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, 66 insertions, 68 deletions

diff --git a/src/charts/barchart/horizontal/percent/horizontalpercentbarchartitem.cpp b/src/charts/barchart/horizontal/percent/horizontalpercentbarchartitem.cpp
index ffebbaae..326c5f45 100644
--- a/src/charts/barchart/horizontal/percent/horizontalpercentbarchartitem.cpp
+++ b/src/charts/barchart/horizontal/percent/horizontalpercentbarchartitem.cpp
@@ -39,50 +39,89 @@ HorizontalPercentBarChartItem::HorizontalPercentBarChartItem(QAbstractBarSeries
 {
 }
 
-void HorizontalPercentBarChartItem::initializeLayout()
+QString HorizontalPercentBarChartItem::generateLabelText(int set, int category, qreal value)
 {
-    qreal categoryCount = m_series->d_func()->categoryCount();
-    qreal setCount = m_series->count();
-    qreal barWidth = m_series->d_func()->barWidth();
+    Q_UNUSED(value)
 
-    m_layout.clear();
-    for(int category = 0; category < categoryCount; category++) {
-        for (int set = 0; set < setCount; set++) {
-            QRectF rect;
-            QPointF topLeft;
-            QPointF bottomRight;
-            if (domain()->type() == AbstractDomain::LogXYDomain || domain()->type() == AbstractDomain::LogXLogYDomain) {
-                topLeft = domain()->calculateGeometryPoint(QPointF(domain()->minX(), category - barWidth / 2), m_validData);
-                bottomRight = domain()->calculateGeometryPoint(QPointF(domain()->minX(), category + barWidth / 2), m_validData);
-            } else {
-                topLeft = domain()->calculateGeometryPoint(QPointF(0, category - barWidth / 2), m_validData);
-                bottomRight = domain()->calculateGeometryPoint(QPointF(0, category + barWidth / 2), m_validData);
-            }
-
-            if (!m_validData)
-                 return;
+    static const QString valueTag(QLatin1String("@value"));
+    qreal p = m_series->d_func()->percentageAt(set, category) * 100.0;
+    QString vString(presenter()->numberToString(p, 'f', 0));
+    QString valueLabel;
+    if (m_series->labelsFormat().isEmpty()) {
+        vString.append(QStringLiteral("%"));
+        valueLabel = vString;
+    } else {
+        valueLabel = m_series->labelsFormat();
+        valueLabel.replace(valueTag, vString);
+    }
+
+    return valueLabel;
+}
 
+void HorizontalPercentBarChartItem::initializeLayout(int set, int category, int layoutIndex,
+                                                     bool resetAnimation)
+{
+    Q_UNUSED(set)
+    Q_UNUSED(resetAnimation)
+
+    QRectF rect;
+
+    int previousSetIndex = layoutIndex - m_categoryCount;
+    if (previousSetIndex >= 0) {
+        rect = m_layout.at(previousSetIndex);
+        rect.setLeft(rect.right());
+    } else {
+        QPointF topLeft;
+        QPointF bottomRight;
+        qreal barWidth = m_series->d_func()->barWidth();
+        if (domain()->type() == AbstractDomain::LogXYDomain
+                || domain()->type() == AbstractDomain::LogXLogYDomain) {
+            topLeft = domain()->calculateGeometryPoint(
+                        QPointF(domain()->minX(), category - barWidth / 2), m_validData);
+            bottomRight = domain()->calculateGeometryPoint(
+                        QPointF(domain()->minX(), category + barWidth / 2), m_validData);
+        } else {
+            topLeft = domain()->calculateGeometryPoint(
+                        QPointF(0, category - barWidth / 2), m_validData);
+            bottomRight = domain()->calculateGeometryPoint(
+                        QPointF(0, category + barWidth / 2), m_validData);
+        }
+        if (m_validData) {
             rect.setTopLeft(topLeft);
             rect.setBottomRight(bottomRight);
-            m_layout.append(rect.normalized());
         }
     }
+    m_layout[layoutIndex] = rect.normalized();
+}
+
+void HorizontalPercentBarChartItem::markLabelsDirty(QBarSet *barset, int visualIndex, int count)
+{
+    Q_UNUSED(barset)
+    // Percent series need to dirty all labels of the stack
+    QList<QBarSet *> sets = m_barMap.keys();
+    for (int set = 0; set < sets.size(); set++)
+        AbstractBarChartItem::markLabelsDirty(sets.at(set), visualIndex, count);
 }
 
 QVector<QRectF> HorizontalPercentBarChartItem::calculateLayout()
 {
     QVector<QRectF> layout;
+    layout.reserve(m_layout.size());
 
     // Use temporary qreals for accuracy
-    qreal categoryCount = m_series->d_func()->categoryCount();
     qreal setCount = m_series->count();
     qreal barWidth = m_series->d_func()->barWidth();
 
-    for(int category = 0; category < categoryCount; category++) {
-        qreal sum = 0;
-        qreal categorySum = m_series->d_func()->categorySum(category);
-        for (int set = 0; set < setCount; set++) {
-            qreal value = m_series->barSets().at(set)->at(category);
+    QVector<qreal> categorySums(m_categoryCount);
+    QVector<qreal> tempSums(m_categoryCount, 0.0);
+    for (int category = 0; category < m_categoryCount; category++)
+        categorySums[category] = m_series->d_func()->categorySum(category + m_firstCategory);
+    for (int set = 0; set < setCount; set++) {
+        const QBarSet *barSet = m_series->barSets().at(set);
+        for (int category = m_firstCategory; category <= m_lastCategory; category++) {
+            qreal &sum = tempSums[category - m_firstCategory];
+            const qreal &categorySum = categorySums.at(category - m_firstCategory);
+            qreal value = barSet->at(category);
             QRectF rect;
             qreal topX = 0;
             if (sum > 0)
@@ -107,47 +146,6 @@ QVector<QRectF> HorizontalPercentBarChartItem::calculateLayout()
     return layout;
 }
 
-void HorizontalPercentBarChartItem::handleUpdatedBars()
-{
-    // Handle changes in pen, brush, labels etc.
-    int categoryCount = m_series->d_func()->categoryCount();
-    int setCount = m_series->count();
-    int itemIndex(0);
-    static const QString valueTag(QLatin1String("@value"));
-
-    for (int category = 0; category < categoryCount; category++) {
-        for (int set = 0; set < setCount; set++) {
-            QBarSetPrivate *barSet = m_series->d_func()->barsetAt(set)->d_ptr.data();
-            Bar *bar = m_bars.at(itemIndex);
-            bar->setPen(barSet->m_pen);
-            bar->setBrush(barSet->m_brush);
-            bar->update();
-
-            QGraphicsTextItem *label = m_labels.at(itemIndex);
-            qreal p = m_series->d_func()->percentageAt(set, category) * 100.0;
-            QString vString(presenter()->numberToString(p, 'f', 0));
-            QString valueLabel;
-            if (p == 0) {
-                label->setVisible(false);
-            } else {
-                label->setVisible(m_series->isLabelsVisible());
-                if (m_series->labelsFormat().isEmpty()) {
-                    vString.append(QStringLiteral("%"));
-                    valueLabel = vString;
-                } else {
-                    valueLabel = m_series->labelsFormat();
-                    valueLabel.replace(valueTag, vString);
-                }
-            }
-            label->setHtml(valueLabel);
-            label->setFont(barSet->m_labelFont);
-            label->setDefaultTextColor(barSet->m_labelBrush.color());
-            label->update();
-            itemIndex++;
-        }
-    }
-}
-
 #include "moc_horizontalpercentbarchartitem_p.cpp"
 
 QT_CHARTS_END_NAMESPACE