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

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/*!
    \example draganddrop/fridgemagnets
    \title Fridge Magnets Example

    The Fridge Magnets example shows how to supply more than one type
    of MIME-encoded data with a drag and drop operation.

    \image fridgemagnets-example.png

    With this application the user can play around with a collection
    of fridge magnets, using drag and drop to form new sentences from
    the words on the magnets. The example consists of two classes:

    \list
        \o \c DragLabel is a custom widget representing one
           single fridge magnet.
        \o \c DragWidget provides the main application window.
    \endlist

    We will first take a look at the \c DragLabel class, then we will
    examine the \c DragWidget class.

    \section1 DragLabel Class Definition

    Each fridge magnet is represented by an instance of the \c
    DragLabel class:

    \snippet examples/draganddrop/fridgemagnets/draglabel.h 0

    Each instance of this QLabel subclass will be used to display an
    pixmap generated from a text string. Since we cannot store both
    text and a pixmap in a standard label, we declare a private variable
    to hold the original text, and we define an additional member
    function to allow it to be accessed.

    \section1 DragLabel Class Implementation

    In the \c DragLabel constructor, we first create a QImage object
    on which we will draw the fridge magnet's text and frame:

    \snippet examples/draganddrop/fridgemagnets/draglabel.cpp 0

    Its size depends on the current font size, and its format is
    QImage::Format_ARGB32_Premultiplied; i.e., the image is stored
    using a premultiplied 32-bit ARGB format (0xAARRGGBB).

    We then construct a font object that uses the application's
    default font, and set its style strategy. The style strategy tells
    the font matching algorithm what type of fonts should be used to
    find an appropriate default family. The QFont::ForceOutline forces
    the use of outline fonts.

    To draw the text and frame onto the image, we use the QPainter
    class. QPainter provides highly optimized methods to do most of
    the drawing GUI programs require. It can draw everything from
    simple lines to complex shapes like pies and chords. It can also
    draw aligned text and pixmaps.

    \snippet examples/draganddrop/fridgemagnets/draglabel.cpp 1

    A painter can be activated by passing a paint device to the
    constructor, or by using the \l{QPainter::}{begin()} method as we
    do in this example. The \l{QPainter::}{end()} method deactivates
    it. Note that the latter function is called automatically upon
    destruction when the painter is actived by its constructor. The
    QPainter::Antialiasing render hint ensures that the paint engine