Fixed first element being a LineToElement in QPainterPath::connectPath()

This would produce an invalid path, causing potential crashes in various
parts of Qt.

Task-number: QTBUG-16377
Reviewed-by: Gunnar Sletta

2 files changed, 28 insertions, 1 deletions

diff --git a/src/gui/painting/qpainterpath.cpp b/src/gui/painting/qpainterpath.cpp
index ffd0d5c..94e2cd4 100644
--- a/src/gui/painting/qpainterpath.cpp
+++ b/src/gui/painting/qpainterpath.cpp
@@ -1196,7 +1196,8 @@ void QPainterPath::connectPath(const QPainterPath &other)
     int first = d->elements.size();
     d->elements += other.d_func()->elements;
 
-    d->elements[first].type = LineToElement;
+    if (first != 0)
+        d->elements[first].type = LineToElement;
 
     // avoid duplicate points
     if (first > 0 && QPointF(d->elements[first]) == QPointF(d->elements[first - 1])) {
diff --git a/tests/auto/qpainterpath/tst_qpainterpath.cpp b/tests/auto/qpainterpath/tst_qpainterpath.cpp
index d0cddda..66e6d10 100644
--- a/tests/auto/qpainterpath/tst_qpainterpath.cpp
+++ b/tests/auto/qpainterpath/tst_qpainterpath.cpp
@@ -107,6 +107,7 @@ private slots:
     void operators();
 
     void connectPathDuplicatePoint();
+    void connectPathMoveTo();
 
     void translate();
 };
@@ -1169,6 +1170,31 @@ void tst_QPainterPath::connectPathDuplicatePoint()
     QCOMPARE(c, a);
 }
 
+void tst_QPainterPath::connectPathMoveTo()
+{
+    QPainterPath path1;
+    QPainterPath path2;
+    QPainterPath path3;
+    QPainterPath path4;
+
+    path1.moveTo(1,1);
+
+    path2.moveTo(4,4);
+    path2.lineTo(5,6);
+    path2.lineTo(6,7);
+
+    path3.connectPath(path2);
+
+    path4.lineTo(5,5);
+
+    path1.connectPath(path2);
+
+    QVERIFY(path1.elementAt(0).type == QPainterPath::MoveToElement);
+    QVERIFY(path2.elementAt(0).type == QPainterPath::MoveToElement);
+    QVERIFY(path3.elementAt(0).type == QPainterPath::MoveToElement);
+    QVERIFY(path4.elementAt(0).type == QPainterPath::MoveToElement);
+}
+
 void tst_QPainterPath::translate()
 {
     QPainterPath path;