Merge pull request #4598 from Gustry/atlas_expressions

[needs-docs] add layerid and layername to atlas expressions

Author: nyalldawson

src/core/expression/qgsexpression.cpp

@@ -638,6 +638,8 @@ void QgsExpression::initVariableHelp()
   sVariableHelpTexts.insert( QStringLiteral( "layout_dpi" ), QCoreApplication::translate( "variable_help", "Composition resolution (DPI)." ) );
 
   //atlas variables
+  sVariableHelpTexts.insert( QStringLiteral( "atlas_layerid" ), QCoreApplication::translate( "variable_help", "Current atlas coverage layer ID." ) );
+  sVariableHelpTexts.insert( QStringLiteral( "atlas_layername" ), QCoreApplication::translate( "variable_help", "Current atlas coverage layer name." ) );
   sVariableHelpTexts.insert( QStringLiteral( "atlas_totalfeatures" ), QCoreApplication::translate( "variable_help", "Total number of features in atlas." ) );
   sVariableHelpTexts.insert( QStringLiteral( "atlas_featurenumber" ), QCoreApplication::translate( "variable_help", "Current atlas feature number." ) );
   sVariableHelpTexts.insert( QStringLiteral( "atlas_filename" ), QCoreApplication::translate( "variable_help", "Current atlas file name." ) );

src/core/qgsexpressioncontext.cpp

@@ -987,6 +987,8 @@ QgsExpressionContextScope *QgsExpressionContextUtils::atlasScope( const QgsAtlas
   if ( atlas->enabled() && atlas->coverageLayer() )
   {
     scope->setFields( atlas->coverageLayer()->fields() );
+    scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "atlas_layerid" ), atlas->coverageLayer()->id(), true ) );
+    scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "atlas_layername" ), atlas->coverageLayer()->name(), true ) );
   }
 
   if ( atlas->enabled() )