source: trunk/doc/src/examples/digitalclock.qdoc@ 357

/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/

/*!
    \example widgets/digitalclock
    \title Digital Clock Example

    The Digital Clock example shows how to use QLCDNumber to display a 
    number with LCD-like digits.

    \image digitalclock-example.png Screenshot of the Digital Clock example

    This example also demonstrates how QTimer can be used to update a widget
    at regular intervals.

    \section1 DigitalClock Class Definition

    The \c DigitalClock class provides a clock widget showing the time with
    hours and minutes separated by a blinking colon. We subclass QLCDNumber
    and implement a private slot called \c showTime() to update the clock
    display:

    \snippet examples/widgets/digitalclock/digitalclock.h 0

    \section1 DigitalClock Class Implementation

    \snippet examples/widgets/digitalclock/digitalclock.cpp 0

    In the constructor, we first change the look of the LCD numbers. The
    QLCDNumber::Filled style produces raised segments filled with the
    foreground color (typically black). We also set up a one-second timer
    to keep track of the current time, and we connect
    its \l{QTimer::timeout()}{timeout()} signal to the private \c showTime() slot
    so that the display is updated every second. Then, we
    call the \c showTime() slot; without this call, there would be a one-second
    delay at startup before the time is shown.

    \snippet examples/widgets/digitalclock/digitalclock.cpp 1
    \snippet examples/widgets/digitalclock/digitalclock.cpp 2

    The \c showTime() slot is called whenever the clock display needs
    to be updated.

    The current time is converted into a string with the format "hh:mm".
    When QTime::second() is a even number, the colon in the string is
    replaced with a space. This makes the colon appear and vanish every
    other second.

    Finally, we call QLCDNumber::display() to update the widget.
*/