Add QQuickItem::ItemEnabledHasChanged

The itemChange() method has been very useful for Qt Quick Controls 2
to efficiently react to various item changes, but a notification for
the enabled state was missing, so it always had to be handled as a
special case using signals and slots. This change allows QQC2 to handle
enabled state changes the same way e.g. visibility changes are handled.
It's also nice to be able to update a control's internal state before
the actual notifier signal is emitted.

[ChangeLog][QtQuick][QQuickItem] Added a ItemEnabledHasChanged value to
the ItemChange enum. QQuickItem::itemChange(ItemEnabledHasChanged) gets
called when the item's effective enabled state has changed. The new
enabled state is stored in ItemChangeData::boolValue.

Change-Id: Iae96ec21f2b94f453632282473decd1c66097a75
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Robin Burchell <robin.burchell@crimson.no>

4 files changed, 21 insertions, 2 deletions

diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index a8a862bb2f..1e71c20ff3 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -2138,6 +2138,9 @@ void QQuickItemPrivate::updateSubFocusItem(QQuickItem *scope, bool focus)
 
     \value ItemAntialiasingHasChanged The antialiasing has changed. The current
     (boolean) value can be found in QQuickItem::antialiasing.
+
+    \value ItemEnabledHasChanged The item's enabled state has changed.
+    ItemChangeData::boolValue contains the new enabled state. (since Qt 5.10)
 */
 
 /*!
@@ -5927,6 +5930,7 @@ void QQuickItemPrivate::setEffectiveEnableRecur(QQuickItem *scope, bool newEffec
                 scope, q, Qt::OtherFocusReason, QQuickWindowPrivate::DontChangeFocusProperty | QQuickWindowPrivate::DontChangeSubFocusItem);
     }
 
+    itemChange(QQuickItem::ItemEnabledHasChanged, effectiveEnable);
     emit q->enabledChanged();
 }
 
@@ -6099,6 +6103,18 @@ void QQuickItemPrivate::itemChange(QQuickItem::ItemChange change, const QQuickIt
         }
         break;
     }
+    case QQuickItem::ItemEnabledHasChanged: {
+        q->itemChange(change, data);
+        if (!changeListeners.isEmpty()) {
+            const auto listeners = changeListeners; // NOTE: intentional copy (QTBUG-54732)
+            for (const QQuickItemPrivate::ChangeListener &change : listeners) {
+                if (change.types & QQuickItemPrivate::Enabled) {
+                    change.listener->itemEnabledChanged(q);
+                }
+            }
+        }
+        break;
+    }
     case QQuickItem::ItemParentHasChanged: {
         q->itemChange(change, data);
         if (!changeListeners.isEmpty()) {
diff --git a/src/quick/items/qquickitem.h b/src/quick/items/qquickitem.h
index f58946d01d..4a832bbf6f 100644
--- a/src/quick/items/qquickitem.h
+++ b/src/quick/items/qquickitem.h
@@ -173,7 +173,8 @@ public:
         ItemActiveFocusHasChanged, // value.boolValue
         ItemRotationHasChanged,    // value.realValue
         ItemAntialiasingHasChanged, // value.boolValue
-        ItemDevicePixelRatioHasChanged // value.realValue
+        ItemDevicePixelRatioHasChanged, // value.realValue
+        ItemEnabledHasChanged      // value.boolValue
     };
 
     union ItemChangeData {
diff --git a/src/quick/items/qquickitem_p.h b/src/quick/items/qquickitem_p.h
index e56d839de9..74d70da2bc 100644
--- a/src/quick/items/qquickitem_p.h
+++ b/src/quick/items/qquickitem_p.h
@@ -321,7 +321,8 @@ public:
         Children = 0x40,
         Rotation = 0x80,
         ImplicitWidth = 0x100,
-        ImplicitHeight = 0x200
+        ImplicitHeight = 0x200,
+        Enabled = 0x400,
     };
 
     Q_DECLARE_FLAGS(ChangeTypes, ChangeType)
diff --git a/src/quick/items/qquickitemchangelistener_p.h b/src/quick/items/qquickitemchangelistener_p.h
index 83c69a9330..cb0af75c4c 100644
--- a/src/quick/items/qquickitemchangelistener_p.h
+++ b/src/quick/items/qquickitemchangelistener_p.h
@@ -125,6 +125,7 @@ public:
     virtual void itemGeometryChanged(QQuickItem *, QQuickGeometryChange, const QRectF & /* oldGeometry */) {}
     virtual void itemSiblingOrderChanged(QQuickItem *) {}
     virtual void itemVisibilityChanged(QQuickItem *) {}
+    virtual void itemEnabledChanged(QQuickItem *) {}
     virtual void itemOpacityChanged(QQuickItem *) {}
     virtual void itemDestroyed(QQuickItem *) {}
     virtual void itemChildAdded(QQuickItem *, QQuickItem * /* child */ ) {}