Cached clip path not cleared correctly for ancestor that clips to shape

Fix QGraphicsItem to clear clip path for items with an ancestor that
clips to shape.  Added autotest to demonstrate clipping path problem.

Merge-request: 810
Reviewed-by: Alexis
Reviewed-by: Andreas
(cherry picked from commit d14fd301314bcceaf2594a5a18f6d20894c1d353)

2 files changed, 36 insertions, 2 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index 397ffd1..d74a54f 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -5742,10 +5742,12 @@ void QGraphicsItem::prepareGeometryChange()
     if (d_ptr->inSetPosHelper)
         return;
 
-    if (d_ptr->flags & ItemClipsChildrenToShape)
+    if (d_ptr->flags & ItemClipsChildrenToShape
+        || d_ptr->ancestorFlags & QGraphicsItemPrivate::AncestorClipsChildren) {
         d_ptr->invalidateCachedClipPathRecursively();
-    else
+    } else {
         d_ptr->invalidateCachedClipPath();
+    }
 }
 
 /*!
diff --git a/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp b/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
index 12ebd9f..cdc0e60 100644
--- a/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
+++ b/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
@@ -194,6 +194,7 @@ private slots:
     void itemClipsToShape();
     void itemClipsChildrenToShape();
     void itemClipsChildrenToShape2();
+    void itemClipsChildrenToShape3();
     void itemClipsTextChildToShape();
     void itemClippingDiscovery();
     void ancestorFlags();
@@ -4691,6 +4692,37 @@ void tst_QGraphicsItem::itemClipsChildrenToShape2()
 #endif
 }
 
+void tst_QGraphicsItem::itemClipsChildrenToShape3()
+{
+    // Construct a scene with nested children, each 50 pixels offset from the elder.
+    // Set a top-level clipping flag
+    QGraphicsScene scene;
+    QGraphicsRectItem *parent = scene.addRect( 0, 0, 150, 150 );
+    QGraphicsRectItem *child = scene.addRect( 0, 0, 150, 150 );
+    QGraphicsRectItem *grandchild = scene.addRect( 0, 0, 150, 150 );
+    child->setParentItem(parent);
+    grandchild->setParentItem(child);
+    child->setPos( 50, 50 );
+    grandchild->setPos( 50, 50 );
+    parent->setFlag(QGraphicsItem::ItemClipsChildrenToShape);
+
+    QCOMPARE(scene.itemAt(25,25), (QGraphicsItem *)parent);
+    QCOMPARE(scene.itemAt(75,75), (QGraphicsItem *)child);
+    QCOMPARE(scene.itemAt(125,125), (QGraphicsItem *)grandchild);
+    QCOMPARE(scene.itemAt(175,175), (QGraphicsItem *)0);
+
+    // Move child to fully overlap the parent.  The grandchild should
+    // now occupy two-thirds of the scene
+    child->prepareGeometryChange();
+    child->setPos( 0, 0 );
+
+    QCOMPARE(scene.itemAt(25,25), (QGraphicsItem *)child);
+    QCOMPARE(scene.itemAt(75,75), (QGraphicsItem *)grandchild);
+    QCOMPARE(scene.itemAt(125,125), (QGraphicsItem *)grandchild);
+    QCOMPARE(scene.itemAt(175,175), (QGraphicsItem *)0);
+}
+
+
 void tst_QGraphicsItem::itemClipsTextChildToShape()
 {
     // Construct a scene with a rect that clips its children, with one text