diff --git a/src/Series.vala b/src/Series.vala
index 1bdec7e..91d46c0 100644
--- a/src/Series.vala
+++ b/src/Series.vala
@@ -41,8 +41,14 @@ namespace CairoChart {
 
 		public bool zoom_show = true;
 
+		protected Chart chart { get; protected set; default = null; }
+
+		public Series (Chart chart) {
+			this.chart = chart;
+		}
+
 		public virtual Series copy () {
-			var series = new Series ();
+			var series = new Series (chart);
 			series._color = this._color;
 			series.axis_x = this.axis_x.copy ();
 			series.axis_y = this.axis_y.copy ();
@@ -57,9 +63,6 @@ namespace CairoChart {
 			return series;
 		}
 
-		public Series () {
-		}
-
 		public virtual void draw (Chart chart) {
 			var points = chart.math.sort_points(this, sort);
 			line_style.set(chart);
@@ -466,5 +469,17 @@ namespace CairoChart {
 				             + (s.axis_y.title.text == "" ? 0 : sz.width + s.axis_y.font_indent); break;
 			}
 		}
+
+		public virtual double compact_rec_x_pos (Series s, Float128 x, Text text) {
+			var sz = text.get_size(chart.context);
+			return chart.get_scr_x(s, x) - sz.width / 2.0
+			       - sz.width * (x - (s.axis_x.zoom_min + s.axis_x.zoom_max) / 2.0) / (s.axis_x.zoom_max - s.axis_x.zoom_min);
+		}
+
+		public virtual double compact_rec_y_pos (Series s, Float128 y, Text text) {
+			var sz = text.get_size(chart.context);
+			return chart.get_scr_y(s, y) + sz.height / 2.0
+			       + sz.height * (y - (s.axis_y.zoom_min + s.axis_y.zoom_max) / 2.0) / (s.axis_y.zoom_max - s.axis_y.zoom_min);
+		}
 	}
 }
diff --git a/test/ChartTest.vala b/test/ChartTest.vala
index 56541f1..b38b103 100644
--- a/test/ChartTest.vala
+++ b/test/ChartTest.vala
@@ -1,9 +1,9 @@
 using Gtk, CairoChart;
 
 void plot_chart1 (Chart chart) {
-	var s1 = new Series ();
-	var s2 = new Series ();
-	var s3 = new Series ();
+	var s1 = new Series (chart);
+	var s2 = new Series (chart);
+	var s3 = new Series (chart);
 
 	s1.title = new Text("Series 1"); s1.color = Color (1, 0, 0);
 	s1.points = {Point128(0, 0), Point128(2, 1), Point128(1, 3)};
@@ -45,9 +45,9 @@ void plot_chart1 (Chart chart) {
 }
 
 void plot_chart2 (Chart chart) {
-	var s1 = new Series ();
-	var s2 = new Series ();
-	var s3 = new Series ();
+	var s1 = new Series (chart);
+	var s2 = new Series (chart);
+	var s3 = new Series (chart);
 
 	s1.title = new Text("Series 1"); s1.color = Color (1, 0, 0);
 	s1.points = {Point128(-12, 0), Point128(2, 1), Point128(20, 3)};
@@ -93,9 +93,9 @@ void plot_chart2 (Chart chart) {
 }
 
 void plot_chart3 (Chart chart) {
-	var s1 = new Series ();
-	var s2 = new Series ();
-	var s3 = new Series ();
+	var s1 = new Series (chart);
+	var s2 = new Series (chart);
+	var s3 = new Series (chart);
 
 	s1.title = new Text("Series 1"); s1.color = Color (1, 0, 0);
 	s1.points = {Point128(0, 70), Point128(2, 155), Point128(1, -3)};
@@ -141,10 +141,10 @@ void plot_chart3 (Chart chart) {
 }
 
 void plot_chart4 (Chart chart) {
-	var s1 = new Series ();
-	var s2 = new Series ();
-	var s3 = new Series ();
-	var s4 = new Series ();
+	var s1 = new Series (chart);
+	var s2 = new Series (chart);
+	var s3 = new Series (chart);
+	var s4 = new Series (chart);
 
 	s1.axis_x.type = Axis.Type.DATE_TIME;
 	s3.axis_x.type = Axis.Type.DATE_TIME;