Snap nodes in digitizing map tools to grid

python/gui/auto_generated/qgsmapmouseevent.sip.in

@@ -117,6 +117,13 @@ The unsnapped, real mouse cursor position in pixel coordinates.
 Alias to pos()
 
 :return: Mouse position in pixel coordinates
+%End
+
+    void snapToGrid( double precision );
+%Docstring
+Snaps the mapPoint to a grid with the given ``precision``.
+
+.. versionadded:: 3.4
 %End
 
 };

src/gui/qgsmapmouseevent.cpp

@@ -71,6 +71,19 @@ void QgsMapMouseEvent::setMapPoint( const QgsPointXY &point )
   mPixelPoint = mapToPixelCoordinates( point );
 }
 
+void QgsMapMouseEvent::snapToGrid( double precision )
+{
+  if ( precision <= 0 )
+    return;
+
+  mMapPoint.setX( std::round( mMapPoint.x() / precision ) * precision );
+  mMapPoint.setY( std::round( mMapPoint.y() / precision ) * precision );
+
+  // mSnapMatch = QgsPointLocator::Match( mSnapMatch.type(), mSnapMatch.layer(), mSnapMatch.featureId(), mSnapMatch.distance(), mMapPoint, mSnapMatch.vertexIndex(), mSnapMatch.edgePoints() );
+
+  setMapPoint( mMapPoint );
+}
+
 QPoint QgsMapMouseEvent::mapToPixelCoordinates( const QgsPointXY &point )
 {
   double x = point.x(), y = point.y();

src/gui/qgsmapmouseevent.h

@@ -126,6 +126,13 @@ class GUI_EXPORT QgsMapMouseEvent : public QMouseEvent
      */
     QPoint originalPixelPoint() const { return pos(); }
 
+    /**
+     * Snaps the mapPoint to a grid with the given \a precision.
+     *
+     * \since QGIS 3.4
+     */
+    void snapToGrid( double precision );
+
   private:
 
     QPoint mapToPixelCoordinates( const QgsPointXY &point );

src/gui/qgsmaptooladvanceddigitizing.cpp

@@ -17,6 +17,7 @@
 #include "qgsmaptooladvanceddigitizing.h"
 #include "qgsmapcanvas.h"
 #include "qgsadvanceddigitizingdockwidget.h"
+#include "qgsvectorlayer.h"
 
 QgsMapToolAdvancedDigitizing::QgsMapToolAdvancedDigitizing( QgsMapCanvas *canvas, QgsAdvancedDigitizingDockWidget *cadDockWidget )
   : QgsMapToolEdit( canvas )
@@ -38,6 +39,9 @@ void QgsMapToolAdvancedDigitizing::canvasPressEvent( QgsMapMouseEvent *e )
     e->snapPoint();
   }
 
+  if ( currentVectorLayer() )
+    e->snapToGrid( currentVectorLayer()->geometryOptions().geometryPrecision );
+
   cadCanvasPressEvent( e );
 }
 
@@ -72,6 +76,9 @@ void QgsMapToolAdvancedDigitizing::canvasReleaseEvent( QgsMapMouseEvent *e )
     e->snapPoint();
   }
 
+  if ( currentVectorLayer() )
+    e->snapToGrid( currentVectorLayer()->geometryOptions().geometryPrecision );
+
   cadCanvasReleaseEvent( e );
 }
 
@@ -91,6 +98,9 @@ void QgsMapToolAdvancedDigitizing::canvasMoveEvent( QgsMapMouseEvent *e )
     e->snapPoint();
   }
 
+  if ( currentVectorLayer() )
+    e->snapToGrid( currentVectorLayer()->geometryOptions().geometryPrecision );
+
   cadCanvasMoveEvent( e );
 }