Add static methods to get a html preview for a given layer

qgis · Mar 28, 2023 · 66b64bc · 66b64bc
1 parent cfb236e
commit 66b64bc
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diff --git a/python/gui/auto_generated/qgsmaptip.sip.in b/python/gui/auto_generated/qgsmaptip.sip.in
@@ -67,6 +67,22 @@ Clear the current maptip if it exists
     void applyFontSettings();
 %Docstring
 Apply font family and size to match user settings
+%End
+
+    static QString vectorMapTipPreviewText( QgsMapLayer *layer, QgsMapCanvas *mapCanvas, const QString &mapTemplate, const QString &displayExpression );
+%Docstring
+Returns the html that would be displayed in a maptip for a given layer. If the layer has features, the first feature is used
+to evaluate the expressions.
+
+.. versionadded:: 3.32
+%End
+
+    static QString rasterMapTipPreviewText( QgsMapLayer *layer, QgsMapCanvas *mapCanvas, const QString &mapTemplate );
+%Docstring
+Returns the html that would be displayed in a maptip for a given layer. The center pixel of the raster is used to
+evaluate the expressions.
+
+.. versionadded:: 3.32
 %End
 
 };

diff --git a/src/gui/qgsmaptip.cpp b/src/gui/qgsmaptip.cpp
@@ -379,3 +379,71 @@ void QgsMapTip::onLinkClicked( const QUrl &url )
 {
   QDesktopServices::openUrl( url );
 }
+
+
+QString QgsMapTip::vectorMapTipPreviewText( QgsMapLayer *layer, QgsMapCanvas *mapCanvas, const QString &mapTemplate, const QString &displayExpression )
+{
+  // Only spatial layers can have map tips
+  QgsVectorLayer *vlayer = qobject_cast<QgsVectorLayer *>( layer );
+  if ( !vlayer || !vlayer->isSpatial() )
+    return QString();
+
+  // If no map tip template or display expression is set, return an empty string
+  if ( mapTemplate.isEmpty() && displayExpression.isEmpty() )
+    return QString();
+
+  // Create an expression context
+  QgsExpressionContext context( QgsExpressionContextUtils::globalProjectLayerScopes( vlayer ) );
+  context.appendScope( QgsExpressionContextUtils::mapSettingsScope( mapCanvas->mapSettings() ) );
+
+  // Get the first feature if any, and add it to the expression context
+  QgsFeature previewFeature;
+  if ( vlayer->featureCount() > 0 )
+  {
+    QgsFeatureIterator it = vlayer->getFeatures( QgsFeatureRequest().setLimit( 1 ) );
+    it.nextFeature( previewFeature );
+  }
+  else
+  {
+    previewFeature = QgsFeature( vlayer->fields() );
+  }
+  context.setFeature( previewFeature );
+
+  // Generate the map tip text from the context and the mapTipTemplate/displayExpression
+  QString tipText;
+  if ( mapTemplate.isEmpty() )
+  {
+    QgsExpression exp( displayExpression );
+    exp.prepare( &context );
+    tipText = exp.evaluate( &context ).toString();
+  }
+  else
+  {
+    tipText = QgsExpression::replaceExpressionText( mapTemplate, &context );
+  }
+
+  // Insert the map tip text into the html template
+  return QgsMapTip::htmlText( tipText );
+
+}
+
+QString QgsMapTip::rasterMapTipPreviewText( QgsMapLayer *layer, QgsMapCanvas *mapCanvas, const QString &mapTemplate )
+{
+  QgsRasterLayer *rlayer = qobject_cast<QgsRasterLayer *>( layer );
+  if ( !rlayer || mapTemplate.isEmpty() )
+    return QString();
+
+  // Create an expression context
+  QgsExpressionContext context( QgsExpressionContextUtils::globalProjectLayerScopes( layer ) );
+  context.appendScope( QgsExpressionContextUtils::mapSettingsScope( mapCanvas->mapSettings() ) );
+
+  // Get the position of the center of the layer, and add it to the expression context
+  const QgsPointXY mappedPosition { layer->extent().center() };
+  context.appendScope( QgsExpressionContextUtils::mapLayerPositionScope( mappedPosition ) );
+
+  // Generate the map tip text from the context and the mapTipTemplate
+  const QString tipText = QgsExpression::replaceExpressionText( mapTemplate, &context );
+
+  // Insert the map tip text into the html template
+  return QgsMapTip::htmlText( tipText );
+}
diff --git a/src/gui/qgsmaptip.h b/src/gui/qgsmaptip.h
@@ -86,6 +86,20 @@ class GUI_EXPORT QgsMapTip : public QWidget
      */
     void applyFontSettings();
 
+    /**
+     * Returns the html that would be displayed in a maptip for a given layer. If the layer has features, the first feature is used
+     * to evaluate the expressions.
+     * \since QGIS 3.32
+     */
+    static QString vectorMapTipPreviewText( QgsMapLayer *layer, QgsMapCanvas *mapCanvas, const QString &mapTemplate, const QString &displayExpression );
+
+    /**
+     * Returns the html that would be displayed in a maptip for a given layer. The center pixel of the raster is used to
+     * evaluate the expressions.
+     * \since QGIS 3.32
+     */
+    static QString rasterMapTipPreviewText( QgsMapLayer *layer, QgsMapCanvas *mapCanvas, const QString &mapTemplate );
+
   private slots:
     void onLinkClicked( const QUrl &url );
     void resizeContent();