Make it possible to load "text on symbol" labels from expression

qgis · Apr 19, 2018 · 00d8dbf · 00d8dbf
1 parent 49b02bf
commit 00d8dbf
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Showing 3 changed files with 72 additions and 4 deletions.
diff --git a/src/app/qgsvectorlayerlegendwidget.cpp b/src/app/qgsvectorlayerlegendwidget.cpp
@@ -19,6 +19,8 @@
 #include <QStandardItemModel>
 #include <QTreeView>
 
+#include "qgsexpressionbuilderdialog.h"
+#include "qgsmapcanvas.h"
 #include "qgsmaplayerlegend.h"
 #include "qgsrenderer.h"
 #include "qgssymbollayerutils.h"
@@ -32,14 +34,21 @@ QgsVectorLayerLegendWidget::QgsVectorLayerLegendWidget( QWidget *parent )
   mLegendTreeView = new QTreeView;
   mLegendTreeView->setRootIsDecorated( false );
 
-  mTextOnSymbolFormatButton = new QPushButton( tr( "Set Text Format..." ) );
+  mTextOnSymbolFormatButton = new QPushButton( tr( "Set Text Format…" ) );
   connect( mTextOnSymbolFormatButton, &QPushButton::clicked, this, &QgsVectorLayerLegendWidget::openTextFormatWidget );
 
+  mTextOnSymbolFromExpressionButton = new QPushButton( tr( "Set Labels from Expression…" ) );
+  connect( mTextOnSymbolFromExpressionButton, &QPushButton::clicked, this, &QgsVectorLayerLegendWidget::labelsFromExpression );
+
   mTextOnSymbolGroupBox = new QgsCollapsibleGroupBox;
 
+  QHBoxLayout *buttonsLayout = new QHBoxLayout;
+  buttonsLayout->addWidget( mTextOnSymbolFormatButton );
+  buttonsLayout->addWidget( mTextOnSymbolFromExpressionButton );
+
   QVBoxLayout *groupLayout = new QVBoxLayout;
   groupLayout->addWidget( mLegendTreeView );
-  groupLayout->addWidget( mTextOnSymbolFormatButton );
+  groupLayout->addLayout( buttonsLayout );
 
   mTextOnSymbolGroupBox->setTitle( tr( "Text on Symbols" ) );
   mTextOnSymbolGroupBox->setCheckable( true );
@@ -62,13 +71,17 @@ void QgsVectorLayerLegendWidget::setLayer( QgsVectorLayer *layer )
 
   mTextOnSymbolGroupBox->setChecked( legend->textOnSymbolEnabled() );
   mTextOnSymbolTextFormat = legend->textOnSymbolTextFormat();
-  QHash<QString, QString> content = legend->textOnSymbolContent();
+  populateLegendTreeView( legend->textOnSymbolContent() );
+}
 
+
+void QgsVectorLayerLegendWidget::populateLegendTreeView( const QHash<QString, QString> &content )
+{
   QStandardItemModel *model = new QStandardItemModel;
   model->setColumnCount( 2 );
   model->setHorizontalHeaderLabels( QStringList() << tr( "Symbol" ) << tr( "Text" ) );
 
-  const QgsLegendSymbolList lst = layer->renderer()->legendSymbolItems();
+  const QgsLegendSymbolList lst = mLayer->renderer()->legendSymbolItems();
   for ( const QgsLegendSymbolItem &symbolItem : lst )
   {
     if ( !symbolItem.symbol() )
@@ -138,3 +151,44 @@ void QgsVectorLayerLegendWidget::openTextFormatWidget()
 
   mTextOnSymbolTextFormat = textOnSymbolFormatWidget->format();
 }
+
+
+void QgsVectorLayerLegendWidget::labelsFromExpression()
+{
+  QHash<QString, QString> content;
+  QgsRenderContext context( QgsRenderContext::fromMapSettings( mCanvas->mapSettings() ) );
+
+  QgsExpressionBuilderDialog dlgExpression( mLayer );
+  dlgExpression.setExpressionContext( context.expressionContext() );
+  if ( !dlgExpression.exec() )
+    return;
+
+  QgsExpression expr( dlgExpression.expressionText() );
+  expr.prepare( &context.expressionContext() );
+
+  std::unique_ptr< QgsFeatureRenderer > r( mLayer->renderer()->clone() );
+
+  QgsFeature f;
+  QgsFeatureRequest request;
+  request.setSubsetOfAttributes( r->usedAttributes( context ), mLayer->fields() );
+  QgsFeatureIterator fi = mLayer->getFeatures();
+
+  r->startRender( context, mLayer->fields() );
+  while ( fi.nextFeature( f ) )
+  {
+    context.expressionContext().setFeature( f );
+    const QSet<QString> keys = r->legendKeysForFeature( f, context );
+    for ( const QString &key : keys )
+    {
+      if ( content.contains( key ) )
+        continue;
+
+      QString label = expr.evaluate( &context.expressionContext() ).toString();
+      if ( !label.isEmpty() )
+        content[key] = label;
+    }
+  }
+  r->stopRender( context );
+
+  populateLegendTreeView( content );
+}
diff --git a/src/app/qgsvectorlayerlegendwidget.h b/src/app/qgsvectorlayerlegendwidget.h
@@ -25,6 +25,7 @@ class QPushButton;
 class QTreeView;
 
 class QgsCollapsibleGroupBox;
+class QgsMapCanvas;
 class QgsVectorLayer;
 
 /**
@@ -36,6 +37,12 @@ class QgsVectorLayerLegendWidget : public QWidget
   public:
     explicit QgsVectorLayerLegendWidget( QWidget *parent = nullptr );
 
+    //! Sets pointer to map canvas
+    void setMapCanvas( QgsMapCanvas *canvas ) { mCanvas = canvas; }
+
+    //! Returns pointer to map canvas
+    QgsMapCanvas *mapCanvas() const { return mCanvas; }
+
     //! Initialize widget with a map layer
     void setLayer( QgsVectorLayer *layer );
 
@@ -44,13 +51,19 @@ class QgsVectorLayerLegendWidget : public QWidget
 
   private slots:
     void openTextFormatWidget();
+    void labelsFromExpression();
+
+  private:
+    void populateLegendTreeView( const QHash<QString, QString> &content );
 
   private:
     QTreeView *mLegendTreeView = nullptr;
     QPushButton *mTextOnSymbolFormatButton = nullptr;
+    QPushButton *mTextOnSymbolFromExpressionButton = nullptr;
     QgsCollapsibleGroupBox *mTextOnSymbolGroupBox = nullptr;
     QLabel *mTextOnSymbolLabel = nullptr;
 
+    QgsMapCanvas *mCanvas = nullptr;
     QgsVectorLayer *mLayer = nullptr;
     QgsTextFormat mTextOnSymbolTextFormat;
 };

diff --git a/src/app/qgsvectorlayerproperties.cpp b/src/app/qgsvectorlayerproperties.cpp
@@ -302,6 +302,7 @@ QgsVectorLayerProperties::QgsVectorLayerProperties(
   mDiagramFrame->setLayout( diagLayout );
 
   // Legend tab
+  mLegendWidget->setMapCanvas( QgisApp::instance()->mapCanvas() );
   mLegendWidget->setLayer( mLayer );
   mLegendConfigEmbeddedWidget->setLayer( mLayer );