Fix access to bar sets instantiated inside the module

The QBarModelMapper allocates QBarSet instances during initialization.
While this works for pure C++ applications, on the QML side these need
to be of type DeclarativeBarSet to be accessible, but also expose
additional properties.
The C++ module is not aware of QML, also the QBarModelMapper cannot
expose a dynamic allocator without breaking binary compatibility.

Hence, the approach is to create a custom allocator function and export
it from the C++ module. In case a declarative chart is created, the
allocator is replaced with the QML one.

Fixes: QTBUG-71013
Change-Id: I1864d637df37f8cd38d28fdba75da0c5608a612c
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>

1 files changed, 8 insertions, 1 deletions

diff --git a/src/charts/barchart/qbarmodelmapper.cpp b/src/charts/barchart/qbarmodelmapper.cpp
index 966d719f..6a7e18d7 100644
--- a/src/charts/barchart/qbarmodelmapper.cpp
+++ b/src/charts/barchart/qbarmodelmapper.cpp
@@ -540,6 +540,13 @@ void QBarModelMapperPrivate::barValueChanged(int index)
     initializeBarFromModel();
 }
 
+QBarSet *qt_allocate_bar_set_cpp(const QString &label)
+{
+    return new QBarSet(label);
+}
+
+QT_CHARTS_EXPORT QBarSet *(*qt_allocate_bar_set)(const QString &label) = &qt_allocate_bar_set_cpp;
+
 void QBarModelMapperPrivate::initializeBarFromModel()
 {
     if (m_model == 0 || m_series == 0)
@@ -556,7 +563,7 @@ void QBarModelMapperPrivate::initializeBarFromModel()
         QModelIndex barIndex = barModelIndex(i, posInBar);
         // check if there is such model index
         if (barIndex.isValid()) {
-            QBarSet *barSet = new QBarSet(m_model->headerData(i, m_orientation == Qt::Vertical ? Qt::Horizontal : Qt::Vertical).toString());
+            QBarSet *barSet = qt_allocate_bar_set(m_model->headerData(i, m_orientation == Qt::Vertical ? Qt::Horizontal : Qt::Vertical).toString());
             while (barIndex.isValid()) {
                 barSet->append(m_model->data(barIndex, Qt::DisplayRole).toDouble());
                 posInBar++;