the user with ways to interact with your program.
+
This tutorial introduces the concept of actions. Actions are a unified way of supplying the user with ways to interact with your program.
  
Say, for example, we want to let the user clear the text box by clicking a button in the toolbar, from an option in the File menu or through a keyboard shortcut; we can provide all of those through one {{class|KAction}}.
+
For example, if we wanted to let the user of [[Development/Tutorials/Using_KXmlGuiWindow|Tutorial 2 ]] clear the text box by clicking a button in the toolbar, from an option in the File menu or through a keyboard shortcut, it could all be done with one {{class|KAction}}.
  
 
[[image:introtokdetutorial3.png|frame|center]]
 
[[image:introtokdetutorial3.png|frame|center]]
 
==Prerequisites==
 
* [[Development/Tutorials/Programming_Tutorial_KDE_4/Using_KMainWindow|Tutorial 2 - KMainWindow]]
 
* Basic XML knowledge (if you're written HTML, you should be fine)
 
  
 
==KAction==
 
==KAction==
A {{class|KAction}} is an object which contains all the information about the icon and shortcuts you want associated to a certain action. You then connect the action to a [http://doc.trolltech.com/latest/signalsandslots.html slot] which carries out the work of you action.
+
A {{class|KAction}} is an object which contains all the information about the icon and shortcuts that is associated with a certain action. The action is then connected to a [http://doc.trolltech.com/latest/signalsandslots.html slot] which carries out the work of your action.
  
===Creating Your Own===
+
== The Code ==
  
To create an action, you need to <tt>#include <KAction></tt> in your <tt>.cpp</tt> file.
+
===main.cpp===
=====Creating the object=====
+
<syntaxhighlight lang="cpp-qt">
We're going to create an action which will clear the text area (see Tutorial 2). The KAction is built up in a number of steps. The first is creating the KAction
+
#include <KApplication>
<code cppqt>KAction* clearAction = new KAction(actionCollection(), "clear");</code>
+
#include <KAboutData>
This creates a KAction called <tt>clearAction</tt>. The first constructor argument is telling the action that it is part of the <tt>{{class|KActionCollection}} actionCollection()</tt> and the second is simply setting a name for internal use (it doesn't necessarily have to be textually similar to the function of the action).
+
#include <KCmdLineArgs>
=====Text=====
+
Now we have out KAction object, we can start setting its properties. First, we'll set the text that will be displayed in the menu and under its icon in the toolbar.
+
<code cppqt>clearAction->setText(i18n("Clear"));</code>
+
As you can see, the text must be passed through the i18n() function if you want your UI to be translatable.
+
=====Icon=====
+
If you're going to display the action in a toolbar, you're going to want to have an icon depicting the action. To set an icon we simply use the <tt>setIcon()</tt> function thus:
+
<code cppqt>clearAction->setIcon(KIcon("filenew"));</code>
+
Here we're setting the icon to the standard KDE <tt>filenew</tt> icon.
+
=====Shortcut=====
+
We can also set a shortcut that will perform our action. It's as simple as a
+
<code cppqt>clearAction->setShortcut(Qt::CTRL+Qt::Key_W);</code>
+
to set Ctrl+W to be associated to this action.
+
=====Connecting the action=====
+
Now our action is fully set up, we need to connect it to something useful. We're going to connect our action to the <tt>clear()</tt> action belonging to a KTextArea.
+
<code cppqt>
+
connect( clearAction, SIGNAL( triggered(bool) ),
+
        textArea, SLOT( clear() ) );
+
</code>
+
This is the same as it would be done in Qt with a {{qt|QAction}}.
+
  
===KStandardAction===
+
#include "mainwindow.h"
  
For actions which would likely appear in almost every KDE application such as 'quit', 'save', and 'load' there are pre-created convenience KActions, accessed through {{class|KStandardAction}}.
+
int main (int argc, char *argv[])
 
+
{
They are very simple to use. Once you've done <tt>#include <KStandardAction></tt>, you simply need to supply it with what you want the function to do and which KActionCollection to add it to. For example,
+
  KAboutData aboutData( "tutorial3", "tutorial3",
<code cppqt>KStandardAction::quit(kapp, SLOT(quit()), actionCollection());</code>
+
      ki18n("Tutorial 3"), "1.0",
Will Create a KAction with the correct icon, text and shortcut and will even add it to the File menu.
+
      ki18n("A simple text area using KAction etc."),
 +
      KAboutData::License_GPL,
 +
      ki18n("Copyright (c) 2007 Developer") );
 +
  KCmdLineArgs::init( argc, argv, &aboutData );
 +
  KApplication app;
 +
 +
  MainWindow* window = new MainWindow();
 +
  window->show();
 +
  return app.exec();
 +
}
 +
</syntaxhighlight>
 +
This time, very little has changed in <tt>main.cpp</tt>, only the KAboutData constructor has been updated to show that we are now on tutorial 3.
  
==The Code==
 
 
===mainwindow.h===
 
===mainwindow.h===
<code cppqt n>
+
<syntaxhighlight lang="cpp-qt">
 
#ifndef MAINWINDOW_H
 
#ifndef MAINWINDOW_H
 
#define MAINWINDOW_H
 
#define MAINWINDOW_H
  
#include <KMainWindow>
+
#include <KXmlGuiWindow>
 
#include <KTextEdit>
 
#include <KTextEdit>
  
class MainWindow : public KMainWindow
+
class MainWindow : public KXmlGuiWindow
 
{
 
{
 
   public:
 
   public:
Line 68: Line 69:
  
 
#endif
 
#endif
</code>
+
</syntaxhighlight>
 +
Only a function <tt>void setupActions()</tt> has been added which will do all the work setting up the KActions.
 +
 
 
===mainwindow.cpp===
 
===mainwindow.cpp===
<code cppqt n>
+
<syntaxhighlight lang="cpp-qt">
 
#include "mainwindow.h"
 
#include "mainwindow.h"
  
 
#include <KApplication>
 
#include <KApplication>
 
#include <KAction>
 
#include <KAction>
 +
#include <KLocale>
 +
#include <KActionCollection>
 
#include <KStandardAction>
 
#include <KStandardAction>
  
MainWindow::MainWindow(QWidget *parent) : KMainWindow(parent)
+
MainWindow::MainWindow(QWidget *parent)
 +
    : KXmlGuiWindow(parent)
 
{
 
{
 
   textArea = new KTextEdit;
 
   textArea = new KTextEdit;
Line 87: Line 93:
 
void MainWindow::setupActions()
 
void MainWindow::setupActions()
 
{
 
{
   KAction* clearAction = new KAction(actionCollection(), "clear");
+
   KAction* clearAction = new KAction(this);
   clearAction->setText(i18n("Clear"));
+
   clearAction->setText(i18n("&Clear"));
   clearAction->setIcon(KIcon("filenew"));
+
   clearAction->setIcon(KIcon("document-new"));
   clearAction->setShortcut(Qt::CTRL+Qt::Key_W);
+
   clearAction->setShortcut(Qt::CTRL + Qt::Key_W);
   connect(clearAction, SIGNAL(triggered(bool)),  
+
  actionCollection()->addAction("clear", clearAction);
 +
   connect(clearAction, SIGNAL(triggered(bool)),
 
           textArea, SLOT(clear()));
 
           textArea, SLOT(clear()));
  
   KStandardAction::quit(kapp, SLOT(quit()), actionCollection());
+
   KStandardAction::quit(kapp, SLOT(quit()),
 +
                        actionCollection());
  
   setupGUI();
+
   setupGUI(Default, "tutorial3ui.rc");
 
}
 
}
</code>
+
</syntaxhighlight>
===main.cpp===
+
<code cppqt n>
+
#include <KApplication>
+
#include <KAboutData>
+
#include <KCmdLineArgs>
+
  
#include "mainwindow.h"
+
==Explanation==
 +
This builds upon the KXmlGuiWindow code from [[Development/Tutorials/Using_KXmlGuiWindow|Tutorial 2]]. Most of the changes are to <tt>mainwindow.cpp</tt>, an important structural change being that the constructor for MainWindow now calls <tt>setupActions()</tt> instead of <tt>setupGUI()</tt>. <tt>setupActions()</tt> is where the new KAction code goes before finally calling <tt>setupGUI()</tt> itself.
  
int main (int argc, char *argv[])
+
===Creating the KAction object===
{
+
The KAction is built up in a number of steps. The first is including the <tt>KAction</tt> library and then creating the KAction:
  KAboutData aboutData( "tutorial3", "Tutorial 3",
+
<syntaxhighlight lang="cpp-qt">
      "1.0", "A simple text area using KAction etc.",
+
#include <KAction>
      KAboutData::License_GPL, "(c) 2006" );
+
...
  KCmdLineArgs::init( argc, argv, &aboutData );
+
KAction* clearAction = new KAction(this);
  KApplication app;
+
</syntaxhighlight>
+
This creates a new KAction called <tt>clearAction</tt>.
  MainWindow* window = new MainWindow();
+
 
  window->show();
+
===Setting KAction Properties===
  return app.exec();
+
====Text====
}
+
Now that we have our KAction object, we can start setting its properties. The following code sets the text that will be displayed in the menu and under the <tt>KAction</tt>'s icon in the toolbar.
</code>
+
<syntaxhighlight lang="cpp-qt">
 +
clearAction->setText(i18n("&Clear"));
 +
</syntaxhighlight>
 +
Note that the text is passed through the <tt>i18n()</tt> function; this is necessary for the UI to be translatable (more information on this can be found in the [[Development/Tutorials/Localization/i18n|i18n tutorial]]).
 +
 
 +
The text of the action should contain a <tt>&</tt> because that makes it easier to translate in non-latin1 languages. In Japanese, the translation might be <tt>ソース(&S)</tt> and without the <tt>&</tt> in the english text the translators cannot know if they have to add a <tt>&</tt> or not.
 +
 
 +
====Icon====
 +
If the action is going to be displayed in a toolbar, it is nice to have an icon depicting the action. The following code sets the icon to the standard KDE <tt>document-new</tt> icon through the use of the <tt>setIcon()</tt> function:
 +
<syntaxhighlight lang="cpp-qt">
 +
clearAction->setIcon(KIcon("document-new"));
 +
</syntaxhighlight>
 +
 
 +
====Keyboard Shortcut====
 +
Setting a keyboard shortcut to perform our action is equally simple:
 +
<syntaxhighlight lang="cpp-qt">
 +
clearAction->setShortcut(Qt::CTRL + Qt::Key_W);
 +
</syntaxhighlight>
 +
This associates Ctrl+W with the KAction.
 +
 
 +
===Adding to the Collection===
 +
In order for the action to be accessed by the XMLGUI framework (explained in depth later) it must be added to the application's ''action collection''. The action collection is accessed via the <tt>actionCollection()</tt> function like this:
 +
<syntaxhighlight lang="cpp-qt">
 +
actionCollection()->addAction("clear", clearAction);
 +
</syntaxhighlight>
 +
Here, the <tt>clearAction</tt> KAction is added to the collection and given a name of ''clear''. This name (''clear'') is used by the XMLGUI framework to refer to the action, ergo, it should not be localized, since it is used internally only.
 +
 
 +
====Connecting the action====
 +
Now that the action is fully set up, it needs to be connected to something useful. In this case (because we want to clear the text area), we connect our action to the <tt>clear()</tt> action belonging to a KTextEdit (which, unsurprisingly, clears the KTextEdit)
 +
<syntaxhighlight lang="cpp-qt">
 +
connect( clearAction, SIGNAL( triggered(bool) ),
 +
        textArea, SLOT( clear() ) );
 +
</syntaxhighlight>
 +
This is the same as it would be done in Qt with a {{qt|QAction}}.
 +
 
 +
===KStandardAction===
 +
 
 +
For actions which would likely appear in almost every KDE application such as 'quit', 'save', and 'load' there are pre-created convenience KActions, accessed through [http://api.kde.org/4.0-api/kdelibs-apidocs/kdeui/html/namespaceKStandardAction.html KStandardAction].
 +
 
 +
They are very simple to use. Once the library has been included (<tt>#include <KStandardAction></tt>), simply supply it with what you want the function to do and which KActionCollection to add it to. For example:
 +
<syntaxhighlight lang="cpp-qt">
 +
KStandardAction::quit(kapp, SLOT(quit()), actionCollection());
 +
</syntaxhighlight>
 +
This creates a KAction with the correct icon, text and shortcut and even adds it to the File menu.
 +
 
 +
==Adding the action to menus and toolbars==
 +
At the moment, the new "Clear" action has been created but it hasn't been associated with any menus or toolbars. This is done with a KDE technology called XMLGUI, which does nice things like movable toolbars for you.
  
==Putting the actions in the menus and toolbars==
+
==Defining your own help menu==
Now, at the moment, we've only created our new "Clear" action. It won't yet show up in the menus or in the toolbars. To tell the program where to put our actions (and to allow the end-user to move them around) we use a KDE technology called XMLGUI.
+
The help menu is god-given, that is why all KDE help menus look the same. If you want to create your own help menu, search for the explanation around showAboutApplication() in kdelibs.
===XMLGUI===
+
TODO: Mentioning that it will be replaced by liveui
+
  
When you call <tt>setupGUI()</tt> in your {{class|KMainWindow}} class, it calls the XMLGUI system which reads an XML file description of your interface (which we will create in a minute) and creates the buttons and menus appropriately.
+
==XMLGUI==
  
Now obviously XMLGUI needs to know which file is your description file, i.e. it needs to know its name and location. The rule for the naming is the file should be called <tt>appnameui.rc</tt> (where <tt>appname</tt> is the name you set in {{class|KAboutData}}), so in our example, the file will be called <tt>tutorial3ui.rc</tt>. Where the file will be located is handled by CMake.
+
The <tt>setupGUI()</tt> function in {{class|KXmlGuiWindow}} depends on the XMLGUI system to construct the GUI, which XMLGUI does by parsing an XML file description of the interface.
  
===Writing your ''appname''ui.rc File===
+
The rule for naming this XML file is <tt>appnameui.rc</tt>, where <tt>appname</tt> is the name you set in {{class|KAboutData}} (in this case, ''tutorial3''). So in our example, the file is called <tt>tutorial3ui.rc</tt>, and is located in the build directory. Where the file will ultimately be placed is handled by CMake.
  
Since the description of our UI is being defined with XML, the layout of the description must follow strict rules. We won't go through all the rules in this tutorial but for more information, see the _detailed_XMLGUI_page_ (once we have a full explanation of XMLGUI (or possibly liveui if that's done soon :)) on the wiki, I'll link it up).
+
==''appname''ui.rc File==
  
TODO: Walk through what the code below means
+
Since the description of the UI is defined with XML, the layout must follow strict rules. This tutorial will not go into great depth on this topic, but for more information, see the [[Development/Architecture/KDE4/XMLGUI_Technology|detailed XMLGUI page]] (here is an older tutorial: [http://developer.kde.org/documentation/tutorials/xmlui/preface.html]).
  
 
===tutorial3ui.rc===
 
===tutorial3ui.rc===
<code xml n>
+
<syntaxhighlight lang="xml">
 
<?xml version="1.0" encoding="UTF-8"?>
 
<?xml version="1.0" encoding="UTF-8"?>
<kcfg xmlns="http://www.kde.org/standards/kcfg/1.0"
+
<gui name="tutorial3"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+
    version="1"
      xsi:schemaLocation="http://www.kde.org/standards/kcfg/1.0
+
    xmlns="http://www.kde.org/standards/kxmlgui/1.0"
                          http://www.kde.org/standards/kcfg/1.0/kcfg.xsd" >
+
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  <ToolBar name="mainToolBar" >
+
    xsi:schemaLocation="http://www.kde.org/standards/kxmlgui/1.0
    <text>Main Toolbar</text>
+
                        http://www.kde.org/standards/kxmlgui/1.0/kxmlgui.xsd" >
    <Action name="clear" />
+
 
  </ToolBar>
+
 
   <MenuBar>
 
   <MenuBar>
 
     <Menu name="file" >
 
     <Menu name="file" >
      <text>&amp;File</text>
 
 
       <Action name="clear" />
 
       <Action name="clear" />
 
     </Menu>
 
     </Menu>
 
   </MenuBar>
 
   </MenuBar>
</kcfg>
+
 
</code>
+
  <ToolBar name="mainToolBar" >
 +
    <text>Main Toolbar</text>
 +
    <Action name="clear" />
 +
  </ToolBar>
 +
 
 +
</gui>
 +
</syntaxhighlight>
 +
 
 +
The <tt><Toolbar></tt> tag allows you to describe the toolbar, which is the bar across the top of the window normally with icons. Here it is given the unique name ''mainToolBar'' and its user visible name set to ''Main Toolbar'' using the <tt><text></tt> tag. The clear action is added to the toolbar using the <tt><Action></tt> tag, the name parameter in this tag being the string that was passed to the KActionCollection with <tt>addAction()</tt> in <tt>mainwindow.cpp</tt>.
 +
 
 +
Besides having the action in the toolbar, it can also be added to the menubar. Here the action is being added to the ''File'' menu of the <tt>MenuBar</tt> the same way it was added to the toolbar.
 +
 
 +
Change the 'version' attribute of the <tt><nowiki><gui></nowiki></tt> tag if you changed .rc file since the last install to force a system cache update. Be sure it is an integer, if you use a decimal value, it will not work, but will not notify that it didn't. '
 +
 
 +
{{Warning|The version attribute must be an integer number, if you type in version<nowiki>=</nowiki>"1.2" it will dispose of your kittens  (but not eat them).}}
 +
 
 +
Some notes on the interaction between code and the .rc file: Menus appear automatically and should have a <tt><nowiki><text/></nowiki></tt> child tag unless they refer to standard menus. Actions need to be created manually and inserted into the actionCollection() using the name in the .rc file. Actions can be hidden or disabled, whereas menus can't.
  
 
==CMake==
 
==CMake==
Now that we're using XMLGUI, we need to put the <tt>tutorial3ui.rc</tt> somewhere where KDE can find it. This means we need to install our project somewhere.
+
Finally, the <tt>tutorial3ui.rc</tt> needs to go somewhere where KDE can find it (can't just leave it in the source directory!). '''This means the project needs to be installed somewhere.'''
 
===CMakeLists.txt===
 
===CMakeLists.txt===
<code ini n>
+
<syntaxhighlight lang="cmake">
PROJECT(tutorial3)
+
project(tutorial3)
  
FIND_PACKAGE(KDE4 REQUIRED)
+
find_package(KDE4 REQUIRED)
INCLUDE_DIRECTORIES( ${KDE4_INCLUDES} )
+
include_directories(${KDE4_INCLUDES})
  
SET(tutorial3_SRCS  
+
set(tutorial3_SRCS  
 
   main.cpp
 
   main.cpp
 
   mainwindow.cpp
 
   mainwindow.cpp
 
)
 
)
  
KDE4_ADD_EXECUTABLE(tutorial3 ${tutorial3_SRCS})
+
kde4_add_executable(tutorial3 ${tutorial3_SRCS})
  
TARGET_LINK_LIBRARIES( tutorial3 ${KDE4_KDEUI_LIBS})
+
target_link_libraries(tutorial3 ${KDE4_KDEUI_LIBS})
  
 
install(TARGETS tutorial3 DESTINATION ${BIN_INSTALL_DIR})
 
install(TARGETS tutorial3 DESTINATION ${BIN_INSTALL_DIR})
install( FILES tutorial3ui.rc DESTINATION  ${DATA_INSTALL_DIR}/tutorial3 )
+
install(FILES tutorial3ui.rc  
</code>
+
        DESTINATION  ${DATA_INSTALL_DIR}/tutorial3)
 +
</syntaxhighlight>
 +
 
 +
This file is almost identical to the one for tutorial2, but with two extra lines at the end that describe where the files are to be installed. Firstly, the <tt>tutorial3</tt> target is installed to the <tt>BIN_INSTALL_DIR</tt> then the <tt>tutorial3ui.rc</tt> file that describes the layout of the user interface is installed to the application's data directory.
 +
 
 
===Make, Install And Run===
 
===Make, Install And Run===
 
If you don't have write access to where your KDE4 installation directory, you can install it to a folder in your home directory.
 
If you don't have write access to where your KDE4 installation directory, you can install it to a folder in your home directory.
  
To tell CMake where to install the program, set the <tt>DCMAKE_INSTALL_PREFIX</tt> switch. So to install the program to the KDE directory, do
+
To tell CMake where to install the program, set the <tt>DCMAKE_INSTALL_PREFIX</tt> switch. You probably just want to install it somewhere local for testing (it's probably a bit silly to go to the effort of installing these tutorials to your KDE directory), so the following might be appropriate:
cmake . -DCMAKE_INSTALL_PREFIX=$KDEDIR
+
<syntaxhighlight lang="bash">
make install
+
mkdir build && cd build
tutorial3
+
cmake .. -DCMAKE_INSTALL_PREFIX=$HOME
Though, if you just want to install it somewhere local for testing (it's probably a bit silly to go to the effort of installing these tutorials to your KDE directory) you can do something like
+
make install
cmake . -DCMAKE_INSTALL_PREFIX=/home/user/kdetmp
+
$HOME/bin/tutorial3
which will create a KDE-like directory structure under ~/kdetmp
+
</syntaxhighlight>
 +
which will create a KDE-like directory structure in your user's home directory and will install the executable to {{path|$HOME/bin/tutorial3}}.
 +
 
 
==Moving On==
 
==Moving On==
Now that we can make the GUI look like and do whatever we want, we can move on to storing application settings with [[Development/Tutorials/Programming_Tutorial_KDE_4/Using_KConfig|KConfig XT]].
+
Now you can move on to [[Development/Tutorials/Saving_and_loading|saving and loading]].
[[Category:Tutorial]]
+
 
 +
Or you can learn [[Development/Tutorial/Icons|how to add icons to your application]].
 +
 
 +
Or you can learn [[Development/Tutorials/Desktop_File|how to place your application in the K-Menu using .desktop files]].
 +
 
 
[[Category:C++]]
 
[[Category:C++]]

Revision as of 16:18, 13 July 2012

How To Use KActions and XMLGUI
Tutorial Series   Beginner Tutorial
Previous   Tutorial 2 - KXmlGuiWindow, Basic XML knowledge
What's Next   Tutorial 4 - Saving and loading
Further Reading   None

Contents

Abstract

This tutorial introduces the concept of actions. Actions are a unified way of supplying the user with ways to interact with your program.

For example, if we wanted to let the user of Tutorial 2 clear the text box by clicking a button in the toolbar, from an option in the File menu or through a keyboard shortcut, it could all be done with one KAction.

Introtokdetutorial3.png

KAction

A KAction is an object which contains all the information about the icon and shortcuts that is associated with a certain action. The action is then connected to a slot which carries out the work of your action.

The Code

main.cpp

#include <KApplication>
#include <KAboutData>
#include <KCmdLineArgs>
 
#include "mainwindow.h"
 
int main (int argc, char *argv[])
{
  KAboutData aboutData( "tutorial3", "tutorial3",
      ki18n("Tutorial 3"), "1.0",
      ki18n("A simple text area using KAction etc."),
      KAboutData::License_GPL,
      ki18n("Copyright (c) 2007 Developer") );
  KCmdLineArgs::init( argc, argv, &aboutData );
  KApplication app;
 
  MainWindow* window = new MainWindow();
  window->show();
  return app.exec();
}

This time, very little has changed in main.cpp, only the KAboutData constructor has been updated to show that we are now on tutorial 3.

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <KXmlGuiWindow>
#include <KTextEdit>
 
class MainWindow : public KXmlGuiWindow
{
  public:
    MainWindow(QWidget *parent=0);
 
  private:
    KTextEdit* textArea;
    void setupActions();
};
 
#endif

Only a function void setupActions() has been added which will do all the work setting up the KActions.

mainwindow.cpp

#include "mainwindow.h"
 
#include <KApplication>
#include <KAction>
#include <KLocale>
#include <KActionCollection>
#include <KStandardAction>
 
MainWindow::MainWindow(QWidget *parent)
    : KXmlGuiWindow(parent)
{
  textArea = new KTextEdit;
  setCentralWidget(textArea);
 
  setupActions();
}
 
void MainWindow::setupActions()
{
  KAction* clearAction = new KAction(this);
  clearAction->setText(i18n("&Clear"));
  clearAction->setIcon(KIcon("document-new"));
  clearAction->setShortcut(Qt::CTRL + Qt::Key_W);
  actionCollection()->addAction("clear", clearAction);
  connect(clearAction, SIGNAL(triggered(bool)),
          textArea, SLOT(clear()));
 
  KStandardAction::quit(kapp, SLOT(quit()),
                        actionCollection());
 
  setupGUI(Default, "tutorial3ui.rc");
}

Explanation

This builds upon the KXmlGuiWindow code from Tutorial 2. Most of the changes are to mainwindow.cpp, an important structural change being that the constructor for MainWindow now calls setupActions() instead of setupGUI(). setupActions() is where the new KAction code goes before finally calling setupGUI() itself.

Creating the KAction object

The KAction is built up in a number of steps. The first is including the KAction library and then creating the KAction:

#include <KAction>
...
KAction* clearAction = new KAction(this);

This creates a new KAction called clearAction.

Setting KAction Properties

Text

Now that we have our KAction object, we can start setting its properties. The following code sets the text that will be displayed in the menu and under the KAction's icon in the toolbar.

clearAction->setText(i18n("&Clear"));

Note that the text is passed through the i18n() function; this is necessary for the UI to be translatable (more information on this can be found in the i18n tutorial).

The text of the action should contain a & because that makes it easier to translate in non-latin1 languages. In Japanese, the translation might be ソース(&S) and without the & in the english text the translators cannot know if they have to add a & or not.

Icon

If the action is going to be displayed in a toolbar, it is nice to have an icon depicting the action. The following code sets the icon to the standard KDE document-new icon through the use of the setIcon() function:

clearAction->setIcon(KIcon("document-new"));

Keyboard Shortcut

Setting a keyboard shortcut to perform our action is equally simple:

clearAction->setShortcut(Qt::CTRL + Qt::Key_W);

This associates Ctrl+W with the KAction.

Adding to the Collection

In order for the action to be accessed by the XMLGUI framework (explained in depth later) it must be added to the application's action collection. The action collection is accessed via the actionCollection() function like this:

actionCollection()->addAction("clear", clearAction);

Here, the clearAction KAction is added to the collection and given a name of clear. This name (clear) is used by the XMLGUI framework to refer to the action, ergo, it should not be localized, since it is used internally only.

Connecting the action

Now that the action is fully set up, it needs to be connected to something useful. In this case (because we want to clear the text area), we connect our action to the clear() action belonging to a KTextEdit (which, unsurprisingly, clears the KTextEdit)

connect( clearAction, SIGNAL( triggered(bool) ), 
         textArea, SLOT( clear() ) );

This is the same as it would be done in Qt with a QAction.

KStandardAction

For actions which would likely appear in almost every KDE application such as 'quit', 'save', and 'load' there are pre-created convenience KActions, accessed through KStandardAction.

They are very simple to use. Once the library has been included (#include <KStandardAction>), simply supply it with what you want the function to do and which KActionCollection to add it to. For example:

KStandardAction::quit(kapp, SLOT(quit()), actionCollection());

This creates a KAction with the correct icon, text and shortcut and even adds it to the File menu.

Adding the action to menus and toolbars

At the moment, the new "Clear" action has been created but it hasn't been associated with any menus or toolbars. This is done with a KDE technology called XMLGUI, which does nice things like movable toolbars for you.

Defining your own help menu

The help menu is god-given, that is why all KDE help menus look the same. If you want to create your own help menu, search for the explanation around showAboutApplication() in kdelibs.

XMLGUI

The setupGUI() function in KXmlGuiWindow depends on the XMLGUI system to construct the GUI, which XMLGUI does by parsing an XML file description of the interface.

The rule for naming this XML file is appnameui.rc, where appname is the name you set in KAboutData (in this case, tutorial3). So in our example, the file is called tutorial3ui.rc, and is located in the build directory. Where the file will ultimately be placed is handled by CMake.

appnameui.rc File

Since the description of the UI is defined with XML, the layout must follow strict rules. This tutorial will not go into great depth on this topic, but for more information, see the detailed XMLGUI page (here is an older tutorial: [1]).

tutorial3ui.rc

<?xml version="1.0" encoding="UTF-8"?>
<gui name="tutorial3"
     version="1"
     xmlns="http://www.kde.org/standards/kxmlgui/1.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://www.kde.org/standards/kxmlgui/1.0
                         http://www.kde.org/standards/kxmlgui/1.0/kxmlgui.xsd" >
 
  <MenuBar>
    <Menu name="file" >
      <Action name="clear" />
    </Menu>
  </MenuBar>
 
  <ToolBar name="mainToolBar" >
    <text>Main Toolbar</text>
    <Action name="clear" />
  </ToolBar>
 
</gui>

The <Toolbar> tag allows you to describe the toolbar, which is the bar across the top of the window normally with icons. Here it is given the unique name mainToolBar and its user visible name set to Main Toolbar using the <text> tag. The clear action is added to the toolbar using the <Action> tag, the name parameter in this tag being the string that was passed to the KActionCollection with addAction() in mainwindow.cpp.

Besides having the action in the toolbar, it can also be added to the menubar. Here the action is being added to the File menu of the MenuBar the same way it was added to the toolbar.

Change the 'version' attribute of the <gui> tag if you changed .rc file since the last install to force a system cache update. Be sure it is an integer, if you use a decimal value, it will not work, but will not notify that it didn't. '

noframe
 
Warning
The version attribute must be an integer number, if you type in version="1.2" it will dispose of your kittens (but not eat them).


Some notes on the interaction between code and the .rc file: Menus appear automatically and should have a <text/> child tag unless they refer to standard menus. Actions need to be created manually and inserted into the actionCollection() using the name in the .rc file. Actions can be hidden or disabled, whereas menus can't.

CMake

Finally, the tutorial3ui.rc needs to go somewhere where KDE can find it (can't just leave it in the source directory!). This means the project needs to be installed somewhere.

CMakeLists.txt

project(tutorial3)
 
find_package(KDE4 REQUIRED)
include_directories(${KDE4_INCLUDES})
 
set(tutorial3_SRCS 
  main.cpp
  mainwindow.cpp
)
 
kde4_add_executable(tutorial3 ${tutorial3_SRCS})
 
target_link_libraries(tutorial3 ${KDE4_KDEUI_LIBS})
 
install(TARGETS tutorial3 DESTINATION ${BIN_INSTALL_DIR})
install(FILES tutorial3ui.rc 
        DESTINATION  ${DATA_INSTALL_DIR}/tutorial3)

This file is almost identical to the one for tutorial2, but with two extra lines at the end that describe where the files are to be installed. Firstly, the tutorial3 target is installed to the BIN_INSTALL_DIR then the tutorial3ui.rc file that describes the layout of the user interface is installed to the application's data directory.

Make, Install And Run

If you don't have write access to where your KDE4 installation directory, you can install it to a folder in your home directory.

To tell CMake where to install the program, set the DCMAKE_INSTALL_PREFIX switch. You probably just want to install it somewhere local for testing (it's probably a bit silly to go to the effort of installing these tutorials to your KDE directory), so the following might be appropriate:

mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$HOME
make install
$HOME/bin/tutorial3

which will create a KDE-like directory structure in your user's home directory and will install the executable to $HOME/bin/tutorial3.

Moving On

Now you can move on to saving and loading.

Or you can learn how to add icons to your application.

Or you can learn how to place your application in the K-Menu using .desktop files.


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