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/****************************************************************************
**
** 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.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** 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.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page qt-embedded-vnc.html
\brief A guide to using Qt for Embedded Linux applications as VNC servers
and clients.
\title The VNC Protocol and Qt for Embedded Linux
\ingroup qt-embedded-linux
VNC (Virtual Network Computing) software makes it possible to view
and interact with one computer (the "server") from any other
computer or mobile device (the "viewer") anywhere on a network.
\image qt-embedded-vnc-screen.png
VNC clients are available for a vast array of display systems, including
X11, Mac OS X and Windows.
\section1 Configuring Qt with VNC Capabilities
To run a \l{Qt for Embedded Linux} application using the VNC protocol, the
\l{Qt for Embedded Linux} library must be configured and compiled with the
\c -qt-gfx-vnc option:
\snippet doc/src/snippets/code/doc_src_emb-vnc.qdoc 0
\section1 Running a Server Application
Start a server application by specifying the \c -qws command
line option when running the application. (This can also be
specified in the application's source code.)
Use the \c -display command line option to specify the VNC server's
driver and the virtual screen to use. For example:
\snippet doc/src/snippets/code/doc_src_emb-vnc.qdoc 1
The application will act as a VNC server which can be accessed using
an ordinary VNC client, either on the development machine or from a
different machine on a network.
For example, using the X11 VNC client to view the application from the
same machine:
\snippet doc/src/snippets/code/doc_src_emb-vnc.qdoc 2
To interact with the application from another machine on the network,
run a VNC client pointing to the machine that is running the server
application.
\l{Qt for Embedded Linux} will create a 640 by 480 pixel display by
default. Alternatively, the \c QWS_SIZE environment variable can be
used to set another size; e.g., \c{QWS_SIZE=240x320}.
\section1 Running Client Applications
If you want to run more than one application on the same display, you
only need to start the first one as a server application, using the
\c -qws command line option to indicate that it will manage other
windows.
\snippet doc/src/snippets/code/doc_src_emb-vnc.qdoc Starting server
Subsequent client applications can be started \e without the \c -qws
option, but will each require the same \c -display option and argument
as those used for the server.
\snippet doc/src/snippets/code/doc_src_emb-vnc.qdoc Starting clients
However, for the clients, this option will not cause a new VNC server
to be started, but only indicates that their windows will appear on the
virtual screen managed by the server application.
\section1 Related Resources
It is not always necessary to specify the \c -qws command line option
when running a server application as long as the QApplication object
used by the application has been constructed with the
QApplication::GuiServer flag.
See the \l{Running Qt for Embedded Linux Applications}{running applications}
documentation for more details about server and client applications.
\table
\row
\o \bold {The Virtual Framebuffer}
The \l{The Virtual Framebuffer}{virtual framebuffer} is
an alternative technique recommended for development and debugging
purposes.
The virtual framebuffer emulates a framebuffer using a shared
memory region and the \c qvfb tool to display the framebuffer in a
window.
Its use of shared memory makes the virtual framebuffer much faster
and smoother than using the VNC protocol, but it does not operate
over a network.
\o \inlineimage qt-embedded-virtualframebuffer.png
\endtable
*/
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