[pal] Improve line placement algorithm

Avoid placing labels over jagged sections of lines

Sponsored by Andreas Neumann

(cherry-picked from 92ab671)

Author: nyalldawson

src/app/qgslabelingwidget.cpp

@@ -181,4 +181,5 @@ void QgsLabelingWidget::showEngineConfigDialog()
 {
   QgsLabelEngineConfigDialog dlg( this );
   dlg.exec();
+  emit widgetChanged();
 }