Make QAccessibleQuickView::childAt() work properly with overlapping items

The previous code did not consider items that were overlapped due to
having different z coordinates.

The approach used is now the same as found in
QQuickCanvas::mousePressEvent().

Strictly speaking, this is a violation of childAt (since it will
disregard the implementation of childAt of all the descendants along
the path down to the item actually returned.)

However, I don't see any good reason for that the implementation for
childAt() would be different than how mousePressEvent behaves.
It should also perform better than any other solution I managed to
think of.

Change-Id: I2d3fa2282437c7b5533c6149c62fc456ccf2ccfa
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@nokia.com>

4 files changed, 77 insertions, 28 deletions

diff --git a/src/plugins/accessible/quick/qaccessiblequickitem.cpp b/src/plugins/accessible/quick/qaccessiblequickitem.cpp
index 5cedfe62d6..10442b275e 100644
--- a/src/plugins/accessible/quick/qaccessiblequickitem.cpp
+++ b/src/plugins/accessible/quick/qaccessiblequickitem.cpp
@@ -58,26 +58,7 @@ int QAccessibleQuickItem::childCount() const
 
 QRect QAccessibleQuickItem::rect() const
 {
-    // ### no canvas in some cases.
-    // ### Should we really check for 0 opacity?
-    if (!item()->canvas() ||!item()->isVisible() || qFuzzyIsNull(item()->opacity())) {
-        return QRect();
-    }
-
-    QSizeF size = QSizeF(item()->width(), item()->height());
-    // ### If the bounding rect fails, we first try the implicit size, then we go for the
-    // parent size. WE MIGHT HAVE TO REVISIT THESE FALLBACKS.
-    if (size.isEmpty()) {
-        size = QSizeF(item()->implicitWidth(), item()->implicitHeight());
-        if (size.isEmpty())
-            // ### Seems that the above fallback is not enough, fallback to use the parent size...
-            size = QSizeF(item()->parentItem()->width(), item()->parentItem()->height());
-    }
-
-    QRectF sceneRect = item()->mapRectToScene(QRectF(QPointF(0, 0), size));
-    QPoint screenPos = item()->canvas()->mapToGlobal(sceneRect.topLeft().toPoint());
-
-    QRect r = QRect(screenPos, sceneRect.size().toSize());
+    const QRect r = itemScreenRect(item());
 
     if (!r.isValid()) {
         qWarning() << item()->metaObject()->className() << item()->property("accessibleText") << r;
@@ -297,5 +278,33 @@ QVariant QAccessibleQuickItemValueInterface::minimumValue() const
     return item()->property("minimumValue");
 }
 
+/*!
+  \internal
+  Shared between QAccessibleQuickItem and QAccessibleQuickView
+*/
+QRect itemScreenRect(QQuickItem *item)
+{
+    // ### no canvas in some cases.
+    // ### Should we really check for 0 opacity?
+    if (!item->canvas() ||!item->isVisible() || qFuzzyIsNull(item->opacity())) {
+        return QRect();
+    }
+
+    QSize itemSize((int)item->width(), (int)item->height());
+    // ### If the bounding rect fails, we first try the implicit size, then we go for the
+    // parent size. WE MIGHT HAVE TO REVISIT THESE FALLBACKS.
+    if (itemSize.isEmpty()) {
+        itemSize = QSize((int)item->implicitWidth(), (int)item->implicitHeight());
+        if (itemSize.isEmpty())
+            // ### Seems that the above fallback is not enough, fallback to use the parent size...
+            itemSize = QSize((int)item->parentItem()->width(), (int)item->parentItem()->height());
+    }
+
+    QPointF scenePoint = item->mapToScene(QPointF(0, 0));
+    QPoint screenPos = item->canvas()->mapToGlobal(scenePoint.toPoint());
+    return QRect(screenPos, itemSize);
+}
+
+
 
 QT_END_NAMESPACE
diff --git a/src/plugins/accessible/quick/qaccessiblequickitem.h b/src/plugins/accessible/quick/qaccessiblequickitem.h
index 5ef3a19247..75e7081dc0 100644
--- a/src/plugins/accessible/quick/qaccessiblequickitem.h
+++ b/src/plugins/accessible/quick/qaccessiblequickitem.h
@@ -77,6 +77,9 @@ protected:
     QQuickItem *item() const { return static_cast<QQuickItem*>(object()); }
 };
 
+QRect itemScreenRect(QQuickItem *item);
+
+
 class QAccessibleQuickItemValueInterface: public QAccessibleQuickItem, public QAccessibleValueInterface
 {
 public:
diff --git a/src/plugins/accessible/quick/qaccessiblequickview.cpp b/src/plugins/accessible/quick/qaccessiblequickview.cpp
index 6a896efd29..d15e01d96c 100644
--- a/src/plugins/accessible/quick/qaccessiblequickview.cpp
+++ b/src/plugins/accessible/quick/qaccessiblequickview.cpp
@@ -42,6 +42,7 @@
 #include "qaccessiblequickview.h"
 
 #include <QtQuick/qquickitem.h>
+#include <QtQuick/private/qquickitem_p.h>
 
 #include "qaccessiblequickitem.h"
 #include "qdeclarativeaccessible.h"
@@ -69,8 +70,8 @@ QAccessibleInterface *QAccessibleQuickView::parent() const
 QAccessibleInterface *QAccessibleQuickView::child(int index) const
 {
     if (index == 0) {
-        QQuickItem *declarativeRoot = view()->rootObject();
-        return new QAccessibleQuickItem(declarativeRoot);
+        if (QQuickItem *declarativeRoot = view()->rootObject())
+            return new QAccessibleQuickItem(declarativeRoot);
     }
     return 0;
 }
@@ -108,11 +109,48 @@ QString QAccessibleQuickView::text(QAccessible::Text text) const
     return view()->windowTitle();
 }
 
+
+/*!
+  \internal
+
+  Can also return \a item itself
+  */
+static QQuickItem *childAt_helper(QQuickItem *item, int x, int y)
+{
+    if (item->opacity() == 0.0 || !item->isVisible() || !item->isEnabled())
+        return 0;
+
+    if (item->flags() & QQuickItem::ItemClipsChildrenToShape) {
+        if (!itemScreenRect(item).contains(x, y))
+            return 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 *QAccessibleQuickView::childAt(int x, int y) const
 {
-    Q_UNUSED(x);
-    Q_UNUSED(y);
-    return child(0); // return the top-level QML item
+    Q_ASSERT(view());
+    QQuickItem *root = view()->rootItem();
+    if (root) {
+        if (QQuickItem *item = childAt_helper(root, x, y))
+            return QAccessible::queryAccessibleInterface(item);
+    }
+    return 0;
 }
 
 int QAccessibleQuickView::indexOfChild(const QAccessibleInterface *iface) const
diff --git a/src/plugins/accessible/shared/qdeclarativeaccessible.cpp b/src/plugins/accessible/shared/qdeclarativeaccessible.cpp
index 7db5f07cbe..1b35594e74 100644
--- a/src/plugins/accessible/shared/qdeclarativeaccessible.cpp
+++ b/src/plugins/accessible/shared/qdeclarativeaccessible.cpp
@@ -70,9 +70,8 @@ QFlags<QAccessible::RelationFlag> QDeclarativeAccessible::relationTo(const QAcce
 
 QAccessibleInterface *QDeclarativeAccessible::childAt(int x, int y) const
 {
-    // Look for children first.
-    // Start with the last child first, because children are ordered in paint order
-    // (which is opposite of hit test order)
+    // 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()) {