Add QGraphicsItem::focusProxy(), focus proxy support.

Following QWidget's behavior, you can not assign any item in the
same scene as a focus proxy for another item. Also supports nested
focus proxies. You can only assign items in the same scene as
focus proxies. Autotests are included.

Reviewed-By: mbm

5 files changed, 141 insertions, 48 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index ae2a2c3..4e3677a 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -2455,6 +2455,8 @@ void QGraphicsItem::setHandlesChildEvents(bool enabled)
 */
 bool QGraphicsItem::hasFocus() const
 {
+    if (d_ptr->focusProxy)
+        return d_ptr->focusProxy->hasFocus();
     return (d_ptr->scene && d_ptr->scene->focusItem() == this);
 }
 
@@ -2480,12 +2482,16 @@ void QGraphicsItem::setFocus(Qt::FocusReason focusReason)
 {
     if (!d_ptr->scene || !isEnabled() || hasFocus() || !(d_ptr->flags & ItemIsFocusable))
         return;
-    if (isVisible()) {
+    QGraphicsItem *item = this;
+    QGraphicsItem *f;
+    while ((f = item->d_ptr->focusProxy))
+        item = f;
+    if (item->isVisible()) {
         // Visible items immediately gain focus from scene.
-        d_ptr->scene->setFocusItem(this, focusReason);
-    } else if (d_ptr->isWidget) {
+        d_ptr->scene->d_func()->setFocusItemHelper(item, focusReason);
+    } else if (item->d_ptr->isWidget) {
         // Just set up subfocus.
-        static_cast<QGraphicsWidget *>(this)->d_func()->setFocusWidget();
+        static_cast<QGraphicsWidget *>(item)->d_func()->setFocusWidget();
     }
 }
 
@@ -2508,13 +2514,73 @@ void QGraphicsItem::clearFocus()
         // Invisible widget items with focus must explicitly clear subfocus.
         static_cast<QGraphicsWidget *>(this)->d_func()->clearFocusWidget();
     }
-    if (d_ptr->scene->focusItem() == this) {
+    if (hasFocus()) {
         // If this item has the scene's input focus, clear it.
         d_ptr->scene->setFocusItem(0);
     }
 }
 
 /*!
+    \since 4.6
+
+    Returns this item's focus proxy, or 0 if the item
+    does not have any focus proxy.
+
+    \sa setFocusProxy()
+*/
+QGraphicsItem *QGraphicsItem::focusProxy() const
+{
+    return d_ptr->focusProxy;
+}
+
+/*!
+    \since 4.6
+
+    Sets the item's focus proxy to \a item.
+
+    If an item has a focus proxy, the focus proxy will receive
+    input focus when the item gains input focus. The item itself
+    will still have focus (i.e., hasFocus() will return true),
+    but only the focus proxy will receive the keyboard input.
+
+    A focus proxy can itself have a focus proxy, and so on. In
+    such case, keyboard input will be handled by the outermost
+    focus proxy.
+
+    \sa focusProxy()
+*/
+void QGraphicsItem::setFocusProxy(QGraphicsItem *item)
+{
+    if (item == d_ptr->focusProxy)
+        return;
+    if (item == this) {
+        qWarning("QGraphicsItem::setFocusProxy: cannot assign self as focus proxy");
+        return;
+    }
+    if (item) {
+        if (item->d_ptr->scene != d_ptr->scene) {
+            qWarning("QGraphicsItem::setFocusProxy: focus proxy must be in same scene");
+            return;
+        }
+        for (QGraphicsItem *f = item->focusProxy(); f != 0; f = f->focusProxy()) {
+            if (f == this) {
+                qWarning("QGraphicsItem::setFocusProxy: %p is already in the focus proxy chain", item);
+                return;
+            }
+        }
+    }
+
+    QGraphicsItem *lastFocusProxy = d_ptr->focusProxy;
+    d_ptr->focusProxy = item;
+    if (d_ptr->scene) {
+        if (lastFocusProxy)
+            d_ptr->scene->d_func()->focusProxyReverseMap.remove(lastFocusProxy, this);
+        if (item)
+            d_ptr->scene->d_func()->focusProxyReverseMap.insert(item, this);
+    }
+}
+
+/*!
     \since 4.4
     Grabs the mouse input.
 
diff --git a/src/gui/graphicsview/qgraphicsitem.h b/src/gui/graphicsview/qgraphicsitem.h
index a307622..5c9297f 100644
--- a/src/gui/graphicsview/qgraphicsitem.h
+++ b/src/gui/graphicsview/qgraphicsitem.h
@@ -226,6 +226,9 @@ public:
     void setFocus(Qt::FocusReason focusReason = Qt::OtherFocusReason);
     void clearFocus();
 
+    QGraphicsItem *focusProxy() const;
+    void setFocusProxy(QGraphicsItem *item);
+
     void grabMouse();
     void ungrabMouse();
     void grabKeyboard();
diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index 4729634..fee7083 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -122,6 +122,7 @@ public:
         index(-1),
         siblingIndex(-1),
         depth(0),
+        focusProxy(0),
         acceptedMouseButtons(0x1f),
         visible(1),
         explicitlyHidden(0),
@@ -409,6 +410,7 @@ public:
     int index;
     int siblingIndex;
     int depth;
+    QGraphicsItem *focusProxy;
 
     // Packed 32 bytes
     quint32 acceptedMouseButtons : 5;
diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index b017022..4796436 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -491,6 +491,13 @@ void QGraphicsScenePrivate::removeItemHelper(QGraphicsItem *item)
 
     item->d_func()->scene = 0;
 
+    // Unregister focus proxy.
+    QMultiHash<QGraphicsItem *, QGraphicsItem *>::iterator it = focusProxyReverseMap.find(item);
+    while (it != focusProxyReverseMap.end() && it.key() == item) {
+        it.value()->d_ptr->focusProxy = 0;
+        it = focusProxyReverseMap.erase(it);
+    }
+
     // Remove from parent, or unregister from toplevels.
     if (QGraphicsItem *parentItem = item->parentItem()) {
         if (parentItem->scene()) {
@@ -559,6 +566,58 @@ void QGraphicsScenePrivate::removeItemHelper(QGraphicsItem *item)
 /*!
     \internal
 */
+void QGraphicsScenePrivate::setFocusItemHelper(QGraphicsItem *item,
+                                               Qt::FocusReason focusReason)
+{
+    Q_Q(QGraphicsScene);
+    if (item == focusItem)
+        return;
+    if (item && (!(item->flags() & QGraphicsItem::ItemIsFocusable)
+                 || !item->isVisible() || !item->isEnabled())) {
+        item = 0;
+    }
+
+    if (item) {
+        q->setFocus(focusReason);
+        if (item == focusItem)
+            return;
+    }
+
+    if (focusItem) {
+        QFocusEvent event(QEvent::FocusOut, focusReason);
+        lastFocusItem = focusItem;
+        focusItem = 0;
+        sendEvent(lastFocusItem, &event);
+
+        if (lastFocusItem
+            && (lastFocusItem->flags() & QGraphicsItem::ItemAcceptsInputMethod)) {
+            // Reset any visible preedit text
+            QInputMethodEvent imEvent;
+            sendEvent(lastFocusItem, &imEvent);
+
+            // Close any external input method panel
+            for (int i = 0; i < views.size(); ++i)
+                views.at(i)->inputContext()->reset();
+        }
+    }
+
+    if (item) {
+        if (item->isWidget()) {
+            // Update focus child chain.
+            static_cast<QGraphicsWidget *>(item)->d_func()->setFocusWidget();
+        }
+
+        focusItem = item;
+        QFocusEvent event(QEvent::FocusIn, focusReason);
+        sendEvent(item, &event);
+    }
+
+    updateInputMethodSensitivityInViews();
+}
+
+/*!
+    \internal
+*/
 void QGraphicsScenePrivate::addPopup(QGraphicsWidget *widget)
 {
     Q_ASSERT(widget);
@@ -2597,49 +2656,10 @@ QGraphicsItem *QGraphicsScene::focusItem() const
 void QGraphicsScene::setFocusItem(QGraphicsItem *item, Qt::FocusReason focusReason)
 {
     Q_D(QGraphicsScene);
-    if (item == d->focusItem)
-        return;
-    if (item && (!(item->flags() & QGraphicsItem::ItemIsFocusable)
-                 || !item->isVisible() || !item->isEnabled())) {
-        item = 0;
-    }
-
-    if (item) {
-        setFocus(focusReason);
-        if (item == d->focusItem)
-            return;
-    }
-
-    if (d->focusItem) {
-        QFocusEvent event(QEvent::FocusOut, focusReason);
-        d->lastFocusItem = d->focusItem;
-        d->focusItem = 0;
-        d->sendEvent(d->lastFocusItem, &event);
-
-        if (d->lastFocusItem
-            && (d->lastFocusItem->flags() & QGraphicsItem::ItemAcceptsInputMethod)) {
-            // Reset any visible preedit text
-            QInputMethodEvent imEvent;
-            d->sendEvent(d->lastFocusItem, &imEvent);
-
-            // Close any external input method panel
-            for (int i = 0; i < d->views.size(); ++i)
-                d->views.at(i)->inputContext()->reset();
-        }
-    }
-
-    if (item) {
-        if (item->isWidget()) {
-            // Update focus child chain.
-            static_cast<QGraphicsWidget *>(item)->d_func()->setFocusWidget();
-        }
-
-        d->focusItem = item;
-        QFocusEvent event(QEvent::FocusIn, focusReason);
-        d->sendEvent(item, &event);
-    }
-
-    d->updateInputMethodSensitivityInViews();
+    if (item)
+        item->setFocus(focusReason);
+    else
+        d->setFocusItemHelper(item, focusReason);
 }
 
 /*!
diff --git a/src/gui/graphicsview/qgraphicsscene_p.h b/src/gui/graphicsview/qgraphicsscene_p.h
index 9a91acc..a4bbdd2 100644
--- a/src/gui/graphicsview/qgraphicsscene_p.h
+++ b/src/gui/graphicsview/qgraphicsscene_p.h
@@ -130,6 +130,8 @@ public:
     QGraphicsWidget *tabFocusFirst;
     QGraphicsWidget *activeWindow;
     int activationRefCount;
+    void setFocusItemHelper(QGraphicsItem *item, Qt::FocusReason focusReason);
+    QMultiHash<QGraphicsItem *, QGraphicsItem *> focusProxyReverseMap;
 
     QList<QGraphicsWidget *> popupWidgets;
     void addPopup(QGraphicsWidget *widget);