Prevent infinite loop in raster engine on zero dash pattern length.

Task-number: QTBUG-17053
Reviewed-by: Kim

2 files changed, 29 insertions, 0 deletions

diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index 682731a..ba618ea 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -3706,6 +3706,13 @@ void QRasterPaintEnginePrivate::rasterizeLine_dashed(QLineF line,
     const bool squareCap = (pen.capStyle() == Qt::SquareCap);
     const QVector<qreal> pattern = pen.dashPattern();
 
+    qreal patternLength = 0;
+    for (int i = 0; i < pattern.size(); ++i)
+        patternLength += pattern.at(i);
+
+    if (patternLength <= 0)
+        return;
+
     qreal length = line.length();
     Q_ASSERT(length > 0);
     while (length > 0) {
diff --git a/tests/auto/qpainter/tst_qpainter.cpp b/tests/auto/qpainter/tst_qpainter.cpp
index 4cf64f1..c9eca89 100644
--- a/tests/auto/qpainter/tst_qpainter.cpp
+++ b/tests/auto/qpainter/tst_qpainter.cpp
@@ -258,6 +258,8 @@ private slots:
     void QTBUG14614_gradientCacheRaceCondition();
     void drawTextOpacity();
 
+    void QTBUG17053_zeroDashPattern();
+
 private:
     void fillData();
     void setPenColor(QPainter& p);
@@ -4601,6 +4603,26 @@ void tst_QPainter::drawTextOpacity()
     QCOMPARE(image, copy);
 }
 
+void tst_QPainter::QTBUG17053_zeroDashPattern()
+{
+    QImage image(32, 32, QImage::Format_RGB32);
+    image.fill(0xffffffff);
+
+    QImage original = image;
+
+    QVector<qreal> pattern;
+    pattern << qreal(0) << qreal(0);
+
+    QPainter p(&image);
+    QPen pen(Qt::black, 2.0);
+    pen.setDashPattern(pattern);
+
+    p.setPen(pen);
+    p.drawLine(0, 0, image.width(), image.height());
+
+    QCOMPARE(image, original);
+}
+
 QTEST_MAIN(tst_QPainter)
 
 #include "tst_qpainter.moc"