path: root/doc/src/platforms/platform-notes.qdoc

/****************************************************************************
**
** 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.
**
** $QT_BEGIN_LICENSE:FDL$
** 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.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms
** and conditions contained in a signed written agreement between you
** and Nokia.
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

/*!
    \group platform-specific
    \title Platform-Specific Documentation
    \brief Documents describing platform-specific features of Qt.

    These documents describe platform-specific features provided by Qt, and
    discuss issues related to particular platforms and environments.

    \generatelist{related}
*/

/*!
    \page platform-notes.html
    \ingroup platform-specific
    \title Platform and Compiler Notes
    \brief Information about the platforms on which Qt can be used.

    This page contains information about the platforms Qt is currently known
    to run on, with links to platform-specific notes, including any known bugs
    or incompatibilities.

    Information about the combinations of platforms and compilers
    supported by Qt can be found on the \l{Supported Platforms} page.

    \list
    \o \l{Platform and Compiler Notes - Symbian}
    \tableofcontents{1 Platform and Compiler Notes - Symbian}
    \endlist

*/

/*!
    \page platform-notes-symbian.html
    \title Platform and Compiler Notes - Symbian
    \contentspage Platform and Compiler Notes
    \ingroup platform-specific
    \brief Information about the state of support for the Symbian platform.

    This page describes implementation details regarding the Qt for Symbian port. To get 
    started with application development for Symbian devices, read  the \l 
    {http://doc.qt.nokia.com/qtcreator/creator-developing-symbian.html} 
    {Connecting Symbian Devices} document.

    \section1 Source Compatibility

    Qt for Symbian provides the same level of source compatibility guarantee as
    given for other platforms. That is, a program which compiles against a given
    version of Qt for Symbian will also compile against all future versions of the
    same major release.

    \section1 Binary Compatibility

    As with every supported platform, Qt strives to maintain application 
    behavior and binary compatibility throughout the lifetime of the Qt 4.x 
    major version and on the \l {Supported Devices}{Symbian devices that support Qt}.
    Symbian support in Qt SDK and Ovi Store were introduced with Qt 4.6. Each Qt 
    release contains bug fixes that might change the API behavior and thereby 
    affect application compatibility.

    In addition, Symbian devices have different input methods, such as different 
    keyboard styles or touch input, screen sizes, memory, and CPU and GPU 
    capabilities. Therefore, you must test applications on specific target 
    devices to ensure compatibility. In order to build applications that are 
    supported also on earlier devices, select the target in Qt SDK carefully. 
    Generally, an earlier target (such as S60 5th Edition) is supported on a 
    larger number of devices than a later target (such as Symbian Belle).

    \target Supported Devices
    \section1 Supported Devices
    
    The \l {http://developer.qt.nokia.com/wiki/support_for_Symbian}{Support for Symbian} document
    details the Qt support on different Symbian devices.

    The \l {http://www.developer.nokia.com/Community/Wiki/Nokia_Smart_Installer_for_Symbian#Supported_Devices}
    {Nokia Smart Installer for Symbian} document lists how Qt is supported on 
    different Symbian devices through Smart Installer.

    Qt versions are supported by Symbian devices as follows:
    \list
    \o Qt 4.6 is supported by S60 3rd Edition feature pack 1 and newer devices 
    through \l {http://www.developer.nokia.com/Community/Wiki/Nokia_Smart_Installer_for_Symbian}{Smart Installer}.
    \o Qt 4.7.3 is supported by S60 5th Edition and newer devices
    through \l {http://www.developer.nokia.com/Community/Wiki/Nokia_Smart_Installer_for_Symbian}{Smart Installer}.
    \endlist
    
    Symbian devices have a pre-installed Qt support as follows:
    \list
    \o Symbian Anna: Qt 4.7.3 in C: drive. Note that Qt 4.7.4 is supported in Symbian Anna
    through \l {http://www.developer.nokia.com/Community/Wiki/Nokia_Smart_Installer_for_Symbian}{Smart Installer}.
    \o Symbian Belle: Qt 4.7.4 in device firmware (ROM).
    \endlist
    

    \section1 Functionality Support

    The following technologies and classes are not supported:
    \list
    \o QtConcurrent
    \o QtDBus
    \o \l {http://doc.qt.nokia.com/4.8/printing.html}{Printing support}
    \o Qt3Support
    \endlist
    
    The following technologies have limited support:
    

    \table
    \header \o Module
            \o Note
    \row    \o QtSql
            \o The supported drivers are SQLite and QSYMSQL.
    \row    \o QtMultimedia
            \o For support details see \l {Multimedia Support} section.
    \row    \o QtGui
            \o QtGui's widgets are deprecated (i.e. they are available but not 
            recommended to use) in the Symbian port. It is recommended to use \l
            {http://doc.qt.nokia.com/qt-components-symbian-1.1/symbian-components-functional.html}
            {Qt Quick Components for Symbian} instead, because they provide 
            better look and feel on Symbian devices.

            Moreover, the following classes of QtGui \bold {should not 
            be used} in a Symbian application:
            
            \list
            \o QFileDialog with the \c DontUseNativeDialog option
            \o QColorDialog with the \c DontUseNativeDialog option
            \o QFontDialog
            \o QWizard
            \o QCalendarWidget
            \o QDateTimeEdit
            \o QMdiArea
            \o QDockWidget
            \o QMdiSubWindow
            \o QPrintPreviewWidget
            \endlist
            
            QScrollArea: The scrolling and focus handling of QScrollArea's all 
            scrollable widgets, for example QListView, differs from native Avkon 
            list widgets' one. Native Avkon scrollable components support 
            touch-gesture-based scrolling by dragging and flicking the UI 
            component but this functionality is not implemented in Qt widgets. 
            Scrolling by dragging and flicking works also in Qt Quick Components 
            that implements the \l 
            {http://www.developer.nokia.com/Resources/Library/Symbian_Design_Guidelines/}
            {Symbian design guidelines}.

    \endtable

    \section1 Compiler Notes
    
    For the application development the necessary compiler toolchain is included in \l 
    {http://qt.nokia.com/downloads}{Qt SDK}. For instructions compiling Qt 
    itself see the \l
    {http://doc.qt.nokia.com/stable/install-symbian.html}
    {Installing Qt for the Symbian platform} document.

    \section1 Known Issues

    Known issues can be found by visiting the
    \l{http://qt.gitorious.org/qt/pages/QtKnownIssues}{wiki page} with an
    up-to-date list of known issues, and the list of bugs can be found by
    \l{http://bugreports.qt.nokia.com/browse/QTBUG/component/19171}{browsing} the
    S60 component in Qt's public task tracker, located at
    \l{http://bugreports.qt.nokia.com/}{http://bugreports.qt.nokia.com/}.

    For information about mixing exceptions with Symbian leaves, see
    \l{Exception Safety with Symbian}.

    \section1 Required Capabilities

    The Qt libraries are typically signed with \c{All -TCB} capabilites but
    that does not mean your Qt application needs to be signed with the same
    capabilities to function properly. The capabilities your application needs
    to function properly depends on which parts of Qt you use. 
    In a Qt application Symbian capabilities are defined in the
    \l {http://doc.qt.nokia.com/4.8/qmake-variable-reference.html#target-capability}
    {TARGET.CAPABILITY} qmake variable in the project file.
    Here is an overview for which capabilities may be needed when using different modules:

    \table
    \header \o Module
            \o Required Symbian Capability
    \row    \o QtCore
            \o \c PowerMgmt if QProcess::kill(...) or QProcess::terminate(...) is called.
    \row    \o QtCore
            \o \c AllFiles when \l{http://wiki.forum.nokia.com/index.php/Capabilities_%28Symbian_Signed%29/AllFiles_Capability}{accessing specific areas.}
    \row    \o QtDeclarative
            \o \c NetworkServices is automatically added for this module if no capabilities are explicitly specified.
    \row    \o QtNetwork
            \o \c NetworkServices is automatically added for this module if no capabilities are explicitly specified.
    \row    \o QtNetwork
            \o \c ReadUserData is required to include all the phone's SSL certificates in the system's default CA certificate list
                  (for example those added by the user or stored in the SIM card),
                  without this capability only the CA certs built into the phone are used.
    \row    \o QtMultimedia
            \o \c UserEnvironment if QAudioInput is used.
    \row    \o QtWebKit
            \o \c NetworkServices is automatically added for this module if no capabilities are explicitly specified.
    \endtable

    \note Some modules rely on other modules. E.g. QtWebkit and QtDeclarative
    depend on QtNetwork and therefore any application that
    depends on these modules is also likely to need \c NetworkServices capability.

    For more information see the documentation of the individual Qt classes. If
    a class does not mention Symbian capabilities, it requires none.

    \target Multimedia Support
    \section1 Multimedia Support

    Qt Mobility provides a high-level API for multimedia functionality with
    \l{http://doc.qt.nokia.com/qtmobility/multimedia.html}{QtMultimediaKit}.
    In addition, Qt provides the low-level \l {QtMultimedia}{QtMultimedia} 
    module that is internally used by the QtMultimediaKit. For more information
    on developing multimedia applications for Symbian devices, see
    \l {http://www.developer.nokia.com/info/sw.nokia.com/id/4abf12e7-72d8-45ef-b1a2-46184abe18ba/Guide_for_Qt_Multimedia_Developers.html}
    {Guide for Qt Multimedia Developers}.

    Moreover, there is a third multimedia-related module called Phonon. Qt 
    provides two backends for the Phonon module in Symbian: \i MMF and \i Helix. 

    Note that Phonon is a legacy module and the QtMultimediaKit module is 
    replacing Phonon in Qt 5. Although Phonon is supported in Symbian for 
    backwards compatibility and there is no plan to remove Phonon from Symbian 
    any new applications should use QtMultimediaKit in Symbian using Qt 4.7 
    bundle. The QtMultimediaKit feature set is comparable to that in Phonon.        

    The following applies to Phonon:
    \list
    \o MMF Phonon backend supports video and sound playback through Symbian's 
    Multimedia Framework, MMF. Phonon's video playback may show artifacts when 
    the video is moved or resized (for instance, during device orientation 
    changes from portrait to landscape and vice versa). This problem is present 
    on S60 5th Edition and earlier versions, as well as in Symbian Anna devices.
    \o The audio and video formats that Phonon supports depends on what support
    the platform provides for MMF. The emulator is known to have limited
    codec support.
    \o In addition, there exists a backend for the Helix framework. However, since
    it is not shipped with Qt, its availability depends on the Symbian platform
    in use. If the MFF plugin fails to load, the Helix plugin, if present on the
    device, will be loaded instead.
    \endlist

    \section1 Hardware Accelerated Rendering

    The default graphics system on Symbian Anna is OpenVG, which uses OpenVG
    hardware to accelerate \l QPainter functions. There are a few exceptions,
    where Qt will use software rendering fallback.

    Devices like the N8 and C7 only have 32Mb of GPU memory and limited support
    for EGL surface transparency. These devices can be identified by querying
    the\c GL_RENDERER or \c VG_RENDERER string which evaluates to \c {VideoCore III}.
    On these devices, Qt will use software rendering in cases listed below.

        \list
        \o Translucent windows
        \o Dialogs
        \o Popups
        \endlist

    \section1 OpenGL Support in Symbian

     Qt 4.7 introduces the \l {QtOpenGL} module. QtOpenGL is
     supported on devices which support OpenGL ES 2.0. Symbian platforms prior
     to Symbian Anna (and Symbian^3) are not supported.

    \l QGLWidget usage as a \l QGraphicsView viewport is not recommended on
    Symbian. The OpenVG graphics system is not able to manage OpenGL graphics
    resources. Also, a QGLWidget object is not able to release its GPU resources
    when the application goes to the background. If OpenGL functionality is
    needed, \l { http://doc.qt.nokia.com/4.7-snapshot/qapplication.html#setGraphicsSystem}
    {OpenGL graphics system} usage is recommended. If an application
    decides to use QGLWidget, then it is the application's responsibility to
    destroy and release QGLWidget and related OpenGL resources when the
    application goes to the background. Otherwise, the \l{Graphics Out Of Memory monitor}
    may decide to kill the application as it consumes GPU resources while in the
    background.

    \note \l QGLBuffer, \l QGLFramebufferObject, \l QGLPixelBuffer, \l
    QGLShader, and \l QGLShaderProgram are direct GPU resources and it is the
    application's responsibility to manage them.

    \section1 UI Performance in S60 3rd and 5th Edition Devices

    Qt uses the QPainter class to perform low-level painting on widgets and
    other paint devices. QPainter provides functions to draw complex shapes,
    aligned text and pixmaps. It can also do vector path clipping, coordinate
    transformations and Porter-Duff composition. If the underlying graphics
    architecture does not support all of these operations then Qt uses the
    raster graphics system for rendering.
    
    In Symbian Anna (and Symbian^3) Qt uses hardware accelerated graphics as explained above.
    This is enabled by \l
    {http://library.developer.nokia.com/index.jsp?topic=/GUID-E35887BB-7E58-438C-AA27-97B2CDE7E069/GUID-D93978BE-11A3-5CE3-B110-1DEAA5AD566C.html}
    {ScreenPlay Graphics Architecture} in these devices.

    Most of the Symbian S60 3rd and 5th Edition devices have a
    graphics architecture that does not have native support for all functions
    provided by QPainter. In these \l
    {http://library.developer.nokia.com/index.jsp?topic=/GUID-E35887BB-7E58-438C-AA27-97B2CDE7E069/GUID-D93978BE-11A3-5CE3-B110-1DEAA5AD566C.html}
    {non-ScreenPlay} devices Qt uses the raster
    graphics system by default that has a performance penalty compared
    to native Symbian rendering.

    In order to be able to perform all functions provided by QPainter, the
    raster graphics system needs to have pixel level framebuffer access. To
    make this possible in non-ScreenPlay devices Qt has to create an
    additional offscreen buffer that is the target for all Qt rendering
    operations. Qt renders the widget tree to the offscreen buffer and the
    offscreen buffer is blitted to the framebuffer via Symbian Window Server.

    The following table shows the rendering stacks of native Symbian and Qt in
    \l {http://library.developer.nokia.com/index.jsp?topic=/GUID-E35887BB-7E58-438C-AA27-97B2CDE7E069/GUID-D93978BE-11A3-5CE3-B110-1DEAA5AD566C.html}
    {non-ScreenPlay devices}.

    \table
    \header \o Symbian
            \o Qt
    \row    \o \image symbian-rendering-stack-non-screenplay.png
            \o \image symbian-qt-rendering-stack-non-screenplay.png
    \endtable

    The following diagrams show a simplified sequence of drawing a pixmap in
    a non-ScreenPlay device.

    \table
    \header \o Symbian
    \row    \o \image symbian-draw-pixmap-sequence.png
    \endtable

    \table
    \header \o Qt
    \row    \o \image symbian-qt-draw-pixmap-sequence.png
    \endtable

    When compared to a native Symbian application, Qt does an additional blit
    to the offscreen buffer before drawing to the framebuffer. That is the
    performance penalty which needs to be paid to get all functionality
    provided by QPainter in non-ScreenPlay architecture.
*/