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/*!

    \example designer/calculatorform

    \title Calculator Form Example

    The Calculator Form Example shows how to use a form created with

    \QD in an application by using the user interface information from

    a QWidget subclass.  We use \l{Using a Designer UI File in Your Application}

    {uic's auto-connection} feature to automatically connect signals

    from widgets on the form to slots in our code.

    \image calculatorform-example.png Screenshot of the Calculator Form example

    The example presents two spin boxes that are used to input integer values

    and a label that shows their sum. Whenever either of the spin boxes are

    updated, the signal-slot connections between the widgets and the form

    ensure that the label is also updated.

    \section1 Preparation

    The user interface for this example is designed completely using \QD. The

    result is a UI file describing the form, the widgets used, any signal-slot

    connections between them, and other standard user interface properties.

    To ensure that the example can use this file, we need to include a \c FORMS

    declaration in the example's project file:

    \snippet examples/designer/calculatorform/calculatorform.pro 1

    When the project is built, \c uic will create a header file that lets us

    construct the form.

    \section1 CalculatorForm Class Definition

    The \c CalculatorForm class uses the user interface described in the

    \c calculatorform.ui file. To access the form and its contents, we need

    to include the \c ui_calculatorform.h header file created by \c uic

    during the build process:

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

    We define the \c CalculatorForm class by subclassing QWidget because the

    form itself is based on QWidget:

    \snippet examples/designer/calculatorform/calculatorform.h 1

    Apart from the constructor, the class contains two private slots that

    are named according to the auto-connection naming convention required

    by \c uic.

    The private \c ui member variable refers to the form, and is used to

    access the contents of the user interface.

    \section1 CalculatorForm Class Implementation

    The constructor simply calls the base class's constructor and

    sets up the form's user interface.

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

    The user interface is set up with the \c setupUI() function. We pass

    \c this as the argument to this function to use the \c CalculatorForm

    widget itself as the container for the user interface.

    To automatically connect signals from the spin boxes defined in the

    user interface, we use the naming convention that indicates which

    widgets and their signals in the user interface should be connected

    to each slot. The first slot is called whenever the spin box called

    "inputSpinBox1" in the user interface emits the

    \l{QSpinBox::valueChanged()}{valueChanged()} signal:

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

    When this occurs, we use the value supplied by the signal to update the

    output label by setting its new text directly. We access the output label

    and the other spin box via the class's private \c ui variable.

    The second slot is called whenever the second spin box, called

    "inputSpinBox2", emits the \l{QSpinBox::valueChanged()}{valueChanged()}

    signal:

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

    In this case, the value from the first spin box is read and combined

    with the value supplied by the signal. Again, the output label is

    updated directly via the \c ui variable.

*/