qt-creator/doc/pluginhowto/menu.qdoc

/*!
\page menu.html
\title 5. Adding menu and menu-items

In this chapter we will understand how to add entries to existing menus in Qt Creator. We will also learn how to add new
menu entries. Before moving ahead let's take a look at the menu bar in Qt Creator

\inlineimage qtc-menubar-5.png


The menu bar consists of the following set of default menus
\list
\o File
        \list
        \o New
        \o Open
        \o Recent Files
        \endlist
\o Edit
        \list
        \o Advanced 
        \endlist
\o Tools
\o Window
        \list
        \o Panes
        \endlist
\o Help
\endlist

\bold {Note:}\underline{Other menu items like Build and Debug come from plugins. They are not a part of the default menu set}.  

As Qt developers we know that the above menus are shown within a \bold {QMenuBar}; and that there is a \bold {QMenu} associated
with each of the above menus.

\section1 5.1 Core::ActionManager

The main Qt Creator program is nothing but a plugin loader. All of the functionality provided by Qt Creator is provided
by the plugins. The main plugin for Qt Creator is called "core" Without core, Qt Creator really doesn't have a personality

One of the key components of the "core" is the \bold {ActionManager}.\bold {ActionManager} is responsible for registration of menus,
menu-items and keyboard shortcuts. So if we wanted to add a new menu-item or menu, we would have to use
\bold {ActionManager}. The coming subsections explain this better.

To gain access to the \bold {ActionManager}, the following piece of code can be used.
\code
#include <coreplugin/actionmanager/actionmanager.h>
#include <coreplugin/icore.h>
Core::ActionManager* am = Core::ICore::instance()->actionManager();
\endcode

\section1 5.2 Core::ActionContainer

ActionContianer represents menu or menubar in Qt Creator. Instances of ActionContainer are never created directly,
instead they are accessed using ActionManager::createMenu(), ActionManager::createMenuBar() etc; but more on that
later.
There is an ActionContainer associated with each of the default menus in Qt Creator. Fetching ActionContainer for a
given menu can be done using the following code snippet

\code
#include <coreplugin/coreconstants.h>
#include <coreplugin/actionmanager/actionmanager.h>
#include <coreplugin/icore.h>

Core::ActionManager* am = Core::ICore::instance()->actionManager();
Core::ActionContainer* ac = am->actionContainer( ID );
\endcode
The following table lists out the ID to use for each of the menus in Qt Creator. Each of the IDs are defined as \bold {const}
\bold {char*} static variables within the \bold {Core} namespace.

\table  
\header
   \o Menu
   \o ID
\row
   \o File
   \o Core::Constants::M_FILE
\row 
   \o File->New
   \o Core::Constants::M_FILE_NEW
\row
   \o File->Open
   \o Core::Constants::M_FILE_OPEN
\row
   \o Edit
   \o Core::Constants::M_FILE_RECENTFILES
\row   
   \o Edit->Advanced
   \o Core::Constants::M_EDIT_ADVANCED
\row
   \o Tools
   \o Core::Constants::M_TOOLS
\row   
   \o Window
   \o Core::Constants::M_WINDOW
\row   
   \o Window Panes
   \o Core::Constants::M_WINDOW_PANES
\row   
   \o Help
   \o Core::Constants::M_HELP
\endtable

So if we want to catch hold of the "Help" menu, we can use the code snippet as follows
\code
#include <coreplugin/coreconstants.h>
#include <coreplugin/actionmanager/actionmanager.h>
#include <coreplugin/icore.h>

Core::ActionManager* am = Core::ICore::instance()->actionManager();
Core::ActionContainer* ac = am->actionContainer( Core::Constants::M_HELP );
\endcode

\section1 5.3 Registering menu-items.

The Core::Command class represents an action like a menu item, tool button, or shortcut. You don't create Command
objects directly, instead use we use ActionManager::registerAction() to register an action and retrieve a Command. The
Command object represents the user visible action and its properties.

Shown below is the right way to add the "About DoNothing" menu-item from the DoNothing plugin.

\code
#include <coreplugin/coreconstants.h>
#include <coreplugin/actionmanager/actionmanager.h>
#include <coreplugin/actionmanager/command.h>
#include <coreplugin/icore.h>
#include <QKeySequence>

bool DoNothingPlugin::initialize(const QStringList& args, QString *errMsg)
{
    Q_UNUSED(args);
    Q_UNUSED(errMsg);

    // Fetch the action manager
    Core::ActionManager* am = Core::ICore::instance()->actionManager();

    // Create a command for "About DoNothing".
    Core::Command* cmd = am->registerAction(
                                new QAction(tr("About DoNothing"),this),
                                "DoNothingPlugin.AboutDoNothing",
                                QList<int>() <<Core::Constants::C_GLOBAL_ID
                             );

    // Add the command to Help menu
    am->actionContainer(Core::Constants::M_HELP)->addAction(cmd);
    return true;
}
\endcode
\bold {Warning:}\underline { ac->menu()->addAction("About DoNothing") should never be used when adding menu items to Qt Creator.}

After compiling the changes, we can notice that the "About DoNothing" action shows up in the "Help" menu; but at the
beginning.

\inlineimage qtc-helpdonothing-5.png


If the "About DoNothing" menu item is to be placed in between specified menu item the we will make a small update in the code block
\code
bool DoNothingPlugin::initialize(const QStringList& args, QString *errMsg)
{
    .....
    // Add the command to Help menu
    am->actionContainer(Core::Constants::M_HELP)->addAction(showCmd, Core::Constants::G_HELP_HELP);
    return true;
}
\endcode

The effect of the change in code can be seen in the  image below.

\inlineimage qtc-menuitemposition-5.png


When added this way, we will be able to find the "About DoNothing" action in the "Keyboard Shortcuts" dialog box and
also associate a keyboard shortcut with it.

\inlineimage qtc-options-keyboard-5.png


\section1 5.4 Responding to menu-items
Since menu-items are QActions, we can connect to their triggered(bool) or toggled(bool) signal and respond to
trigger/toggled events. The code below shows how to do this
\code
class DoNothingPlugin : public ExtensionSystem::IPlugin
{
    Q_OBJECT

private slots:
    void about();
};

bool DoNothingPlugin::initialize(const QStringList& args, QString *errMsg)
{
    ......
    QAction *action = new QAction(tr("About DoNothing"),this);
    Core::Command* cmd = am->registerAction(action,
                                            "DoNothingPlugin.AboutDoNothing",
                                            QList<int>() << 0);
    ......
    connect(action, SIGNAL(triggered(bool)), this, SLOT(about()));
    return true;
}

void DoNothingPlugin::about()
{
    QMessageBox::information(0, "About DoNothing Plugin",
    "Seriously dude, this plugin does nothing");
}
\endcode

After compiling the changes and clicking on the "About DoNothing" menu-item, we can see the information dialog box
as shown below.

\inlineimage  qtc-menuresponse-5.png


If you wanted the message box to have the Qt Creator main window as its parent, then you can use the following code
for the about() slot.

\code
void DoNothingPlugin::about()
{
    QMessageBox::information(Core::ICore::instance()->mainWindow(),
                             "About DoNothing Plugin",
                             "Seriously dude, this plugin does nothing");
}   
\endcode

\section1 5.5 Adding menus
The procedure for adding menus is the same. Instead of creating a \bold {Core::Command}, we create a \bold {Core::ActionContainer}
and add it to the \bold {MENU_BAR}. The following code snippet highlights the changes from our previous version.
\code
bool DoNothingPlugin::initialize(const QStringList& args, QString *errMsg)
{
    Q_UNUSED(args);
    Q_UNUSED(errMsg);

    // Fetch the action manager
    Core::ActionManager* am = Core::ICore::instance()->actionManager();

    // Create a DoNothing menu
    Core::ActionContainer* ac = am->createMenu("DoNothingPlugin.DoNothingMenu");
    ac->menu()->setTitle("DoNothing");

    // Create a command for "About DoNothing".
    QAction *action = new QAction(tr("About DoNothing",this));
    Core::Command* cmd = am->registerAction(action,"DoNothingPlugin.AboutDoNothing",QList<int>() << 0);

    // Add DoNothing menu to the menubar
    am->actionContainer(Core::Constants::MENU_BAR)->addMenu(ac);

    // Add the "About DoNothing" action to the DoNothing menu
    ac->addAction(cmd);

    // Connect the action
    connect(action, SIGNAL(triggered(bool)), this, SLOT(about()));
    return true;
}
\endcode
After recompiling the changes, you will be able to notice the DoNothing menu as shown in the screenshot below.

\inlineimage qtc-donothingleft-5.png

\section1 5.6 Placing menus and menu-items
It is possible to insert menus and menu-items anywhere you want. Shown below is a code snippet that inserts the
"DoNothing" menu before the "Help" menu.
\code
bool DoNothingPlugin::initialize(const QStringList& args, QString *errMsg)
{
    Q_UNUSED(args);
    Q_UNUSED(errMsg);

    // Fetch the action manager
    Core::ActionManager* am = Core::ICore::instance()->actionManager();

    // Create a DoNothing menu
    Core::ActionContainer* ac = am->createMenu("DoNothingPlugin.DoNothingMenu");
    ac->menu()->setTitle("DoNothing");

    // Create a command for "About DoNothing".
    QAction *action = new QAction(tr("About DoNothing"),this);
    Core::Command* cmd = am->registerAction(action,"DoNothingPlugin.AboutDoNothing",QList<int>() << 0);

    // Insert the "DoNothing" menu between "Window" and "Help".
    QMenu* windowMenu = am->actionContainer(Core::Constants::M_HELP)->menu();
    QMenuBar* menuBar = am->actionContainer(Core::Constants::MENU_BAR)->menuBar();
    menuBar->insertMenu(windowMenu->menuAction(), ac->menu());

    // Add the "About DoNothing" action to the DoNothing menu
    ac->addAction(cmd);

    // Connect the action
    connect(action, SIGNAL(triggered(bool)), this, SLOT(about()));
    return true;
}
\endcode

After compiling the changes, we can now notice that change in position of the "DoNothing" menu.

\inlineimage qtc-donothingright-5.png


You can use a similar technique for customizing the position of menu-items.

*/