Sketcher: Fix checkbox behavior for Element checkboxes

This creates new method overload for changing layer of exact
ElementItem. This fixes strange behavior of the checkboxes for elements
that were dependent not on what user clicked but on what is selected.

Fixes: #8814

src/Mod/Sketcher/Gui/TaskSketcherElements.cpp

@@ -239,6 +239,11 @@ public:
         }
     }
 
+    Sketcher::SketchObject* getSketchObject() const
+    {
+        return sketchView->getSketchObject();
+    }
+
     int ElementNbr;
     int StartingVertex;
     int MidVertex;
@@ -586,6 +591,47 @@ void ElementView::changeLayer(int layer)
     doc->commitTransaction();
 }
 
+void ElementView::changeLayer(ElementItem* item, int layer)
+{
+    App::Document* doc = App::GetApplication().getActiveDocument();
+
+    if (!doc) {
+        return;
+    }
+
+    doc->openTransaction("Geometry Layer Change");
+
+    auto sketchObject = item->getSketchObject();
+
+    auto geometry = sketchObject->Geometry.getValues();
+    auto newGeometry(geometry);
+
+    auto geoid = item->ElementNbr;
+
+    // currently only internal geometry can be changed from one layer to another
+    if (geoid >= 0) {
+        auto currentLayer = getSafeGeomLayerId(geometry[geoid]);
+
+        if (currentLayer != layer) {
+            auto geo = geometry[geoid]->clone();
+            setSafeGeomLayerId(geo, layer);
+            newGeometry[geoid] = geo;
+
+            sketchObject->Geometry.setValues(std::move(newGeometry));
+            sketchObject->solve();
+        }
+    }
+    else {
+        Gui::TranslatedUserWarning(
+            sketchObject,
+            QObject::tr("Unsupported visual layer operation"),
+            QObject::tr("It is currently unsupported to move external geometry to another "
+                        "visual layer. External geometry will be omitted"));
+    }
+
+    doc->commitTransaction();
+}
+
 void ElementView::contextMenuEvent(QContextMenuEvent* event)
 {
     QMenu menu;
@@ -788,14 +834,11 @@ void ElementView::onIndexHovered(QModelIndex index)
     Q_EMIT onItemHovered(itemFromIndex(index));
 }
 
-void ElementView::onIndexChecked(QModelIndex, Qt::CheckState state)
+void ElementView::onIndexChecked(QModelIndex index, Qt::CheckState state)
 {
-    if (state == Qt::Checked) {
-        changeLayer(static_cast<int>(ElementItem::Layer::Default));
-    }
-    else {
-        changeLayer(static_cast<int>(ElementItem::Layer::Hidden));
-    }
+    auto item = itemFromIndex(index);
+
+    changeLayer(item, static_cast<int>(state == Qt::Checked ? ElementItem::Layer::Default : ElementItem::Layer::Hidden));
 }
 
 ElementItem* ElementView::itemFromIndex(const QModelIndex& index)

src/Mod/Sketcher/Gui/TaskSketcherElements.h

@@ -109,6 +109,7 @@ Q_SIGNALS:
 
 private:
     void changeLayer(int layer);
+    void changeLayer(ElementItem* item, int layer);
 };
 
 class ElementFilterList;