Add support for configurable fonts

A style's default font is specified in qtquickcontrols2.conf in
a "Font" group under the style's section. QSettings supports the
following two alternative syntaxes:

    [Default]
    Font\Family=Open Sans
    Font\PixelSize=20

or

    [Default\Font]
    Family=Open Sans
    PixelSize=20

[ChangeLog][Controls] Added support for specifying the default
font for different styles in qtquickcontrols2.conf.

Change-Id: I54e1efb79a2913eab35174dbf09b6956fe740e28
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

3 files changed, 189 insertions, 2 deletions

diff --git a/src/quickcontrols2/qquicktheme.cpp b/src/quickcontrols2/qquicktheme.cpp
new file mode 100644
index 00000000..54653e6b
--- /dev/null
+++ b/src/quickcontrols2/qquicktheme.cpp
@@ -0,0 +1,112 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt Quick Controls 2 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 "qquicktheme_p.h"
+#include "qquickstyle_p.h"
+
+#include <QtCore/qmetaobject.h>
+#include <QtCore/qsettings.h>
+
+#include <functional>
+
+QT_BEGIN_NAMESPACE
+
+#if QT_CONFIG(settings)
+static void readValue(const QSharedPointer<QSettings> &settings, const QString &name, std::function<void(const QVariant &)> setValue)
+{
+    const QVariant var = settings->value(name);
+    if (var.isValid())
+        setValue(var);
+}
+
+template <typename Enum>
+static Enum toEnumValue(const QVariant &var)
+{
+    // ### TODO: expose QFont enums to the meta object system using Q_ENUM
+    //QMetaEnum enumeration = QMetaEnum::fromType<Enum>();
+    //bool ok = false;
+    //int value = enumeration.keyToValue(var.toByteArray(), &ok);
+    //if (!ok)
+    //    value = var.toInt();
+    //return static_cast<Enum>(value);
+
+    return static_cast<Enum>(var.toInt());
+}
+
+QFont *readFont(const QSharedPointer<QSettings> &settings)
+{
+    const QVariant var = settings->value(QStringLiteral("Font"));
+    if (var.isValid())
+        return new QFont(var.value<QFont>());
+
+    QFont f;
+    settings->beginGroup(QStringLiteral("Font"));
+    readValue(settings, QStringLiteral("Family"), [&f](const QVariant &var) { f.setFamily(var.toString()); });
+    readValue(settings, QStringLiteral("PointSize"), [&f](const QVariant &var) { f.setPointSizeF(var.toReal()); });
+    readValue(settings, QStringLiteral("PixelSize"), [&f](const QVariant &var) { f.setPixelSize(var.toInt()); });
+    readValue(settings, QStringLiteral("StyleHint"), [&f](const QVariant &var) { f.setStyleHint(toEnumValue<QFont::StyleHint>(var.toInt())); });
+    readValue(settings, QStringLiteral("Weight"), [&f](const QVariant &var) { f.setWeight(toEnumValue<QFont::Weight>(var)); });
+    readValue(settings, QStringLiteral("Style"), [&f](const QVariant &var) { f.setStyle(toEnumValue<QFont::Style>(var.toInt())); });
+    settings->endGroup();
+    return new QFont(f);
+}
+#endif // QT_CONFIG(settings)
+
+QQuickTheme::QQuickTheme(const QString &style)
+    : QQuickProxyTheme()
+{
+#if QT_CONFIG(settings)
+    QSharedPointer<QSettings> settings = QQuickStylePrivate::settings(style);
+    if (settings)
+        m_styleFont.reset(readFont(settings));
+#endif
+}
+
+const QFont *QQuickTheme::font(Font type) const
+{
+    Q_UNUSED(type);
+    return m_styleFont.data();
+}
+
+QFont QQuickTheme::resolveFont(const QFont &font) const
+{
+    if (!m_styleFont)
+        return font;
+
+    return m_styleFont->resolve(font);
+}
+
+QT_END_NAMESPACE
diff --git a/src/quickcontrols2/qquicktheme_p.h b/src/quickcontrols2/qquicktheme_p.h
new file mode 100644
index 00000000..7ddd1d1d
--- /dev/null
+++ b/src/quickcontrols2/qquicktheme_p.h
@@ -0,0 +1,73 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt Quick Controls 2 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 QQUICKTHEME_P_H
+#define QQUICKTHEME_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtQuickControls2/private/qquickproxytheme_p.h>
+#include <QtCore/qscopedpointer.h>
+#include <QtGui/qfont.h>
+
+QT_BEGIN_NAMESPACE
+
+class Q_QUICKCONTROLS2_PRIVATE_EXPORT QQuickTheme :  public QQuickProxyTheme
+{
+public:
+    QQuickTheme(const QString &name);
+
+    const QFont *font(Font type = SystemFont) const override;
+
+protected:
+    QFont resolveFont(const QFont &font) const;
+
+private:
+    QScopedPointer<QFont> m_styleFont;
+};
+
+QT_END_NAMESPACE
+
+#endif // QQUICKTHEME_P_H
diff --git a/src/quickcontrols2/quickcontrols2.pri b/src/quickcontrols2/quickcontrols2.pri
index bf96607b..31b8e66f 100644
--- a/src/quickcontrols2/quickcontrols2.pri
+++ b/src/quickcontrols2/quickcontrols2.pri
@@ -14,7 +14,8 @@ HEADERS += \
     $$PWD/qquickstyle_p.h \
     $$PWD/qquickstyleplugin_p.h \
     $$PWD/qquickstyleselector_p.h \
-    $$PWD/qquickstyleselector_p_p.h
+    $$PWD/qquickstyleselector_p_p.h \
+    $$PWD/qquicktheme_p.h
 
 SOURCES += \
     $$PWD/qquickanimatednode.cpp \
@@ -28,7 +29,8 @@ SOURCES += \
     $$PWD/qquickproxytheme.cpp \
     $$PWD/qquickstyle.cpp \
     $$PWD/qquickstyleplugin.cpp \
-    $$PWD/qquickstyleselector.cpp
+    $$PWD/qquickstyleselector.cpp \
+    $$PWD/qquicktheme.cpp
 
 qtConfig(quick-listview):qtConfig(quick-pathview) {
     HEADERS += \