Repair LayerForm appearance

Set default roughness height to zero in GUI.

Restore dynamic updating of LayerForm when creating or moving/deleting a layer.

GUI/View/Sample/SampleForm.cpp

@@ -117,6 +117,8 @@ void SampleForm::onLayerAdded(LayerItem* layerItem)
 
     // same row => button is above!
     m_layout->insertWidget(rowInLayout, new AddLayerWidget(this, layerItem, m_ec), 0, Qt::AlignTop);
+
+    updateRowVisibilities();
 }
 
 void SampleForm::onLayerMoved(LayerItem* layerItem)
@@ -148,6 +150,8 @@ void SampleForm::onLayerMoved(LayerItem* layerItem)
 
     // same row => button is above!
     m_layout->insertWidget(rowInLayout, al, 0, Qt::AlignTop);
+
+    updateRowVisibilities();
 }
 
 void SampleForm::onAboutToRemoveLayer(LayerItem* layerItem)
@@ -176,6 +180,12 @@ void SampleForm::onAboutToRemoveLayer(LayerItem* layerItem)
     delete addLayerWidget;
 }
 
+void SampleForm::updateRowVisibilities()
+{
+    for (auto* c : findChildren<LayerForm*>())
+        c->updateLayerPositionDependentElements();
+}
+
 LayerForm* SampleForm::findNextLayerForm(QWidget* w)
 {
     while (w != nullptr && dynamic_cast<LayerForm*>(w) == nullptr) {