QPainterPath: fix handling of fill rules

fillRule() contained a major blunder: instead of checking if the
d-pointer was allocated, and return a default value if it wasn't,
it checked whether the path contained any points. This means that

  QPainterPath p;
  p.setFillRule(x);
  Q_ASSERT(p.fillRule() == x);

was failing.

As a drive-by to test this change, fix another mistake in clear():
clear is documented to clear the elements in a path, but instead
it also changed the fill rule.

This commit partially reverses 697910e5fbd382e78bc1bcbac3f5824aded059b4.

Change-Id: Ieb8145694b672439c3380d9ccb87d1206a2dd115
Done-with: Milian Wolff
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
(cherry picked from commit 0b4ccbf81ee2009051169f2f0918442b56512b20)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 12 insertions, 3 deletions

diff --git a/src/gui/painting/qpainterpath.cpp b/src/gui/painting/qpainterpath.cpp
index 38acc66ba4..9479cadd8f 100644
--- a/src/gui/painting/qpainterpath.cpp
+++ b/src/gui/painting/qpainterpath.cpp
@@ -1369,7 +1369,7 @@ void QPainterPath::addRegion(const QRegion &region)
 */
 Qt::FillRule QPainterPath::fillRule() const
 {
-    return isEmpty() ? Qt::OddEvenFill : d_func()->fillRule;
+    return !d_func() ? Qt::OddEvenFill : d_func()->fillRule;
 }
 
 /*!
diff --git a/src/gui/painting/qpainterpath_p.h b/src/gui/painting/qpainterpath_p.h
index 24feaf410b..c283b7f27e 100644
--- a/src/gui/painting/qpainterpath_p.h
+++ b/src/gui/painting/qpainterpath_p.h
@@ -292,7 +292,6 @@ inline void QPainterPathPrivate::clear()
     elements.clear();
 
     cStart = 0;
-    fillRule = Qt::OddEvenFill;
     bounds = {};
     controlBounds = {};
 
diff --git a/tests/auto/gui/painting/qpainterpath/tst_qpainterpath.cpp b/tests/auto/gui/painting/qpainterpath/tst_qpainterpath.cpp
index 12a8fff33b..dcba95d33c 100644
--- a/tests/auto/gui/painting/qpainterpath/tst_qpainterpath.cpp
+++ b/tests/auto/gui/painting/qpainterpath/tst_qpainterpath.cpp
@@ -173,8 +173,18 @@ void tst_QPainterPath::clear()
     p1.setFillRule(Qt::WindingFill);
     QVERIFY(p1 != p3);
     p1.clear();
-    QCOMPARE(p1.fillRule(), Qt::OddEvenFill);
+    QVERIFY(p1 != p3);
+    p1.setFillRule(Qt::OddEvenFill);
     QCOMPARE(p1, p2);
+
+    QPainterPath p4;
+    QCOMPARE(p4.fillRule(), Qt::OddEvenFill);
+    p4.setFillRule(Qt::WindingFill);
+    QCOMPARE(p4.fillRule(), Qt::WindingFill);
+    p4.clear();
+    QCOMPARE(p4.fillRule(), Qt::WindingFill);
+    p4 = QPainterPath();
+    QCOMPARE(p4.fillRule(), Qt::OddEvenFill);
 }
 
 void tst_QPainterPath::reserveAndCapacity()