source: trunk/tools/designer/src/lib/sdk/taskmenu.qdoc@ 651

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/*!
    \class QDesignerTaskMenuExtension
    \brief The QDesignerTaskMenuExtension class allows you to add custom
    menu entries to Qt Designer's task menu.
    \inmodule QtDesigner

    QDesignerTaskMenuExtension provides an interface for creating
    custom task menu extensions. It is typically used to create task
    menu entries that are specific to a plugin in \QD.

    \QD uses the QDesignerTaskMenuExtension to feed its task
    menu. Whenever a task menu is requested, \QD will query
    for the selected widget's task menu extension.

    \image taskmenuextension-example-faded.png

    A task menu extension is a collection of QActions. The actions
    appear as entries in the task menu when the plugin with the
    specified extension is selected. The image above shows the custom
    \gui {Edit State...} action which appears in addition to \QD's
    default task menu entries: \gui Cut, \gui Copy, \gui Paste etc.

    To create a custom task menu extension, your extension class must
    inherit from both QObject and QDesignerTaskMenuExtension. For
    example:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.qdoc 9

    Since we are implementing an interface, we must ensure that it
    is made known to the meta-object system using the Q_INTERFACES()
    macro. This enables \QD to use the qobject_cast() function to
    query for supported interfaces using nothing but a QObject
    pointer.

    You must reimplement the taskActions() function to return a list
    of actions that will be included in \QD task menu. Optionally, you
    can reimplement the preferredEditAction() function to set the
    action that is invoked when selecting your plugin and pressing
    \key F2. The preferred edit action must be one of the actions
    returned by taskActions() and, if it's not defined, pressing the
    \key F2 key will simply be ignored.

    In \QD, extensions are not created until they are required. A
    task menu extension, for example, is created when you click the
    right mouse button over a widget in \QD's workspace. For that
    reason you must also construct an extension factory, using either
    QExtensionFactory or a subclass, and register it using \QD's
    \l {QExtensionManager}{extension manager}.

    When a task menu extension is required, \QD's \l
    {QExtensionManager}{extension manager} will run through all its
    registered factories calling QExtensionFactory::createExtension()
    for each until it finds one that is able to create a task menu
    extension for the selected widget. This factory will then make an
    instance of the extension.

    There are four available types of extensions in \QD:
    QDesignerContainerExtension, QDesignerMemberSheetExtension,
    QDesignerPropertySheetExtension, and QDesignerTaskMenuExtension.
    \QD's behavior is the same whether the requested extension is
    associated with a container, a member sheet, a property sheet or a
    task menu.

    The QExtensionFactory class provides a standard extension factory,
    and can also be used as an interface for custom extension
    factories. You can either create a new QExtensionFactory and
    reimplement the QExtensionFactory::createExtension() function. For
    example: