graphgallery example: Streamline the code a bit

- Populate the data rows using reserve()/append() instead
  of resize() / assign.
- Use prefix increment
- Use QStringView when splitting the data file lines

Pick-to: 6.5
Task-number: QTBUG-110698
Change-Id: I70fed07a9850e2636e6085b9a9190f1e5a062a67
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>

6 files changed, 44 insertions, 47 deletions

diff --git a/examples/datavisualization/graphgallery/highlightseries.cpp b/examples/datavisualization/graphgallery/highlightseries.cpp
index c2aab2db..8ce75ac0 100644
--- a/examples/datavisualization/graphgallery/highlightseries.cpp
+++ b/examples/datavisualization/graphgallery/highlightseries.cpp
@@ -65,14 +65,16 @@ void HighlightSeries::handlePositionChange(const QPoint &position)
 
     QSurfaceDataArray *dataArray = new QSurfaceDataArray;
     dataArray->reserve(endZ - startZ);
-    for (int i = startZ; i < endZ; i++) {
-        QSurfaceDataRow *newRow = new QSurfaceDataRow(endX - startX);
+    for (int i = startZ; i < endZ; ++i) {
+        QSurfaceDataRow *newRow = new QSurfaceDataRow;
+        newRow->reserve(endX - startX);
         QSurfaceDataRow *srcRow = srcArray.at(i);
-        for (int j = startX, p = 0; j < endX; j++, p++) {
+        for (int j = startX; j < endX; ++j) {
             QVector3D pos = srcRow->at(j).position();
-            (*newRow)[p].setPosition(QVector3D(pos.x(), pos.y() + 0.1f, pos.z()));
+            pos.setY(pos.y() + 0.1f);
+            newRow->append(QSurfaceDataItem(pos));
         }
-        *dataArray << newRow;
+        dataArray->append(newRow);
     }
 
     dataProxy()->resetArray(dataArray);
diff --git a/examples/datavisualization/graphgallery/rainfalldata.cpp b/examples/datavisualization/graphgallery/rainfalldata.cpp
index 8765db2c..11b67565 100644
--- a/examples/datavisualization/graphgallery/rainfalldata.cpp
+++ b/examples/datavisualization/graphgallery/rainfalldata.cpp
@@ -14,7 +14,7 @@ using namespace Qt::StringLiterals;
 RainfallData::RainfallData()
 {
     // In data file the months are in numeric format, so create custom list
-    for (int i = 1; i <= 12; i++)
+    for (int i = 1; i <= 12; ++i)
         m_numericMonths << QString::number(i);
 
     m_columnCount = m_numericMonths.size();
@@ -65,7 +65,7 @@ void RainfallData::updateYearsList(int start, int end)
 {
     m_years.clear();
 
-    for (int i = start; i <= end; i++)
+    for (int i = start; i <= end; ++i)
         m_years << QString::number(i);
 
     m_rowCount = m_years.size();
@@ -79,15 +79,14 @@ void RainfallData::addDataSet()
     VariantDataItemList *itemList = new VariantDataItemList;
 
     // Read data from a data file into the data item list
-    QTextStream stream;
     QFile dataFile(":/data/raindata.txt");
     if (dataFile.open(QIODevice::ReadOnly | QIODevice::Text)) {
-        stream.setDevice(&dataFile);
+        QTextStream stream(&dataFile);
         while (!stream.atEnd()) {
             QString line = stream.readLine();
             if (line.startsWith('#')) // Ignore comments
                 continue;
-            QStringList strList = line.split(',', Qt::SkipEmptyParts);
+            const auto strList = QStringView{line}.split(',', Qt::SkipEmptyParts);
             // Each line has three data items: Year, month, and rainfall value
             if (strList.size() < 3) {
                 qWarning() << "Invalid row read from data:" << line;
@@ -96,8 +95,8 @@ void RainfallData::addDataSet()
             // Store year and month as strings, and rainfall value as double
             // into a variant data item and add the item to the item list.
             VariantDataItem *newItem = new VariantDataItem;
-            for (int i = 0; i < 2; i++)
-                newItem->append(strList.at(i).trimmed());
+            for (int i = 0; i < 2; ++i)
+                newItem->append(strList.at(i).trimmed().toString());
             newItem->append(strList.at(2).trimmed().toDouble());
             itemList->append(newItem);
         }
diff --git a/examples/datavisualization/graphgallery/scatterdatamodifier.cpp b/examples/datavisualization/graphgallery/scatterdatamodifier.cpp
index f018c81b..575515a4 100644
--- a/examples/datavisualization/graphgallery/scatterdatamodifier.cpp
+++ b/examples/datavisualization/graphgallery/scatterdatamodifier.cpp
@@ -71,24 +71,21 @@ void ScatterDataModifier::addData()
 
     //! [4]
     QScatterDataArray *dataArray = new QScatterDataArray;
-    dataArray->resize(m_itemCount);
-    QScatterDataItem *ptrToDataArray = &dataArray->first();
+    dataArray->reserve(m_itemCount);
     //! [4]
 
 #ifdef RANDOM_SCATTER
-    for (int i = 0; i < m_itemCount; i++) {
-        ptrToDataArray->setPosition(randVector());
-        ptrToDataArray++;
-    }
+    for (int i = 0; i < m_itemCount; ++i)
+        dataArray->append(QScatterDataItem(randVector()));
 #else
     //! [5]
-    float limit = qSqrt(m_itemCount) / 2.0f;
-    for (int i = -limit; i < limit; i++) {
-        for (int j = -limit; j < limit; j++) {
-            ptrToDataArray->setPosition(QVector3D(float(i) + 0.5f,
-                                                  qCos(qDegreesToRadians(float(i * j) / m_curveDivider)),
-                                                  float(j) + 0.5f));
-            ptrToDataArray++;
+    const float limit = qSqrt(m_itemCount) / 2.0f;
+    for (int i = -limit; i < limit; ++i) {
+        for (int j = -limit; j < limit; ++j) {
+            const float x = float(i) + 0.5f;
+            const float y = qCos(qDegreesToRadians(float(i * j) / m_curveDivider));
+            const float z = float(j) + 0.5f;
+            dataArray->append(QScatterDataItem({x, y, z}));
         }
     }
     //! [5]
@@ -148,12 +145,12 @@ void ScatterDataModifier::changeShadowQuality(int quality)
 
 void ScatterDataModifier::setBackgroundEnabled(int enabled)
 {
-    m_graph->activeTheme()->setBackgroundEnabled((bool)enabled);
+    m_graph->activeTheme()->setBackgroundEnabled(enabled == Qt::Checked);
 }
 
 void ScatterDataModifier::setGridEnabled(int enabled)
 {
-    m_graph->activeTheme()->setGridEnabled((bool)enabled);
+    m_graph->activeTheme()->setGridEnabled(enabled == Qt::Checked);
 }
 
 void ScatterDataModifier::toggleItemCount()
@@ -186,11 +183,9 @@ void ScatterDataModifier::toggleRanges()
 
 QVector3D ScatterDataModifier::randVector()
 {
-    return QVector3D(
-                (float)(QRandomGenerator::global()->bounded(100)) / 2.0f -
-                (float)(QRandomGenerator::global()->bounded(100)) / 2.0f,
-                (float)(QRandomGenerator::global()->bounded(100)) / 100.0f -
-                (float)(QRandomGenerator::global()->bounded(100)) / 100.0f,
-                (float)(QRandomGenerator::global()->bounded(100)) / 2.0f -
-                (float)(QRandomGenerator::global()->bounded(100)) / 2.0f);
+    auto *generator = QRandomGenerator::global();
+    const auto x = float(generator->bounded(100)) / 2.0f - float(generator->bounded(100)) / 2.0f;
+    const auto y = float(generator->bounded(100)) / 100.0f - float(generator->bounded(100)) / 100.0f;
+    const auto z = float(generator->bounded(100)) / 2.0f - float(generator->bounded(100)) / 2.0f;
+    return {x, y, z};
 }
diff --git a/examples/datavisualization/graphgallery/surfacegraph.cpp b/examples/datavisualization/graphgallery/surfacegraph.cpp
index 6147c437..b5f5a1de 100644
--- a/examples/datavisualization/graphgallery/surfacegraph.cpp
+++ b/examples/datavisualization/graphgallery/surfacegraph.cpp
@@ -211,7 +211,7 @@ bool SurfaceGraph::initialize(const QSize &minimumGraphSize, const QSize &maximu
     pmpHighlight.drawRect(border, border, 35, height - 2 * border);
     pmpHighlight.setPen(Qt::black);
     int step = (height - 2 * border) / 5;
-    for (int i = 0; i < 6; i++) {
+    for (int i = 0; i < 6; ++i) {
         int yPos = i * step + border;
         pmpHighlight.drawLine(border, yPos, 55, yPos);
         const int height = 550 - (i * 110);
diff --git a/examples/datavisualization/graphgallery/surfacegraphmodifier.cpp b/examples/datavisualization/graphgallery/surfacegraphmodifier.cpp
index 3ab9f7eb..3b2e2f3a 100644
--- a/examples/datavisualization/graphgallery/surfacegraphmodifier.cpp
+++ b/examples/datavisualization/graphgallery/surfacegraphmodifier.cpp
@@ -154,19 +154,19 @@ void SurfaceGraphModifier::fillSqrtSinProxy()
     //! [1]
     QSurfaceDataArray *dataArray = new QSurfaceDataArray;
     dataArray->reserve(sampleCountZ);
-    for (int i = 0 ; i < sampleCountZ ; i++) {
-        QSurfaceDataRow *newRow = new QSurfaceDataRow(sampleCountX);
+    for (int i = 0 ; i < sampleCountZ ; ++i) {
+        QSurfaceDataRow *newRow = new QSurfaceDataRow;
+        newRow->reserve(sampleCountX);
         // Keep values within range bounds, since just adding step can cause minor drift due
         // to the rounding errors.
         float z = qMin(sampleMax, (i * stepZ + sampleMin));
-        int index = 0;
-        for (int j = 0; j < sampleCountX; j++) {
+        for (int j = 0; j < sampleCountX; ++j) {
             float x = qMin(sampleMax, (j * stepX + sampleMin));
             float R = qSqrt(z * z + x * x) + 0.01f;
             float y = (qSin(R) / R + 0.24f) * 1.61f;
-            (*newRow)[index++].setPosition(QVector3D(x, y, z));
+            newRow->append(QSurfaceDataItem({x, y, z}));
         }
-        *dataArray << newRow;
+        dataArray->append(newRow);
     }
 
     m_sqrtSinProxy->resetArray(dataArray);
diff --git a/examples/datavisualization/graphgallery/topographicseries.cpp b/examples/datavisualization/graphgallery/topographicseries.cpp
index ea0be77d..ea6767e0 100644
--- a/examples/datavisualization/graphgallery/topographicseries.cpp
+++ b/examples/datavisualization/graphgallery/topographicseries.cpp
@@ -30,20 +30,21 @@ void TopographicSeries::setTopographyFile(const QString file, float width, float
 
     QSurfaceDataArray *dataArray = new QSurfaceDataArray;
     dataArray->reserve(imageHeight);
-    for (int i = 0; i < imageHeight; i++) {
+    for (int i = 0; i < imageHeight; ++i) {
         int p = i * widthBits;
         float z = height - float(i) * stepZ;
-        QSurfaceDataRow *newRow = new QSurfaceDataRow(imageWidth);
-        for (int j = 0; j < imageWidth; j++) {
+        QSurfaceDataRow *newRow = new QSurfaceDataRow;
+        newRow->reserve(imageWidth);
+        for (int j = 0; j < imageWidth; ++j) {
             uchar aa = bits[p + 0];
             uchar rr = bits[p + 1];
             uchar gg = bits[p + 2];
             uint color = uint((gg << 16) + (rr << 8) + aa);
             float y = float(color) / packingFactor;
-            (*newRow)[j].setPosition(QVector3D(float(j) * stepX, y, z));
-            p = p + 4;
+            newRow->append(QSurfaceDataItem({float(j) * stepX, y, z}));
+            p += 4;
         }
-        *dataArray << newRow;
+        dataArray->append(newRow);
     }
 
     dataProxy()->resetArray(dataArray);