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/*!

    \example designer/calculatorbuilder

    \title Calculator Builder Example

    The Calculator Builder example shows how to create a user interface from

    a \QD form at run-time, using the QUiLoader class.

    \image calculatorbuilder-example.png

    We use the form created in the \l{designer/calculatorform}{Calculator Form}

    example to show that the same user interface can be generated when the

    application is executed or defined when the application is built.

    \section1 Preparation

    The \l{designer/calculatorform}{Calculator Form} example defines a user

    interface that we can use without modification. In this example, we use a

    \l{The Qt Resource System}{resource file} to contain the \c{calculatorform.ui}

    file created in the previous example, but it could be stored on disk instead.

    To generate a form at run time, we need to link the example against the

    \c QtUiTools module library. The project file we use contains all the

    necessary information to do this:

    \snippet examples/designer/calculatorbuilder/calculatorbuilder.pro 0

    All the other necessary files are declared as usual.

    \section1 CalculatorForm Class Definition

    The \c CalculatorForm class defines the widget used to host the form's

    user interface:

    \snippet examples/designer/calculatorbuilder/calculatorform.h 0

    Note that we do not need to include a header file to describe the user

    interface. We only define two public slots, using the auto-connection

    naming convention required by \c uic, and declare private variables

    that we will use to access widgets provided by the form after they are

    constructed.

    \section1 CalculatorForm Class Implementation

    We will need to use the QUiLoader class that is provided by the

    \c libQtUiTools library, so we first ensure that we include the header

    file for the module:

    \snippet examples/designer/calculatorbuilder/calculatorform.cpp 0

    The constructor uses a form loader object to construct the user

    interface that we retrieve, via a QFile object, from the example's

    resources:

    \snippet examples/designer/calculatorbuilder/calculatorform.cpp 1

    By including the user interface in the example's resources, we ensure

    that it will be present when the example is run. The \c{loader.load()}

    function takes the user interface description contained in the file

    and constructs the form widget as a child widget of the \c{CalculatorForm}.

    We are interested in three widgets in the generated user interface:

    two spin boxes and a label. For convenience, we retrieve pointers to

    these widgets from the widget that was constructed by the \c FormBuilder,

    and we record them for later use. The \c qFindChild() template function

    allows us to query widgets in order to find named child widgets.

    \snippet examples/designer/calculatorbuilder/calculatorform.cpp 2

    The widgets created by the form loader need to be connected to the

    specially-named slots in the \c CalculatorForm object. We use Qt's

    meta-object system to enable these connections:

    \snippet examples/designer/calculatorbuilder/calculatorform.cpp 3

    The form widget is added to a layout, and the window title is set:

    \snippet examples/designer/calculatorbuilder/calculatorform.cpp 4

    The two slots that modify widgets provided by the form are defined

    in a similar way to those in the \l{designer/calculatorform}{Calculator

    Form} example, except that we read the values from the spin boxes and

    write the result to the output widget via the pointers we recorded in

    the constructor:

    \snippet examples/designer/calculatorbuilder/calculatorform.cpp 5

    \codeline

    \snippet examples/designer/calculatorbuilder/calculatorform.cpp 7

    The advantage of this approach is that we can replace the form when the

    application is run, but we can still manipulate the widgets it contains

    as long as they are given appropriate names.

*/