Development/Tutorials/Using KActions: Difference between revisions

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{{TutorialBrowser|
 
series=Beginner Tutorial|
 
name=How To Use KActions and XMLGUI|
 
pre=[[Development/Tutorials/Using_KXmlGuiWindow|Tutorial 2 - KXmlGuiWindow]], Basic XML knowledge|
 
next=[[Development/Tutorials/Saving_and_loading|Tutorial 4 - Saving and loading]]|
 
reading=None
}}
 
==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 [[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 [http://doc.qt.io/qt-5/qaction.html QAction].
 
[[image:tutorial3-kf5.png|frame|center]]
 
==QAction==
 
A [http://doc.qt.io/qt-5/qaction.html QAction] 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.qt.io/qt-5/signalsandslots.html slot] which carries out the work of your action.
 
==The Code==
 
===main.cpp===
<syntaxhighlight lang="cpp-qt">
#include <cstdlib>
#include <QApplication>
#include <QCommandLineParser>
 
#include <KAboutData>
#include <KLocalizedString>
 
#include "mainwindow.h"
int main (int argc, char *argv[])
{
    QApplication app(argc, argv);
    KLocalizedString::setApplicationDomain("tutorial3");
   
    KAboutData aboutData(
                        // The program name used internally. (componentName)
                        QStringLiteral("tutorial3"),
                        // A displayable program name string. (displayName)
                        i18n("Tutorial 3"),
                        // The program version string. (version)
                        QStringLiteral("1.0"),
                        // Short description of what the app does. (shortDescription)
                        i18n("A simple text area using KAction etc."),
                        // The license this code is released under
                        KAboutLicense::GPL,
                        // Copyright Statement (copyrightStatement = QString())
                        i18n("(c) 2015"),
                        // Optional text shown in the About box.
                        // Can contain any information desired. (otherText)
                        i18n("Some text..."),
                        // The program homepage string. (homePageAddress = QString())
                        QStringLiteral("http://example.com/"),
                        // The bug report email address
                        // (bugsEmailAddress = QLatin1String("[email protected]")
                        QStringLiteral("submit@bugs.kde.org"));
    aboutData.addAuthor(i18n("Name"), i18n("Task"), QStringLiteral("[email protected]"),
                        QStringLiteral("http://your.website.com"), QStringLiteral("OSC Username"));
    KAboutData::setApplicationData(aboutData);
    QCommandLineParser parser;
    parser.addHelpOption();
    parser.addVersionOption();
    aboutData.setupCommandLine(&parser);
    parser.process(app);
    aboutData.processCommandLine(&parser);
   
    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.
 
===mainwindow.h===
<syntaxhighlight lang="cpp-qt">
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <KXmlGuiWindow>
 
class KTextEdit;
class MainWindow : public KXmlGuiWindow
{
  public:
    MainWindow(QWidget *parent=0);
  private:
    KTextEdit* textArea;
    void setupActions();
};
#endif
</syntaxhighlight>
Only a function <tt>void setupActions()</tt> has been added which will do all the work setting up the QActions.
 
===mainwindow.cpp===
<syntaxhighlight lang="cpp-qt">
#include <QApplication>
#include <QAction>
 
#include <KTextEdit>
#include <KLocalizedString>
#include <KActionCollection>
#include <KStandardAction>
 
#include "mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) : KXmlGuiWindow(parent)
{
  textArea = new KTextEdit();
  setCentralWidget(textArea);
 
  setupActions();
}
 
void MainWindow::setupActions()
{
    QAction* clearAction = new QAction(this);
    clearAction->setText(i18n("&Clear"));
    clearAction->setIcon(QIcon::fromTheme("document-new"));
    actionCollection()->setDefaultShortcut(clearAction, Qt::CTRL + Qt::Key_W);
    actionCollection()->addAction("clear", clearAction);
    connect(clearAction, SIGNAL(triggered(bool)), textArea, SLOT(clear()));
   
    KStandardAction::quit(qApp, SLOT(quit()), actionCollection());
   
    setupGUI(Default, "tutorial3ui.rc");
}
</syntaxhighlight>
 
==Explanation==
 
This builds upon the KXmlGuiWindow code from [[Development/Tutorials/Using_KXmlGuiWindow/KF5|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 QAction code goes before finally calling <tt>setupGUI()</tt> itself.
 
===Creating the QAction object===
The QAction is built up in a number of steps. The first is including the <tt>QAction</tt> header and then creating the QAction:
<syntaxhighlight lang="cpp-qt">
#include <QAction>
...
QAction* clearAction = new QAction(this);
</syntaxhighlight>
This creates a new QAction called <tt>clearAction</tt>.
 
===Setting QAction Properties===
====Text====
Now that we have our QAction object, we can start setting its properties. The following code sets the text that will be displayed in the menu and under the <tt>QAction</tt>'s icon in the toolbar.
<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 the <tt>document-new</tt> icon through the use of the <tt>setIcon()</tt> function:
<syntaxhighlight lang="cpp-qt">
clearAction->setIcon(QIcon::fromTheme("document-new"));
</syntaxhighlight>
 
====Keyboard Shortcut====
Setting a keyboard shortcut to perform our action is equally simple:
<syntaxhighlight lang="cpp-qt">
actionCollection()->setDefaultShortcut(clearAction, Qt::CTRL + Qt::Key_W);
</syntaxhighlight>
This associates Ctrl+W with the QAction.
 
===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> QAction 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>
 
===KStandardAction===
 
For actions which would likely appear in almost every KDE application such as 'quit', 'save', and 'load' there are pre-created convenience QActions, accessed through {{kde|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 QActionCollection to add it to. For example:
<syntaxhighlight lang="cpp-qt">
KStandardAction::quit(qApp, SLOT(quit()), actionCollection());
</syntaxhighlight>
Here we call the QApplicaton's [http://doc.qt.io/qt-5/qapplication.html#quit quit] method whenever the KStandardAction quit is triggered. We are able to access that QApplication method via the [http://doc.qt.io/qt-5/qapplication.html#qApp qApp] macro.
 
In the end, this creates a QAction 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 from the {{class|KHelpMenu}} class in XMLGUI.
 
==XMLGUI==
 
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.
 
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.
 
==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 [[Development/Architecture/KDE4/XMLGUI_Technology|detailed XMLGUI page]].
 
===tutorial3ui.rc===
<syntaxhighlight lang="xml">
<?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>
    <Menu >
      <text>A&amp;nother Menu</text>
      <Action name="clear" />
    </Menu >
  </MenuBar>
  <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==
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''', unlike in the previous tutorials.
 
===CMakeLists.txt===
<syntaxhighlight lang="cmake">
project (tutorial3)
 
cmake_minimum_required(VERSION 2.8.12 FATAL_ERROR)
set(QT_MIN_VERSION "5.3.0")
set(KF5_MIN_VERSION "5.2.0")
 
find_package(ECM 1.0.0 REQUIRED NO_MODULE)
set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH} ${ECM_KDE_MODULE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 
include(KDEInstallDirs)
include(KDECMakeSettings)
include(KDECompilerSettings)
include(FeatureSummary)
 
find_package(Qt5 ${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS
    Core    # QCommandLineParser, QStringLiteral
    Widgets # QApplication, QAction
)
 
find_package(KF5 ${KF5_MIN_VERSION} REQUIRED COMPONENTS
    CoreAddons      # KAboutData
    I18n            # KLocalizedString
    XmlGui          # KXmlGuiWindow, KActionCollection
    TextWidgets    # KTextEdit
    ConfigWidgets  # KStandardActions
)
   
 
feature_summary(WHAT ALL INCLUDE_QUIET_PACKAGES FATAL_ON_MISSING_REQUIRED_PACKAGES)
   
set(tutorial3_SRCS main.cpp mainwindow.cpp)
 
add_executable(tutorial3 ${tutorial3_SRCS})
 
target_link_libraries(tutorial3
    Qt5::Widgets
    KF5::CoreAddons
    KF5::I18n
    KF5::XmlGui
    KF5::TextWidgets
    KF5::ConfigWidgets
)
 
install(TARGETS tutorial3  ${INSTALL_TARGETS_DEFAULT_ARGS})
install(FILES tutorial3ui.rc DESTINATION ${KXMLGUI_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>INSTALL_TARGETS_DEFAULT_ARGS</tt> then the <tt>tutorial3ui.rc</tt> file that describes the layout of the user interface is installed to the application's data directory under <tt>KXMLGUI_INSTALL_DIR</tt>.
 
===Make, Install And Run===
This is probably the trickiest part. Where you install the files, especially <tt>tutorial3ui.rc</tt> is important. Normally, you'd want to install it where KDE software is installed by your distribution, which is usually under {{path|/usr}}. That, however, would require root/admin access and If you don't have that, 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. 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:
<syntaxhighlight lang="bash">
mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$HOME
make install
</syntaxhighlight>
which will create a KDE-like directory structure in your user's home directory. Specifically, it will create the directories {{path|$HOME/bin/}} and {{path|$HOME/share/}} and will install the executable to {{path|$HOME/bin/tutorial3}} and the <tt>tutorial3ui.rc</tt> file to {{path|$HOME/share/kxmlgui/tutorial3/tutorial3ui.rc}}.
 
However, to be able to run the program properly, you will need to let the system know where the XMLGUI file is. Since we installed it in a nonstandard location, we'll have to explicitly to do so every time. The following command would suffice:
<syntaxhighlight lang="bash">
XDG_DATA_DIRS=$HOME/share:$XDG_DATA_DIRS $HOME/bin/tutorial3
</syntaxhighlight>
This temporarily adds (prepends) the newly created "share" location to <tt>XDG_DATA_DIRS</tt>, the standard path for application data files.
 
==Moving On==
Now you can move on to [[Development/Tutorials/Saving_and_loading|saving and loading]].
 
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]].
 
{{Attention||The source code on this page applies only the current KDE Frameworks 5 ("KF5") version. For the older KDE Development Platform ("KDE4"), See [[Development/Tutorials/First_program/KDE4]]}}
 
[[Category:C++]]

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