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/*!

    \example webkit/previewer

    \title Previewer Example

    The Previewer example shows how to use QtWebKit's QWebView to preview

    HTML data written in a QPlainTextEdit.

    \image previewer-example.png

    \section1 The User Interface

    Before we begin, we create a user interface using \QD. Two QGroupBox

    objects - the editor group box and the previewer group box are separated

    by a QSplitter. In the editor group box, we have a QPlainTextEdit object,

    \c plainTextEdit, and two QPushButton objects. In the previewer group box,

    we have a QWebView object, \c webView.

    \image previewer-ui.png

    \section1 Previewer Class Definition

    The \c Previewer class is a subclass of both QWidget and Ui::Form.

    We subclass Ui::Form in order to embed the \QD user interface form

    created earlier. This method of embedding forms is known as the

    \l{The Multiple Inheritance Approach}{multiple inheritance approach}.

    In our \c previewer.h file, we have a constructor and a slot,

    \c on_previewButton_clicked().

    \snippet examples/webkit/previewer/previewer.h 0

    \section1 Previewer Class Implementation

    The \c{Previewer}'s constructor is only responsible for setting up the

    user interface.

    \snippet examples/webkit/previewer/previewer.cpp 0

    The \c on_previewButton_clicked() is a slot corresponding to the

    \c{previewButton}'s \l{QPushButton::}{clicked()} signal. When the

    \c previewButton is clicked, we extract the contents of \c plainTextEdit,

    and then invoke the \l{QWebView::}{setHtml()} function to display our

    contents as HTML.

    \snippet examples/webkit/previewer/previewer.cpp 1

    \section1 MainWindow Class Definition

    The \c MainWindow class for the Previewer example is a subclass of

    QMainWindow with a constructor and five private slots: \c open(),

    \c openUrl(), \c save(), \c about() and \c updateTextEdit().

    \snippet examples/webkit/previewer/mainwindow.h 0

    The private objects in \c MainWindow are \c centralWidget, which is

    a \c Previewer object, \c fileMenu, \c helpMenu and the QAction objects

    \c openAct, \c openUrlAct, \c saveAct, \c exitAct, \c aboutAct and

    \c aboutQtAct.

    \snippet examples/webkit/previewer/mainwindow.h 1

    There are three private functions: \c createActions(), \c createMenus()

    and \c setStartupText(). The \c createActions() and \c createMenus()

    functions are necessary to set up the main window's actions and

    assign them to the \gui File and \gui Help menus. The \c setStartupText()

    function, on the other hand, displays a description about the example

    in its HTML Previewer window.

    \section1 MainWindow Class Implementation

    The \c{MainWindow}'s constructor invokes \c createActions() and

    \c createMenus() to set up the \gui File menu and \gui Help menu. Then,

    the \c Previewer object, \c centralWidget, is set to the main window's

    central widget. Also, we connect \c webView's

    \l{QWebView::}{loadFinished()} signal to our \c updateTextEdit() slot.

    Finally, we call the \c setStartupText() function to display the

    description of the example.

    \snippet examples/webkit/previewer/mainwindow.cpp 0

    Within the \c createActions() function, we instantiate all our private

    QAction objects which we declared in \c{mainwindow.h}. We set the

    short cut and status tip for these actions and connect their

    \l{QAction::}{triggered()} signal to appropriate slots.

    \snippet examples/webkit/previewer/mainwindow.cpp 1

    \dots

    The \c createMenus() function instantiates the QMenu items, \c fileMenu

    and \c helpMenu and adds them to the main window's

    \l{QMainWindow::menuBar()}{menu bar}.

    \snippet examples/webkit/previewer/mainwindow.cpp 2

    The example also provides an \c about() slot to describe its purpose.

    \snippet examples/webkit/previewer/mainwindow.cpp 3

    The \c MainWindow class provides two types of \gui Open functions:

    \c open() and \c openUrl(). The \c open() function opens an HTML file

    with \c fileName, and reads it with QTextStream. The function then

    displays the output on \c plainTextEdit. The file's name is obtained

    using QFileDialog's \l{QFileDialog::}{getOpenFileName()} function.

    \snippet examples/webkit/previewer/mainwindow.cpp 4

    The \c openUrl() function, on the other hand, displays a QInputDialog

    to obtain a URL, and displays it on \c webView.

    \snippet examples/webkit/previewer/mainwindow.cpp 5

    In order to save a HTML file, the \c save() function first extracts the

    contents of \c plainTextEdit and displays a QFileDialog to obtain

    \c fileName. Then, we use a QTextStream object, \c in, to write to

    \c file.

    \snippet examples/webkit/previewer/mainwindow.cpp 6

    Earlier, in \c{MainWindow}'s constructor, we connected \c{webView}'s

    \l{QWebView::}{loadFinished()} signal to our private \c updateTextEdit()

    slot. This slot updates the contents of \c plainTextEdit with the HTML

    source of the web page's main frame, obtained using \l{QWebFrame}'s

    \l{QWebFrame::}{toHtml()} function.

    \snippet examples/webkit/previewer/mainwindow.cpp 7

    To provide a description about the Previewer example, when it starts up,

    we use the \c setStartupText() function, as shown below:

    \snippet examples/webkit/previewer/mainwindow.cpp 8

    \section1 The \c{main()} Function

    The \c main() function instantiates a \c MainWindow object, \c mainWindow,

    and displays it with the \l{QWidget::}{show()} function.

    \snippet examples/webkit/previewer/main.cpp 0

*/