// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
    \page qtquickcontrols-styles.html
    \title Styling Qt Quick Controls

    \section1 Available Styles

    Qt Quick Controls comes with a selection of styles.

    \section2 Basic Style

    \image qtquickcontrols-basic.png
           {Gallery of controls in Basic style}

    The \l {Basic Style} is a simple and light-weight all-round style that offers
    the maximum performance for Qt Quick Controls.

    \section2 Fusion Style

    \include style-screenshots.qdocinc {file} {Fusion} {fusion}

    The \l {Fusion Style} is a platform-agnostic style that offers a desktop-oriented
    look and feel for Qt Quick Controls.

    \section2 Imagine Style

    \image qtquickcontrols-imagine.png
           {Gallery of controls in Imagine style}

    The \l {Imagine Style} is based on image assets. The style comes with a default
    set of images which can easily be changed by providing a directory
    with images using a predefined naming convention.

    \section2 macOS Style

    \include style-screenshots.qdocinc {file} {macOS} {macos}

    The \l {macOS Style} is a native-looking style for macOS.
    \note this style is only available for applications running on macOS.

    \section2 iOS Style

    \include style-screenshots.qdocinc {file} {iOS} {ios}

    The \l {iOS Style} is a native-looking style for iOS based on image assets.
    \note this style is only available for applications running on iOS.

    \section2 Material Style

    \include style-screenshots.qdocinc {file} {Material} {material}

    The \l {Material Style} offers an appealing design based on the
    \l {https://www.google.com/design/spec/material-design/introduction.html}
    {Google Material Design Guidelines}, but requires more system resources than
    the Basic style.

    \section2 Universal Style

    \include style-screenshots.qdocinc {file} {Universal} {universal}

    The \l {Universal Style} offers an appealing design based on the
    Microsoft Universal Design Guidelines,
    but requires more system resources than the Basic style.

    \section2 Windows Style

    \image qtquickcontrols-windows.png
           {Gallery of controls in Windows style}

    The \l {Windows Style} is a native-looking style for Windows.
    \note this style is only available for applications running on Windows.

    \section2 FluentWinUI3 Style

    \include style-screenshots.qdocinc {file} {FluentWinUI3} {fluentwinui3}

    The \l {FluentWinUI3 Style} is a modern, native-looking style designed for platforms
    running Windows 11 and above, which follows the Fluent UI and the WinUI 3 design guidelines.
    The FluentWinUI3 can be run on all supported platforms.

    \section1 Using Styles in Qt Quick Controls

    \section2 Default Styles

    If no style is explicitly set, a default style will be used. The style that
    is used depends on the operating system:

    \list
    \li Android: \l {Material Style}
    \li iOS: \l {iOS Style}
    \li Linux: \l {Fusion Style}
    \li macOS: \l {macOS Style}
    \li Windows: \l {Windows Style}
    \endlist

    For all other operating systems, the \l {Basic Style} is used.

    \section2 Compile-Time Style Selection

    Compile-time style selection is a way of specifying a style to use by
    directly or indirectly importing it in QML. Since it is selected at compile
    time, you cannot change the style at run time if you use compile-time style
    selection.

    The most convenient way to use comile-time style selection is to import the
    \e{QtQuick.Controls.Native} style. \c{QtQuick.Controls.Native} in turn
    imports the \l{Default Styles}{default style} for the target platform. If
    you import \c{QtQuick.Controls.Native}, you should not import any specific
    other styles, nor the (run-time selected) \c{QtQuick.Controls} module.
    \c{QtQuick.Controls.Native} imports the platform-default style for you and
    that style handles its fallback. You can't have more than one top-level
    style at the same time. For example:

    \qml
    // Refrain from importing QtQuick.Controls or specific styles.
    import QtQuick.Controls.Native

    ApplicationWindow {
        // ...
    }
    \endqml

    However, you can also import one specific style at compile time,
    disregarding the platform defaults. For example, to import the Material
    style:

    \qml
    // The style must be imported before any other QtQuick.Controls imports
    // in order for run-time style selection API like QQuickStyle::name() to
    // work.
    import QtQuick.Controls.Material

    ApplicationWindow {
        // ...
    }
    \endqml

    Notice that \c {QtQuick.Controls} (which is responsible for run-time style
    selection) is not imported. The fallback style is specified by the qmldir
    of the style:

    \badcode
    module QtQuick.Controls.Material
    # ...
    import QtQuick.Controls.Basic auto
    \endcode

    The benefit of compile-time style selection is that the
    \l {The QML script compiler}{QML compiler} knows which specific style
    is in use and can generate C++ code for bindings.

    Another benefit is that the \c {QtQuick.Controls} plugin is not used and
    therefore does not need to be deployed with the application.

    Explicit imports are also necessary if your application is built
    \l {Static Builds}{statically}.

    A disadvantage of compile-time style selection is that one executable
    cannot support multiple styles, as each style requires its own.

    See \l {Mixing Style Selection} for information about mixing
    compile-time and run-time style selection.

    \section2 Run-Time Style Selection

    Run-time style selection is a way of specifying a style to use by importing
    \c QtQuick.Controls:

    \qml
    import QtQuick.Controls
    \endqml

    The \c{QtQuick.Controls} plugin will import the style that was set at runtime
    via one of the following approaches:

    \list
    \li \l[CPP]{QQuickStyle::setStyle()}
    \li The \c -style command line argument
    \li The \l {Supported Environment Variables in Qt Quick Controls}
        {QT_QUICK_CONTROLS_STYLE environment variable}
    \li The \l {Qt Quick Controls Configuration File}{qtquickcontrols2.conf
        configuration file}
    \endlist

    The priority of these approaches follows the order they are listed,
    from highest to lowest. That is, using \c QQuickStyle to set the style will
    always take priority over using the command line argument, for example.

    Similarly, the fallback style can be set via one of the following methods:
    \list
    \li \l[CPP]{QQuickStyle::setFallbackStyle()}
    \li The \l {Supported Environment Variables in Qt Quick Controls}
        {QT_QUICK_CONTROLS_FALLBACK_STYLE environment variable}
    \li The \l {Qt Quick Controls Configuration File}{qtquickcontrols2.conf
        configuration file}
    \endlist

    \note you can only dynamically choose the fallback style if it hasn't been
    chosen statically in the main style's qmldir file.

    The benefit of run-time style selection is that a single application binary
    can support multiple styles, meaning that the end user can choose which
    style to run the application with.

    A disadvantage of this approach is that \l {The QML script compiler}
    {QML compiler} can't know which specific style is in use and therefore
    cannot generate C++ code for bindings on properties of Qt Quick Controls
    types. This does not affect the QML compiler's abilities to generate C++
    for bindings on types from other modules.

    See \l {Mixing Style Selection} for information about mixing
    run-time and compile-time style selection.

    \section2 Style-specific APIs

    Several styles expose APIs specific to that style, for example the
    \l{Material Style} attached object or the \l{Universal Style} attached
    object. These style-specific APIs are only available when their style is
    actually selected, directly or indirectly, using either compile-time or
    run-time style selection.

    \section2 Mixing Style Selection

    It is recommended to only use either compile-time or run-time style
    selection in your application. However, if your application loads third
    party QML code, for example, it may not be possible to control which
    imports are used. If you do mix the two approaches, be aware of the
    following limitations:

    \list
    \li Compile-time style selection overrides run-time style selection.
    \li The style that you want to use should always be explicitly imported
        before any other Controls import. If you don't do this, theming (such
        as fonts and palettes) will not behave as expected. The first
        explicitly imported style is also what QQuickStyle::name() will report.
        \omit
        (Also, \e only the first imported style's QQuick*Theme::initialize()
        will be called (assuming it's one of the built-in styles). This is not
        unique to compile-time selection, as only one theme's initialize
        function is ever called, but it is worth pointing out that the order
        matters)
        \endomit
    \li The last explicitly imported style is what will actually be used. For
        example, if you import \c QtQuick.Controls first and then
        \c QtQuick.Controls.Material, the Material style's Button.qml will be
        used when a Button is created.
        Due to the previous point about theming, it is for this reason that you
        should never explicitly import two different styles in the same
        application.
    \li If you intend to use compile-time style selection but load code that
        imports \c QtQuick.Controls, be aware that calling QQuickStyle::name()
        before a style has been explicitly imported will cause the platform
        default to be reported. If you can't avoid this, set the style to match
        the compile-time one beforehand via \l QQuickStyle::setStyle() or one
        of the other ways listed in \l {Run-Time Style Selection}.
    \endlist

    \section3 Using QQuickStyle in C++

    \l[CPP]{QQuickStyle} provides C++ API for configuring a specific
    style. The following example runs a Qt Quick Controls application
    with the Material style:

    \code
    QQuickStyle::setStyle("Material");
    \endcode

    See the detailed description of \l[CPP]{QQuickStyle} for more
    details.

    \section3 Command line argument

    Passing a \c -style command line argument is the convenient way to test different
    styles. It takes precedence over the other methods listed below. The following
    example runs a Qt Quick Controls application with the Material style:

    \code
    ./app -style Material
    \endcode

    \section3 Environment variable

    Setting the \c QT_QUICK_CONTROLS_STYLE environment variable can be used to set
    a system-wide style preference. It takes precedence over the configuration file
    mentioned below. The following example runs a Qt Quick Controls application with
    the Universal style:

    \code
    QT_QUICK_CONTROLS_STYLE=Universal ./app
    \endcode

    See \l {Supported Environment Variables in Qt Quick Controls} for the full list
    of supported environment variables.

    \section3 Configuration file

    Qt Quick Controls support a special configuration file, \c :/qtquickcontrols2.conf,
    that is built into an application's resources.

    The configuration file can specify the preferred style (may be overridden by either
    of the methods described earlier) and certain style-specific attributes. The following
    example specifies that the preferred style is the Material style.

    \code
    [Controls]
    Style=Material
    \endcode

    See \l {Qt Quick Controls Configuration File} for more details about the
    configuration file.

    \section1 Related Information
    \list
    \li \l {Basic Style}
    \li \l {Fusion Style}
    \li \l {Imagine Style}
    \li \l {Material Style}
    \li \l {Universal Style}
    \li \l {FluentWinUI3 Style}
    \li \l {Customizing Qt Quick Controls}
    \li \l {Using File Selectors with Qt Quick Controls}
    \li \l {Deploying Qt Quick Controls Applications}
    \li \l {Qt Quick Controls Configuration File}
    \li \l {Supported Environment Variables in Qt Quick Controls}
    \endlist
*/
