Bindings for QgsCategorizedSymbolRenderer::createCategories

also contains some code modernization

python/core/auto_generated/symbology/qgscategorizedsymbolrenderer.sip.in

@@ -279,6 +279,19 @@ Returns the count of symbols matched.
 .. versionadded:: 3.4
 %End
 
+
+    static QgsCategoryList createCategories( const QVariantList &values, const QgsSymbol *symbol, QgsVectorLayer *layer = 0, const QString &fieldName = QString() );
+%Docstring
+Create categories for a list of ``values``.
+The returned symbols in the category list will be a modification of ``symbol``.
+
+If ``layer`` and ``fieldName`` are specified it will try to find nicer values
+to represent the description for the categories based on the respective field
+configuration.
+
+.. versionadded:: 3.6
+%End
+
   protected:
 
 

src/core/symbology/qgscategorizedsymbolrenderer.cpp

@@ -30,6 +30,8 @@
 #include "qgslogger.h"
 #include "qgsproperty.h"
 #include "qgsstyle.h"
+#include "qgsfieldformatter.h"
+#include "qgsfieldformatterregistry.h"
 
 #include <QDomDocument>
 #include <QDomElement>
@@ -1032,3 +1034,40 @@ int QgsCategorizedSymbolRenderer::matchToSymbols( QgsStyle *style, const QgsSymb
 
   return matched;
 }
+
+QgsCategoryList QgsCategorizedSymbolRenderer::createCategories( const QList<QVariant> &values, const QgsSymbol *symbol, QgsVectorLayer *layer, const QString &attributeName )
+{
+  QgsCategoryList cats;
+  QVariantList vals = values;
+  // sort the categories first
+  QgsSymbolLayerUtils::sortVariantList( vals, Qt::AscendingOrder );
+
+  if ( layer && !attributeName.isNull() )
+  {
+    const QgsFields fields = layer->fields();
+    for ( const QVariant &value : vals )
+    {
+      QgsSymbol *newSymbol = symbol->clone();
+      if ( !value.isNull() )
+      {
+        int fieldIdx = fields.lookupField( attributeName );
+        QString categoryName = value.toString();
+        if ( fieldIdx != -1 )
+        {
+          const QgsField field = fields.at( fieldIdx );
+          const QgsEditorWidgetSetup setup = field.editorWidgetSetup();
+          const QgsFieldFormatter *formatter = QgsApplication::fieldFormatterRegistry()->fieldFormatter( setup.type() );
+          categoryName = formatter->representValue( layer, fieldIdx, setup.config(), QVariant(), value );
+        }
+        cats.append( QgsRendererCategory( value, newSymbol,  categoryName, true ) );
+      }
+    }
+  }
+
+  // add null (default) value
+  QgsSymbol *newSymbol = symbol->clone();
+  cats.append( QgsRendererCategory( QVariant(), newSymbol, QString(), true ) );
+
+  return cats;
+}
+

src/core/symbology/qgscategorizedsymbolrenderer.h

@@ -247,6 +247,19 @@ class CORE_EXPORT QgsCategorizedSymbolRenderer : public QgsFeatureRenderer
     int matchToSymbols( QgsStyle *style, QgsSymbol::SymbolType type,
                         QVariantList &unmatchedCategories SIP_OUT, QStringList &unmatchedSymbols SIP_OUT, bool caseSensitive = true, bool useTolerantMatch = false );
 
+
+    /**
+     * Create categories for a list of \a values.
+     * The returned symbols in the category list will be a modification of \a symbol.
+     *
+     * If \a layer and \a fieldName are specified it will try to find nicer values
+     * to represent the description for the categories based on the respective field
+     * configuration.
+     *
+     * \since QGIS 3.6
+     */
+    static QgsCategoryList createCategories( const QVariantList &values, const QgsSymbol *symbol, QgsVectorLayer *layer = nullptr, const QString &fieldName = QString() );
+
   protected:
     QString mAttrName;
     QgsCategoryList mCategories;

src/gui/symbology/qgscategorizedsymbolrendererwidget.cpp

@@ -638,44 +638,12 @@ void QgsCategorizedSymbolRendererWidget::changeCategorySymbol()
   }
 }
 
-static void _createCategories( QgsCategoryList &cats, QList<QVariant> &values, QgsSymbol *symbol, QgsVectorLayer *layer, const QString &attrName )
-{
-  // sort the categories first
-  QgsSymbolLayerUtils::sortVariantList( values, Qt::AscendingOrder );
-
-  int num = values.count();
-
-  const QgsFields fields = layer->fields();
-  for ( int i = 0; i < num; i++ )
-  {
-    QVariant value = values[i];
-    QgsSymbol *newSymbol = symbol->clone();
-    if ( ! value.isNull() )
-    {
-      int fieldIdx = fields.lookupField( attrName );
-      QString categoryName = value.toString();
-      if ( fieldIdx != -1 )
-      {
-        QgsField field = fields.at( fieldIdx );
-        const QgsEditorWidgetSetup setup = field.editorWidgetSetup();
-        const QgsFieldFormatter *formatter = QgsApplication::fieldFormatterRegistry()->fieldFormatter( setup.type() );
-        categoryName = formatter->representValue( layer, fieldIdx, setup.config(), QVariant(), value );
-      }
-      cats.append( QgsRendererCategory( value, newSymbol,  categoryName, true ) );
-    }
-  }
-
-  // add null (default) value
-  QgsSymbol *newSymbol = symbol->clone();
-  cats.append( QgsRendererCategory( QVariant( "" ), newSymbol, QString(), true ) );
-}
-
 
 void QgsCategorizedSymbolRendererWidget::addCategories()
 {
   QString attrName = mExpressionWidget->currentField();
   int idx = mLayer->fields().lookupField( attrName );
-  QList<QVariant> unique_vals;
+  QList<QVariant> uniqueValues;
   if ( idx == -1 )
   {
     // Lets assume it's an expression
@@ -693,21 +661,21 @@ void QgsCategorizedSymbolRendererWidget::addCategories()
     {
       context.setFeature( feature );
       QVariant value = expression->evaluate( &context );
-      if ( unique_vals.contains( value ) )
+      if ( uniqueValues.contains( value ) )
         continue;
-      unique_vals << value;
+      uniqueValues << value;
     }
   }
   else
   {
-    unique_vals = mLayer->uniqueValues( idx ).toList();
+    uniqueValues = mLayer->uniqueValues( idx ).toList();
   }
 
   // ask to abort if too many classes
-  if ( unique_vals.size() >= 1000 )
+  if ( uniqueValues.size() >= 1000 )
   {
     int res = QMessageBox::warning( nullptr, tr( "Classify Categories" ),
-                                    tr( "High number of classes. Classification would yield %1 entries which might not be expected. Continue?" ).arg( unique_vals.size() ),
+                                    tr( "High number of classes. Classification would yield %1 entries which might not be expected. Continue?" ).arg( uniqueValues.size() ),
                                     QMessageBox::Ok | QMessageBox::Cancel,
                                     QMessageBox::Cancel );
     if ( res == QMessageBox::Cancel )
@@ -722,8 +690,7 @@ void QgsCategorizedSymbolRendererWidget::addCategories()
     return;
 #endif
 
-  QgsCategoryList cats;
-  _createCategories( cats, unique_vals, mCategorizedSymbol.get(), mLayer, attrName );
+  QgsCategoryList cats = QgsCategorizedSymbolRenderer::createCategories( uniqueValues, mCategorizedSymbol.get(), mLayer, attrName );
   bool deleteExisting = false;
 
   if ( !mOldClassificationAttribute.isEmpty() &&