HG_REPOSITORIES/LPP/INSTRUMENTATION/USERS/JEANDET/qtcharts Commit - r2850:57e4c71e5532

Clear chart image to transparent when necessary....

Miikka Heikkinen -

r2850:57e4c71e5532

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r2850:57e4c71e5532

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src/charts/qabstractseries.cpp +4 -4

                     hardware and drivers.
                 \li Polar charts do not support accelerated series.
                 \li Mouse events are not supported for accelerated series.
-                \li Enabling chart drop shadow is not recommended when using accelerated series,
+                \li Enabling chart drop shadow or using transparent chart background color is not recommended
-                    as that can slow the frame rate down significantly.
+                    when using accelerated series, as that can slow the frame rate down significantly.
                 \endlist
                 These additional restrictions stem from the fact that the accelerated series is drawn on a
                     hardware and drivers.
                 \li Polar charts do not support accelerated series.
                 \li Mouse events are not supported for accelerated series.
-                \li Enabling chart drop shadow is not recommended when using accelerated series,
+                \li Enabling chart drop shadow or using transparent chart background color is not recommended
-                    as that can slow the frame rate down significantly.
+                    when using accelerated series, as that can slow the frame rate down significantly.
                 \endlist
                 The default value is \c{false}.

src/chartsqml2/declarativechart.cpp +12 -1

             {
                 m_sceneImage = 0;
                 m_sceneImageDirty = false;
+                m_sceneImageNeedsClear = false;
                 m_guiThreadId = QThread::currentThreadId();
                 m_paintThreadId = 0;
                 m_updatePending = false;
                 if (!m_sceneImage || chartSize != m_sceneImage->size()) {
                     delete m_sceneImage;
                     m_sceneImage = new QImage(chartSize, QImage::Format_ARGB32);
-                    m_sceneImage->fill(Qt::transparent);
+                    m_sceneImageNeedsClear = true;
                 }
+                if (m_sceneImageNeedsClear) {
+                    m_sceneImage->fill(Qt::transparent);
+                    // Don't clear the flag if chart background has any transparent element to it
+                    if (m_chart->backgroundBrush().color().alpha() == 0xff && !m_chart->isDropShadowEnabled())
+                        m_sceneImageNeedsClear = false;
+                }
                 QPainter painter(m_sceneImage);
                 if (antialiasing()) {
                     painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing
             {
                 QBrush b = m_chart->backgroundBrush();
                 if (b.style() != Qt::SolidPattern || color != b.color()) {
+                    if (color.alpha() < 0xff)
+                        m_sceneImageNeedsClear = true;
                     b.setStyle(Qt::SolidPattern);
                     b.setColor(color);
                     m_chart->setBackgroundBrush(b);
             void DeclarativeChart::setDropShadowEnabled(bool enabled)
             {
                 if (enabled != m_chart->isDropShadowEnabled()) {
+                    m_sceneImageNeedsClear = true;
                     m_chart->setDropShadowEnabled(enabled);
                     dropShadowEnabledChanged(enabled);
                 }
             void DeclarativeChart::setBackgroundRoundness(qreal diameter)
             {
                 if (m_chart->backgroundRoundness() != diameter) {
+                    m_sceneImageNeedsClear = true;
                     m_chart->setBackgroundRoundness(diameter);
                     emit backgroundRoundnessChanged(diameter);
                 }

src/chartsqml2/declarativechart.h +1 0

                 Qt::HANDLE m_guiThreadId;
                 DeclarativeMargins *m_margins;
                 GLXYSeriesDataManager *m_glXYDataManager;
+                bool m_sceneImageNeedsClear;
             };
             QT_CHARTS_END_NAMESPACE

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