void paintMarkers(Graphics g, VerticalPixelAddressMap pixmap, AddressIndexMap addrMap) {
			int count = 0;
			for (MarkerSetImpl markers : markerSets) {
				count++;
				if (markers.active) {
					markers.paintMarkers(g, count++, pixmap, addrMap);
				}
			}
		}
Use this close listener approach instead of plugin events, since we don't get a
ProgramClosedPluginEvent when a trace view is closed, but we can listen for its
domain object closing, which works for plain programs, too.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/marker/MarkerManager.java