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/*!
    \page configure-options.html
    \title Qt Configure Options
    \brief Configuring Qt's compile options

    \c configure is a command-line tool which determines how to build Qt for a
    particular platform. Configure can exclude a feature in Qt as well
    as determine how Qt builds and deploys applications onto host platforms.
    This page discusses some of the configure options, but for
    the full list of options, enter the command \c{configure -h}. Configure
    should be run from the main Qt source directory.

    Unless stated otherwise, the commands in this page are for the Linux
    platforms. On \macos and on Windows, the \c PATH and directory structure
    are different, therefore the commands will vary. Also, on Windows systems,
    the configure script is called \e configure.bat.

    After running \c configure, build the sources with the \c make tool
    belonging to the chosen toolchain.

    \section1 Source, Build, and Install Directories

    The \e source directory contains the source code that is obtained from
    the source package or git repository. The \e build directory is where the
    build-related files such as Makefiles, object files, and other intermediate
    files are stored. The \e install directory is where the binaries and
    libraries are installed, for use either by the system or by the
    application.

    It is recommended to keep these directories separate by shadow-building and
    using the \c -prefix option. This enables you to keep the Qt \e source tree
    clean from the build artifacts and binaries, which are stored in a separate
    directory. This method is very convenient if you want to have multiple
    builds from the same source tree, but for different configurations. To
    shadow-build, run \c configure from a separate directory:

    \badcode
    mkdir ~/qt-build
    cd ~/qt-build
    ~/qt-source/configure -prefix /opt/Qt5.9
    qmake
    \endcode

    Configuring with the \c -prefix option means that the Qt binaries and
    libraries are installed into another directory, which is \c /opt/Qt5.9 in
    this case. Running \c qmake generates the Makefiles in the \e ~/qt-build
    directory and not in the \e source directory. After the Makefiles are in
    place, run the following commands to build the Qt binaries and libraries,
    and install them:

    \badcode
    make
    make install
    \endcode

    \note The 'make install' step is required only if Qt is configured with a
    \e -prefix, which is the default on Unix-based platforms unless the
    \e -developer-build configure option is used. On Windows, Qt is configured
    as a non-prefix build by default.

    \note The \c -developer-build is meant for developing Qt and not for
    shipping applications. Such a build contains more exported symbols than
    a standard build and compiles with a higher warning level.

    \section1 Modules and Features

    Qt consists of different \l{All Modules}{modules} whose sources can be
    found in different directories inside the top-level source directory.
    Users can explicitly exclude specific top-level directories to limit build
    times. Furthermore, each Qt module might have features that can also be
    explicitly enabled or disabled.

    \section2 Excluding Qt Modules

    Configure's \c -skip option allows top-level source directories to be
    excluded from the Qt build. Note that many directories contain multiple Qt
    modules. For example, to exclude Qt NFC and Qt Bluetooth from the Qt build,
    provide \c{-skip qtconnectivity} as the argument to configure.

    \code
    ./configure -skip qtconnectivity
    \endcode

    \section2 Including or Excluding Features

    The \c{-feature-}\e{<feature>} and \c{-no-feature-}\e{<feature>} options
    include and exclude specific features, respectively.

    For example, to disable \l Accessibility, provide
    \c -no-feature-accessibility as the argument:
    \code
    ./configure -no-feature-accessibility
    \endcode

    Use \c{configure -list-features} to show a list of all available features
    on the command line. Note that features can depend on other features, so
    disabling a feature might have side-effects on other features.

    The \l{Qt Configuration Tool} that is part of \l{Qt for Device Creation}
    allows the tweaking of features and dependencies through a convenient user
    interface.

    \section1 Third-Party Libraries

    The Qt source packages include third-party libraries. To set whether Qt
    should use the system's versions of the libraries or to use the bundled
    version, pass either \c -system or \c -qt before the name of the library to
    configure.

    The table below summarizes the third-party options:
    \table
    \header
        \li Library Name
        \li Bundled in Qt
        \li Installed in System
    \row
        \li zlib
        \li \c -qt-zlib
        \li \c -system-zlib
    \row
        \li libjpeg
        \li \c -qt-libjpeg
        \li \c -system-libjpeg
    \row
        \li libpng
        \li \c -qt-libpng
        \li \c -system-libpng
    \row
        \li xcb
        \li \c -qt-xcb
        \li \c -system-xcb
    \row
        \li freetype
        \li \c -qt-freetype
        \li \c -system-freetype
    \row
        \li PCRE
        \li \c -qt-pcre
        \li \c -system-pcre
    \row
        \li HarfBuzz-NG
        \li \c -qt-harfbuzz
        \li \c -system-harfbuzz
    \endtable

    It is also possible to disable support for these libraries by using
    \c -no instead of \c{-qt}. For example, to use the system's xcb library
    and disable zlib support, enter the following:

    \code
    ./configure -no-zlib -qt-libjpeg -qt-libpng -system-xcb
    \endcode

    For a full list of options, consult the help with \c {configure -help}.

    \section1 Compiler Options

    The \c -platform option sets the host platform and the compiler for building
    the Qt sources. The list of supported platforms and compilers is found in
    the \l{Supported Platforms}{supported platforms} page while the
    full list is available in \e{qtbase/mkspecs} directory.

    For example, on Ubuntu Linux systems, Qt can be compiled by several
    compilers such as clang or g++:

    \code
    ./configure -platform linux-clang
    ./configure -platform linux-g++
    ./configure -platform linux-g++-32
    \endcode

    For \l{Qt for Windows}{Windows} machines, either MinGW or Visual Studio
    toolchains can be used to compile Qt.

    \code
    configure.bat -platform win32-g++
    configure.bat -platform win32-msvc
    \endcode

    Afterwards, the generated Makefiles will use the appropriate compiler
    commands.

    \section1 Cross-Compilation Options

    To configure Qt for cross-platform development and deployment, the
    development toolchain for the target platform needs to be set up. This
    set up varies among the \l{Supported Platforms}.

    Common options are:
    \list
    \li \c -xplatform - the target platform. Valid xplatform options are the same
    as the \c -platform options which are found in \e{qtbase/mkspecs}.
    \li \c -device - a specific device or chipsets. The list of devices that configure is compatible with are
    found in \e{qtbase/mkspecs/devices}. For more information, visit the \l{http://wiki.qt.io/Category:Devices}{Devices}
    Wiki page.
    \li \c -device-option - sets additional qmake variables. For example, \c{-device-option CROSS_COMPILE=}\e{<path-to-toolchain>} provides
    the environment variable, \c{CROSS_COMPILE}, as needed by certain devices.
    \endlist

    \note Toolchains for non-desktop targets often come with a so-called \e
    sysroot which Qt needs to be configured against.

    \section2 Specific Options for Platforms

    The following pages provide guidelines on how to configure Qt for specific
    platform development:
    \list
    \li \l{Building Qt 5 for Android} Wiki page
    \li \l{Qt for iOS - Building from Source}
    \li \l{Qt for WinRT#Building from source}{Qt for WinRT - Building from Source}
    \li \l{Qt for Embedded Linux#Configuring a Specific Device}{Qt for Embedded Linux - Building from Source}
    \li \l{http://wiki.qt.io/Qt_RaspberryPi}{Qt for Raspberry Pi} - a community-driven site for
    Raspberry devices
    \li \l{http://wiki.qt.io/Category:Devices}{Devices} - a list of other devices and chipsets
    \endlist

    \section1 OpenGL Options for Windows

    On Windows, Qt can be configured with the system OpenGL or with \l{ANGLE}.
    By default, Qt is configured to use dynamic OpenGL. This means that it tries
    to use system OpenGL and falls back to ANGLE, which is bundled with Qt and
    depends on the DirectX SDK, if native OpenGL does not work. ANGLE enables
    running Qt applications that depend on OpenGL, without installing the latest
    OpenGL drivers. If ANGLE also fails, Qt will fall back to software rendering,
    which is the slowest but most safe of the rendering methods.

    The \c -opengl option can be used to configure Qt to use
    the OpenGL in the target system, a different version of OpenGL ES (with or
    without ANGLE), or dynamically switch between the available OpenGL
    implementations.

    \code
    configure.bat -opengl dynamic
    \endcode

    With the \c dynamic option, Qt will try to use native OpenGL first. If that
    fails, it will fall back to ANGLE and finally to software rendering in case
    of ANGLE failing as well.

    \code
    configure.bat -opengl desktop
    \endcode

    With the \c desktop option, Qt uses the OpenGL installed on Windows,
    requiring that the OpenGL in the target Windows machine is compatible with
    the application. The \c -opengl option accepts two versions of OpenGL ES, \c
    es2 for OpenGL ES 2.0 or \c es1 for OpenGL ES Common Profile.

    \code
    configure.bat -opengl es2
    \endcode

    You can also use \c{-opengl dynamic}, which enable applications to
    dynamically switch between the available options at runtime. For more
    details about the benefits of using dynamic GL-switching, see
    \l{Graphics Drivers}.
*/