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/*!

    \example mainwindows/dockwidgets

    \title Dock Widgets Example

    The Dock Widgets example shows how to add dock windows to an

    application. It also shows how to use Qt's rich text engine.

    \image dockwidgets-example.png Screenshot of the Dock Widgets example

    The application presents a simple business letter template, and has

    a list of customer names and addresses and a list of standard

    phrases in two dock windows. The user can click a customer to have

    their name and address inserted into the template, and click one or

    more of the standard phrases. Errors can be corrected by clicking

    the Undo button. Once the letter has been prepared it can be printed

    or saved as HTML.

    \section1 MainWindow Class Definition

    Here's the class definition:

    \snippet examples/mainwindows/dockwidgets/mainwindow.h 0

    We will now review each function in turn.

    \section1 MainWindow Class Implementation

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 0

    We start by including \c <QtGui>, a header file that contains the

    definition of all classes in the \l QtCore and \l QtGui

    libraries. This saves us from having to include

    every class individually and is especially convenient if we add new

    widgets. We also include \c mainwindow.h.

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 1

    In the constructor, we start by creating a QTextEdit widget. Then we call

    QMainWindow::setCentralWidget(). This function passes ownership of

    the QTextEdit to the \c MainWindow and tells the \c MainWindow that

    the QTextEdit will occupy the \c MainWindow's central area.

    Then we call \c createActions(), \c createMenus(), \c

    createToolBars(), \c createStatusBar(), and \c createDockWindows()

    to set up the user interface. Finally we call \c setWindowTitle() to

    give the application a title, and \c newLetter() to create a new

    letter template.

    We won't quote the \c createActions(), \c createMenus(), \c

    createToolBars(), and \c createStatusBar() functions since they

    follow the same pattern as all the other Qt examples.

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 9

    We create the customers dock window first, and in addition to a

    window title, we also pass it a \c this pointer so that it becomes a

    child of \c MainWindow. Normally we don't have to pass a parent

    because widgets are parented automatically when they are laid out:

    but dock windows aren't laid out using layouts.

    We've chosen to restrict the customers dock window to the left and

    right dock areas. (So the user cannot drag the dock window to the

    top or bottom dock areas.) The user can drag the dock window out of

    the dock areas entirely so that it becomes a free floating window.

    We can change this (and whether the dock window is moveable or

    closable) using QDockWidget::setFeatures().

    Once we've created the dock window we create a list widget with the

    dock window as parent, then we populate the list and make it the

    dock window's widget. Finally we add the dock widget to the \c

    MainWindow using \c addDockWidget(), choosing to put it in the right

    dock area.

    We undertake a similar process for the paragraphs dock window,

    except that we don't restrict which dock areas it can be dragged to.

    Finally we set up the signal-slot connections. If the user clicks a

    customer or a paragraph their \c currentTextChanged() signal will be

    emitted and we connect these to \c insertCustomer() and

    addParagraph() passing the text that was clicked.

    We briefly discuss the rest of the implementation, but have now

    covered everything relating to dock windows.

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 2

    In this function we clear the QTextEdit so that it is empty. Next we

    create a QTextCursor on the QTextEdit. We move the cursor to the

    start of the document and create and format a frame. We then create

    some character formats and a table format. We insert a table into

    the document and insert the company's name and address into a table

    using the table and character formats we created earlier. Then we

    insert the skeleton of the letter including two markers \c NAME and

    \c ADDRESS. We will also use the \c{Yours sincerely,} text as a marker.

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 6

    If the user clicks a customer we split the customer details into

    pieces. We then look for the \c NAME marker using the \c find()

    function. This function selects the text it finds, so when we call

    \c insertText() with the customer's name the name replaces the marker.

    We then look for the \c ADDRESS marker and replace it with each line

    of the customer's address. Notice that we wrapped all the insertions

    between a \c beginEditBlock() and \c endEditBlock() pair. This means

    that the entire name and address insertion is treated as a single

    operation by the QTextEdit, so a single undo will revert all the

    insertions.

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 7

    This function works in a similar way to \c insertCustomer(). First

    we look for the marker, in this case, \c {Yours sincerely,}, and then

    replace it with the standard paragraph that the user clicked. Again

    we use a \c beginEditBlock() ... \c endEditBlock() pair so that the

    insertion can be undone as a single operation.

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 3

    Qt's QTextDocument class makes printing documents easy. We simply

    take the QTextEdit's QTextDocument, set up the printer and print the

    document.

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 4

    QTextEdit can output its contents in HTML format, so we prompt the

    user for the name of an HTML file and if they provide one we simply

    write the QTextEdit's contents in HTML format to the file.

    \snippet examples/mainwindows/dockwidgets/mainwindow.cpp 5

    If the focus is in the QTextEdit, pressing \key Ctrl+Z undoes as

    expected. But for the user's convenience we provide an

    application-wide undo function that simply calls the QTextEdit's

    undo: this means that the user can undo regardless of where the

    focus is in the application.

*/