[calamares] Add reload() to update model after underlying data

src/calamares/VariantModel.cpp

@@ -70,15 +70,21 @@ findNth( const VariantModel::IndexVector& skiplist, quintptr value, int n )
 VariantModel::VariantModel( const QVariant* p )
     : m_p( p )
 {
-    int x = 0;
-    overallLength( *p, x, -1, nullptr );
-    m_rows.reserve( x );
-    x = 0;
-    overallLength( *p, x, -1, &m_rows );
+    reload();
 }
 
 VariantModel::~VariantModel() {}
 
+void VariantModel::reload()
+{
+    int x = 0;
+    overallLength( *m_p, x, -1, nullptr );
+    m_rows.clear();  // Start over
+    m_rows.reserve( x );  // We'll need this much
+    x = 0;
+    overallLength( *m_p, x, -1, &m_rows );
+}
+
 int
 VariantModel::columnCount( const QModelIndex& index ) const
 {

src/calamares/VariantModel.h

@@ -33,7 +33,9 @@
  * VariantMap's data structure.
  *
  * Take care of object lifetimes and that the underlying
- * QVariant does not change during use.
+ * QVariant does not change during use. If the QVariant
+ * **does** change, call reload() to re-build the internal
+ * representation of the tree.
  */
 class VariantModel : public QAbstractItemModel
 {
@@ -56,6 +58,13 @@ public:
 
     ~VariantModel() override;
 
+    /** @brief Re-build the internal tree
+     *
+     * Call this when the underlying variant is changed, which
+     * might impact how the tree is laid out.
+     */
+    void reload();
+
     int columnCount( const QModelIndex& index ) const override;
     int rowCount( const QModelIndex& index ) const override;