performLayout method
Implementation
@override
void performLayout(ChantContext ctxt) {
super.performLayout(ctxt);
cssClass = 'InsertionCursor';
addVisualizer(DividerLineVisualizer(ctxt, 0, ctxt.staffLineCount * 2));
origin = Point(bounds.width / 2, origin.y);
bounds = bounds.copyWith(width: 0, height: 0);
finishLayout(ctxt);
}