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** Copyright (C) 2016 The Qt Company Ltd.
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** This file is part of the Qt Quick Controls 2 module of the Qt Toolkit.
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** Alternatively, this file may be used under the terms of the GNU Lesser
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or later as published by the Free
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****************************************************************************/

#include "qquickstyle.h"
#include "qquickstyle_p.h"
#include "qquickstyleattached_p.h"

#include <QtCore/qdir.h>
#include <QtCore/qdebug.h>
#include <QtCore/qsettings.h>
#include <QtCore/qlibraryinfo.h>
#include <QtGui/private/qguiapplication_p.h>
#include <QtQml/private/qqmlmetatype_p.h>
#include <QtQml/qqmlengine.h>
#include <QtQml/qqmlfile.h>

QT_BEGIN_NAMESPACE

/*!
    \class QQuickStyle
    \brief The QQuickStyle class allows configuring the application style.
    \inmodule QtQuickControls2
    \since 5.7

    QQuickStyle provides API for querying and configuring the application
    \l {Styling Qt Quick Controls 2}{styles} of Qt Quick Controls 2.

    \code
    #include <QGuiApplication>
    #include <QQmlApplicationEngine>
    #include <QQuickStyle>

    int main(int argc, char *argv[])
    {
        QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
        QGuiApplication app(argc, argv);

        QQuickStyle::setStyle("Material");

        QQmlApplicationEngine engine;
        engine.load(QUrl("qrc:/main.qml"));

        return app.exec();
    }
    \endcode

    \note The style must be configured \b before loading QML that imports
    Qt Quick Controls 2. It is not possible to change the style after the QML
    types have been registered.

    The style can also be specified as a path to a custom style, such as
    \c ":/mystyle". See \l {Creating a Custom Style} for more details about
    building custom styles. Custom styles do not need to implement all controls.
    By default, the styling system uses the \l {Default style} as a fallback
    for controls that a custom style does not provide. It is possible to
    specify a different fallback style to customize or extend one of the
    built-in styles.

    \code
    QQuickStyle::setStyle(":/mystyle");
    QQuickStyle::setFallbackStyle("Material");
    \endcode

    \sa {Styling Qt Quick Controls 2}
*/

// TODO: QQmlImportDatabase::defaultImportPathList()
static QStringList defaultImportPathList()
{
    QStringList importPaths;
    importPaths.reserve(3);
    importPaths += QLibraryInfo::location(QLibraryInfo::Qml2ImportsPath);

    if (Q_UNLIKELY(!qEnvironmentVariableIsEmpty("QML2_IMPORT_PATH"))) {
        const QByteArray envImportPath = qgetenv("QML2_IMPORT_PATH");
        importPaths += QString::fromLatin1(envImportPath).split(QDir::listSeparator(), QString::SkipEmptyParts);
    }

    importPaths += QStringLiteral("qrc:/qt-project.org/imports");
    importPaths += QCoreApplication::applicationDirPath();
    return importPaths;
}

struct QQuickStyleSpec
{
    QQuickStyleSpec() : custom(false), resolved(false) { }

    QString name()
    {
        if (!resolved)
            resolve();
        return style.mid(style.lastIndexOf(QLatin1Char('/')) + 1);
    }

    QString path()
    {
        if (!resolved)
            resolve();
        QString s = style;
        if (QQmlFile::isLocalFile(s))
            s = QQmlFile::urlToLocalFileOrQrc(s);
        return s.left(s.lastIndexOf(QLatin1Char('/')) + 1);
    }

    void setStyle(const QString &s)
    {
        style = s;
        resolved = false;
        resolve();
    }

    void setFallbackStyle(const QString &fallback, const QByteArray &method)
    {
        fallbackStyle = fallback;
        fallbackMethod = method;
    }

    static QString findStyle(const QString &path, const QString &name)
    {
        QDir dir(path);
        if (!dir.exists())
            return QString();

        if (name.isEmpty())
            return dir.absolutePath() + QLatin1Char('/');

        const QStringList entries = dir.entryList(QStringList(), QDir::Dirs | QDir::NoDotAndDotDot);
        for (const QString &entry : entries) {
            if (entry.compare(name, Qt::CaseInsensitive) == 0)
                return dir.absoluteFilePath(entry);
        }

        return QString();
    }

    void resolve(const QUrl &baseUrl = QUrl())
    {
        if (style.isEmpty())
            style = QGuiApplicationPrivate::styleOverride;
        if (style.isEmpty())
            style = QString::fromLatin1(qgetenv("QT_QUICK_CONTROLS_STYLE"));
        if (fallbackStyle.isEmpty())
            setFallbackStyle(QString::fromLatin1(qgetenv("QT_QUICK_CONTROLS_FALLBACK_STYLE")), "QT_QUICK_CONTROLS_FALLBACK_STYLE");
        if (style.isEmpty() || fallbackStyle.isEmpty()) {
            QSharedPointer<QSettings> settings = QQuickStyleAttached::settings(QStringLiteral("Controls"));
            if (settings) {
                if (style.isEmpty())
                    style = settings->value(QStringLiteral("Style")).toString();
                if (fallbackStyle.isEmpty())
                    setFallbackStyle(settings->value(QStringLiteral("FallbackStyle")).toString(), ":/qtquickcontrols2.conf");
            }
        }
        custom = style.contains(QLatin1Char('/'));

        if (baseUrl.isValid()) {
            QString path = QQmlFile::urlToLocalFileOrQrc(baseUrl);
            QString stylePath = findStyle(path, style);
            if (!stylePath.isEmpty()) {
                style = stylePath;
                resolved = true;
            }
        }

        if (QGuiApplication::instance()) {
            if (!custom) {
                const QStringList stylePaths = QQuickStylePrivate::stylePaths();
                for (const QString &path : stylePaths) {
                    QString stylePath = findStyle(path, style);
                    if (!stylePath.isEmpty()) {
                        custom = !stylePath.startsWith(baseUrl.toLocalFile());
                        style = stylePath;
                        resolved = true;
                        break;
                    }
                }
            }
            resolved = true;
        }
    }

    void reset()
    {
        custom = false;
        resolved = false;
        style.clear();
        fallbackStyle.clear();
        fallbackMethod.clear();
    }

    bool custom;
    bool resolved;
    QString style;
    QString fallbackStyle;
    QByteArray fallbackMethod;
};

Q_GLOBAL_STATIC(QQuickStyleSpec, styleSpec)

QStringList QQuickStylePrivate::stylePaths()
{
    // system/custom style paths
    QStringList paths;
    if (Q_UNLIKELY(!qEnvironmentVariableIsEmpty("QT_QUICK_CONTROLS_STYLE_PATH"))) {
        const QByteArray value = qgetenv("QT_QUICK_CONTROLS_STYLE_PATH");
        paths += QString::fromLatin1(value).split(QDir::listSeparator(), QString::SkipEmptyParts);
    }

    // built-in import paths
    const QString targetPath = QStringLiteral("QtQuick/Controls.2");
    const QStringList importPaths = defaultImportPathList();
    for (const QString &importPath : importPaths) {
        QDir dir(importPath);
        if (dir.cd(targetPath))
            paths += dir.absolutePath();
    }

    return paths;
}

QString QQuickStylePrivate::fallbackStyle()
{
    return styleSpec()->fallbackStyle;
}

bool QQuickStylePrivate::isCustomStyle()
{
    return styleSpec()->custom;
}

void QQuickStylePrivate::init(const QUrl &baseUrl)
{
    QQuickStyleSpec *spec = styleSpec();
    spec->resolve(baseUrl);

    if (!spec->fallbackStyle.isEmpty()) {
        QString fallbackStyle = spec->findStyle(baseUrl.toLocalFile(), spec->fallbackStyle);
        if (fallbackStyle.isEmpty()) {
            if (spec->fallbackStyle.compare(QStringLiteral("Default")) != 0) {
                qWarning() << "ERROR: unable to locate fallback style" << spec->fallbackStyle;
                qInfo().nospace().noquote() << spec->fallbackMethod << ": the fallback style must be the name of one of the built-in Qt Quick Controls 2 styles.";
            }
            spec->fallbackStyle.clear();
        }
    }
}

void QQuickStylePrivate::reset()
{
    styleSpec()->reset();
}

/*!
    Returns the name of the application style.

    \note The application style can be specified by passing a \c -style command
          line argument. Therefore \c name() may not return a fully resolved
          value if called before constructing a QGuiApplication.
*/
QString QQuickStyle::name()
{
    return styleSpec()->name();
}

/*!
    Returns the path of an overridden application style, or an empty
    string if the style is one of the built-in Qt Quick Controls 2 styles.

    \note The application style can be specified by passing a \c -style command
          line argument. Therefore \c path() may not return a fully resolved
          value if called before constructing a QGuiApplication.
*/
QString QQuickStyle::path()
{
    return styleSpec()->path();
}

/*!
    Sets the application style to \a style.

    \note The style must be configured \b before loading QML that imports Qt Quick Controls 2.
          It is not possible to change the style after the QML types have been registered.
*/
void QQuickStyle::setStyle(const QString &style)
{
    if (QQmlMetaType::isModule(QStringLiteral("QtQuick.Controls"), 2, 0)) {
        qWarning() << "ERROR: QQuickStyle::setStyle() must be called before loading QML that imports Qt Quick Controls 2.";
        return;
    }

    styleSpec()->setStyle(style);
}

/*!
    \since 5.8
    Sets the application fallback style to \a style.

    \note The fallback style must be the name of one of the built-in Qt Quick Controls 2 styles, e.g. "Material".

    \note The style must be configured \b before loading QML that imports Qt Quick Controls 2.
          It is not possible to change the style after the QML types have been registered.

    The fallback style can be also specified by setting the \c QT_QUICK_CONTROLS_FALLBACK_STYLE
    \l {Supported Environment Variables in Qt Quick Controls 2}{environment variable}.
*/
void QQuickStyle::setFallbackStyle(const QString &style)
{
    if (QQmlMetaType::isModule(QStringLiteral("QtQuick.Controls"), 2, 0)) {
        qWarning() << "ERROR: QQuickStyle::setFallbackStyle() must be called before loading QML that imports Qt Quick Controls 2.";
        return;
    }

    styleSpec()->setFallbackStyle(style, "QQuickStyle::setFallbackStyle()");
}

/*!
    \since 5.9
    Returns the names of the available built-in styles.

    \note The method must be called \b after creating an instance of QGuiApplication.
*/
QStringList QQuickStyle::availableStyles()
{
    QStringList styles;
    if (!QGuiApplication::instance()) {
        qWarning() << "ERROR: QQuickStyle::availableStyles() must be called after creating an instance of QGuiApplication.";
        return styles;
    }

    const QStringList stylePaths = QQuickStylePrivate::stylePaths();
    for (const QString &path : stylePaths) {
        QDir dir(path);
        styles += dir.entryList(QStringList(), QDir::Dirs | QDir::NoDotAndDotDot);
        styles.removeAll(QStringLiteral("designer"));
    }
    styles.prepend(QStringLiteral("Default"));
    styles.removeDuplicates();
    return styles;
}

QT_END_NAMESPACE