Make labeling map tools aware that it's possible to edit

properties of the form coalesce("new aux field", 'some' || 'expression') Refs #44475
qgis · Sep 28, 2021 · 9db24c2 · 9db24c2
1 parent bbd8a5c
commit 9db24c2
Show file tree

Hide file tree

Showing 2 changed files with 44 additions and 1 deletion.
diff --git a/src/app/labeling/qgsmaptoollabel.cpp b/src/app/labeling/qgsmaptoollabel.cpp
@@ -520,12 +520,37 @@ QString QgsMapToolLabel::dataDefinedColumnName( QgsPalLayerSettings::Property p,
       QgsExpression expression( property.expressionString() );
       if ( expression.prepare( &context ) )
       {
+        // maybe the expression is effectively a single node in this context...
         const QgsExpressionNode *node = expression.rootNode()->effectiveNode();
         if ( node->nodeType() == QgsExpressionNode::ntColumnRef )
         {
           const QgsExpressionNodeColumnRef *columnRef = qgis::down_cast<const QgsExpressionNodeColumnRef *>( node );
           return columnRef->name();
         }
+
+        // ok, it's not. But let's be super smart and helpful for users!
+        // maybe it's a COALESCE("some field", 'some' || 'fallback' || 'expression') type expression, where the user wants to override
+        // some labels with a value stored in a field but all others use some expression
+        if ( node->nodeType() == QgsExpressionNode::ntFunction )
+        {
+          const QgsExpressionNodeFunction *functionNode = qgis::down_cast<const QgsExpressionNodeFunction *>( node );
+          if ( const QgsExpressionFunction *function = QgsExpression::QgsExpression::Functions()[functionNode->fnIndex()] )
+          {
+            if ( function->name() == QLatin1String( "coalesce" ) )
+            {
+              if ( const QgsExpressionNode *firstArg = functionNode->args()->list().value( 0 ) )
+              {
+                const QgsExpressionNode *firstArgNode = firstArg->effectiveNode();
+                if ( firstArgNode->nodeType() == QgsExpressionNode::ntColumnRef )
+                {
+                  const QgsExpressionNodeColumnRef *columnRef = qgis::down_cast<const QgsExpressionNodeColumnRef *>( firstArgNode );
+                  return columnRef->name();
+                }
+              }
+            }
+          }
+        }
+
       }
       break;
     }

diff --git a/tests/src/app/testqgsmaptoollabel.cpp b/tests/src/app/testqgsmaptoollabel.cpp
@@ -378,7 +378,7 @@ class TestQgsMapToolLabel : public QObject
 
     void dataDefinedColumnName()
     {
-      QgsVectorLayer *vl1 = new QgsVectorLayer( QStringLiteral( "Point?crs=epsg:3946&field=label_x_1:string&field=label_y_1:string&field=label_x_2:string&field=label_y_2:string" ), QStringLiteral( "vl1" ), QStringLiteral( "memory" ) );
+      QgsVectorLayer *vl1 = new QgsVectorLayer( QStringLiteral( "Point?crs=epsg:3946&field=label_x_1:string&field=label_y_1:string&field=label_x_2:string&field=label_y_2:string&field=override_x_field:string" ), QStringLiteral( "vl1" ), QStringLiteral( "memory" ) );
       QVERIFY( vl1->isValid() );
       QgsProject::instance()->addMapLayer( vl1 );
 
@@ -445,6 +445,24 @@ class TestQgsMapToolLabel : public QObject
       QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::AlwaysShow, pls1, vl1 ), QString() );
       QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::PositionX, pls1, vl1 ), QStringLiteral( "label_x_2" ) );
       QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::PositionY, pls1, vl1 ), QStringLiteral( "label_y_2" ) );
+
+      // another smart situation -- an expression which uses coalesce to store per-feature overrides in a field, otherwise falling back to some complex expression
+      pls1.dataDefinedProperties().setProperty( QgsPalLayerSettings::PositionX, QgsProperty::fromExpression( QStringLiteral( "coalesce(\"override_x_field\", $x + 10)" ) ) );
+      pls1.dataDefinedProperties().setProperty( QgsPalLayerSettings::PositionY, QgsProperty::fromExpression( QStringLiteral( "COALESCE(case when @var_1 = '1' then \"label_y_1\" else \"label_y_2\" end, $y-20)" ) ) );
+      vl1->setLabeling( new QgsVectorLayerSimpleLabeling( pls1 ) );
+      vl1->setLabelsEnabled( true );
+
+      QgsExpressionContextUtils::setProjectVariable( QgsProject::instance(), QStringLiteral( "var_1" ), QStringLiteral( "1" ) );
+
+      QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::AlwaysShow, pls1, vl1 ), QString() );
+      QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::PositionX, pls1, vl1 ), QStringLiteral( "override_x_field" ) );
+      QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::PositionY, pls1, vl1 ), QStringLiteral( "label_y_1" ) );
+
+      QgsExpressionContextUtils::setProjectVariable( QgsProject::instance(), QStringLiteral( "var_1" ), QStringLiteral( "2" ) );
+
+      QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::AlwaysShow, pls1, vl1 ), QString() );
+      QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::PositionX, pls1, vl1 ), QStringLiteral( "override_x_field" ) );
+      QCOMPARE( tool->dataDefinedColumnName( QgsPalLayerSettings::PositionY, pls1, vl1 ), QStringLiteral( "label_y_2" ) );
     }