Improve hit testing so that it works better with ignored items

The hit testing won't work very well with the upcoming patch that
changes which items that can be ignored.
(basically it doesn't consider the isAccessible flag,
so childAt_helper might return a node that was supposed to be ignored)

Earlier this was a sensible optimization in order to avoid too many heap
allocations and deallocations of interfaces, but these are cheap now, so
we can do it the do it the 'proper way' (i.e. before this patch we
didn't respect the a11y hierarchy as given by QAccessibleInterface
child() and parent(). This also uses the QAccessibleInterface::rect()
directly now instead of using the itemScreenRect() function, which
was shared between QAccessibleQuickWindow and QAccessibleQuickItem.

Since this changes the order of child interfaces to paint order (i.e.
second child interface is on top of first child interface), we need to
ensure that we hit test child interfaces in the correct order.
They should now always be processe...

src/quick/accessible/qaccessiblequickitem.cpp

@@ -82,17 +82,42 @@ bool QAccessibleQuickItem::clipsChildren() const
     return static_cast<QQuickItem *>(item())->clip();
 }
 
+QAccessibleInterface *QAccessibleQuickItem::childAt(int x, int y) const
+{
+    if (item()->clip()) {
+        if (!rect().contains(x, y))
+            return 0;
+    }
+
+    const QList<QQuickItem*> kids = accessibleUnignoredChildren(item(), true);
+    for (int i = kids.count() - 1; i >= 0; --i) {
+        QAccessibleInterface *childIface = QAccessible::queryAccessibleInterface(kids.at(i));
+        if (QAccessibleInterface *childChild = childIface->childAt(x, y))
+            return childChild;
+        if (childIface && !childIface->state().invisible) {
+            if (childIface->rect().contains(x, y))
+                return childIface;
+        }
+    }
+
+    return 0;
+}
+
 QAccessibleInterface *QAccessibleQuickItem::parent() const
 {
     QQuickItem *parent = item()->parentItem();
+    QQuickWindow *window = item()->window();
+    QQuickItem *ci = window ? window->contentItem() : 0;
+    while (parent && parent != ci)
+        parent = parent->parentItem();
+
     if (parent) {
-        QQuickWindow *window = item()->window();
-        // Jump out to the scene widget if the parent is the root item.
-        // There are two root items, QQuickWindow::rootItem and
-        // QQuickView::declarativeRoot. The former is the true root item,
-        // but is not a part of the accessibility tree. Check if we hit
-        // it here and return an interface for the scene instead.
-        if (window && (parent == window->contentItem())) {
+        if (parent == ci) {
+            // Jump out to the scene widget if the parent is the root item.
+            // There are two root items, QQuickWindow::rootItem and
+            // QQuickView::declarativeRoot. The former is the true root item,
+            // but is not a part of the accessibility tree. Check if we hit
+            // it here and return an interface for the scene instead.
             return QAccessible::queryAccessibleInterface(window);
         } else {
             return QAccessible::queryAccessibleInterface(parent);
@@ -121,6 +146,19 @@ int QAccessibleQuickItem::indexOfChild(const QAccessibleInterface *iface) const
     return kids.indexOf(static_cast<QQuickItem*>(iface->object()));
 }
 
+QList<QQuickItem *> accessibleUnignoredChildren(QQuickItem *item, bool paintOrder)
+{
+    QList<QQuickItem *> items;
+    QList<QQuickItem*> childItems = paintOrder ? QQuickItemPrivate::get(item)->paintOrderChildItems()
+                                               : item->childItems();
+    Q_FOREACH (QQuickItem *child, childItems) {
+        QQuickItemPrivate *itemPrivate = QQuickItemPrivate::get(child);
+        if (itemPrivate->isAccessible)
+            items.append(child);
+    }
+    return items;
+}
+
 QList<QQuickItem *> QAccessibleQuickItem::childItems() const
 {
     if (    role() == QAccessible::Button ||
@@ -133,13 +171,7 @@ QList<QQuickItem *> QAccessibleQuickItem::childItems() const
             role() == QAccessible::ProgressBar)
         return QList<QQuickItem *>();
 
-    QList<QQuickItem *> items;
-    Q_FOREACH (QQuickItem *child, item()->childItems()) {
-        QQuickItemPrivate *itemPrivate = QQuickItemPrivate::get(child);
-        if (itemPrivate->isAccessible)
-            items.append(child);
-    }
-    return items;
+    return accessibleUnignoredChildren(item());
 }
 
 QAccessible::State QAccessibleQuickItem::state() const

src/quick/accessible/qaccessiblequickitem_p.h

@@ -53,6 +53,7 @@ public:
     QRect viewRect() const;
 
     bool clipsChildren() const;
+    QAccessibleInterface *childAt(int x, int y) const;
 
     QAccessibleInterface *parent() const;
     QAccessibleInterface *child(int index) const;
@@ -118,6 +119,7 @@ private:
 };
 
 QRect itemScreenRect(QQuickItem *item);
+QList<QQuickItem *> accessibleUnignoredChildren(QQuickItem *item, bool paintOrder = false);
 
 
 #endif // QT_NO_ACCESSIBILITY

src/quick/accessible/qaccessiblequickview.cpp

@@ -53,7 +53,7 @@ QAccessibleQuickWindow::QAccessibleQuickWindow(QQuickWindow *object)
 QQuickItem *QAccessibleQuickWindow::rootItem() const
 {
     if (QQuickItem *ci = window()->contentItem()) {
-        const QList<QQuickItem *> &childItems = ci->childItems();
+        const QList<QQuickItem *> &childItems = accessibleUnignoredChildren(ci);
         if (!childItems.isEmpty())
             return childItems.first();
     }
@@ -110,56 +110,17 @@ QString QAccessibleQuickWindow::text(QAccessible::Text text) const
     return window()->title();
 }
 
-
-/*!
-  \internal
-
-  Can also return \a item itself
-  */
-static QQuickItem *childAt_helper(QQuickItem *item, int x, int y)
-{
-    if (!item->isVisible() || !item->isEnabled())
-        return 0;
-
-    if (item->flags() & QQuickItem::ItemClipsChildrenToShape) {
-        if (!itemScreenRect(item).contains(x, y))
-            return 0;
-    }
-
-    QAccessibleInterface *accessibleInterface = QAccessible::queryAccessibleInterface(item);
-    // this item has no Accessible attached property
-    if (!accessibleInterface)
-        return 0;
-
-    if (accessibleInterface->childCount() == 0) {
-        return (itemScreenRect(item).contains(x, y)) ? item : 0;
-    }
-
-    QQuickItemPrivate *itemPrivate = QQuickItemPrivate::get(item);
-
-    QList<QQuickItem *> children = itemPrivate->paintOrderChildItems();
-    for (int i = children.count() - 1; i >= 0; --i) {
-        QQuickItem *child = children.at(i);
-        if (QQuickItem *childChild = childAt_helper(child, x, y))
-            return childChild;
-    }
-
-    QRect screenRect = itemScreenRect(item);
-
-    if (screenRect.contains(x, y))
-        return item;
-
-    return 0;
-}
-
 QAccessibleInterface *QAccessibleQuickWindow::childAt(int x, int y) const
 {
     Q_ASSERT(window());
-    QQuickItem *root = rootItem();
-    if (root) {
-        if (QQuickItem *item = childAt_helper(root, x, y))
-            return QAccessible::queryAccessibleInterface(item);
-        return QAccessible::queryAccessibleInterface(root);
+    for (int i = childCount() - 1; i >= 0; --i) {
+        QAccessibleInterface *childIface = child(i);
+        if (childIface && !childIface->state().invisible) {
+            if (QAccessibleInterface *iface = childIface->childAt(x, y))
+                return iface;
+            if (childIface->rect().contains(x, y))
+                return childIface;
+        }
     }
     return 0;
 }

src/quick/accessible/qqmlaccessible.cpp

@@ -54,27 +54,6 @@ QQmlAccessible::~QQmlAccessible()
 {
 }
 
-QAccessibleInterface *QQmlAccessible::childAt(int x, int y) const
-{
-    // Note that this function will disregard stacking order.
-    // (QAccessibleQuickView::childAt() does this correctly and more efficient)
-
-    // If the item clips its children, we can return early if the coordinate is outside its rect
-    if (clipsChildren()) {
-        if (!rect().contains(x, y))
-            return 0;
-    }
-
-    for (int i = childCount() - 1; i >= 0; --i) {
-        QAccessibleInterface *childIface = child(i);
-        if (childIface && !childIface->state().invisible) {
-            if (childIface->rect().contains(x, y))
-                return childIface;
-        }
-    }
-    return 0;
-}
-
 QAccessible::State QQmlAccessible::state() const
 {
     QAccessible::State state;

src/quick/accessible/qqmlaccessible_p.h

@@ -64,7 +64,6 @@ public:
     void *interface_cast(QAccessible::InterfaceType t);
 
     virtual QRect viewRect() const = 0;
-    QAccessibleInterface *childAt(int, int) const;
     QAccessible::State state() const;
 
     QStringList actionNames() const;
@@ -72,7 +71,6 @@ public:
     QStringList keyBindingsForAction(const QString &actionName) const;
 
 protected:
-    virtual bool clipsChildren() const = 0;
     // For subclasses, use instantiateObject factory method outside the class.
     QQmlAccessible(QObject *object);
 };