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/*!

    \example webkit/domtraversal

    \title DOM Traversal Example

    The DOM Traversal example shows how to use the QWebElement class to access

    the structure of a Web page.

    \image webkit-domtraversal.png

    The QWebElement class provides an API that can be used to examine the structure

    and content of a Web page via a Document Object Model (DOM) interface. It can be

    used for basic traversal of the document structure, to search for particular

    elements (see the \l{Simple Selector Example}), and to modify content in-place.

    This example uses a QWebView widget to display the Web page, and a dock widget

    holds the QTreeWidget that shows the document structure. These widgets are

    placed in an instance of the \c Window class, which we describe below.

    \section1 Window Class Definition

    The \c Window class is derived from QMainWindow and its user interface is created

    using \l{Qt Designer}. As a result, the class is also derived from the user

    interface class created by \l uic:

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

    Two important functions to note are the \c on_webView_loadFinished() slot and

    the \c examineChildElements() function. The former is automatically called

    when the QWebView widget finishes loading a page \mdash see the

    \l{#Further Reading}{Further Reading} section for more information on this

    mechanism.

    The \c examineChildElements() function is used to traverse the document structure

    and add items to the QTreeWidget.

    \section1 Window Class Implementation

    In the \c Window class constructor, we call the \l{QWidget::}{setupUi()} function

    to set up the user interface described in the \c{window.ui} file:

    \snippet examples/webkit/domtraversal/window.cpp Window constructor

    When the Web page is loaded, the \c on_webView_loadFinished() slot is called. Here,

    we clear the tree widget and begin inspection of the document by obtaining the

    document element from the page's main frame:

    \snippet examples/webkit/domtraversal/window.cpp begin document inspection

    At this point, we call the \c examineChildElements() function to traverse the

    document, starting with the child elements of the document element for which we

    will create top level items in the tree widget.

    The \c examineChildElements() function accepts a parent element and a parent item.

    Starting with the first child element, which we obtain with the element's

    \l{QWebElement::}{firstChild()} function, we examine each child element of the

    parent item. For each valid (non-null) element, which we check by calling its

    \l{QWebElement::}{isNull()} function, we create a new QTreeWidgetItem instance with

    the element name and add it to the parent item.

    \snippet examples/webkit/domtraversal/window.cpp traverse document

    We recursively examine the child elements for each element by calling

    \c examineChildElements() with the current child element and the newly-created item.

    To obtain the next element at the same level in the document, we call its

    \l{QWebElement::}{nextSibling()} function.

    This recursive approach to reading the document makes it easy to create a simple

    representation of the document structure in a tree widget.

    For completeness, we show the \c setUrl() function, which is provided to allow the

    document URL to be set from the example's \c main() function.

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

    \section1 Starting the Example

    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 Qt home page will load, and the

    tree widget will be updated to show the document structure. Navigating to another

    page will cause the tree widget to be updated to show the document structure of

    the new page.

    \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. The user interface

    contains a QWebView widget called \c webView whose \l{QWebView::}{loadFinished()}

    signal is automatically connected to the \c on_webView_loadFinished() slot when

    we call \l{QWidget::}{setupUi()} in the \c Window constructor.

*/