4 files changed, 32 insertions, 13 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index 486e0b5..12aaba5 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -309,6 +309,11 @@
     and is always initialized to 1.
     Use QStyleOptionGraphicsItem::levelOfDetailFromTransform for a more
     fine-grained value.
+
+    \value ItemHasNoContents The item does not paint anything (i.e., calling
+    paint() on the item has no effect). You should set this flag on items that
+    do not need to be painted to ensure that Graphics View avoids unnecessary
+    painting preparations.
 */
 
 /*!
@@ -9108,6 +9113,9 @@ QDebug operator<<(QDebug debug, QGraphicsItem::GraphicsItemFlag flag)
     case QGraphicsItem::ItemUsesExtendedStyleOption:
         str = "ItemUsesExtendedStyleOption";
         break;
+    case QGraphicsItem::ItemHasNoContents:
+        str = "ItemHasNoContents";
+        break;
     }
     debug << str;
     return debug;
diff --git a/src/gui/graphicsview/qgraphicsitem.h b/src/gui/graphicsview/qgraphicsitem.h
index def773e..737ea80 100644
--- a/src/gui/graphicsview/qgraphicsitem.h
+++ b/src/gui/graphicsview/qgraphicsitem.h
@@ -95,7 +95,8 @@ public:
         ItemIgnoresParentOpacity = 0x40,
         ItemDoesntPropagateOpacityToChildren = 0x80,
         ItemStacksBehindParent = 0x100,
-        ItemUsesExtendedStyleOption = 0x200
+        ItemUsesExtendedStyleOption = 0x200,
+        ItemHasNoContents = 0x400
         // NB! Don't forget to increase the d_ptr->flags bit field by 1 when adding a new flag.
     };
     Q_DECLARE_FLAGS(GraphicsItemFlags, GraphicsItemFlag)
diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index acd2fcc..9d5b58a 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -350,11 +350,11 @@ public:
     quint32 unused : 3;
 
     // New 32 bits
-    quint32 flags : 10;
+    quint32 flags : 11;
     quint32 dirtyChildrenBoundingRect : 1;
     quint32 inDirtyList : 1;
     quint32 paintedViewBoundingRectsNeedRepaint : 1;
-    quint32 padding : 19; // feel free to use
+    quint32 padding : 18; // feel free to use
 
     // Optional stacking order
     int globalStackingOrder;
diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index b105c9c..eaebd1a 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -295,9 +295,13 @@ static inline bool QRectF_intersects(const QRectF &s, const QRectF &r)
 static inline void _q_adjustRect(QRectF *rect)
 {
     Q_ASSERT(rect);
-    if (!rect->width())
+    bool nullWidth = !rect->width();
+    bool nullHeight = !rect->height();
+    if (nullWidth && nullHeight)
+        return;
+    if (nullWidth)
         rect->adjust(-0.00001, 0, 0.00001, 0);
-    if (!rect->height())
+    else if (nullHeight)
         rect->adjust(0, -0.00001, 0, 0.00001);
 }
 
@@ -5079,22 +5083,23 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
             }
         }
         QRectF brect = item->boundingRect();
-        _q_adjustRect(&brect);
-        const QRect paintedViewBoundingRect = transform.mapRect(brect).toRect().adjusted(-1, -1, 1, 1);
-        item->d_ptr->paintedViewBoundingRects.insert(widget, paintedViewBoundingRect);
-        viewBoundingRect = paintedViewBoundingRect & exposedRegion.boundingRect();
+        if (!brect.size().isNull()) {
+            // ### This does not take the clip into account.
+            _q_adjustRect(&brect);
+            const QRect paintedViewBoundingRect = transform.mapRect(brect).toRect().adjusted(-1, -1, 1, 1);
+            item->d_ptr->paintedViewBoundingRects.insert(widget, paintedViewBoundingRect);
+            viewBoundingRect = paintedViewBoundingRect & exposedRegion.boundingRect();
+        }
     } else {
         transform = parentTransform;
     }
 
-    // Find and sort children.
-    QList<QGraphicsItem *> children = item ? item->d_ptr->children : topLevelItems;
-    qSort(children.begin(), children.end(), qt_notclosestLeaf);
-
     bool childClip = (item && (item->d_ptr->flags & QGraphicsItem::ItemClipsChildrenToShape));
     bool dontDrawItem = !item || viewBoundingRect.isEmpty();
     bool dontDrawChildren = item && dontDrawItem && childClip;
     childClip &= !dontDrawChildren & !children.isEmpty();
+    if (item && item->d_ptr->flags & QGraphicsItem::ItemHasNoContents)
+        dontDrawItem = true;
 
     // Clip children.
     if (childClip) {
@@ -5103,6 +5108,11 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
         painter->setClipPath(item->shape(), Qt::IntersectClip);
     }
 
+    // Find and sort children.
+    QList<QGraphicsItem *> children = item ? item->d_ptr->children : topLevelItems;
+    if (!dontDrawChildren)
+        qSort(children.begin(), children.end(), qt_notclosestLeaf);
+
     // Draw children behind
     int i;
     if (!dontDrawChildren) {