Accelerating lineseries with OpenGL

Added support for QAbstractSeries::useOpenGL property.
When true, the series in question is drawn on a separate
offscreen buffer using OpenGL and then superimposed on
the chart. Currently this property is only supported
for line and scatter series.

Change-Id: I174fec541f9f3c23464270c1fe08f824af16a0fb
Reviewed-by: Titta Heikkala <titta.heikkala@theqtcompany.com>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@theqtcompany.com>

1 files changed, 118 insertions, 0 deletions

diff --git a/examples/charts/openglseries/datasource.cpp b/examples/charts/openglseries/datasource.cpp
new file mode 100644
index 00000000..64b45405
--- /dev/null
+++ b/examples/charts/openglseries/datasource.cpp
@@ -0,0 +1,118 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd
+** All rights reserved.
+** For any questions to The Qt Company, please use contact form at http://qt.io
+**
+** This file is part of the Qt Charts module.
+**
+** Licensees holding valid commercial license for Qt may use this file in
+** accordance with the Qt License Agreement provided with the Software
+** or, alternatively, in accordance with the terms contained in a written
+** agreement between you and The Qt Company.
+**
+** If you have questions regarding the use of this file, please use
+** contact form at http://qt.io
+**
+****************************************************************************/
+
+#include "datasource.h"
+#include <QtCore/QtMath>
+
+QT_CHARTS_USE_NAMESPACE
+
+DataSource::DataSource(QObject *parent) :
+    QObject(parent),
+    m_index(-1)
+{
+    generateData(0, 0, 0);
+}
+
+void DataSource::update(QAbstractSeries *series, int seriesIndex)
+{
+    if (series) {
+        QXYSeries *xySeries = static_cast<QXYSeries *>(series);
+        const QVector<QVector<QPointF> > &seriesData = m_data.at(seriesIndex);
+        if (seriesIndex == 0)
+            m_index++;
+        if (m_index > seriesData.count() - 1)
+            m_index = 0;
+
+        QVector<QPointF> points = seriesData.at(m_index);
+        // Use replace instead of clear + append, it's optimized for performance
+        xySeries->replace(points);
+    }
+}
+
+void DataSource::handleSceneChanged()
+{
+    m_dataUpdater.start();
+}
+
+void DataSource::updateAllSeries()
+{
+    static int frameCount = 0;
+    static QString labelText = QStringLiteral("FPS: %1");
+
+    for (int i = 0; i < m_seriesList.size(); i++)
+        update(m_seriesList[i], i);
+
+    frameCount++;
+    int elapsed = m_fpsTimer.elapsed();
+    if (elapsed >= 1000) {
+        elapsed = m_fpsTimer.restart();
+        qreal fps = qreal(0.1 * int(10000.0 * (qreal(frameCount) / qreal(elapsed))));
+        m_fpsLabel->setText(labelText.arg(QString::number(fps, 'f', 1)));
+        frameCount = 0;
+    }
+}
+
+void DataSource::startUpdates(const QList<QXYSeries *> &seriesList, QLabel *fpsLabel)
+{
+    m_seriesList = seriesList;
+    m_fpsLabel = fpsLabel;
+
+    m_dataUpdater.setInterval(0);
+    m_dataUpdater.setSingleShot(true);
+    QObject::connect(&m_dataUpdater, &QTimer::timeout,
+                     this, &DataSource::updateAllSeries);
+
+    m_fpsTimer.start();
+    updateAllSeries();
+}
+
+void DataSource::generateData(int seriesCount, int rowCount, int colCount)
+{
+    // Remove previous data
+    foreach (QVector<QVector<QPointF> > seriesData, m_data) {
+        foreach (QVector<QPointF> row, seriesData)
+            row.clear();
+    }
+
+    m_data.clear();
+
+    qreal xAdjustment = 20.0 / (colCount * rowCount);
+    qreal yMultiplier = 3.0 / qreal(seriesCount);
+
+    // Append the new data depending on the type
+    for (int k(0); k < seriesCount; k++) {
+        QVector<QVector<QPointF> > seriesData;
+        qreal height = qreal(k) * (10.0 / qreal(seriesCount)) + 0.3;
+        for (int i(0); i < rowCount; i++) {
+            QVector<QPointF> points;
+            points.reserve(colCount);
+            for (int j(0); j < colCount; j++) {
+                qreal x(0);
+                qreal y(0);
+                // data with sin + random component
+                y = height + (yMultiplier * qSin(3.14159265358979 / 50 * j)
+                              + (yMultiplier * (qreal) rand() / (qreal) RAND_MAX));
+                // 0.000001 added to make values logaxis compatible
+                x = 0.000001 + 20.0 * (qreal(j) / qreal(colCount)) + (xAdjustment * qreal(i));
+                points.append(QPointF(x, y));
+            }
+            seriesData.append(points);
+        }
+        m_data.append(seriesData);
+    }
+}