Optimize barcharts painting

Previously, bar charts used to recreate the bar chart visuals from
scratch whenever any change to the bar data occurred.
The following changes were made:
- Graphics items are generated only for visible bars and labels
- Graphics items are reused if layout or data changes
- Labels are not generated unless they are visible
- Only newly added bars are animated from scratch; existing bars
  will retain their size, making things more visually pleasing.

With these optimizations, the size of the bar series is irrelevant
to the painting performance, only thing that matters is how many
bars and labels are actually within visible range.

Task-number: QTBUG-52442
Change-Id: If3199a86e6819ef6219d2eb5f06d729c0bdbd2ae
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>

1 files changed, 17 insertions, 17 deletions

diff --git a/src/charts/barchart/qbarset.cpp b/src/charts/barchart/qbarset.cpp
index f62fc806..d7832293 100644
--- a/src/charts/barchart/qbarset.cpp
+++ b/src/charts/barchart/qbarset.cpp
@@ -312,6 +312,7 @@ QBarSet::~QBarSet()
 void QBarSet::setLabel(const QString label)
 {
     d_ptr->m_label = label;
+    d_ptr->setLabelsDirty(true);
     emit labelChanged();
 }
 
@@ -390,7 +391,6 @@ void QBarSet::replace(const int index, const qreal value)
     }
 }
 
-
 /*!
     Returns value of set indexed by \a index.
     If the index is out of bounds 0.0 is returned.
@@ -437,6 +437,7 @@ void QBarSet::setPen(const QPen &pen)
 {
     if (d_ptr->m_pen != pen) {
         d_ptr->m_pen = pen;
+        d_ptr->setVisualsDirty(true);
         emit d_ptr->updatedBars();
         emit penChanged();
     }
@@ -460,6 +461,7 @@ void QBarSet::setBrush(const QBrush &brush)
 {
     if (d_ptr->m_brush != brush) {
         d_ptr->m_brush = brush;
+        d_ptr->setVisualsDirty(true);
         emit d_ptr->updatedBars();
         emit brushChanged();
     }
@@ -483,6 +485,7 @@ void QBarSet::setLabelBrush(const QBrush &brush)
 {
     if (d_ptr->m_labelBrush != brush) {
         d_ptr->m_labelBrush = brush;
+        d_ptr->setLabelsDirty(true);
         emit d_ptr->updatedBars();
         emit labelBrushChanged();
     }
@@ -506,10 +509,10 @@ void QBarSet::setLabelFont(const QFont &font)
 {
     if (d_ptr->m_labelFont != font) {
         d_ptr->m_labelFont = font;
+        d_ptr->setLabelsDirty(true);
         emit d_ptr->updatedBars();
         emit labelFontChanged();
     }
-
 }
 
 /*!
@@ -600,7 +603,8 @@ QBarSetPrivate::QBarSetPrivate(const QString label, QBarSet *parent) : QObject(p
     m_label(label),
     m_pen(QChartPrivate::defaultPen()),
     m_brush(QChartPrivate::defaultBrush()),
-    m_labelBrush(QChartPrivate::defaultBrush())
+    m_labelBrush(QChartPrivate::defaultBrush()),
+    m_visualsDirty(true)
 {
 }
 
@@ -612,41 +616,43 @@ void QBarSetPrivate::append(QPointF value)
 {
     if (isValidValue(value)) {
         m_values.append(value);
-        emit restructuredBars();
+        emit valueAdded(m_values.size() - 1, 1);
     }
 }
 
 void QBarSetPrivate::append(QList<QPointF> values)
 {
+    int originalIndex = m_values.count();
     for (int i = 0; i < values.count(); i++) {
         if (isValidValue(values.at(i)))
             m_values.append(values.at(i));
     }
-    emit restructuredBars();
+    emit valueAdded(originalIndex, values.size());
 }
 
 void QBarSetPrivate::append(QList<qreal> values)
 {
-    int index = m_values.count();
+    int originalIndex = m_values.count();
+    int index = originalIndex;
     for (int i = 0; i < values.count(); i++) {
         if (isValidValue(values.at(i))) {
             m_values.append(QPointF(index, values.at(i)));
             index++;
         }
     }
-    emit restructuredBars();
+    emit valueAdded(originalIndex, values.size());
 }
 
 void QBarSetPrivate::insert(const int index, const qreal value)
 {
     m_values.insert(index, QPointF(index, value));
-    emit restructuredBars();
+    emit valueAdded(index, 1);
 }
 
 void QBarSetPrivate::insert(const int index, const QPointF value)
 {
     m_values.insert(index, value);
-    emit restructuredBars();
+    emit valueAdded(index, 1);
 }
 
 int QBarSetPrivate::remove(const int index, const int count)
@@ -663,20 +669,14 @@ int QBarSetPrivate::remove(const int index, const int count)
         m_values.removeAt(index);
         c++;
     }
-    emit restructuredBars();
+    emit valueRemoved(index, removeCount);
     return removeCount;
 }
 
 void QBarSetPrivate::replace(const int index, const qreal value)
 {
     m_values.replace(index, QPointF(index, value));
-    emit updatedLayout();
-}
-
-void QBarSetPrivate::replace(const int index, const QPointF value)
-{
-    m_values.replace(index, value);
-    emit updatedLayout();
+    emit valueChanged(index);
 }
 
 qreal QBarSetPrivate::pos(const int index)