Fix rendering lines with Antialiasing render hint

When rendering with QPainter::Antialiasing set, lines need to be drawn
in one set. Otherwise, each line is rendered with the anti-aliasing
applied, causing the overlap to create a stronger area, which almost
looks like a point from the point series. As a consequence, prefer
drawPath() in that case.

Task-number: QTBUG-61782
Change-Id: Ib2b44475e2e9ca0c28da7e898744bd72b992f5fd
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/charts/linechart/linechartitem.cpp b/src/charts/linechart/linechartitem.cpp
index f41e5bc2..f31c69b4 100644
--- a/src/charts/linechart/linechartitem.cpp
+++ b/src/charts/linechart/linechartitem.cpp
@@ -406,7 +406,9 @@ void LineChartItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *opt
         painter->drawPath(m_linePath);
     } else {
         painter->setBrush(QBrush(Qt::NoBrush));
-        if (m_linePen.style() != Qt::SolidLine || alwaysUsePath) {
+        if (m_linePen.style() != Qt::SolidLine
+                || painter->renderHints().testFlag(QPainter::Antialiasing)
+                || alwaysUsePath) {
             // If pen style is not solid line, always fall back to path painting
             // to ensure proper continuity of the pattern
             painter->drawPath(m_linePath);