source: trunk/doc/src/examples/simpleselector.qdoc@ 1168

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/*!
    \example webkit/simpleselector
    \title Simple Selector Example

    The Simple Selector example shows how to use QWebElement to access the
    Document Object Model (DOM) in a Web page.

    \image webkit-simpleselector.png

    The QWebElement class enables access to the document structure and content in a Web page,
    as represented by a QWebFrame instance. It can be used for basic traversal of the document
    structure (see the \l{DOM Traversal Example}), to search for particular elements, and to
    modify any elements found.

    This example uses a QWebView widget to display a Web page. A QLineEdit widget and QPushButton
    allow the user to enter a query and highlight the results in the page. These widgets are
    contained in an instance of the \c Window class, which we described below.

    \section1 Window Class Definition

    The \c Window class describes the example's user interface and this is partially described
    by the \c window.ui file, created using \l{Qt Designer}:

    \snippet examples/webkit/simpleselector/window.h Window class definition

    We use \l{Using a Designer UI File in Your Application#The Multiple Inheritance Approach}
    {multiple inheritance} to include the user interface description. We define slots that
    will automatically respond to signals emitted by certain user interface controls.

    \section1 Window Class Implementation

    Since the layout of the user interface is provided by the \c{window.ui} user interface file,
    we only need to call the \l{QWidget::}{setupUi()} in the constructor:

    \snippet examples/webkit/simpleselector/window.cpp Window class constructor

    This adds all the controls to the window and sets up connections between their signals
    and suitably-named slots in the \c Window class. The QLineEdit instance was given a name of
    \c elementLineEdit in Qt Designer, so the \c{on_elementLineEdit_returnPressed()} slot is
    automatically connected to its \l{QLineEdit::}{returnPressed()} signal.

    This slot performs the main work of this example. We begin by obtaining a QWebFrame
    instance for the current page shown in the QWebView widget. Each QWebFrame contains
    a QWebElement instance that represents the document, and we obtain this in order to
    examine its contents:

    \snippet examples/webkit/simpleselector/window.cpp return pressed

    Taking the contents of the QLineEdit as the query text, we call the element's
    \l{QWebElement::}{findAll()} function to obtain a list of elements that match the
    query.

    For each element obtained, we modify its style by setting its \c style attribute
    to give it a yellow background color.

    Since we also want the query to be performed when the user clicks the \gui Highlight
    button, we also implement the \c{on_highlightButton_clicked()} slot to simply call
    the \c{on_elementLineEdit_returnPressed()} slot when it is invoked:

    \snippet examples/webkit/simpleselector/window.cpp button clicked

    For completeness, we also implement a \c setUrl() function which simply passes on
    a QUrl instance to the equivalent function in the QWebView widget:

    \snippet examples/webkit/simpleselector/window.cpp set URL

    \section1 Starting the Example

    The main function implementation is simple. We set up the application, create
    a \c Window instance, set its URL, and show it:

    \snippet examples/webkit/simpleselector/main.cpp main program

    When the application's event loop is run, the WebKit home page will load, and the
    user can then begin to start running queries against the contents of the page.
    The highlighting can only be removed by reloading the page. To do this, open a
    context menu over the page and select the \gui Reload menu item.

    \section1 Further Reading

    The QWebElement documentation contains more information about DOM access for the
    QtWebKit classes.

    In this example, we take advantage of Qt's
    \l{Using a Designer UI File in Your Application#Automatic Connections}{auto-connection}
    feature to avoid explicitly connecting signals to slots.
*/