From 8134541fc3229177ec7545fa0d3ea49eadc8f00c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Nilsen?= <bjorn.nilsen@nokia.com>
Date: Fri, 12 Jun 2009 13:27:57 +0200
Subject: QGraphicsItems are repainted when outside the view's exposed region.

The problem was that we used QRect::isEmpty() on the item's bounding
rect intersected with the exposed region's bounding rect as a criteria
for whether the item should be drawn or not. This does not work as
expected with partial updates, where the boundingRect() of the exposed
region easily can cover the entire viewport area.

The item should *only* be drawn if its bounding rect intersects with
the exposed region (and not the exposed region's bounding rect).

Auto-test included.
---
 src/gui/graphicsview/qgraphicsscene.cpp        | 11 +++++----
 tests/auto/qgraphicsview/tst_qgraphicsview.cpp | 34 ++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index 55d8a1d..673fd23 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -5074,8 +5074,8 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
     }
 
     // Calculate the full transform for this item.
-    QRect viewBoundingRect;
     bool wasDirtyParentSceneTransform = false;
+    bool dontDrawItem = true;
     QTransform transform;
     if (item) {
         if (item->d_ptr->itemIsUntransformable()) {
@@ -5091,15 +5091,17 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
             transform = item->d_ptr->sceneTransform;
             transform *= viewTransform;
         }
-        
+
         QRectF brect = item->boundingRect();
         // ### This does not take the clip into account.
         _q_adjustRect(&brect);
-        viewBoundingRect = transform.mapRect(brect).toRect();
+        QRect viewBoundingRect = transform.mapRect(brect).toRect();
         item->d_ptr->paintedViewBoundingRects.insert(widget, viewBoundingRect);
         viewBoundingRect.adjust(-1, -1, 1, 1);
         if (exposedRegion)
-            viewBoundingRect &= exposedRegion->boundingRect();
+            dontDrawItem = !exposedRegion->intersects(viewBoundingRect);
+        else
+            dontDrawItem = viewBoundingRect.isEmpty();
     }
 
     // Find and sort children.
@@ -5154,7 +5156,6 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
     }
 
     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) || invisibleButChildIgnoresParentOpacity))
diff --git a/tests/auto/qgraphicsview/tst_qgraphicsview.cpp b/tests/auto/qgraphicsview/tst_qgraphicsview.cpp
index 06b4a78..78d09ba 100644
--- a/tests/auto/qgraphicsview/tst_qgraphicsview.cpp
+++ b/tests/auto/qgraphicsview/tst_qgraphicsview.cpp
@@ -194,6 +194,7 @@ private slots:
     void mouseTracking();
     void mouseTracking2();
     void render();
+    void exposeRegion();
 
     // task specific tests below me
     void task172231_untransformableItems();
@@ -3323,6 +3324,39 @@ void tst_QGraphicsView::render()
     QCOMPARE(r4->paints, 2);
 }
 
+void tst_QGraphicsView::exposeRegion()
+{
+    RenderTester *item = new RenderTester(QRectF(0, 0, 20, 20));
+    QGraphicsScene scene;
+    scene.addItem(item);
+
+    CustomView view;
+    view.setScene(&scene);
+    view.show();
+#ifdef Q_WS_X11
+    qt_x11_wait_for_window_manager(&view);
+#endif
+    QTest::qWait(125);
+
+    item->paints = 0;
+    view.lastUpdateRegions.clear();
+
+    // Update a small area in the viewport's topLeft() and bottomRight().
+    // (the boundingRect() of this area covers the entire viewport).
+    QWidget *viewport = view.viewport();
+    QRegion expectedExposeRegion = QRect(0, 0, 5, 5);
+    expectedExposeRegion += QRect(viewport->rect().bottomRight() - QPoint(5, 5), QSize(5, 5));
+    viewport->update(expectedExposeRegion);
+    qApp->processEvents();
+
+    // Make sure it triggers correct repaint on the view.
+    QCOMPARE(view.lastUpdateRegions.size(), 1);
+    QCOMPARE(view.lastUpdateRegions.at(0), expectedExposeRegion);
+
+    // Make sure the item didn't get any repaints.
+    QCOMPARE(item->paints, 0);
+}
+
 void tst_QGraphicsView::task253415_reconnectUpdateSceneOnSceneChanged()
 {
     QGraphicsView view;
-- 
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