Add QQuickStyle

Now that we have a good place for it, we can share a common base class
for QQuickMaterialStyle and QQuickUniversalStyle. QQuickStyle implements
the inheritance pattern for attached styles, in one place.

Change-Id: I459d98f96ce7c6de1ce7ef716e859f459278d8ad
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>

3 files changed, 289 insertions, 0 deletions

diff --git a/src/controls/controls.pri b/src/controls/controls.pri
index 4db9fea4..005ee839 100644
--- a/src/controls/controls.pri
+++ b/src/controls/controls.pri
@@ -1,10 +1,12 @@
 HEADERS += \
     $$PWD/qquickproxytheme_p.h \
+    $$PWD/qquickstyle_p.h \
     $$PWD/qquickstyleselector_p.h \
     $$PWD/qquickstyleselector_p_p.h \
     $$PWD/qquickpaddedrectangle_p.h
 
 SOURCES += \
     $$PWD/qquickproxytheme.cpp \
+    $$PWD/qquickstyle.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..b83f8c2a
--- /dev/null
+++ b/src/controls/qquickstyle.cpp
@@ -0,0 +1,201 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 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_p.h"
+
+#include <QtQuick/private/qquickitem_p.h>
+
+QT_BEGIN_NAMESPACE
+
+static QQuickStyle *attachedStyle(const QMetaObject *type, QObject *object, bool create = false)
+{
+    if (!object)
+        return Q_NULLPTR;
+    int idx = -1;
+    return qobject_cast<QQuickStyle *>(qmlAttachedPropertiesObject(&idx, object, type, create));
+}
+
+static QQuickStyle *findParentStyle(const QMetaObject *type, QObject *object)
+{
+    QQuickItem *item = qobject_cast<QQuickItem *>(object);
+    if (item) {
+        // lookup parent items
+        QQuickItem *parent = item->parentItem();
+        while (parent) {
+            QQuickStyle *style = attachedStyle(type, parent);
+            if (style)
+                return style;
+            parent = parent->parentItem();
+        }
+
+        // fallback to item's window
+        QQuickWindow *window = item->window();
+        if (window) {
+            QQuickStyle *style = attachedStyle(type, window);
+            if (style)
+                return style;
+        }
+    }
+
+    // lookup parent window
+    QQuickWindow *window = qobject_cast<QQuickWindow *>(object);
+    if (window) {
+        QQuickWindow *parentWindow = qobject_cast<QQuickWindow *>(window->parent());
+        if (parentWindow) {
+            QQuickStyle *style = attachedStyle(type, window);
+            if (style)
+                return style;
+        }
+    }
+
+    // fallback to engine (global)
+    if (object) {
+        QQmlEngine *engine = qmlEngine(object);
+        if (engine) {
+            QByteArray name = QByteArray("_q_") + type->className();
+            QQuickStyle *style = engine->property(name).value<QQuickStyle*>();
+            if (!style) {
+                style = attachedStyle(type, engine, true);
+                engine->setProperty(name, QVariant::fromValue(style));
+            }
+            return style;
+        }
+    }
+
+    return Q_NULLPTR;
+}
+
+static QList<QQuickStyle *> findChildStyles(const QMetaObject *type, QObject *object)
+{
+    QList<QQuickStyle *> children;
+
+    QQuickItem *item = qobject_cast<QQuickItem *>(object);
+    if (!item) {
+        QQuickWindow *window = qobject_cast<QQuickWindow *>(object);
+        if (window) {
+            item = window->contentItem();
+
+            foreach (QObject *child, window->children()) {
+                QQuickWindow *childWindow = qobject_cast<QQuickWindow *>(child);
+                if (childWindow) {
+                    QQuickStyle *style = attachedStyle(type, childWindow);
+                    if (style)
+                        children += style;
+                }
+            }
+        }
+    }
+
+    if (item) {
+        foreach (QQuickItem *child, item->childItems()) {
+            QQuickStyle *style = attachedStyle(type, child);
+            if (style)
+                children += style;
+            else
+                children += findChildStyles(type, child);
+        }
+    }
+
+    return children;
+}
+
+QQuickStyle::QQuickStyle(QObject *parent) : QObject(parent)
+{
+    QQuickItem *item = qobject_cast<QQuickItem *>(parent);
+    if (item)
+        QQuickItemPrivate::get(item)->addItemChangeListener(this, QQuickItemPrivate::Parent);
+}
+
+QQuickStyle::~QQuickStyle()
+{
+    QQuickItem *item = qobject_cast<QQuickItem *>(parent());
+    if (item)
+        QQuickItemPrivate::get(item)->removeItemChangeListener(this, QQuickItemPrivate::Parent);
+
+    setParentStyle(Q_NULLPTR);
+}
+
+QList<QQuickStyle *> QQuickStyle::childStyles() const
+{
+    return m_childStyles;
+}
+
+QQuickStyle *QQuickStyle::parentStyle() const
+{
+    return m_parentStyle;
+}
+
+void QQuickStyle::setParentStyle(QQuickStyle *style)
+{
+    if (m_parentStyle != style) {
+        QQuickStyle *oldParent = m_parentStyle;
+        if (m_parentStyle)
+            m_parentStyle->m_childStyles.removeOne(this);
+        m_parentStyle = style;
+        if (style)
+            style->m_childStyles.append(this);
+        parentStyleChange(style, oldParent);
+    }
+}
+
+void QQuickStyle::init()
+{
+    QQuickStyle *parentStyle = findParentStyle(metaObject(), parent());
+    if (parentStyle)
+        setParentStyle(parentStyle);
+
+    QList<QQuickStyle *> children = findChildStyles(metaObject(), parent());
+    foreach (QQuickStyle *child, children)
+        child->setParentStyle(this);
+}
+
+void QQuickStyle::parentStyleChange(QQuickStyle *newParent, QQuickStyle *oldParent)
+{
+    Q_UNUSED(newParent);
+    Q_UNUSED(oldParent);
+}
+
+void QQuickStyle::itemParentChanged(QQuickItem *item, QQuickItem *parent)
+{
+    QQuickStyle *style = attachedStyle(metaObject(), item);
+    if (style) {
+        QQuickStyle *parentStyle = findParentStyle(metaObject(), parent);
+        if (parentStyle)
+            style->setParentStyle(parentStyle);
+    }
+}
+
+QT_END_NAMESPACE
diff --git a/src/controls/qquickstyle_p.h b/src/controls/qquickstyle_p.h
new file mode 100644
index 00000000..3d4431cd
--- /dev/null
+++ b/src/controls/qquickstyle_p.h
@@ -0,0 +1,86 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 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_P_H
+#define QQUICKSTYLE_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 <QtQml/qqml.h>
+#include <QtCore/qlist.h>
+#include <QtCore/qobject.h>
+#include <QtCore/qpointer.h>
+#include <QtQuick/private/qquickitemchangelistener_p.h>
+
+QT_BEGIN_NAMESPACE
+
+class QQuickStyle : public QObject, public QQuickItemChangeListener
+{
+    Q_OBJECT
+
+public:
+    explicit QQuickStyle(QObject *parent = Q_NULLPTR);
+    ~QQuickStyle();
+
+protected:
+    void init();
+
+    QList<QQuickStyle *> childStyles() const;
+
+    QQuickStyle *parentStyle() const;
+    void setParentStyle(QQuickStyle *style);
+
+    virtual void parentStyleChange(QQuickStyle *newParent, QQuickStyle *oldParent);
+
+    void itemParentChanged(QQuickItem *item, QQuickItem *parent) Q_DECL_OVERRIDE;
+
+private:
+    QList<QQuickStyle *> m_childStyles;
+    QPointer<QQuickStyle> m_parentStyle;
+};
+
+QT_END_NAMESPACE
+
+#endif // QQUICKSTYLE_P_H