Add public API for setting and getting the style from C++

TODO: setup QtLabsControls C++ module docs

Task-number: QTBUG-50787
Change-Id: I382bad34df88d13fb9a74b3d2f9203280dfb4a66
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>

6 files changed, 264 insertions, 47 deletions

diff --git a/src/controls/controls.pri b/src/controls/controls.pri
index dcc40024..a0c82fce 100644
--- a/src/controls/controls.pri
+++ b/src/controls/controls.pri
@@ -1,6 +1,7 @@
 HEADERS += \
     $$PWD/qquickcolorimageprovider_p.h \
     $$PWD/qquickproxytheme_p.h \
+    $$PWD/qquickstyle.h \
     $$PWD/qquickstyleattached_p.h \
     $$PWD/qquickstyleselector_p.h \
     $$PWD/qquickstyleselector_p_p.h \
@@ -9,6 +10,7 @@ HEADERS += \
 SOURCES += \
     $$PWD/qquickcolorimageprovider.cpp \
     $$PWD/qquickproxytheme.cpp \
+    $$PWD/qquickstyle.cpp \
     $$PWD/qquickstyleattached.cpp \
     $$PWD/qquickstyleselector.cpp \
     $$PWD/qquickpaddedrectangle.cpp
diff --git a/src/controls/qquickstyle.cpp b/src/controls/qquickstyle.cpp
new file mode 100644
index 00000000..e6be5efd
--- /dev/null
+++ b/src/controls/qquickstyle.cpp
@@ -0,0 +1,168 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt Labs Controls module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** 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
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qquickstyle.h"
+#include "qquickstyleattached_p.h"
+
+#include <QtCore/qsettings.h>
+#include <QtGui/private/qguiapplication_p.h>
+#include <QtQml/private/qqmlmetatype_p.h>
+#include <QtQml/qqmlfile.h>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QQuickStyle
+    \brief The QQQuickStyle class allows configuring the application style.
+    \inmodule QtLabsControls
+
+    QQuickStyle provides API for querying and configuring the application
+    \l {Styling Qt Labs Controls}{styles} of Qt Labs Controls.
+
+    \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 Labs Controls. It is not possible to change the style after the QML
+    types have been registered.
+
+    \sa {Styling Qt Labs Controls}
+*/
+
+struct QQuickStyleSpec
+{
+    QQuickStyleSpec() : 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 = !s.isEmpty();
+    }
+
+    void resolve()
+    {
+        style = QGuiApplicationPrivate::styleOverride;
+        if (style.isEmpty())
+            style = QString::fromLatin1(qgetenv("QT_LABS_CONTROLS_STYLE"));
+        if (style.isEmpty()) {
+            QSharedPointer<QSettings> settings = QQuickStyleAttached::settings(QStringLiteral("Controls"));
+            if (settings)
+                style = settings->value(QStringLiteral("Style")).toString();
+        }
+        resolved = QGuiApplication::instance();
+    }
+
+    bool resolved;
+    QString style;
+};
+
+Q_GLOBAL_STATIC(QQuickStyleSpec, styleSpec)
+
+/*!
+    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 Labs Controls 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.
+
+    \note The style must be configured \b before loading QML that imports Qt Labs Controls.
+          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("Qt.labs.controls"), 1, 0)) {
+        qWarning() << "ERROR: QQuickStyle::setStyle() must be called before loading QML that imports Qt Labs Controls.";
+        return;
+    }
+
+    styleSpec()->setStyle(style);
+}
+
+QT_END_NAMESPACE
diff --git a/src/controls/qquickstyle.h b/src/controls/qquickstyle.h
new file mode 100644
index 00000000..062b7fbb
--- /dev/null
+++ b/src/controls/qquickstyle.h
@@ -0,0 +1,56 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt Labs Controls module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** 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
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QQUICKSTYLE_H
+#define QQUICKSTYLE_H
+
+#include <QtCore/qurl.h>
+#include <QtCore/qstring.h>
+#include <QtLabsControls/qtlabscontrolsglobal.h>
+
+QT_BEGIN_NAMESPACE
+
+class Q_LABSCONTROLS_EXPORT QQuickStyle
+{
+public:
+    static QString name();
+    static QString path();
+    static void setStyle(const QString &style);
+};
+
+QT_END_NAMESPACE
+
+#endif // QQUICKSTYLE_H
diff --git a/src/controls/qquickstyleselector.cpp b/src/controls/qquickstyleselector.cpp
index 792812cf..a9778b07 100644
--- a/src/controls/qquickstyleselector.cpp
+++ b/src/controls/qquickstyleselector.cpp
@@ -34,6 +34,7 @@
 
 #include "qquickstyleselector_p.h"
 #include "qquickstyleselector_p_p.h"
+#include "qquickstyle.h"
 
 #include <QtCore/QDir>
 #include <QtCore/QMutex>
@@ -45,7 +46,6 @@
 #include <QtCore/QSettings>
 
 #include <QtGui/private/qguiapplication_p.h>
-#include <QtLabsControls/private/qquickstyleattached_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -58,15 +58,6 @@ QQuickStyleSelectorPrivate::QQuickStyleSelectorPrivate()
 
 QQuickStyleSelector::QQuickStyleSelector() : d_ptr(new QQuickStyleSelectorPrivate)
 {
-    Q_D(QQuickStyleSelector);
-    d->style = QGuiApplicationPrivate::styleOverride.toLower();
-    if (d->style.isEmpty())
-        d->style = QString::fromLatin1(qgetenv("QT_LABS_CONTROLS_STYLE")).toLower();
-    if (d->style.isEmpty()) {
-        QSharedPointer<QSettings> settings = QQuickStyleAttached::settings(QStringLiteral("Controls"));
-        if (settings)
-            d->style = settings->value(QStringLiteral("Style")).toString().toLower();
-    }
 }
 
 QQuickStyleSelector::~QQuickStyleSelector()
@@ -82,22 +73,6 @@ static bool isLocalScheme(const QString &file)
     return local;
 }
 
-QString QQuickStyleSelector::select(const QString &fileName) const
-{
-    Q_D(const QQuickStyleSelector);
-    QUrl url(d->baseUrl.toString() + QLatin1Char('/') + fileName);
-    if (isLocalScheme(url.scheme()) || url.isLocalFile()) {
-        if (isLocalScheme(url.scheme())) {
-            QString equivalentPath = QLatin1Char(':') + url.path();
-            QString selectedPath = d->select(equivalentPath);
-            url.setPath(selectedPath.remove(0, 1));
-        } else {
-            url = QUrl::fromLocalFile(d->select(url.toLocalFile()));
-        }
-    }
-    return url.toString();
-}
-
 static QString selectionHelper(const QString &path, const QString &fileName, const QStringList &selectors)
 {
     /* selectionHelper does a depth-first search of possible selected files. Because there is strict
@@ -124,6 +99,35 @@ static QString selectionHelper(const QString &path, const QString &fileName, con
     return path + fileName;
 }
 
+QString QQuickStyleSelector::select(const QString &fileName) const
+{
+    Q_D(const QQuickStyleSelector);
+    const QString overridePath = QQuickStyle::path();
+    if (!overridePath.isEmpty()) {
+        const QString stylePath = overridePath + QQuickStyle::name() + QLatin1Char('/');
+        if (QFile::exists(stylePath + fileName)) {
+            // the style name is included to the path, so exclude it from the selectors.
+            // the rest of the selectors (os, locale) are still valid, though.
+            const QString selectedPath = selectionHelper(stylePath, fileName, d->allSelectors(false));
+            if (selectedPath.startsWith(QLatin1Char(':')))
+                return QLatin1String("qrc") + selectedPath;
+            return QUrl::fromLocalFile(selectedPath).toString();
+        }
+    }
+
+    QUrl url(d->baseUrl.toString() + QLatin1Char('/') + fileName);
+    if (isLocalScheme(url.scheme()) || url.isLocalFile()) {
+        if (isLocalScheme(url.scheme())) {
+            QString equivalentPath = QLatin1Char(':') + url.path();
+            QString selectedPath = d->select(equivalentPath);
+            url.setPath(selectedPath.remove(0, 1));
+        } else {
+            url = QUrl::fromLocalFile(d->select(url.toLocalFile()));
+        }
+    }
+    return url.toString();
+}
+
 QString QQuickStyleSelectorPrivate::select(const QString &filePath) const
 {
     QFileInfo fi(filePath);
@@ -132,32 +136,23 @@ QString QQuickStyleSelectorPrivate::select(const QString &filePath) const
         return filePath;
 
     QString ret = selectionHelper(fi.path().isEmpty() ? QString() : fi.path() + QLatin1Char('/'),
-            fi.fileName(), allSelectors());
+            fi.fileName(), allSelectors(true));
 
     if (!ret.isEmpty())
         return ret;
     return filePath;
 }
 
-QString QQuickStyleSelector::style() const
-{
-    Q_D(const QQuickStyleSelector);
-    return d->style;
-}
-
-void QQuickStyleSelector::setStyle(const QString &s)
-{
-    Q_D(QQuickStyleSelector);
-    d->style = s;
-}
-
-QStringList QQuickStyleSelectorPrivate::allSelectors() const
+QStringList QQuickStyleSelectorPrivate::allSelectors(bool includeStyle) const
 {
     QMutexLocker locker(&sharedDataMutex);
     updateSelectors();
     QStringList selectors = sharedData->staticSelectors;
-    if (!style.isEmpty())
-        selectors.prepend(style);
+    if (includeStyle) {
+        QString style = QQuickStyle::name();
+        if (!style.isEmpty())
+            selectors.prepend(style.toLower());
+    }
     return selectors;
 }
 
diff --git a/src/controls/qquickstyleselector_p.h b/src/controls/qquickstyleselector_p.h
index d972dd95..56a3b386 100644
--- a/src/controls/qquickstyleselector_p.h
+++ b/src/controls/qquickstyleselector_p.h
@@ -62,9 +62,6 @@ public:
 
     QString select(const QString &fileName) const;
 
-    QString style() const;
-    void setStyle(const QString &s);
-
     void setBaseUrl(const QUrl &base);
     QUrl baseUrl() const;
 
diff --git a/src/controls/qquickstyleselector_p_p.h b/src/controls/qquickstyleselector_p_p.h
index e4df1035..dc91af5f 100644
--- a/src/controls/qquickstyleselector_p_p.h
+++ b/src/controls/qquickstyleselector_p_p.h
@@ -69,9 +69,8 @@ public:
     static void addStatics(const QStringList &); //For loading GUI statics from other Qt modules
     QQuickStyleSelectorPrivate();
     QString select(const QString &filePath) const;
-    QStringList allSelectors() const;
+    QStringList allSelectors(bool includeStyle) const;
 
-    QString style;
     QUrl baseUrl;
 };