[composer] Fix editing of map item variables

On behalf of Faunalia, sponsored by ENEL

python/core/qgsexpressioncontext.sip

@@ -296,6 +296,13 @@ class QgsExpressionContext
      */
     int indexOfScope( QgsExpressionContextScope* scope ) const;
 
+    /** Returns the index of the first scope with a matching name within the context.
+     * @param scopeName name of scope to find
+     * @returns index of scope, or -1 if scope was not found within the context.
+     * @note added in QGIS 3.0
+     */
+    int indexOfScope( const QString& scopeName ) const;
+
     /** Returns a list of variables names set by all scopes in the context.
      * @returns list of unique variable names
      * @see filteredVariableNames

src/app/composer/qgscomposeritemwidget.cpp

@@ -114,7 +114,9 @@ void QgsComposerItemWidget::updateVariables()
 {
   QgsExpressionContext* context = mItem->createExpressionContext();
   mVariableEditor->setContext( context );
-  mVariableEditor->setEditableScopeIndex( context->scopeCount() - 1 );
+  int editableIndex = context->indexOfScope( tr( "Composer Item" ) );
+  if ( editableIndex >= 0 )
+    mVariableEditor->setEditableScopeIndex( editableIndex );
   delete context;
 }
 

src/core/qgsexpressioncontext.cpp

@@ -312,6 +312,19 @@ int QgsExpressionContext::indexOfScope( QgsExpressionContextScope* scope ) const
   return mStack.indexOf( scope );
 }
 
+int QgsExpressionContext::indexOfScope( const QString& scopeName ) const
+{
+  int index = 0;
+  Q_FOREACH ( const QgsExpressionContextScope* scope, mStack )
+  {
+    if ( scope->name() == scopeName )
+      return index;
+
+    index++;
+  }
+  return -1;
+}
+
 QStringList QgsExpressionContext::variableNames() const
 {
   QStringList names;

src/core/qgsexpressioncontext.h

@@ -334,6 +334,13 @@ class CORE_EXPORT QgsExpressionContext
      */
     int indexOfScope( QgsExpressionContextScope* scope ) const;
 
+    /** Returns the index of the first scope with a matching name within the context.
+     * @param scopeName name of scope to find
+     * @returns index of scope, or -1 if scope was not found within the context.
+     * @note added in QGIS 3.0
+     */
+    int indexOfScope( const QString& scopeName ) const;
+
     /** Returns a list of variables names set by all scopes in the context.
      * @returns list of unique variable names
      * @see filteredVariableNames

tests/src/core/testqgsexpressioncontext.cpp

@@ -37,6 +37,7 @@ class TestQgsExpressionContext : public QObject
     void contextScopeCopy();
     void contextScopeFunctions();
     void contextStack();
+    void scopeByName();
     void contextCopy();
     void contextStackFunctions();
     void evaluate();
@@ -302,6 +303,17 @@ void TestQgsExpressionContext::contextStack()
   QCOMPARE( scopes.at( 0 ), scope1 );
 }
 
+void TestQgsExpressionContext::scopeByName()
+{
+  QgsExpressionContext context;
+  QCOMPARE( context.indexOfScope( "test1" ), -1 );
+  context << new QgsExpressionContextScope( "test1" );
+  context << new QgsExpressionContextScope( "test2" );
+  QCOMPARE( context.indexOfScope( "test1" ), 0 );
+  QCOMPARE( context.indexOfScope( "test2" ), 1 );
+  QCOMPARE( context.indexOfScope( "not in context" ), -1 );
+}
+
 void TestQgsExpressionContext::contextCopy()
 {
   QgsExpressionContext context;