Add QGraphicsItem::itemChangeEnabled().

This function allows the user to disable notifications for item changes.
In QSimpleCanvasItem, all notifications are disabled by default, and
you can enable them one at a time. QGraphicsItem's behavior is to by
default enable all notifications.

A side effect of this change is that I've removed one optimization in
favor of another: by not constructing a QVariant at all when there's no
notification we get maximum performance, at the expense of constructing
it twice if there is a notification.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem.h b/src/gui/graphicsview/qgraphicsitem.h
index 737ea80..7c87176 100644
--- a/src/gui/graphicsview/qgraphicsitem.h
+++ b/src/gui/graphicsview/qgraphicsitem.h
@@ -129,6 +129,7 @@ public:
         ItemZValueHasChanged,
         ItemOpacityChange,
         ItemOpacityHasChanged
+        // NB! Don't forget to increase d_ptr->itemChangesEnabled when adding a new entry.
     };
 
     enum CacheMode {
@@ -165,6 +166,10 @@ public:
     void setFlag(GraphicsItemFlag flag, bool enabled = true);
     void setFlags(GraphicsItemFlags flags);
 
+    bool itemChangeEnabled(GraphicsItemChange change) const;
+    void setItemChangeEnabled(GraphicsItemChange change, bool enabled);
+    void setItemChangesEnabled(bool enabled);
+
     CacheMode cacheMode() const;
     void setCacheMode(CacheMode mode, const QSize &cacheSize = QSize());