Fixed rendering bugs when scrolling graphics items with drop shadows.

We can't clip source pixmaps to the device rect, as there's no way of
knowing which parts of the source pixmap are needed for the part of the
graphics effect that's unclipped.

Reviewed-by: Bjørn Erik Nilsen

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/auto/qgraphicseffect/tst_qgraphicseffect.cpp b/tests/auto/qgraphicseffect/tst_qgraphicseffect.cpp
index 795431b..1007d61 100644
--- a/tests/auto/qgraphicseffect/tst_qgraphicseffect.cpp
+++ b/tests/auto/qgraphicseffect/tst_qgraphicseffect.cpp
@@ -72,6 +72,7 @@ private slots:
     void drawPixmapItem();
     void deviceCoordinateTranslateCaching();
     void inheritOpacity();
+    void dropShadowClipping();
 };
 
 void tst_QGraphicsEffect::initTestCase()
@@ -590,6 +591,28 @@ void tst_QGraphicsEffect::inheritOpacity()
     QTRY_VERIFY(item->numRepaints > numRepaints);
 }
 
+void tst_QGraphicsEffect::dropShadowClipping()
+{
+    QImage img(128, 128, QImage::Format_ARGB32_Premultiplied);
+    img.fill(0xffffffff);
+
+    QGraphicsScene scene;
+    QGraphicsRectItem *item = new QGraphicsRectItem(-5, -500, 10, 1000);
+    item->setGraphicsEffect(new QGraphicsDropShadowEffect);
+    item->setPen(Qt::NoPen);
+    item->setBrush(Qt::red);
+
+    scene.addItem(item);
+
+    QPainter p(&img);
+    scene.render(&p, img.rect(), QRect(-64, -64, 128, 128));
+    p.end();
+
+    for (int y = 1; y < img.height(); ++y)
+        for (int x = 0; x < img.width(); ++x)
+            QCOMPARE(img.pixel(x, y), img.pixel(x, y-1));
+}
+
 QTEST_MAIN(tst_QGraphicsEffect)
 #include "tst_qgraphicseffect.moc"