function parseVisibleItems(chart, handler) {
	var datasets = chart.data.datasets;
	var meta, i, j, ilen, jlen;

	for (i = 0, ilen = datasets.length; i < ilen; ++i) {
		if (!chart.isDatasetVisible(i)) {
			continue;
		}

		meta = chart.getDatasetMeta(i);
		for (j = 0, jlen = meta.data.length; j < jlen; ++j) {
			var element = meta.data[j];
			if (!element._view.skip) {
				handler(element);
			}
		}
	}
}
Helper function to traverse all of the visible elements in the chart
@param chart {chart} the chart
@param handler {Function} the callback to execute for each visible item