diff --git a/src/core/composer/qgsscalebarstyle.h b/src/core/composer/qgsscalebarstyle.h
index 9f2a69f2052..56ea11a57ef 100644
--- a/src/core/composer/qgsscalebarstyle.h
+++ b/src/core/composer/qgsscalebarstyle.h
@@ -39,7 +39,11 @@ class CORE_EXPORT QgsScaleBarStyle
     virtual void draw( QPainter* p, double xOffset = 0 ) const = 0; //to do by every subclass
     virtual void drawLabels( QPainter* p ) const; //default implementation provided
     virtual QRectF calculateBoxSize() const; //default implementation provided
-    virtual QString name() const = 0; //return name of the style
+    /**
+     * Get a name for this style.
+     * Needs to be remiplmeented by subclasses.
+     */
+    virtual QString name() const = 0;
 
   private:
     QgsScaleBarStyle(); //default constructor forbidden
diff --git a/src/core/diagram/qgsdiagram.h b/src/core/diagram/qgsdiagram.h
index aeef499282f..c53394101e0 100644
--- a/src/core/diagram/qgsdiagram.h
+++ b/src/core/diagram/qgsdiagram.h
@@ -51,6 +51,10 @@ class CORE_EXPORT QgsDiagram
 
     /** Draws the diagram at the given position (in pixel coordinates)*/
     virtual void renderDiagram( const QgsFeature& feature, QgsRenderContext& c, const QgsDiagramSettings& s, QPointF position ) = 0;
+
+    /**
+     * Get a descriptive name for this diagram type.
+     */
     virtual QString diagramName() const = 0;
     /** Returns the size in map units the diagram will use to render.*/
     virtual QSizeF diagramSize( const QgsAttributes& attributes, const QgsRenderContext& c, const QgsDiagramSettings& s ) = 0;
diff --git a/src/core/geometry/qgsabstractgeometry.h b/src/core/geometry/qgsabstractgeometry.h
index 5c2eea0b1ac..9db4b2f440d 100644
--- a/src/core/geometry/qgsabstractgeometry.h
+++ b/src/core/geometry/qgsabstractgeometry.h
@@ -328,7 +328,14 @@ class CORE_EXPORT QgsAbstractGeometry
      */
     virtual double vertexAngle( QgsVertexId vertex ) const = 0;
 
+    /**
+     * Returns the number of vertexes of which this geometry is built.
+     */
     virtual int vertexCount( int part = 0, int ring = 0 ) const = 0;
+
+    /**
+     * Returns the number of rings of which this geometry is built.
+     */
     virtual int ringCount( int part = 0 ) const = 0;
 
     /** Returns count of parts contained in the geometry.
diff --git a/src/core/geometry/qgssurface.h b/src/core/geometry/qgssurface.h
index c115745a64c..54f2e113f1e 100644
--- a/src/core/geometry/qgssurface.h
+++ b/src/core/geometry/qgssurface.h
@@ -30,6 +30,10 @@ class CORE_EXPORT QgsSurface: public QgsAbstractGeometry
 {
   public:
 
+    /**
+     * Get a polygon representation of this surface.
+     * Ownership is transferred to the caller.
+     */
     virtual QgsPolygonV2* surfaceToPolygon() const = 0;
 
     /** Returns the minimal bounding box for the geometry
diff --git a/src/core/raster/qgsrasterresampler.h b/src/core/raster/qgsrasterresampler.h
index 0991edebaea..52963ec2d3b 100644
--- a/src/core/raster/qgsrasterresampler.h
+++ b/src/core/raster/qgsrasterresampler.h
@@ -30,8 +30,18 @@ class QgsRasterResampler
   public:
     virtual ~QgsRasterResampler() {}
     virtual void resample( const QImage& srcImage, QImage& dstImage ) = 0;
+
+    /**
+     * Get a descriptive type identifier for this raster resampler.
+     * Needs to be implemented by subclasses.
+     */
     virtual QString type() const = 0;
-    virtual QgsRasterResampler * clone() const = 0;
+    /**
+     * Get a deep copy of this object.
+     * Needs to be reimplemented by subclasses.
+     * Ownership is transferred to the caller.
+     */
+    virtual QgsRasterResampler* clone() const = 0;
 };
 
 #endif // QGSRASTERRESAMPLER_H
diff --git a/src/core/symbology-ng/qgssymbol.h b/src/core/symbology-ng/qgssymbol.h
index 49a055d9684..792e65a6697 100644
--- a/src/core/symbology-ng/qgssymbol.h
+++ b/src/core/symbology-ng/qgssymbol.h
@@ -190,6 +190,11 @@ class CORE_EXPORT QgsSymbol
 
     QString dump() const;
 
+    /**
+     * Get a deep copy of this symbol.
+     * Needs to be reimplemented by subclasses.
+     * Ownership is transferred to the caller.
+     */
     virtual QgsSymbol* clone() const = 0;
 
     void toSld( QDomDocument &doc, QDomElement &element, QgsStringMap props ) const;
diff --git a/src/gui/qgsannotationitem.h b/src/gui/qgsannotationitem.h
index 534b25edb87..921932d71b0 100644
--- a/src/gui/qgsannotationitem.h
+++ b/src/gui/qgsannotationitem.h
@@ -103,10 +103,28 @@ class GUI_EXPORT QgsAnnotationItem: public QgsMapCanvasItem, public QgsAnnotatio
     void setFrameBackgroundColor( const QColor& c ) { mFrameBackgroundColor = c; }
     QColor frameBackgroundColor() const { return mFrameBackgroundColor; }
 
+    /**
+     * Serialize to XML. The doc is used to generate new nodes.
+     * Needs to be reimplemented by subclasses.
+     */
     virtual void writeXml( QDomDocument& doc ) const = 0;
+
+    /**
+     * Deserialize from XML. The itemElem is used as source for the information.
+     * Needs to be reimplemented by subclasses
+     */
     virtual void readXml( const QDomDocument& doc, const QDomElement& itemElem ) = 0;
 
+    /**
+     * Serialize to XML. The doc is used to generate new nodes.
+     * Should be called by subclasses in their writeXml method.
+     */
     void _writeXml( QDomDocument& doc, QDomElement& itemElem ) const;
+
+    /**
+     * Deserialize from XML. The itemElem is used as source for the information.
+     * Should be called from subclasses in their readXml method.
+     */
     void _readXml( const QDomDocument& doc, const QDomElement& annotationElem );
 
     virtual void setItemData( int role, const QVariant& value ) override;
diff --git a/src/gui/qgsdatadefinedbutton.h b/src/gui/qgsdatadefinedbutton.h
index 1b7df5d6747..8d29471a1bf 100644
--- a/src/gui/qgsdatadefinedbutton.h
+++ b/src/gui/qgsdatadefinedbutton.h
@@ -41,6 +41,10 @@ class GUI_EXPORT QgsDataDefinedAssistant: public QDialog
   public:
     QgsDataDefinedAssistant() : mMapCanvas( nullptr ) {}
 
+    /**
+     * Get the data defined which was defined by this assistant.
+     * Needs to be reimplemented by subclasses.
+     */
     virtual QgsDataDefined dataDefined() const = 0;
 
     /** Sets the map canvas associated with the widget. This allows the widget to retrieve the current
diff --git a/src/plugins/qgsapplydialog.h b/src/plugins/qgsapplydialog.h
index 05e1942a9d1..5ff55f1e468 100644
--- a/src/plugins/qgsapplydialog.h
+++ b/src/plugins/qgsapplydialog.h
@@ -30,6 +30,11 @@ class QgsApplyDialog: public QDialog
   public:
     QgsApplyDialog(): QDialog() {}
     ~QgsApplyDialog() {}
+
+    /**
+     * This method is called when changes should be applied.
+     * It needs to be implemented by subclasses.
+     */
     virtual void apply() const = 0;
 };