qtquick: Don't assume in the C++ that the tab bar has a list view

Getting the tab index by QPoint is now done in QML, so it can
be overridden by the user.

src/qtquick/views/TabBar_qtquick.cpp

@@ -40,33 +40,6 @@ void TabBar_qtquick::init()
     });
 }
 
-QHash<int, QQuickItem *> TabBar_qtquick::qmlTabs() const
-{
-    if (!m_tabBarQmlItem) {
-        qWarning() << Q_FUNC_INFO << "No visual tab bar item yet" << this;
-        return {};
-    }
-
-    /// Returns the list of QtQuickControls tabs in our tab bar
-    QHash<int, QQuickItem *> tabs;
-
-    if (QQuickItem *internalListView = listView()) {
-        const auto childItems = internalListView->childItems();
-        if (!childItems.isEmpty()) {
-            for (QQuickItem *item : childItems.first()->childItems()) {
-                bool ok = false;
-                const int index = item->property("tabIndex").toInt(&ok);
-                if (ok)
-                    tabs.insert(index, item);
-            }
-        }
-    } else {
-        qWarning() << Q_FUNC_INFO << "Couldn't find the internal ListView";
-    }
-
-    return tabs;
-}
-
 int TabBar_qtquick::tabAt(QPoint localPt) const
 {
     // QtQuick's TabBar doesn't provide any API for this.
@@ -79,14 +52,13 @@ int TabBar_qtquick::tabAt(QPoint localPt) const
 
     const QPointF globalPos = m_tabBarQmlItem->mapToGlobal(localPt);
 
-    const QHash<int, QQuickItem *> tabs = qmlTabs();
-    for (auto it = tabs.keyValueBegin(); it != tabs.keyValueEnd(); ++it) {
-        QQuickItem *tab = it->second;
-        if (tab->contains(tab->mapFromGlobal(globalPos))) {
-            const int index = it->first;
-            return index;
-        }
-    }
+    QVariant index;
+    const bool res = QMetaObject::invokeMethod(m_tabBarQmlItem, "getTabIndexAtPosition",
+                                               Q_RETURN_ARG(QVariant, index),
+                                               Q_ARG(QVariant, globalPos));
+
+    if (res)
+        return index.toInt();
 
     return -1;
 }
@@ -154,27 +126,6 @@ QQuickItem *TabBar_qtquick::tabAt(int index) const
     return nullptr;
 }
 
-QQuickItem *TabBar_qtquick::listView() const
-{
-    // Returns the internal ListView of the TabBar
-    if (!m_tabBarQmlItem) {
-        qWarning() << Q_FUNC_INFO << "No visual tab bar item yet";
-        return nullptr;
-    }
-
-    const QList<QQuickItem *> children = m_tabBarQmlItem->childItems();
-    if (children.size() != 1) {
-        return nullptr;
-    }
-
-    for (QQuickItem *child : children.constFirst()->childItems()) {
-        if (qstrcmp(child->metaObject()->className(), "QQuickListView") == 0)
-            return child;
-    }
-
-    return nullptr;
-}
-
 void TabBar_qtquick::moveTabTo(int from, int to)
 {
     Q_UNUSED(from);

src/qtquick/views/TabBar_qtquick.h

@@ -72,9 +72,7 @@ protected:
     void init() override;
 
 private:
-    QHash<int, QQuickItem *> qmlTabs() const;
     QQuickItem *tabAt(int index) const;
-    QQuickItem *listView() const;
     QPointer<QQuickItem> m_tabBarQmlItem;
     KDBindings::ScopedConnection m_tabBarAutoHideChanged;
 };

src/qtquick/views/qml/TabBar.qml

@@ -16,23 +16,62 @@ import QtQuick.Controls 2.9
 TabBarBase {
     id: root
 
+    // Helper, only applies if you're using the TabBar from QQControls.
+    // Returns the internal ListView
     function getInternalListView() {
         for(var i = 0; i < tabBar.children.length; ++i) {
             if (tabBar.children[i].toString().startsWith("QQuickListView"))
                 return tabBar.children[i];
         }
 
+        console.warn("Couldn't find the internal ListView");
         return null;
     }
 
     function getTabAtIndex(index) {
         var listView = getInternalListView();
+        var content = listView.children[0];
+
+        var curr = 0;
+        for (var i = 0; i < content.children.length; ++i) {
+            var candidate = content.children[i];
+            if (typeof candidate.tabIndex == "undefined") {
+                // All tabs need to have "tabIndex" property.
+                continue;
+            }
+
+            if (curr == index)
+                return candidate;
+
+            curr++;
+        }
+
         if (index < listView.children.length)
             return listView.children[0].children[index];
 
         return null;
     }
 
+    function getTabIndexAtPosition(globalPoint) {
+        var listView = getInternalListView();
+        var content = listView.children[0];
+
+        for (var i = 0; i < content.children.length; ++i) {
+            var candidate = content.children[i];
+            if (typeof candidate.tabIndex == "undefined") {
+                // All tabs need to have "tabIndex" property.
+                continue;
+            }
+
+            var localPt = candidate.mapFromGlobal(globalPoint.x, globalPoint.y);
+            if (candidate.contains(localPt)) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+
     implicitHeight: tabBar.implicitHeight
 
     onCurrentTabIndexChanged: {

src/qtquick/views/qml/TabBarBase.qml

@@ -67,4 +67,12 @@ Item {
     function getTabAtIndex(index) {
         console.warn("Override this function in the actual derived tab bar!");
     }
+
+    /// Returns the index of the tab that's at localPoint
+    /// Returns -1 if no tab there.
+    /// This is called by C++ and needs to be implemented in the derived class.
+    /// See TabBar.qml for an example.
+    function getTabIndexAtPosition(localPoint) {
+        console.warn("Override this function in the actual derived tab bar!");
+    }
 }