From 877b494897a01b1b7d948410ca7d47285191d6d9 2012-08-16 09:49:51
From: Tero Ahola <tero.ahola@digia.com>
Date: 2012-08-16 09:49:51
Subject: [PATCH] Fixed paint and mouse event issues with QLineSeries

1. The bounding rectangle of QLineSeries item did not take line width
into account; this caused paint issues if the width is bigger than 1.
2. The width of the shape of the item was always 1. This caused
problems with mouse events; onClicked was not always signaled, even
if you click on top (but not in the middle of) a thick line series.

---

diff --git a/demos/chartinteractions/chart.cpp b/demos/chartinteractions/chart.cpp
index 986f5ae..38c4064 100644
--- a/demos/chartinteractions/chart.cpp
+++ b/demos/chartinteractions/chart.cpp
@@ -20,6 +20,7 @@
 
 #include <QValuesAxis>
 #include <QAbstractAxis>
+#include <cmath>
 #include <QDebug>
 
 #include "chart.h"
@@ -36,22 +37,23 @@ Chart::~Chart()
 
 void Chart::clickPoint(const QPointF &point)
 {
-    //Get all points from the series.
-    QList<QPointF> points = m_series->points();
-    //Construct a small rectangle around the clicked point
-    //to identify the real point clicked from the series.
-    QRectF clickRect(point.x() - 0.5, point.y() - 0.5, 1.0, 1.0);
-
-    //Find the clicked point to be moved.
-    foreach (QPointF p, points) {
-        if (clickRect.contains(p)) {
+    // Find the closes data point
+    m_movingPoint = QPoint();
+    m_clicked = false;
+    foreach (QPointF p, m_series->points()) {
+        if (distance(p, point) < distance(m_movingPoint, point)) {
             m_movingPoint = p;
             m_clicked = true;
-            return;
         }
     }
 }
 
+qreal Chart::distance(const QPointF &p1, const QPointF &p2)
+{
+    return sqrt((p1.x() - p2.x()) * (p1.x() - p2.x())
+                + (p1.y() - p2.y()) * (p1.y() - p2.y()));
+}
+
 void Chart::setPointClicked(bool clicked)
 {
    m_clicked = clicked;
diff --git a/demos/chartinteractions/chart.h b/demos/chartinteractions/chart.h
index f9e021a..242aa65 100644
--- a/demos/chartinteractions/chart.h
+++ b/demos/chartinteractions/chart.h
@@ -41,6 +41,7 @@ public:
     void setPointClicked(bool clicked);
 
 private:
+    qreal distance(const QPointF &p1, const QPointF &p2);
     QLineSeries *m_series;
     QPointF m_movingPoint;
 
diff --git a/demos/chartinteractions/main.cpp b/demos/chartinteractions/main.cpp
index 22ab027..7b5db6c 100644
--- a/demos/chartinteractions/main.cpp
+++ b/demos/chartinteractions/main.cpp
@@ -46,6 +46,9 @@ int main(int argc, char *argv[])
     Chart* chart = new Chart(0, 0, series);
     chart->legend()->hide();
     chart->addSeries(series);
+    QPen p = series->pen();
+    p.setWidth(5);
+    series->setPen(p);
     chart->createDefaultAxes();
     chart->setTitle("Drag'n drop to move data points");
 
diff --git a/src/linechart/linechartitem.cpp b/src/linechart/linechartitem.cpp
index dba8ffd..f52b115 100644
--- a/src/linechart/linechartitem.cpp
+++ b/src/linechart/linechartitem.cpp
@@ -25,10 +25,9 @@
 #include <QPainter>
 #include <QGraphicsSceneMouseEvent>
 
-
 QTCOMMERCIALCHART_BEGIN_NAMESPACE
 
-//TODO: optimize : remove points which are not visible
+const qreal mouseEventMinWidth(14);
 
 LineChartItem::LineChartItem(QLineSeries* series,ChartPresenter *presenter):
     XYChart(series, presenter),
@@ -49,7 +48,13 @@ QRectF LineChartItem::boundingRect() const
 
 QPainterPath LineChartItem::shape() const
 {
-    return m_path;
+    // Increase the size of the path slightly to make mouse interactions more natural
+    QPainterPathStroker s;
+    s.setCapStyle(Qt::RoundCap);
+    s.setJoinStyle(Qt::RoundJoin);
+    qreal spacing = qMax(mouseEventMinWidth, (qreal) m_linePen.width());
+    s.setWidth(spacing);
+    return s.createStroke(m_path);
 }
 
 void LineChartItem::updateGeometry()
@@ -71,8 +76,18 @@ void LineChartItem::updateGeometry()
     }
 
     prepareGeometryChange();
+
     m_path = linePath;
-    m_rect = linePath.boundingRect();
+
+    // When defining bounding rectangle,
+    // 1. take the line width into account (otherwise you will get drawing artifacts) and
+    // 2. take the shape into account (otherwise you will not get mouse events through on border
+    // areas).
+    const qreal sqrtOf2 = 1.414214;
+    const qreal spacing = qMax(mouseEventMinWidth / 2.0,
+                               sqrtOf2 * (qreal) m_linePen.width() / 2.0);
+    m_rect = m_path.boundingRect().adjusted(-spacing, -spacing, spacing, spacing);
+
     setPos(origin());
 }
 
@@ -86,8 +101,6 @@ void LineChartItem::handleUpdated()
     update();
 }
 
-//painter
-
 void LineChartItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
 {
     Q_UNUSED(widget)
diff --git a/src/linechart/linechartitem_p.h b/src/linechart/linechartitem_p.h
index 0907104..fee7758 100644
--- a/src/linechart/linechartitem_p.h
+++ b/src/linechart/linechartitem_p.h
@@ -45,7 +45,7 @@ class LineChartItem :  public XYChart , public QGraphicsItem
      Q_INTERFACES(QGraphicsItem)
 public:
      explicit LineChartItem(QLineSeries *series,ChartPresenter *presenter);
-    ~LineChartItem() {};
+    ~LineChartItem() {}
 
     //from QGraphicsItem
     QRectF boundingRect() const;