From f4b980d7defa3c3aa15cd9d8aeb50ee669322453 2012-03-16 13:29:37
From: Jani Honkonen <jani.honkonen@digia.com>
Date: 2012-03-16 13:29:37
Subject: [PATCH] Refactoring pie series and animations.

---

diff --git a/demos/piechartcustomization/main.cpp b/demos/piechartcustomization/main.cpp
index 13d9b17..3bbe47c 100644
--- a/demos/piechartcustomization/main.cpp
+++ b/demos/piechartcustomization/main.cpp
@@ -351,6 +351,7 @@ public:
         m_endAngle->setSingleStep(1);
 
         QPushButton *addSlice = new QPushButton("Add slice");
+        QPushButton *insertSlice = new QPushButton("Insert slice");
 
         QFormLayout* seriesSettingsLayout = new QFormLayout();
         seriesSettingsLayout->addRow("Horizontal position", m_hPosition);
@@ -359,6 +360,7 @@ public:
         seriesSettingsLayout->addRow("Start angle", m_startAngle);
         seriesSettingsLayout->addRow("End angle", m_endAngle);
         seriesSettingsLayout->addRow(addSlice);
+        seriesSettingsLayout->addRow(insertSlice);
         QGroupBox* seriesSettings = new QGroupBox("Series");
         seriesSettings->setLayout(seriesSettingsLayout);
 
@@ -368,6 +370,7 @@ public:
         connect(m_startAngle, SIGNAL(valueChanged(double)), this, SLOT(updateSerieSettings()));
         connect(m_endAngle, SIGNAL(valueChanged(double)), this, SLOT(updateSerieSettings()));
         connect(addSlice, SIGNAL(clicked()), this, SLOT(addSlice()));
+        connect(insertSlice, SIGNAL(clicked()), this, SLOT(insertSlice()));
 
         // slice settings
         m_sliceName = new QLabel("<click a slice>");
@@ -526,6 +529,16 @@ public Q_SLOTS:
         *m_series << new CustomSlice(10.0, "Slice " + QString::number(m_series->count()));
     }
 
+    void insertSlice()
+    {
+        if (!m_slice)
+            return;
+
+        int i = m_series->slices().indexOf(m_slice);
+
+        m_series->insert(i, new CustomSlice(10.0, "Slice " + QString::number(m_series->count())));
+    }
+
     void removeSlice()
     {
         if (!m_slice)
diff --git a/examples/piechartdrilldown/main.cpp b/examples/piechartdrilldown/main.cpp
index 078bcaf..03347a1 100644
--- a/examples/piechartdrilldown/main.cpp
+++ b/examples/piechartdrilldown/main.cpp
@@ -78,6 +78,7 @@ int main(int argc, char *argv[])
     DrilldownChart* drilldownChart =  new DrilldownChart(&window);
     drilldownChart->setRenderHint(QPainter::Antialiasing);
     drilldownChart->setChartTheme(QChart::ChartThemeVanilla);
+    drilldownChart->setAnimationOptions(QChart::AllAnimations);
 
     QPieSeries* yearSeries = new QPieSeries(&window);
     yearSeries->setTitle("Sales by year - All");
diff --git a/src/animations/chartanimator.cpp b/src/animations/chartanimator.cpp
index 7ef3645..a8964fc 100644
--- a/src/animations/chartanimator.cpp
+++ b/src/animations/chartanimator.cpp
@@ -184,11 +184,25 @@ void ChartAnimator::updateLayout(XYChartItem* item, QVector<QPointF>& newPoints)
     QTimer::singleShot(0,animation,SLOT(start()));
 }
 
-void ChartAnimator::applyLayout(PieChartItem* item, QVector<PieSliceLayout> &layout)
+void ChartAnimator::addAnimation(PieChartItem* item, QPieSlice *slice, PieSliceLayout &layout)
 {
     PieAnimation* animation = static_cast<PieAnimation*>(m_animations.value(item));
     Q_ASSERT(animation);
-    animation->setValues(layout);
+    animation->addSlice(slice, layout);
+}
+
+void ChartAnimator::removeAnimation(PieChartItem* item, QPieSlice *slice)
+{
+    PieAnimation* animation = static_cast<PieAnimation*>(m_animations.value(item));
+    Q_ASSERT(animation);
+    animation->removeSlice(slice);
+}
+
+void ChartAnimator::updateLayout(PieChartItem* item, QVector<PieSliceLayout> &layout)
+{
+    PieAnimation* animation = static_cast<PieAnimation*>(m_animations.value(item));
+    Q_ASSERT(animation);
+    animation->updateValues(layout);
 }
 
 void ChartAnimator::updateLayout(PieChartItem* item, PieSliceLayout &layout)
diff --git a/src/animations/chartanimator_p.h b/src/animations/chartanimator_p.h
index cb28d53..21e8e0d 100644
--- a/src/animations/chartanimator_p.h
+++ b/src/animations/chartanimator_p.h
@@ -32,7 +32,9 @@ public:
     void updateLayout(XYChartItem* item, QVector<QPointF>& layout);
     void applyLayout(AxisItem* item, QVector<qreal>& layout);
 
-    void applyLayout(PieChartItem* item, QVector<PieSliceLayout> &layout);
+    void addAnimation(PieChartItem* item, QPieSlice *slice, PieSliceLayout &layout);
+    void removeAnimation(PieChartItem* item, QPieSlice *slice);
+    void updateLayout(PieChartItem* item, QVector<PieSliceLayout> &layout);
     void updateLayout(PieChartItem* item, PieSliceLayout &layout);
 
     void setState(State state,const QPointF& point = QPointF());
diff --git a/src/animations/pieanimation.cpp b/src/animations/pieanimation.cpp
index 367c782..03e79d9 100644
--- a/src/animations/pieanimation.cpp
+++ b/src/animations/pieanimation.cpp
@@ -16,53 +16,10 @@ PieAnimation::~PieAnimation()
 {
 }
 
-void PieAnimation::setValues(QVector<PieSliceLayout>& newValues)
+void PieAnimation::updateValues(QVector<PieSliceLayout>& newValues)
 {
-    PieSliceAnimation *animation = 0;
-
-    foreach (PieSliceLayout endLayout, newValues) {
-        animation = m_animations.value(endLayout.m_data);
-        if (animation) {
-            // existing slice
-            animation->stop();
-            animation->updateValue(endLayout);
-        } else {
-            // new slice
-            animation = new PieSliceAnimation(m_item);
-            m_animations.insert(endLayout.m_data, animation);
-            PieSliceLayout startLayout = endLayout;
-            startLayout.m_radius = 0;
-            //startLayout.m_startAngle = 0;
-            //startLayout.m_angleSpan = 0;
-            animation->setValue(startLayout, endLayout);
-        }
-        animation->setDuration(1000);
-        animation->setEasingCurve(QEasingCurve::OutQuart);
-        QTimer::singleShot(0, animation, SLOT(start())); // TODO: use sequential animation?
-    }
-
-    foreach (QPieSlice *s, m_animations.keys()) {
-        bool isFound = false;
-        foreach (PieSliceLayout layout, newValues) {
-            if (s == layout.m_data)
-                isFound = true;
-        }
-        if (!isFound) {
-            // slice has been deleted
-            animation = m_animations.value(s);
-            animation->stop();
-            PieSliceLayout endLayout = m_animations.value(s)->currentSliceValue();
-            endLayout.m_radius = 0;
-            // TODO: find the actual angle where this slice disappears
-            endLayout.m_startAngle = endLayout.m_startAngle + endLayout.m_angleSpan;
-            endLayout.m_angleSpan = 0;
-            animation->updateValue(endLayout);
-            animation->setDuration(1000);
-            animation->setEasingCurve(QEasingCurve::OutQuart);
-            connect(animation, SIGNAL(finished()), this, SLOT(destroySliceAnimationComplete()));
-            QTimer::singleShot(0, animation, SLOT(start()));
-        }
-    }
+    foreach (PieSliceLayout endLayout, newValues)
+        updateValue(endLayout);
 }
 
 void PieAnimation::updateValue(PieSliceLayout& endLayout)
@@ -70,9 +27,47 @@ void PieAnimation::updateValue(PieSliceLayout& endLayout)
     PieSliceAnimation *animation = m_animations.value(endLayout.m_data);
     Q_ASSERT(animation);
     animation->stop();
+
+    animation->updateValue(endLayout);
+    animation->setDuration(1000);
+    animation->setEasingCurve(QEasingCurve::OutQuart);
+
+    QTimer::singleShot(0, animation, SLOT(start()));
+}
+
+void PieAnimation::addSlice(QPieSlice *slice, PieSliceLayout endLayout)
+{
+    PieSliceAnimation *animation = new PieSliceAnimation(m_item);
+    m_animations.insert(slice, animation);
+
+    PieSliceLayout startLayout = endLayout;
+    startLayout.m_radius = 0;
+    startLayout.m_startAngle = endLayout.m_startAngle + (endLayout.m_angleSpan/2);
+    startLayout.m_angleSpan = 0;
+    animation->setValue(startLayout, endLayout);
+
+    animation->setDuration(1000);
+    animation->setEasingCurve(QEasingCurve::OutQuart);
+    QTimer::singleShot(0, animation, SLOT(start()));
+}
+
+void PieAnimation::removeSlice(QPieSlice *slice)
+{
+    PieSliceAnimation *animation = m_animations.value(slice);
+    Q_ASSERT(animation);
+    animation->stop();
+
+    PieSliceLayout endLayout = animation->currentSliceValue();
+    endLayout.m_radius = 0;
+    // TODO: find the actual angle where this slice disappears
+    endLayout.m_startAngle = endLayout.m_startAngle + endLayout.m_angleSpan;
+    endLayout.m_angleSpan = 0;
+
     animation->updateValue(endLayout);
     animation->setDuration(1000);
     animation->setEasingCurve(QEasingCurve::OutQuart);
+
+    connect(animation, SIGNAL(finished()), this, SLOT(destroySliceAnimationComplete()));
     QTimer::singleShot(0, animation, SLOT(start()));
 }
 
diff --git a/src/animations/pieanimation_p.h b/src/animations/pieanimation_p.h
index 4e70469..b840008 100644
--- a/src/animations/pieanimation_p.h
+++ b/src/animations/pieanimation_p.h
@@ -16,8 +16,10 @@ class PieAnimation : public ChartAnimation
 public:
     PieAnimation(PieChartItem *item);
     ~PieAnimation();
-    void setValues(QVector<PieSliceLayout>& newValues);
+    void updateValues(QVector<PieSliceLayout>& newValues);
     void updateValue(PieSliceLayout& newValue);
+    void addSlice(QPieSlice *slice, PieSliceLayout endLayout);
+    void removeSlice(QPieSlice *slice);
 
 public: // from QVariantAnimation
     void updateCurrentValue(const QVariant &value);
diff --git a/src/piechart/piechartitem.cpp b/src/piechart/piechartitem.cpp
index 0fd7ba7..22e6eac 100644
--- a/src/piechart/piechartitem.cpp
+++ b/src/piechart/piechartitem.cpp
@@ -6,7 +6,7 @@
 #include "chartanimator_p.h"
 #include <QDebug>
 #include <QPainter>
-
+#include <QTimer>
 
 QTCOMMERCIALCHART_BEGIN_NAMESPACE
 
@@ -15,7 +15,12 @@ PieChartItem::PieChartItem(QGraphicsItem *parent, QPieSeries *series)
     m_series(series)
 {
     Q_ASSERT(series);
-    connect(series, SIGNAL(changed()), this, SLOT(handleSeriesChanged()));
+    connect(series, SIGNAL(added(QList<QPieSlice*>)), this, SLOT(handleSlicesAdded(QList<QPieSlice*>)));
+    connect(series, SIGNAL(removed(QList<QPieSlice*>)), this, SLOT(handleSlicesRemoved(QList<QPieSlice*>)));
+    connect(series, SIGNAL(piePositionChanged()), this, SLOT(handlePieLayoutChanged()));
+    connect(series, SIGNAL(pieSizeChanged()), this, SLOT(handlePieLayoutChanged()));
+
+    QTimer::singleShot(0, this, SLOT(initialize()));
 
     // Note: the following does not affect as long as the item does not have anything to paint
     setZValue(ChartPresenter::PieSeriesZValue);
@@ -35,7 +40,41 @@ void PieChartItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QW
     //painter->drawRect(m_debugRect);
 }
 
-void PieChartItem::handleSeriesChanged()
+void PieChartItem::initialize()
+{
+    handleSlicesAdded(m_series->m_slices);
+}
+
+void PieChartItem::handleSlicesAdded(QList<QPieSlice*> slices)
+{
+    foreach (QPieSlice *s, slices) {
+        PieSlice* slice = new PieSlice(this);
+        m_slices.insert(s, slice);
+        connect(s, SIGNAL(changed()), this, SLOT(handleSliceChanged()));
+        connect(slice, SIGNAL(clicked()), s, SIGNAL(clicked()));
+        connect(slice, SIGNAL(hoverEnter()), s, SIGNAL(hoverEnter()));
+        connect(slice, SIGNAL(hoverLeave()), s, SIGNAL(hoverLeave()));
+
+        PieSliceLayout layout = calculateSliceLayout(s);
+
+        if (m_animator)
+            m_animator->addAnimation(this, s, layout);
+        else
+            setLayout(layout);
+    }
+}
+
+void PieChartItem::handleSlicesRemoved(QList<QPieSlice*> slices)
+{
+    foreach (QPieSlice *s, slices) {
+        if (m_animator)
+            m_animator->removeAnimation(this, s);
+        else
+            destroySlice(s);
+    }
+}
+
+void PieChartItem::handlePieLayoutChanged()
 {
     QVector<PieSliceLayout> layout = calculateLayout();
     applyLayout(layout);
@@ -46,15 +85,8 @@ void PieChartItem::handleSliceChanged()
 {
     QPieSlice* slice = qobject_cast<QPieSlice *>(sender());
     Q_ASSERT(m_slices.contains(slice));
-
-    //qDebug() << "PieChartItem::handleSliceChanged" << slice->label();
-
-    // TODO: Optimize. No need to calculate everything.
-    QVector<PieSliceLayout> layout = calculateLayout();
-    foreach (PieSliceLayout sl, layout) {
-        if (sl.m_data == slice)
-            updateLayout(sl);
-    }
+    PieSliceLayout layout = calculateSliceLayout(slice);
+    updateLayout(layout);
     update();
 }
 
@@ -67,45 +99,50 @@ void PieChartItem::handleGeometryChanged(const QRectF& rect)
 {
     prepareGeometryChange();
     m_rect = rect;
-    QVector<PieSliceLayout> sliceLayout = calculateLayout();
-    applyLayout(sliceLayout);
-    update();
+    handlePieLayoutChanged();
 }
 
-
-QVector<PieSliceLayout> PieChartItem::calculateLayout()
+void PieChartItem::calculatePieLayout()
 {
     // find pie center coordinates
-    QPointF center;
-    center.setX(m_rect.left() + (m_rect.width() * m_series->pieHorizontalPosition()));
-    center.setY(m_rect.top() + (m_rect.height() * m_series->pieVerticalPosition()));
+    m_pieCenter.setX(m_rect.left() + (m_rect.width() * m_series->pieHorizontalPosition()));
+    m_pieCenter.setY(m_rect.top() + (m_rect.height() * m_series->pieVerticalPosition()));
 
     // find maximum radius for pie
-    qreal radius = m_rect.height() / 2;
+    m_pieRadius = m_rect.height() / 2;
     if (m_rect.width() < m_rect.height())
-        radius = m_rect.width() / 2;
+        m_pieRadius = m_rect.width() / 2;
 
     // apply size factor
-    radius *= m_series->pieSize();
+    m_pieRadius *= m_series->pieSize();
+}
 
+PieSliceLayout PieChartItem::calculateSliceLayout(QPieSlice *slice)
+{
+    PieSliceLayout sliceLayout;
+    sliceLayout.m_data = slice;
+    sliceLayout.m_center = PieSlice::sliceCenter(m_pieCenter, m_pieRadius, slice);
+    sliceLayout.m_radius = m_pieRadius;
+    sliceLayout.m_startAngle = slice->startAngle();
+    sliceLayout.m_angleSpan = slice->m_angleSpan;
+    return sliceLayout;
+}
+
+QVector<PieSliceLayout> PieChartItem::calculateLayout()
+{
+    calculatePieLayout();
     QVector<PieSliceLayout> layout;
     foreach (QPieSlice* s, m_series->slices()) {
-        PieSliceLayout sliceLayout;
-        sliceLayout.m_data = s;
-        sliceLayout.m_center = PieSlice::sliceCenter(center, radius, s);
-        sliceLayout.m_radius = radius;
-        sliceLayout.m_startAngle = s->startAngle();
-        sliceLayout.m_angleSpan = s->m_angleSpan;
-        layout << sliceLayout;
+        if (m_slices.contains(s)) // calculate layout only for those slices that are already visible
+            layout << calculateSliceLayout(s);
     }
-
     return layout;
 }
 
 void PieChartItem::applyLayout(QVector<PieSliceLayout> &layout)
 {
     if (m_animator)
-        m_animator->applyLayout(this, layout);
+        m_animator->updateLayout(this, layout);
     else
         setLayout(layout);
 }
@@ -121,53 +158,20 @@ void PieChartItem::updateLayout(PieSliceLayout &layout)
 void PieChartItem::setLayout(QVector<PieSliceLayout> &layout)
 {
     foreach (PieSliceLayout l, layout) {
-
-        // find slice
         PieSlice *slice = m_slices.value(l.m_data);
-        if (!slice) {
-            // add a new slice
-            slice = new PieSlice(this);
-            m_slices.insert(l.m_data, slice);
-
-            // connect signals
-            connect(l.m_data, SIGNAL(changed()), this, SLOT(handleSliceChanged()));
-            connect(slice, SIGNAL(clicked()), l.m_data, SIGNAL(clicked()));
-            connect(slice, SIGNAL(hoverEnter()), l.m_data, SIGNAL(hoverEnter()));
-            connect(slice, SIGNAL(hoverLeave()), l.m_data, SIGNAL(hoverLeave()));
-        }
-
-        // update
+        Q_ASSERT(slice);
         slice->setLayout(l);
+        slice->updateData(l.m_data);
         slice->updateGeometry();
         slice->update();
     }
-
-    // delete slices
-    foreach (QPieSlice *s, m_slices.keys()) {
-
-        bool found = false;
-        foreach (PieSliceLayout l, layout) {
-            if (l.m_data == s)
-                found = true;
-        }
-
-        if (!found)
-            destroySlice(s);
-    }
 }
 
 void PieChartItem::setLayout(PieSliceLayout &layout)
 {
     // find slice
     PieSlice *slice = m_slices.value(layout.m_data);
-    if (!slice) {
-        slice = new PieSlice(this);
-        m_slices.insert(layout.m_data, slice);
-        connect(layout.m_data, SIGNAL(changed()), this, SLOT(handleSliceChanged()));
-        connect(slice, SIGNAL(clicked()), layout.m_data, SIGNAL(clicked()));
-        connect(slice, SIGNAL(hoverEnter()), layout.m_data, SIGNAL(hoverEnter()));
-        connect(slice, SIGNAL(hoverLeave()), layout.m_data, SIGNAL(hoverLeave()));
-    }
+    Q_ASSERT(slice);
     slice->setLayout(layout);
     if (m_series->m_slices.contains(layout.m_data)) // Slice has been deleted if not found. Animations ongoing...
         slice->updateData(layout.m_data);
diff --git a/src/piechart/piechartitem_p.h b/src/piechart/piechartitem_p.h
index 6ea55c7..7a3b4db 100644
--- a/src/piechart/piechartitem_p.h
+++ b/src/piechart/piechartitem_p.h
@@ -23,12 +23,17 @@ public: // from QGraphicsItem
     void paint(QPainter *, const QStyleOptionGraphicsItem *, QWidget *);
 
 public Q_SLOTS:
-    void handleSeriesChanged();
+    void initialize();
+    void handleSlicesAdded(QList<QPieSlice*> slices);
+    void handleSlicesRemoved(QList<QPieSlice*> slices);
+    void handlePieLayoutChanged();
     void handleSliceChanged();
     void handleDomainChanged(qreal, qreal, qreal, qreal);
     void handleGeometryChanged(const QRectF& rect);
 
 public:
+    void calculatePieLayout();
+    PieSliceLayout calculateSliceLayout(QPieSlice *slice);
     QVector<PieSliceLayout> calculateLayout();
     void applyLayout(QVector<PieSliceLayout> &layout);
     void updateLayout(PieSliceLayout &layout);
diff --git a/src/piechart/pieslice.cpp b/src/piechart/pieslice.cpp
index 20f576c..dae1f67 100644
--- a/src/piechart/pieslice.cpp
+++ b/src/piechart/pieslice.cpp
@@ -39,7 +39,7 @@ PieSlice::~PieSlice()
 
 QRectF PieSlice::boundingRect() const
 {
-    return m_slicePath.boundingRect().united(m_labelTextRect);
+    return m_boundingRect;
 }
 
 QPainterPath PieSlice::shape() const
@@ -112,7 +112,8 @@ void PieSlice::updateGeometry()
     // update text position
     m_labelTextRect.moveBottomLeft(labelTextStart);
 
-    //qDebug() << "PieSlice::updateGeometry" << m_labelText << boundingRect() << m_startAngle << m_startAngle + m_angleSpan;
+    // update bounding rect
+    m_boundingRect = m_slicePath.boundingRect().united(m_labelArmPath.boundingRect()).united(m_labelTextRect);
 }
 
 void PieSlice::updateData(const QPieSlice* sliceData)
diff --git a/src/piechart/pieslice_p.h b/src/piechart/pieslice_p.h
index ec50820..bd08fdb 100644
--- a/src/piechart/pieslice_p.h
+++ b/src/piechart/pieslice_p.h
@@ -58,6 +58,7 @@ public:
 
 private:
     PieSliceLayout m_layout;
+    QRectF m_boundingRect;
 
     QPainterPath m_slicePath;
     bool m_isExploded;
diff --git a/src/piechart/qpieseries.cpp b/src/piechart/qpieseries.cpp
index 9fe5bf9..6f69802 100644
--- a/src/piechart/qpieseries.cpp
+++ b/src/piechart/qpieseries.cpp
@@ -77,7 +77,7 @@ void QPieSeries::add(QList<QPieSlice*> slices)
         connect(s, SIGNAL(hoverLeave()), this, SLOT(sliceHoverLeave()));
     }
 
-    emit changed();
+    emit added(slices);
 }
 
 /*!
@@ -124,7 +124,7 @@ void QPieSeries::insert(int i, QPieSlice* slice)
     connect(slice, SIGNAL(hoverEnter()), this, SLOT(sliceHoverEnter()));
     connect(slice, SIGNAL(hoverLeave()), this, SLOT(sliceHoverLeave()));
 
-    emit changed();
+    emit added(QList<QPieSlice*>() << slice);
 }
 
 /*!
@@ -138,10 +138,11 @@ void QPieSeries::remove(QPieSlice* slice)
         Q_ASSERT(0); // TODO: how should this be reported?
         return;
     }
-    emit changed();
 
     updateDerivativeData();
 
+    emit removed(QList<QPieSlice*>() << slice);
+
     delete slice;
     slice = NULL;
 }
@@ -154,14 +155,15 @@ void QPieSeries::clear()
     if (m_slices.count() == 0)
         return;
 
+    QList<QPieSlice*> slices = m_slices;
     foreach (QPieSlice* s, m_slices) {
         m_slices.removeOne(s);
         delete s;
     }
 
-    emit changed();
-
     updateDerivativeData();
+
+    emit removed(slices);
 }
 
 /*!
@@ -173,6 +175,14 @@ int QPieSeries::count() const
 }
 
 /*!
+    Returns true is the series is empty.
+*/
+bool QPieSeries::isEmpty() const
+{
+    return m_slices.isEmpty();
+}
+
+/*!
     Returns a list of slices that belong to this series.
 */
 QList<QPieSlice*> QPieSeries::slices() const
@@ -203,7 +213,7 @@ void QPieSeries::setPiePosition(qreal relativeHorizontalPosition, qreal relative
     if (m_pieRelativeHorPos != relativeHorizontalPosition || m_pieRelativeVerPos != relativeVerticalPosition) {
         m_pieRelativeHorPos = relativeHorizontalPosition;
         m_pieRelativeVerPos = relativeVerticalPosition;
-        emit changed();
+        emit piePositionChanged();
     }
 }
 
@@ -257,7 +267,7 @@ void QPieSeries::setPieSize(qreal relativeSize)
 
     if (m_pieRelativeSize != relativeSize) {
         m_pieRelativeSize = relativeSize;
-        emit changed();
+        emit pieSizeChanged();
     }
 }
 
@@ -427,13 +437,9 @@ void QPieSeries::updateDerivativeData()
     foreach (QPieSlice* s, m_slices)
         m_total += s->value();
 
-    // TODO: emit totalChanged?
-
-    // we must have some values
-    if (m_total == 0) {
-        qDebug() << "QPieSeries::updateDerivativeData() total == 0";
-        Q_ASSERT(m_total > 0); // TODO: is this the correct way to handle this?
-    }
+    // nothing to show..
+    if (m_total == 0)
+        return;
 
     // update slice attributes
     qreal sliceAngle = m_pieStartAngle;
@@ -465,6 +471,7 @@ void QPieSeries::updateDerivativeData()
             changed << s;
     }
 
+    // emit signals
     foreach (QPieSlice* s, changed)
         emit s->changed();
 }
diff --git a/src/piechart/qpieseries.h b/src/piechart/qpieseries.h
index 2b3a976..8d949f1 100644
--- a/src/piechart/qpieseries.h
+++ b/src/piechart/qpieseries.h
@@ -33,6 +33,7 @@ public:
 
     // calculated data
     int count() const;
+    bool isEmpty() const;
     qreal total() const;
 
     // pie customization
@@ -70,7 +71,12 @@ Q_SIGNALS:
     void clicked(QPieSlice* slice);
     void hoverEnter(QPieSlice* slice);
     void hoverLeave(QPieSlice* slice);
-    void changed(); // TODO: hide this in PIMPL
+
+    // TODO: hide these in PIMPL
+    void added(QList<QPieSlice*> slices);
+    void removed(QList<QPieSlice*> slices);
+    void piePositionChanged();
+    void pieSizeChanged();
 
 private Q_SLOTS: // TODO: should be private and not visible in the interface at all
     void sliceChanged();