/**************************************************************************** ** ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). ** All rights reserved. ** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the documentation of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:FDL$ ** 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 Technology Preview License Agreement accompanying ** this package. ** ** GNU Free Documentation License ** Alternatively, this file may be used under the terms of the GNU Free ** Documentation License version 1.3 as published by the Free Software ** Foundation and appearing in the file included in the packaging of this ** file. ** ** If you have questions regarding the use of this file, please contact ** Nokia at qt-info@nokia.com. ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \page qt-embedded-displaymanagement.html \title Qt for Embedded Linux Display Management \ingroup qt-embedded-linux When rendering, the default behavior for each Qt for Embedded Linux client is to render its widgets into memory, while the server is responsible for putting the contents of the memory onto the screen. The server uses the screen driver to copy the content of the memory to the display. The screen driver is loaded by the server application when it starts running, using Qt's \l {How to Create Qt Plugins}{plugin system}. Contents: \tableofcontents \section1 Available Drivers \l{Qt for Embedded Linux} provides drivers for the Linux framebuffer, the virtual framebuffer, transformed screens, VNC servers and multi screens. Run the \c configure script to list the available drivers: \if defined(QTOPIA_DOCS) \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 0 \else \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 1 \endif \if defined(QTOPIA_DOCS) In the default Qt Extended configuration, only an unaccelerated Linux framebuffer driver (\c /dev/fb0) is enabled. The various drivers can be enabled and disabled using the \c configure script. For example: \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 2 \else In the default Qt configuration, only an unaccelerated Linux framebuffer driver (\c /dev/fb0) is enabled. The various drivers can be enabled and disabled using the \c configure script. For example: \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 3 \endif Custom screen drivers can be implemented by subclassing the QScreen class and creating a screen driver plugin (derived from the QScreenDriverPlugin class). The default implementation of the QScreenDriverFactory class will automatically detect the plugin, loading the driver into the server application at run-time. \section1 Specifying a Driver To specify which driver to use, set the QWS_DISPLAY environment variable. For example (if the current shell is bash, ksh, zsh or sh): \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 4 The valid values for the \c argument are \c LinuxFb, \c QVFb, \c VNC, \c Transformed, \c Multi and \l {QScreenDriverPlugin::keys()}{keys} identifying custom drivers, and the \c {} argument is used to separate screens that are using the same screen driver and to enable multiple displays (see the \l {Running Qt for Embedded Linux Applications} documentation for more details). The driver specific options are described in the table below. \table \header \o Driver Specific Option \o Available For \o Description \row \o \c tty= \o LinuxFb \o Passes the device file to the console the application is running on. \row \o \c nographicsmodeswitch \o LinuxFb \o Ensures that the application is not in graphics mode. \row \o \c littleendian \o LinuxFb \o Tells the driver it must handle a little-endian frame buffer in a big-endian system. \row \o \c mmWidth= \target mmWidth \o LinuxFb, QVFb \o The screen's physical width (used to calculate DPI). \row \o \c mmHeight= \target mmHeight \o LinuxFb, QVFb \o The screen's physical height (used to calculate DPI). \row \o \c \o LinuxFb \o \row \o \c \o VNC, Transformed, Multi \o Specifies a subdriver. \row \o \c \o Transformed \o Specifies the rotation of the screen. The valid values of \c X are 90, 180 and 270. \row \o \c offset= \o Multi \o Specifies the coordinates of a subscreen's top-left corner (by default 0,0). \endtable The QWS_DISPLAY environment variable can also be set using the \c -display option when running an application. For example: \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 5 \section1 Subdrivers and Multiple Drivers The VNC, Transformed and Multi screen drivers depend on subdrivers. The general syntax for specifying a driver is as follows: \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 6 In the case of subdrivers, it is important to add a space between each subdriver and before the display number to separate the various drivers and displays. Note that \c Multi screen drivers can have several subdrivers. For example: \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 7 Note also that the VNC screen driver defaults to a virtual screen driver if no subdriver is specified. In this case the VNC driver accepts a few additional (optional) arguments specifying the size and depth of the default virtual screen: \list \o \c {size=} \o \c {depth=} \o \c {mmHeight=} \o \c {mmWidth=} \endlist Example running the VNC screen driver with a virtual screen of size 720x480 with 32 bits per pixel: \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 8 Example running the VNC screen driver on top of the Linux framebuffer driver: \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 9 In this last example, Qt is using two screen drivers simultaneously, displaying output on both the device's screen and across a network on VNC client displays. */