[FEATURE] Support single click to select with freehand select tool

This brings the behaviour of the freehand select into line with
the select by rectangle tool, which allows clicks without drag to
select a single feature.

(fix #14747)

src/app/qgsmaptoolselectfreehand.cpp

@@ -68,12 +68,29 @@ void QgsMapToolSelectFreehand::canvasReleaseEvent( QgsMapMouseEvent* e )
   if ( !mRubberBand )
     return;
 
+  bool singleSelect = false;
+  if ( mRubberBand->numberOfVertices() > 0 && mRubberBand->numberOfVertices() <= 2 )
+  {
+    // single click, not drag - create a rectangle around clicked point
+    QgsVectorLayer* vlayer = QgsMapToolSelectUtils::getCurrentVectorLayer( mCanvas );
+    if ( vlayer )
+    {
+      QRect selectRect;
+      QgsMapToolSelectUtils::expandSelectRectangle( selectRect, vlayer, e->pos() );
+      QgsMapToolSelectUtils::setRubberBand( mCanvas, selectRect, mRubberBand );
+      singleSelect = true;
+    }
+  }
+
   if ( mRubberBand->numberOfVertices() > 2 )
   {
     QgsGeometry* shapeGeom = mRubberBand->asGeometry();
-    QgsMapToolSelectUtils::setSelectFeatures( mCanvas, shapeGeom, e );
+    QgsMapToolSelectUtils::setSelectFeatures( mCanvas, shapeGeom,
+        e->modifiers() & Qt::ShiftModifier,
+        e->modifiers() & Qt::ControlModifier, singleSelect );
     delete shapeGeom;
   }
+
   mRubberBand->reset( QGis::Polygon );
   delete mRubberBand;
   mRubberBand = nullptr;