QQuickTabBar: introduce index/tabBar/position attached properties

The upcoming Fusion style tab buttons are visually different depending
on whether the tab bar is at the top or at the bottom. Let styles access
the tab bar via attached properties to be able to visualize such things.

[ChangeLog][Controls][TabBar] Added index/tabBar/position attached
properties.

Change-Id: I1ff8105ac8600dad3ed5c6aafc6d85cf06283bed
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 123 insertions, 0 deletions

diff --git a/src/quicktemplates2/qquicktabbar.cpp b/src/quicktemplates2/qquicktabbar.cpp
index c255ef1b4e..2f025dcf86 100644
--- a/src/quicktemplates2/qquicktabbar.cpp
+++ b/src/quicktemplates2/qquicktabbar.cpp
@@ -116,6 +116,28 @@ public:
     QQuickTabBar::Position position;
 };
 
+class QQuickTabBarAttachedPrivate : public QObjectPrivate
+{
+    Q_DECLARE_PUBLIC(QQuickTabBarAttached)
+
+public:
+    QQuickTabBarAttachedPrivate()
+        : index(-1),
+          tabBar(nullptr)
+    {
+    }
+
+    static QQuickTabBarAttachedPrivate *get(QQuickTabBarAttached *attached)
+    {
+        return attached->d_func();
+    }
+
+    void update(QQuickTabBar *tabBar, int index);
+
+    int index;
+    QQuickTabBar *tabBar;
+};
+
 QQuickTabBarPrivate::QQuickTabBarPrivate()
     : updatingLayout(false),
       hasContentWidth(false),
@@ -351,6 +373,11 @@ void QQuickTabBar::resetContentHeight()
         d->updateLayout();
 }
 
+QQuickTabBarAttached *QQuickTabBar::qmlAttachedProperties(QObject *object)
+{
+    return new QQuickTabBarAttached(object);
+}
+
 void QQuickTabBar::updatePolish()
 {
     Q_D(QQuickTabBar);
@@ -385,16 +412,29 @@ void QQuickTabBar::itemAdded(int index, QQuickItem *item)
     QQuickItemPrivate::get(item)->setCulled(true); // QTBUG-55129
     if (QQuickTabButton *button = qobject_cast<QQuickTabButton *>(item))
         QObjectPrivate::connect(button, &QQuickTabButton::checkedChanged, d, &QQuickTabBarPrivate::updateCurrentIndex);
+    QQuickTabBarAttached *attached = qobject_cast<QQuickTabBarAttached *>(qmlAttachedPropertiesObject<QQuickTabBar>(item));
+    if (attached)
+        QQuickTabBarAttachedPrivate::get(attached)->update(this, index);
     if (isComponentComplete())
         polish();
 }
 
+void QQuickTabBar::itemMoved(int index, QQuickItem *item)
+{
+    QQuickTabBarAttached *attached = qobject_cast<QQuickTabBarAttached *>(qmlAttachedPropertiesObject<QQuickTabBar>(item));
+    if (attached)
+        QQuickTabBarAttachedPrivate::get(attached)->update(this, index);
+}
+
 void QQuickTabBar::itemRemoved(int index, QQuickItem *item)
 {
     Q_D(QQuickTabBar);
     Q_UNUSED(index);
     if (QQuickTabButton *button = qobject_cast<QQuickTabButton *>(item))
         QObjectPrivate::disconnect(button, &QQuickTabButton::checkedChanged, d, &QQuickTabBarPrivate::updateCurrentIndex);
+    QQuickTabBarAttached *attached = qobject_cast<QQuickTabBarAttached *>(qmlAttachedPropertiesObject<QQuickTabBar>(item));
+    if (attached)
+        QQuickTabBarAttachedPrivate::get(attached)->update(nullptr, -1);
     if (isComponentComplete())
         polish();
 }
@@ -406,4 +446,87 @@ QAccessible::Role QQuickTabBar::accessibleRole() const
 }
 #endif
 
+/*!
+    \qmlattachedproperty int QtQuick.Controls::TabBar::index
+    \since QtQuick.Controls 2.3
+    \readonly
+
+    This attached property holds the index of each tab button in the TabBar.
+
+    It is attached to each tab button of the TabBar.
+*/
+
+/*!
+    \qmlattachedproperty TabBar QtQuick.Controls::TabBar::tabBar
+    \since QtQuick.Controls 2.3
+    \readonly
+
+    This attached property holds the tab bar that manages this tab button.
+
+    It is attached to each tab button of the TabBar.
+*/
+
+/*!
+    \qmlattachedproperty enumeration QtQuick.Controls::TabBar::position
+    \since QtQuick.Controls 2.3
+    \readonly
+
+    This attached property holds the position of the tab bar.
+
+    It is attached to each tab button of the TabBar.
+
+    Possible values:
+    \value TabBar.Header The tab bar is at the top, as a window or page header.
+    \value TabBar.Footer The tab bar is at the bottom, as a window or page footer.
+*/
+
+void QQuickTabBarAttachedPrivate::update(QQuickTabBar *newTabBar, int newIndex)
+{
+    Q_Q(QQuickTabBarAttached);
+    const int oldIndex = index;
+    const QQuickTabBar *oldTabBar = tabBar;
+    const QQuickTabBar::Position oldPos = q->position();
+
+    index = newIndex;
+    tabBar = newTabBar;
+
+    if (oldTabBar != newTabBar) {
+        if (oldTabBar)
+            QObject::disconnect(oldTabBar, &QQuickTabBar::positionChanged, q, &QQuickTabBarAttached::positionChanged);
+        if (newTabBar)
+            QObject::connect(newTabBar, &QQuickTabBar::positionChanged, q, &QQuickTabBarAttached::positionChanged);
+        emit q->tabBarChanged();
+    }
+
+    if (oldIndex != newIndex)
+        emit q->indexChanged();
+    if (oldPos != q->position())
+        emit q->positionChanged();
+}
+
+QQuickTabBarAttached::QQuickTabBarAttached(QObject *parent)
+    : QObject(*(new QQuickTabBarAttachedPrivate), parent)
+{
+}
+
+int QQuickTabBarAttached::index() const
+{
+    Q_D(const QQuickTabBarAttached);
+    return d->index;
+}
+
+QQuickTabBar *QQuickTabBarAttached::tabBar() const
+{
+    Q_D(const QQuickTabBarAttached);
+    return d->tabBar;
+}
+
+QQuickTabBar::Position QQuickTabBarAttached::position() const
+{
+    Q_D(const QQuickTabBarAttached);
+    if (!d->tabBar)
+        return QQuickTabBar::Header;
+    return d->tabBar->position();
+}
+
 QT_END_NAMESPACE