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/****************************************************************************
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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
*/
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