Add easy way to get plot area point from point

User cannot just click the screen and get the correct position on the
graph's coordinates. That require's calculating plot area position from
the mousearea click position. This patch adds method to lineseries
for calculating the graph coordinates from plot area click.

Task-number: QTBUG-134499
Change-Id: Id020d040f87c5c8cfe6661aee941b1dd783f0e49
Reviewed-by: Sami Varanka <sami.varanka@qt.io>

src/graphs2d/linechart/qlineseries.cpp

@@ -146,4 +146,23 @@ void QLineSeries::setCapStyle(Qt::PenCapStyle newCapStyle)
     emit update();
 }
 
+
+/*!
+    \qmlmethod LineSeries::getDataPointCoordinates(real x, real y)
+    Returns \a x and \a y rendercoordinates converted into data point
+    coordinates.
+*/
+/*!
+    Returns \a x and \a y rendercoordinates converted into data point
+    coordinates.
+
+*/
+QPointF QLineSeries::getDataPointCoordinates(qreal x, qreal y)
+{
+    Q_D(QLineSeries);
+
+    auto oPoint = d->m_graph->getDataPointCoordinates(x, y);
+    return oPoint;
+}
+
 QT_END_NAMESPACE

src/graphs2d/linechart/qlineseries.h

@@ -30,6 +30,8 @@ public:
     Qt::PenCapStyle capStyle() const;
     void setCapStyle(Qt::PenCapStyle newCapStyle);
 
+    Q_REVISION(6, 10) Q_INVOKABLE QPointF getDataPointCoordinates(qreal x, qreal y);
+
 Q_SIGNALS:
     void widthChanged();
     void capStyleChanged();

src/graphs2d/qgraphsview.cpp

@@ -207,6 +207,15 @@ bool QGraphsView::hasSeries(QObject *series)
     return m_seriesList.contains(series);
 }
 
+QPointF QGraphsView::getDataPointCoordinates(qreal x, qreal y)
+{
+    if (m_pointRenderer)
+        return m_pointRenderer->reverseRenderCoordinates(x, y);
+
+    return QPointF();
+}
+
+
 void QGraphsView::addAxis(QAbstractAxis *axis)
 {
     if (axis) {

src/graphs2d/qgraphsview_p.h

@@ -86,6 +86,8 @@ public:
         return m_seriesList;
     }
 
+    QPointF getDataPointCoordinates(qreal x, qreal y);
+
     QQmlListProperty<QObject> seriesList();
     static void appendSeriesFunc(QQmlListProperty<QObject> *list, QObject *series);
     static qsizetype countSeriesFunc(QQmlListProperty<QObject> *list);

src/graphs2d/qsgrenderer/pointrenderer.cpp

@@ -839,4 +839,38 @@ bool PointRenderer::handleHoverMove(QHoverEvent *event)
     return handled;
 }
 
+
+QPointF PointRenderer::reverseRenderCoordinates(qreal x, qreal y)
+{
+    m_areaWidth = width();
+    m_areaHeight = height();
+
+    m_maxVertical = m_graph->m_axisRenderer->m_axisVerticalValueRange > 0
+                        ? 1.0 / m_graph->m_axisRenderer->m_axisVerticalValueRange
+                        : 100.0;
+    m_maxHorizontal = m_graph->m_axisRenderer->m_axisHorizontalValueRange > 0
+                          ? 1.0 / m_graph->m_axisRenderer->m_axisHorizontalValueRange
+                          : 100.0;
+
+    auto vmin = m_graph->m_axisRenderer->m_axisVerticalMinValue
+                        > m_graph->m_axisRenderer->m_axisVerticalMaxValue
+                    ? std::abs(m_graph->m_axisRenderer->m_axisVerticalMinValue)
+                    : m_graph->m_axisRenderer->m_axisVerticalMinValue;
+
+    m_verticalOffset = (vmin / m_graph->m_axisRenderer->m_axisVerticalValueRange) * m_areaHeight;
+
+    auto hmin = m_graph->m_axisRenderer->m_axisHorizontalMinValue
+                        > m_graph->m_axisRenderer->m_axisHorizontalMaxValue
+                    ? std::abs(m_graph->m_axisRenderer->m_axisHorizontalMinValue)
+                    : m_graph->m_axisRenderer->m_axisHorizontalMinValue;
+
+    m_horizontalOffset = (hmin / m_graph->m_axisRenderer->m_axisHorizontalValueRange) * m_areaWidth;
+    qreal x0;
+    qreal y0;
+
+    reverseRenderCoordinates(m_graph->m_axisRenderer, x, y, &x0, &y0);
+
+    return QPointF(x0, y0);
+}
+
 QT_END_NAMESPACE

src/graphs2d/qsgrenderer/pointrenderer_p.h

@@ -45,6 +45,8 @@ public:
     void afterUpdate(QList<QAbstractSeries *> &cleanupSeries);
     bool handleHoverMove(QHoverEvent *event);
 
+   QPointF reverseRenderCoordinates(qreal x, qreal y);
+
 private:
     struct PointGroup
     {

tests/auto/qml2dtest/graphsview/tst_graphsview.qml

@@ -135,6 +135,18 @@ Item {
             compare(initial.theme.colorScheme, Qt.Dark)
             compare(initial.theme.seriesColors.length, 5)
         }
+
+        function test_2_getDataPointCoordinate() {
+            var point = lineInitial.getDataPointCoordinates(0, 0)
+            compare(point.x, 0)
+            compare(point.y, 8)
+            var point = lineInitial.getDataPointCoordinates(1, 1)
+            compare(point.x, 0.2)
+            compare(point.y, 7.794871794871795)
+            var point = lineInitial.getDataPointCoordinates(4, 4)
+            compare(point.x, 0.8)
+            compare(point.y, 7.17948717948718)
+        }
     }
 
     TestCase {